5.0 Design and Engineering
5.1 General Requirements
5.1.1 The design of the Plant shall be energy efficient, environmentally compliant and consumption of utilities shall be minimized.
5.1.2 Maximum consideration shall be given to the design philosophy from the point of view of ease and stable operation & maintenance, including start-up, shut down, normal operation, emergency/ shut down and other possible operating conditions.
5.1.3 Design shall consider:
a. Safety of personnel during operation and maintenance
b. Operability and reliability
c. Future expansion
d. Interchangeability of equipment and parts
e. Protection against environmental conditions such as dust, sandstorms, corrosive gases and/or vapors, mechanical shocks, water etc.
5.1.4 Equipment selection will be supported by proven track record. In general, this means that similar equipment will have been in operating service for a minimum of 2 years. Final approval will be at Company discretion.
5.1.5 Design of facilities, outside the facilities battery limits and falling under the purview of other statutory authorities such as Royal Commission for Jubail, Saudi Port Authorities shall be subjected to their review and approval.
5.1.6 Design of facilities at the interface points with Saudi ARAMCO shall be subject to Saudi ARAMCO’s review and approval.
5.1.7 General Design guidelines as drawn up by Royal Commission for Al-Jubail and Yanbu in their
“USERS INFORMATION GUIDE FOR INDUSTRIES” shall be followed.
5.1.8 Asbestos materials or material containing asbestos shall not be used for any service.
5.1.9 Upstream and downstream straight length of control valves shall be designed with spacing as per PIP PCEC V001 to avoid erosion, noise and failures.
5.1.10 Ejectors in vacuum service and process filters shall be provided with spare. Some specific
requirements to be considered when the design is being prepared are covered in the following subsections.
These requirements are not all-inclusive and shall be considered as minimum requirements.
5.1.11 Many liquids are capable of building up an electrical charges when subjected to agitation or friction such as occurs during their flow through piping, agitation within vessel or when subjected to other vigorous mechanical movement. Proper arrangements shall be provided to prevent electrostatic ignition as per API RP 2003. For bonding, grounding and static electricity refer SES E11-E03 and E11-S03.
5.1.12 All lines such as Natural gas, Nitrogen, Instrument Air, Plant Air, etc. connected to process
equipment shall be equipped with double block valves, bleeder valve and a “figure eight” slip blind.
5.1.13 Double block & Bleed valves shall be provided for drains from equipment containing liquid light hydrocarbons.
5.1.14 Equipment that may be removed from service during operation of the unit shall be furnished with single block valves and valve drain or valve vent and drain.
5.1.15 Dual check valves will be provided on a case by case basis where process-to-service connections are made.
5.1.16 Provide positive isolation arrangement for all hazardous material including nitrogen connection to vessels, boilers, furnaces etc. requiring entry for inspection, repair or maintenance. This shall be in compliance to work Permit Procedure and Safe Work Procedure.
5.2 Design Pressure:
5.2.1 Equipment design will be based on process requirements and be in accordance with international codes and standards as further defined under Project Specifications.
5.2.2 In determining the max. Operating pressure, normal variations in pressure that may be expected to arise, Liquid static head, fluid friction losses under clean & fouled conditions and pump & compressor head characteristics shall be considered.
5.2.3 Equipment that is purged by evacuation or that normally operates at vacuum conditions is to be designed for full vacuum.
5.2.4 Equipment that is normally in steam service shall be designed for full vacuum at 150ºC.
5.2.5 Equipment that is steamed out shall be designed for half vacuum (50 kPag external pressure) at 150ºC.
5.2.6 For all exchangers the low-pressure side shall be equal to or greater than two-thirds (10/13rd) the design pressure of high-pressure side. Otherwise, Tube failure conditions should be evaluated as a relieving contingency as per API RP 521.
5.2.7 The Tube failure conditions must be evaluated (even if the 10/13rd rule is applied) if the high pressure side of the exchanger operates at 6900 kPag or more and contains vapor or a liquid that
can flash or result in vaporization of liquid on the low-pressure side.
5.2.8 In case of exchangers like combined feed-Effluent type of exchangers where both the sides are subject to operating pressure together, if the high-pressure design pressure is above 5500 kPag, the low-pressure side shall be designed for a differential pressure of 150% design differential pressure of the compressor or 1375 kPag, whichever is greater. (The exchanger shall bear a notation to this effect on the code stamp attached to the exchanger so that it will be taken into account while hydrostatic testing).
5.2.9 ASME Section VIII requires that vessels subject to internal pressure be designed for at least the most severe condition of coincident pressure and temperature expected in normal service. However, it is also necessary that a suitable margin be provided above the pressure at which the vessel will normally be operating to allow for probable pressure surges in the vessel up to the setting of the pressure relieving device, and to provide sufficient blowdown to reseat the relieving device.
5.2.10 The design pressure of equipment, located in the discharge of a centrifugal compressor, is normally the maximum operating pressure + 10% minimum or 1.75 bar, whichever is greater. If the compressor curve is available, the shutoff head should be used. For reciprocating compressors discharge equipment, the margin will be normally the maximum operating pressure plus 15% minimum or 1.75 bar, whichever is greater.
5.2.11 For compressor inter-stage systems, the design pressure must be evaluated considering the settling out pressure developed by open minimum flow recycles lines (not applicable to reciprocating compressors).
5.2.12 Particular attention should be given to liquid-filled equipment and fluctuations imposed by control devices and other similar occurrences. The maximum operating pressure should be the greater of the following:
a. The discharge pressure of the feed pump when operating with normal suction pressure and the
discharge blocked.
b. The discharge pressure of the pump when operating at normal pump differential pressure and with suction pressure at maximum (corresponding to maximum liquid level and design pressure of pump suction vessel to tank).
c. If an exchanger outlet can be blocked off, the exchanger will be designed for pump shutoff
pressure.
5.3 Design Temperature
5.3.1 To properly establish the maximum and minimum design temperatures, all modes of operation must be considered; e.g. start-up, shutdown, relieving conditions, steaming out, dryout etc.
5.3.2 When equipment is depressurized by venting, auto refrigeration effects can result in low temperatures. Minimum Design Metal Temperature (MDMT) corresponding to the temperature resulting from depressurizing the contents to its ultimate blow-down pressure shall be considered.(Shall be thoroughly reviewed if it requires a change in the material of construction of the vessel).
5.4 Corrosion Allowance
5.4.1 For Carbon Steel and Low alloy equipment, the following corrosion allowances to be used.
Process fluids 3.0 mm
Steam 3.0 mm
Water (PTW, DMW, BFW) 3.0 mm
DKW, FFW, CCW, WW, Steam condensate)
Air (Plant, Instrument) 1.0 mm
Sea Water 4.5 mm
5.4.2 Corrosion allowance given under 1 above is applicable for equipment only and not for piping.
5.4.3 The corrosion allowance for stainless steel equipment is 0 mm.
5.4.4 When the surface in contact with the fluid is lined with anti-corrosion material, the corrosion allowance is also 0 mm.
5.4.5 Corrosion allowance is not provided for the tube in the heat exchanger. However, in specific corrosion case, suitable material or higher corrosion allowance may be used as specified in the data sheet.
5.5 Systems Hydraulics
A sketch will be drawn for all the systems indicating the equipment and all the major piping for systems under consideration. Sketches will show the nodes, which will be referenced for pressure drop calculations.
The sketches will show source and destination pressures, pressure drops for control valves, equipment and the calculated pressure drops for pipes. The presentation of the calculated values will be in a tabular form listing the type of fluid, the values for flows, velocity, pressure drop. Also listed will be the applicable values of velocity from section 5.6.3, 5.6.4, 5.6.5, 5.6.6 & 5.6.7 of this manual.
5.5.1 Net Positive Suction Head (NPSH)
1. Static head will be measured from the bottom of horizontal drums, from the tangent line of vertical vessels with bottom draw-offs, from the bottom elevation of the outlet nozzle for side draw-offs to the centerline of a horizontal or rotary pump.
For vertical centrifugal pumps, the NPSH is to be calculated to the top of the plinth. Plinth height to be confirmed by the Civil group. For horizontal centrifugal pumps, the elevation of pump centerline above grade will be taken as one (1) m for large pumps (30kW) or 0.7 m for small pumps (<30 k W), unless the actual elevation is known.
2. Final Net Positive Suction Head available (NPSHA) will be confirmed after equipment and piping layout study is complete.
3. For sub-cooled liquids, the source pressure will be the minimum operating pressure and the vapor pressure will be at the maximum process temperature.
4. Suction line losses will be based on the rated capacity of the pump. The pressure drop through any permanent filter will be calculated on the basis of 50% filter clogging.
5. If pumped liquid has entrained gas, then NPSHA is half of the calculated value.
6. The design flow quantity will be the maximum quantity as shown on process flow diagram. The
safety margins noted in the following table will be (NPSHA-NPSHR=Safety Margin) for
centrifugal and rotary pumps. Seawater intake basin pumps will be validated by a third party.
No safety margin will be used for reciprocating pumps other than the friction and acceleration
losses.
Table 1 – NPSH Safety Margin
5.5.2 Rated and Maximum Pump Suction Pressure:
The rated pump suction pressure is the pressure existing at the pump suction with the pump operating at rated capacity. The maximum pump suction pressure will be determined from the most onerous of the following:
a. Relief valve setting plus static head (at normal liquid level) from suction source.
b. For a suction system unprotected by a relief valve, the shutoff pressure of the upstream booster pump will be used.
c. For gravity feed systems, the maximum static head.
d. For sub cooled liquids, vapor pressure at the maximum ambient temperature + static head.
5.5.3 Rated Head:
The rated head is the head required at pump rated capacity and rated suction pressure to overcome process pressure, static pressure, line and equipment pressure drop and control valve pressure drop. Pumps should be checked for suction and discharge relieving conditions.
See ASME Section 1 boiler code for additional head requirements for boiler feed water pumps. For pumps, cold start-up with high densities will be checked to ensure that there is enough head and driver power available to get started.
Pumping system will be rechecked when a certified performance curve for the pump and the approved piping layout is available. The system control valve will compensate for revisions to system pressure.
5.6 General Hydraulic Design Criteria
5.7 Control Valves:
5.8 Isolation Blinds
5.8.1 Generally, permanent isolation blinds will be installed at battery limits and where specified for equipment in fouling service or where frequent maintenance is anticipated. All equipment which can be entered for maintenance or inspection shall have the ability to be positively isolated by temporary or permanent blinds.
Generally, where a permanent blind is required, spectacle blinds will be installed for lines up to 8” and a paddle blind and spacer will be supplied for 10” And above. This is generalized guidance and piping specifications shall be used to determine final provision.
5.8.2 All isolation blinds shall be suitable for the equipment pressure rating.
5.9 Equipment Sparing Guidelines
Major equipment will be spared as indicated below. In addition, maintenance spare parts will be
identified and purchased along with each piece of major process equipment.
Table 8 – Major Equipment Spares
5.10 Process Equipment
5.10.1 Pressure Vessels and Drums
5. Sparing philosophy for Specialist equipment eg. Extruders, pelleters, bagging machines will be developed on a case by case basis.
6. Reciprocating compressor sparing shall be addressed on a case by case basis.
5.10.2 Storage Tanks
5.10.3 Columns:
a. Trayed Columns
General:
1. Tray columns shall be designed to satisfy the desired separation and throughput requirement. Detailed design shall include determination of the following:
Column Diameter.
Tray type.
Tray spacing.
Tray layout and down comer size.
Tray hydraulics/pressure drop.
Required number of actual trays.
Tray Efficiency.
Column-condenser duty and specification.
Column-reboiler duty and specification.
2. Trayed columns are to be designed for a maximum of 85 percent of flood.
3. When specifying the maximum allowable pressure drop across column, the related effect on overall operating plant shall be consider.
Downcomers:
1. Overflow Weirs: For columns smaller than 1.8 m diameter, chord overflow weirs on downcomer inlets shall be used.
2. Down comer Contraction Pressure loss: The clearance between the downcomer and the tray below shall be based on a maximum pressure drop of 25 mm of liquid.
3. The recommended minimum clearance is 38 mm. Increases in clearance shall be in 6mm increments up to a maximum of the overflow weir height.
4. If the clearance is greater than the static liquid seal height on the tray at the minimum liquid rate, an inlet weir shall be provided to ensure that the downcomer is always sealed with the tray liquid, to avoid vapor blow-back through the down comer.
Drawoff:
1. Withdrawals shall be from the inlet of the fractionating tray, from a blank tray or from a pan extending across the column. A complete pan shall be used when appreciable liquid hold up is required, for example for product surge or water setting.
2. The following general principles shall be used when designing drawoffs:
a) Partial drawoffs at tray inlet:
– A recessed box shall be used under the downcomer with the drawoff nozzle on the bottom or side of the box.
– The downcomer liquid velocity shall not exceed 0.06 m/s based on the horizontal cross section.
– The depth of the box shall be 1.5 times the drawoff nozzle diameter with a minimum of 150 mm. If the length to depth ratio of the box exceeds 1.5, a flat anti-vortex baffle shall be provided at tray level.
– The drawoff box shall not restrict the downcomer entrance on the tray below.
b) Total drawoffs at Tray Inlets: For total drawoff, a high overflow weir shall be provided which will prevent the liquid from flowing onto the next tray. The tray spacing shall be sufficient to allow, at maximum tray pressure drop, overflow of the weir plate without filling the downcomer. A drawoff nozzle behind the downcomer shall be high enough to ensure that the downcomer shall be sealed at the maximum anticipated tray pressure drop.
c) Blank Trays for Drawoffs:
– Vapour riser shall be provided in a blank tray. The risers are sized for pressure drop of 13 to 50 mm of liquid. The riser shall be 150 mm higher than the high liquid level. Flat baffles of the risers shall be placed above and below the risers to improve the vapor distribution over the blank tray. The annular area between the baffles and the riser shall not be less than the riser cross section.
– For partial drawoff, the overflow weir shall be notched to a depth of 200 to 250 mm to minimize changes of overflow rate with fluctuation in liquid level.
– Normal tray spacing is usually provided below a blank tray and above the high liquid level on the blank tray.
3. Drawoff Nozzle sizing:
a. Partial Drawoffs
(i) The nozzle size for a partial drawoff shall be based on a liquid velocity through the nozzle of 0.9 m/s. For this velocity the required nozzle diameter shall be determined from the following equation:
D = 37.3 Q raise power 0.5
Where
D = nozzle diameter, mm
Q = liquid rate through nozzle, L/s
ii) If the calculated nozzle size is less than the line size, the latter is used.
b. Total Drawoffs
(i) The theoretical nozzle size shall be calculated from the equation:
D = 54.8 Q raise power 0.4
(ii) The actual nozzle size shall have an area at least 20 percent greater than the calculated theoretical size.
4. Vapor drawoffs, bottom drawoffs, and blank tray drawoffs shall have the same size as the connecting lines in cases where a liquid head of 0.3 m or greater is available. When the available liquid head is less than 0.3 m, the formula shown in 3.b.i) above shall be used.
5. Coke Strainers: In vacuum pipe stills and cracked products fractionators, coke strainers shall be used to keep large pieces of coke out of pump suction lines.
Inlets:
Feed inlet shall be designed based on the following:
1. Top Tray Liquid Inlet: The top tray liquid inlet shall be installed behind a false downcomer. A baffle shall be placed above the inlet over the downcomer to prevent the liquid from spraying over the top of the false downcomer.
2. Interplate Liquid Inlets: For the interplate liquid inlet, a pipe shall be used parallel and close to the downcomer and placed as close as possible to the end tray above. The pipe shall discharge against the downcomer at an angle of 45°. Holes or slots shall be designed in the inlet pipe to give a 1.7 kPa pressure drop, using the standard sharp – edge orifice formula with a discharge coefficient of 0.6.
3. Vapor Inlets: A vapor inlet shall be located below a tray and centered on the column. A flush nozzle shall be used discharging across the tray transverse to the liquid flow.
4. Vapor-Liquid Inlet : A tangential nozzle with a helical baffle shall be used when low pressure drop is desirable. When pressure drop is not critical, an interplate liquid inlet should be used.
5 Inlet Sizes: Inlet nozzles are normally the same size as the connecting lines.
B. Packed Columns:
The packed columns shall be restricted to clean fluids since packed construction is susceptible to clogging. Packed columns shall be used mainly in the following services:
(i) Where separation of corrosive material is required
(ii) Where low pressure drop per theoretical tray is required, for example in vacuum fractionating distillation.
(iii) Where columns with high efficiencies and small diameters (0.6 m and smaller) are required.
(iv) Where low hold-up is required, for example in batch distillation of thermally degradable liquids.
(v) Where severe thermal shocks often occur.
Packed towers are to be designed for a maximum of 75 percent of flood.
Packing Material:
The desired properties of a packing material shall be:
(i) Low weight per unit volume
(ii) Large surface area per unit volume
(iii) Large free cross-section and volume
(iv) Low liquid hold-up
(v) Mechanical strength
(vi) Chemical inertness
Packings shall be normally made from stainless steels, plastics, or ceramics. Packings may be grouped into two general types: Random packing and structured packing.
Design Consideration for Random packing:
1. Support Screens or Plates: Heavy screens or perforated plates shall be used to support the various packed sections within a column. The screens or plates shall have adequate mechanical strength for the packed section. Furthermore, pressure drop across the screen or plates shall be commensurate with those across the packed sections.
2. Bed Limiters and Hold-Downs:
a) Packed section design shall prevent the packing from migrating within the column or out through the connecting piping. Bed limiters shall be used with metal or plastic packings to prevent expansion of the bed at high flow rates. They shall be designed with openings small enough to prevent the passage of individual pieces of packing. Bed limiters shall always be attached to the column wall by means of a support ring or bolting clips.
b) Bed hold-downs are used with ceramic packing to prevent the upper portion of the bed from fluidizing and breaking up at high flow rates. The hold-down rests directly on the packed bed and relies solely on its weight to restrict bed movement. In the event of a surge, or upset condition, the bed hold-down does not have sufficient weight to prevent damage.
Design Considerations for Structured Packing:
a) Structured packing shall be composed of rigid modules stacked upon each other.
Internals:
Reflux inlet:
a. The reflux inlet is normally at the column top center and the flow passes through an expansion elbow to reduce the liquid velocity below 1.5 m/s. A circular perforated plate with a 90°, V-notched overflow weir is normally provided about 0.6 m above the packing and below the reflux inlet pipe at the column center. The diameter of this plate is normally 0.7 times the column diameter. The weir notches shall extend 25 mm above the expected liquid level on the plate.
b. Liquid distribution holes 13 mm in diameter are normally placed evenly over the plate to give a pressure drop of 25 to 50 mm liquid.
c. The standard orifice formula with a 0.6 discharge coefficient is normally used to determine the number of holes. A 100 mm thick wire mesh deenergizer pad is normally installed on the plate under the liquid inlet. The pad diameter shall be twice the inlet pipe diameter.
d. Riser/orifice type inlet distributors are preferred for use in small diameter columns (upto 0.9 m).
Side Stream Drawoff
Feed Inlet
a. A side stream drawoff normally consists of a circular plate with sufficient vapor risers and a drawoff pipe.
b. The downcomers normally discharge onto a distributor plate similar to that discussed for reflux inlet, but including a depressed section forming a liquid seal which prevents vapor from entering the downcomers.
c. The vapor risers shall extend 150 mm above the liquid level. Circular baffles of the same diameter as the risers are normally installed horizontally above the riser openings at a distance that makes the area around the baffle at least equal to the riser cross-sectional area. The baffles improve vapor
distribution into the packing. At least 0.3 m shall be provided above the baffles to the packing.
a. If the feed is all liquid and below its initial flash point, it shall be introduced in the same manner as the reflux. If the feed is all gas, a perforated tee or ring distributor is recommended. If the feed is a mixture of vapor and liquid a perforated ring discharging onto the shell of the column shall be installed.
b. As the liquid runs down the shell, vapors are easily disengaged. The liquid is diverted from the shell to a perforated plate. For vapor flow around the plate and in the curtain between the plate and the deflector cone, a space of 49 percent of the column area shall be available. The shell height available.
c. Liquid Surge:
for disengaging above the deflector shall be at least 0.3 m. The design pressure drop through the holes in the feed distributor shall be about 1.7 kPa.
Liquid surge volume shall be provided at total drawoff trays and in column bottoms to satisfy plant control and emergency requirements as per Table 11:
Table 11
c. Other requirements:
1. The steam out connection will be below the normal liquid level to allow for wet steaming.
2. Towers shall be provided with a steam out connection with a block valve and blind. The steam-out connection shall be below the normal liquid level to allow for wet streaming.
3. The distillation section shall be at least 5 percent over designed (1.05 of the design production capacity), when over design factor is not specified.
5.10.4 Shell and Tube Exchangers
5.10.5 Air cooled Heat Exchangers
5.10.6 Plate and Frame Exchangers
a. Sizing Criteria
Cooling water system shall be designed such that cooling water pressure in the Plate Heat
5.10.7 Pumps:
Exchanger is significantly higher than the Sea Water (SW) pressure whereby, any leakage does take place inside the heat exchanger, Cooling water will ingress into the SW network and not vice versa due to differential pressure.
5.10.8 Compressors
a. Layout and piping arrangement
1. The head specification will be verified when a certified performance curve for the compressor or fan and the approved piping/equipment layout of system is available.
2. For packaged or skid mounted units, the performance specification will be based on package or skid inlet and outlet flange conditions.
3. Permanent strainers shall be provided on centrifugal compressor suction lines 24” and smaller. Temporary strainers to be provided for lines larger than 24” and design shall be agreed upon with SABIC. Strainers will be designed in order to withstand both forward and reverse flow under surging conditions.
4. Permanent strainers will be installed at the inlet hood of centrifugal air compressors.
5. Check valves shall be provided for individual discharge line of compressors when discharging into a system from which gas may flow backward through the compressor and where any back flow may cause hazard or damage to equipment.
6. When computing pressure drop in compressor suction lines, the conversion of static pressure to kinetic energy shall be considered. Because of the size of compressor suction lines, they are frequently swaged down well upstream of the compressor to match compressor case nozzle size. Include the swage and reduced line size in the piping size calculations. The compressor guarantees shall be based upon the static pressure specified at the compressor flanges.
7. Provide two ejectors for hot well tank in compressor turbine condensate vacuum system. One ejector for normal use and the other one as stand-by.
8. Reciprocating compressors shall be provided with an installed spare. For high capacity compressor, spare compressor shall be decided on case to case basis.
9. The potential for compressor surge and the need for an anti-surge control system shall be clearly established.
10. Refer to API-617 & 618 for Centrifugal & reciprocating compressor general control system guidelines.
11. For reciprocating compressors above 75 KW, a combination of re-circulating bypass control and step control may be used, as recommended by the manufacturer.
12. The volume between the compressor discharge flange and the check valve on the discharge side of the compressor should be kept at a maximum.
13. Reciprocating compressor discharge temperature shall be limited to a maximum of 150 ºC for most gases and up to a max. 135 ºC for hydrogen rich gases (MW 12 or less) as recommended by API-618.
14. Check valve with damper required on large volume machines.
b. Drains
All compressor piping will have adequate drains and vents piped to a safe disposal area.
c. Valving and Isolation
Block valves will be provided at the following locations in pump, turbine and compressor piping:
5.10.9 Steam Turbines
a. In suction and discharge piping of pumps.
b. At the equipment for auxiliary piping of gland oil, flushing oil and cooling water.
c. In all auxiliary piping, when necessary, to allow removal of the equipment during operation of the unit.
a. Layout and Piping arrangement
1. Ensure all low points of the piping system and at the turbine are adequately drained.
2. Steam turbine drain lines are to be of the same specification as the steam inlet lines.
3. Refer to SABIC Specification for general Purpose Steam Turbines G06-S01 and G06-S02.
4. Check valve with damper required on large volume machines.
b. Valving and Isolation
1. A bleed vent and drain are required between a block valve and a turbine stop valve.
2. Block valves shall be provided at the following locations in turbine piping:
a. In suction and discharge piping of turbines.
b. At the equipment for auxiliary piping of gland oil, flushing oil, and cooling water.
c. In all auxiliary piping, when necessary, to allow removal of the equipment during operation of the unit.
5.10.10 Filters
a. Scope
The pressure drop across the entire filter will be specified. Both dirty and clean pressures
shall be specified. All filters will be provided with differential pressure indication.
5.11 Process Systems
5.11.1 Sea water System
a. System Requirement
1. Provide Fiberglass Reinforced Plastic (FRP) or equivalent spools on Seawater outlet lines for all cooling water (CCW) coolers.
2. Provide self-cleaning system for Seawater intake pit strainers.
3. Fiberglass Reinforced Plastic (FRP) shall be used as the piping material for Seawater service.
b. Isolation and Sectioning
Butterfly valves are not preferred for Seawater isolation of the plate heat exchanger, due to frequent maintenance problems.
5.11.2 Portable and drinking water
1. All drinking / potable water piping and eye wash piping shall be insulated to prevent heating during summer.
2. Potable water quality and temperature shall be considered for safety Shower eye wash facilities including the selected locations.
5.11.3 Pressure Relief and Venting System
a. Functional Requirement
1. The Pressure relief and venting system shall provide safe discharge and disposal of gases and liquids resulting from:
a. Relief of excess pressure caused by process upset conditions.
b. System depressurization either in response to an emergency, e.g. fire, or as part of a normal procedure, e.g. shutdown prior to maintenance.
b. Design
1. System Design:
The discharge from pressure relief valves shall generally be routed to an environmentally safe location as indicated below:
Table 14 – PSVs Discharge Location
2. Liquid Discharge to Lower Pressure Process System or Vessel
A lower pressure system or vessel shall be capable of handling the required liquid relief discharge rate. Flashing at the lower pressure shall be taken into consideration.
3. Liquid Discharge to an Oily-Water Sewer:
Liquid discharge to an oily-water sewer shall be non-volatile and non-toxic and shall be via a blow down drum. The maximum liquid relief rate shall be within the oil removal capability of the oily-water treating system.
4. Discharge of vapours into a closed system terminating in a vent stack, which releases the vapours to the atmosphere, is acceptable when allowed by regulations. A closed vent stack system shall not be used to discharge high-volume continuous vapour sources.
5. Discharge velocity shall not exceed 80 percent of sonic velocity for hydrocarbon vents.
6. Relief Discharges Containing Oxygen:
Pressure relief discharges to a flare shall not exceed 6 percent oxygen by volume.
7. High Pressure Ethylene Systems:
Special consideration shall be given to relief of systems and equipment handling ethylene
at high pressure (>4500 psig [>300 barg]).
At pressures around 300 barg and temperatures less than 60 0C, ethylene will behave like a liquid as it expands through relief valve. Conversely, at similar pressures and temperature greater than 60 0C, ethylene will act as gas. This is because ethylene passes through the critical point when it expands from ~60 0C and 300 barg. PSVs designed for vapour service will not pop even with system pressures as much as 130 percent of the valve set point.
8. Equipment without pressure relieving devices shall be provided with an outlet that cannot
be completely blocked off. The minimum outlet opening shall be sized so that the maximum pressure, which can be developed in the equipment, is not greater than the design pressure.
9. High Integrity Pressure Protection (HIPPS) Special requirement:
A PSV designed for fire case shall be provided to protect each vessel in addition to a
HIPPS system only if the fire case is valid. The response time of HIPPS system shall be
such that the maximum pressure in any component shall not exceed its design pressure
by more than 10%.
10. Equipment and pipe sizing:
a. There are two fundamental elements in the sizing of equipment and piping. These are:
i. Establish rates and conditions for individual relief sources.
ii. Establish the overall flaring scenarios.
The first of the above elements is required to determine the design requirements for
individual relief valves, its inlet and outlet lines and sub-headers according to built-up
backpressure limitations.
b. The overall flaring scenarios must be identified to determine the design requirements for
the main system components, i.e.:
1. Flare headers.
2. Knock-out drums.
3. Flare stack and flare tips.
The overall flaring scenarios shall be identified by preparing flare load summary, tabulating separately the emergencies creating the flare loads along with their corresponding flow rates, temperatures and molecular weights as well as relief valve set pressure for each process areas. Flaring quantity under each emergency shall be calculated for the whole plant and the maximum of them shall be considered for flare system design.
Establish rates and conditions for individual relief sources:
Fire calculations are based on probable fire areas not to exceed 7.6 meter radius.
11. Relief Valve design shall comply with :
a. API RP 520 Parts I & II
b. API RP 521 (Sections 1, 2 and 3)
c. API 2000
a. Operating pressures over 95% of the relief valve set pressure are not acceptable. Vessels that operate between 90 and 95 percent of the set pressure require pilot operated pressure relief valves.
b. Spare safety valves are required for certain services. This includes equipment that cannot be removed from service without shutting down the entire process and services where plugging, fouling and corrosion are likely to occur or where valve testing or maintenance is required between turnarounds. Spare safety valve requirements need to be evaluated on a case- by-case basis.
c. Special Protection for Devices in Dirty or Fouling Service:
Pressure relief in dirty, waxing, polymerizing or other service where fouling is likely, shall be provided with a continuous flushing system on the underside of the seat or disk.
d. Rupture Disks and Rupture Pins:
Rupture disks and rupture pins shall not be used without prior approval. They shall comply with the requirements of API RP 520 PT I, ASME SEC VIII D1 AB and ASME SEC VIII D1 BB, Paragraph UG-127.
Only non-fragmenting rupture disks shall be used in series upstream of a pressure relief valve.
e. In cases where pressure relief valves are installed to protect more than one equipment designed to different ASME codes, number and sizing of the pressure relief valves shall be in compliance with the requirements of the most stringent ASME Code or project specification.
f. Furnace waste heat recovery steam drum pressure relief valves shall be designed and sized in accordance with Section-1 of the ASME Code. Waste heat recovery system pressure relief valves other than those on the steam drums may be in accordance with Section-VIII, Division 1 of the ASME Code.
g. At pressures above 6900 kpag, use of a 5% margin between design and operation pressure requires a pilot operated relief valve.
h. Design criteria for the flare equipment/system shall comply with API RP 520 and API RP 521.
12. Flare stack and flare tip design:
d. Flare stack requirements:
The elevated flare stack diameter shall be equal to or greater than the flare header diameter unless an exception is approved by SABIC.
The elevated flare stacks shall be of the jacking demountable type. All flares shall be provided with continuously operating or pulsating pilots to prevent flame out and to ensure that all releases to the flare are burned.
e. Flare shall be of smokeless for 20% of design flow for elevated flares. For ground flare, smokeless design shall be for 100% flare capacity.
13. Knock-out drum and pump design:
a. The Pump out pump will be rated for 50% of the maximum instantaneous liquid flow into the knockout drum.
b. Knockout drum liquid will be assumed to be at its bubble point.
c. Onsite liquid knock out drums shall be provided with a pump and a spare, each sized (in additional to the above requirements) to empty a half full drum within 2 hours.
14. Piping network calculation:
i. These design activities are normally performed using commercially available software packages and computer models. Manual methods and common design criteria may be found in API RP 521.
a. CONTRACTOR shall follow API specifications and supplement with industry practice. Relief system shall be designed in accordance with the most recent revision available of the following specifications / codes:
b. ASME Pressure Vessels Code, Section VIII, Division 1
c. ASME B31.3
d. ASME B31.4
e. API 620
f. API RP 2003
g. SES S03-E01 and addendum.
h. Applicable local codes and standards.
Relief valves shall have the capability for in situ testing (without lifting).
ii. The cumulative total of all non recoverable inlet losses shall not exceed 3% of the valve set pressure.
c. Pilots and Flare ignition
Normally lit flare tips shall be equipped with pilot burners with alternative source provided as back up.
d. Purge Gas
1. Each system shall be continuously purged with nitrogen or fuel gas supplied upstream in headers and sub-headers.
2. Flashback Protection:
Purge requirements for proprietary flare tips shall be established with the supplier.
Plugged vents for purging of the pressure relief system prior to start-up shall be installed on each tailpipe and unit headers. After start-up, a small stream of continuous purge gas need only be injected into the main flare header at the point farthest from the flare. A flow meter with a low flow alarm shall be installed at the purge gas injection point.
A larger amount of purge gas is usually required after a hot release to prevent air from entering the system when the system gas inventory cools and contracts. This additional gas injection shall be on automatic temperature and pressure control.
e. Control and Monitoring
Required instrumentation shall be provided including the following:
1. Steam flow control shall be provided for flare system.
2. Camera shall be provided for monitoring the flame of Flare Stack from inside the Central Control Room (CCR).
3. Control and monitoring from CCR
Table 15 – Control and monitoring from CCR
f. Safeguarding and shutdown
1. In the event that the liquid level in the flare knockout drum rises to the high level, a controlled automatic production shutdown should be initiated.
2. A high level alarm shall be provided on a vessel protected by a PSV relieving to atmosphere, if there is a possibility that liquid will flood the vessel during an upset condition.
3. Discharges to the atmosphere shall be in the vapour state and shall be below their auto-ignition temperature. The discharges shall also meet all applicable air quality control requirements. Vent system knockout drums shall be sized to handle the maximum emergency relief load.
4. If a heater is installed in the flare knock-out drum, a low level trip should ensure that the element is completely immersed during operation. The heater should be protected by a high temperature cut-out.
g. Measurements
Systems shall be equipped with flow devices located downstream knock-out drums continuously measuring the rates of fluid being flared as input to DCS.
h. Insulation
Insulation is normally not required on Flare header system.
i. isolation and Sectioning
Leaks into flare systems shall be minimized by proper selection of valves (tight shut-off).
1. PSVs requiring inlet isolation valves:
a. All relief valves that discharge to the flare will have full port block valves on the inlet and on the outlet. These block valves will be locked open. ¾” vents will be installed between the safety relief valve and all block valves. For systems requiring a depressurizing line, a line bypass gate valve around the relief valve may be utilized.
b. Inlet isolation valves will be required whenever there is a spare relief valve.
c. Inlet isolation valves will be required on PSVs on equipment that would take a long time (>6 hrs) to isolate and clear for maintenance.
d. PSV isolation valves will be required where a spare is installed.
2. Pressure relief valve installations and relief valve installations with an upstream rupture disc which requires maintenance and/or testing between turnarounds shall be provided with block valves.
3. Block valves used on the inlet or outlet of a pressure relief valve shall have full round port areas equal or greater than the inlet and outlet size of the pressure relief valve. Block valves shall be used only as permitted in the applicable codes.
4. PSVs not requiring inlet isolation valves:
a. Relief valves on spared equipment where the PSV’s do not discharge to the flare.
b. PSVs on equipment that can be isolated without affecting the process where the PSVs do not discharge to the flare.
c. Thermal relief PSVs in water service, unless service is critical and cannot be shut down and depressurized such as BFW etc.
d. PSVs in place solely to relieve exchanger tube rupture cases.
e. PSVs which can meet the specific plant turnaround duration and where the equipment can be isolated and cleared for maintenance in short duration (< 6 hrs.)
When isolation valves are deemed necessary, the following must be adhered to avoid inadvertent closure or failure of PSV isolation valves.
a. Position downstream PSV isolation valves downstream of any line expansion.
b. Limit rho.v2 <100,000 kg/m/s2 for any isolation valves downstream of PSVs and blow down valves to avoid the self closing, where rho is density and v is velocity.
c. For PSV and Emergency Depressurization isolation valves, spindle orientation shall be vertical for ball valves and horizontal or below horizontal of gate valves.
j. Layout and Piping requirement
1. Atmospheric vent pipes shall be designed and supported to prevent pipe failure caused by kinetic forces that develop during a discharge.
2. Thermal relief:
Thermal relief valves shall discharge to a lower pressure whenever possible. When this is
not practical and the fluid is water or oily water they may be discharged to an oily water
sewer or to grade, otherwise, discharge shall be to a safe disposal system.
3. Pressure Relief Device Location:
Vessels may contain internals which can foul or plug the route of the relief valve. In these cases, the relief valve shall originate from a position on the vessel (or connecting line in vapor service) where the potential overpressure originates (e.g. feed heat source, fire). On Towers or vessels containing demister pads or packing, pressure relief devices shall be located so that dislodgement of the demister pad or packing would not obstruct the pressure relief device, or mechanical reinforcement is provided to prevent dislodgement.
4. Venting to Closed System:
The design of the flare and vent systems should take account of the following layout consideration:
a. Flare stack, vent headers and relief valve tail pipes should be routed without pockets and sloped to allow free drainage to the respective knock out drum and low point drain.
b. Relief valves and other pressure protection devices should be located at high points in the process systems to minimize liquid carry over.
c. Each unit will have a Flare Header Knock Out Drum at the battery limit to minimize elevation requirements of the flare header.
d. To prevent accumulation of the liquids in the system, relief system piping shall be free of pockets and shall slope downward toward the knockout drum for good drainage.
e. Special consideration are necessary when closed pressure relief systems are required to handle either extremely hot, cold or heavy vapours or reactive chemicals for example, pyrophoric or corrosive materials.
f. Vent gas line to flare stack shall be elevated higher than seal drum inlet connection to have slope to seal drum to avoid condensate accumulation.
g. All safety valve outlet piping shall be designed as per API 520 to avoid stress to safety valves. Outlet piping shall be extended away from walkway/ access area as per standard.
h. The relief valves shall be removable and provide a monorail or hoist for accessing highly elevated valves.
5. Atmospheric relief vents:
Drain Holes,
A 6mm (1/4 inch) drain valve shall be provided at the low point in an atmospheric vent to prevent the collection of condensate, rain or snow in the discharge pipe. The drain shall be protected from freezing and shall be piped for safe disposal so that the opening will not endanger personnel or, in the event of fire, impinge on a vessel surface.
6. Vent Snuffing:
Snuffing steam or inert gas connections shall be provided on all atmospheric vent stacks that handle flammable vapours. Steam or inert gas is required to extinguish fires that may start at the vent outlet. Snuffing steam connections are not required in gas plants located outside refineries or in the offsite pressure storage vessels, where steam for this purpose is usually not available.
7. Flame Arrestors:
The applicability of flame arrestors on atmospheric tank vents and other vents to atmosphere shall be evaluated for each individual situation taking into consideration such factors as the out flow of vapours, likely composition of materials within the tank or system, weather conditions, presence of possible depositing materials in the air, ability to maintain the arrestors, proximity to flames, etc. Flame arrestor elements can become plugged with atmospheric dust, process products and products of corrosion or ice during cold weather.
8. Sitting and Safe Location of Discharge Vents to Atmosphere.
Atmospheric relief vents shall terminate at a location which satisfies all of the following:
a. At least 2 m (6 ft) above the highest adjacent structure or tower.
b. At least 4 m (12 ft) above the highest platform.
c. At least 5 m (15 ft) above grade.
Located at least 15 m (50 ft) or 120 pipe diameters, whichever is greater, away from the nearest platform, structure or tower when located at an elevation lower than platform, structure or tower.
Located at least 30 m (100 ft) or 120 pipe diameters, whichever is greater, away from the tops of flue gas stacks or other ignition sources, regardless of the atmospheric vent elevation.
9. Safety valves shall be installed in locations with proper access for easy operation &maintenance. Proper & sufficiently rigid pipe supports shall be provided on safety valve outlet piping to withstand large reaction force during operation.
10. Pressure relieving devices shall be located and installed so that they are readily accessible for inspection and repair. (Easy access shall be provided for removal).
11. When two or more pressure relieving devices are placed on one connection, the inlet internal cross-sectional area of this connection shall be at least equal to the combined inlet areas of the safety devices connected to it.
k. Safety Requirement
The design of the flare and vent system shall take account of the following safety considerations:
a. The flare system should be designed to operate within all specified criteria for backpressure, velocity, noise and erosion.
b. Satisfactory operation of the flare ignition system shall be ensured at all times.
c. Flame impingement from flare tips on nearby structures shall be prevented.
d. The formation of ice or hydrates causing potential blockages should be safeguarded against throughout the system. Preventive measures include:
– The uses of flare knock out drum heaters.
– Winterization of liquid dead legs, e.g. knock out drum outlet piping.
– Insulation and heat tracing of dead legs upstream blow down valves and PSVs.
– Provision of a separate low temperature flare header to avoid mixing of low temperature gas with hot, wet gas.
e. Flare and vent headers should be continuously purged with nitrogen or fuel gas to prevent the ingress of air which may create an explosive mixture.
a. Environmental Requirement
1. A flare gas recovery system shall be considered for all new installations, if feasible.
2. The specification, location and orientation of flare and vent tips shall ensure that all requirements with respect to radiation levels, gas dispersion and potential liquid spill -over are met.
b. Pre-commissioning Requirement & Commissioning requirement:
1. Spectacle blinds shall be provided as required to perform leak testing of system, excluding flare stack piping from knock out drum outlets.
2. All relief valves shall be bench tested which shall be witnessed and certified by SABIC’s Quality Assurance group prior to final installation.
c. Precaution
1. Release of corrosive or toxic vapour may require chemical neutralization or conversion by combustion to less toxic material.
2. Vessels shall be protected from the development of vacuum conditions by adequately sized vent nozzles and vacuum breaker.
3. Car seal open valves, locked open valves, etc. cannot be used to avoid installation of safety valves.
4. Location of relief valve and vents especially for flammable/toxic releases should consider nearby ignition sources, critical instrument or other equipment and requirement/frequency of accessing the nearby area for routine jobs.
5. Identification of releases (normal and shutdown) that must be diverted into the flare stack header for ultimate disposal. List with reference to equipment should be provided.
6. Small equipment with low operating pressure should not be allowed to govern the design of the flare header.
7. The safety devices on all vessels shall be so installed that their proper functioning will not
be hindered by the nature of the vessel’s contents. Safety relief and pilot operated valves
shall be connected to the vessel in the vapour space above any contained liquid or to
piping connected to the vapour space in the vessel which is to be protected.
5.11.4 Steam Generation and Distribution:
a. Design
1. The steam drum shall have at least 1 (one) minute hold-up time from low water alarm to low-low water cut-off and at least 5 min of hold-up from the low-low water cut-off level to the highest down-comer at design maximum continuous rating (MCR) condition. Low-low water cut-off level shall be located at least 50 mm above the highest down-comer.
2. Steam lines and headers to turbine drives shall be protected with adequate water boots and steam traps.
3. All Steam vent lines stack shall be extended above or away from the Air fan coolers to ensure proper performance of Air Fan Coolers (AFCs).
4. All steam/ condensate drain lines shall be connected to trench in angular direction to avoid concrete trench damage and have a suitable protection cover to avoid splashing.
5. Pumping system for the steam condensate is preferred rather than pumping traps.
6. Blow down of boilers shall be controlled by remote operated valve (subject to SABIC’s approval).
7. Provide flue gas/ Air preheating system in all Boilers.
8. Boiler Feed water shall be used for the purpose of de-superheating.
9. Install block valves prior to shut-off valve of the inlet of each De Mineralized Water train.
10. Provide adequate nos. of sight glasses at various heights in order to check the resin levels. Provide appropriate lighting arrangement near the sight glass for viewing the level (for DM water unit).
11. Check valves shall be provided in process steam and steam-out piping, and purge or inert gas piping connected to process equipment or lines. For lines in steam service, a drain valve shall be provided near the process block valve to aid in warming the steam line and assuring that it is free and clear of condensate.
12. BFW pumps shall be provided with an installed spare pump.
b. Control and Instrumentation
Required instrumentation and control shall be provided including the following:
1. All boiler Steam drum local level gauges for VHP Steam must be magnetic type. Do not use Glass or mica in contact with boiler water.
2. On-line Dissolved Oxygen Analyzer shall be installed for Deaerator water outlet stream.
3. On-line oxygen analyzer shall be installed for all Boiler flue gas stacks.
4. Requirements described in the following SES shall be adhered to:
– SES-X01-S01
– SES-X01-S05
– SES-X01-S04
c. Layout And Piping requirement
All steam traps for condensate removal shall be provided with a strainer, block, drain & bypass valves. A flash drum and level control valve combination shall be used in place of steam trap for reboilers.
d. Valving and Isolation
1. Block valves will be provided in the steam piping adjacent to the equipment at the following locations:
a. In the steam inlet line to steam driven equipment.
b. In the steam extraction lines from steam driven equipment.
c. In the vacuum exhaust lines from steam driven equipment when the equipment may be shut down for sustained periods during operation of the unit.
d. In the exhaust lines of the backpressure turbines.
e. At the equipment for auxiliary piping of gland steam, flushing steam, cooling water, and all auxiliary piping, when necessary, to allow for removal of the equipment during operation of the unit.
2. Double block & Bleed valves shall be provided, where stream cross contamination must be prevented or positive isolation is required.
3. Double block & Bleed valves shall be provided, for permanently piped steam out and nitrogen purge connections. Also use blind and check valves as appropriate.
4. Bypass valves for header warm-up and equalization shall be provided on HP and VHP steam isolation valves 4-inches larger. The bypass valve should preferably be within the valve body itself. Alternately it shall be separate. The bypass arrangement shall consist of two valves in series to accommodate the high-pressure drop during line commissioning.
5. Check valves in low-pressure steam lines to re-boilers and exchangers to prevent header contamination in case of tube leakage.
6. Fuel supply block valves to boilers shall be installed per the appropriate codes. Additionally, an isolation valve at grade located 15-m from the equipment shall be provided for rapid isolation in an emergency. This valve may serve multiple equipment in case furnaces are grouped together and isolation as a group is acceptable to SABIC.
7. All boiler & incinerator stacks should have the sampling platforms & portholes as per US EPA.
8. The sampling platforms for the sampling portholes must be provided 360 degrees around the stack.
9. There should be 4 sampling portholes on each stack, 4 inch in diameter, each 90 degrees apart.
10. There should be adequate platforms & hooks/structures provided for carrying out particulate matter sampling as per US EPA.
11. The location of the sampling portholes should be as per US EPA.
5.11.5 Fired Heaters
a. Design
1. Burners shall be designed based on all operating cases and different fuel mixtures. Effect on NOx, SOx emissions & burner duty to be indicated by the Contractor for different fuel mixtures.
2. ID / FD fan shall be driven by steam turbine and motor driven shall be Stand-by.
3. Motor of ID / FD fan shall be able to start-up on Auto-mode in case Turbine fails without any interruption to plant load and operation.
4. Fuel gas system to be designed to operate at as low pressure as practical to achieve operating temperatures. Piping and control valves, including furnace fuel gas control valves to be designed for minimum pressure drop.
5. Installation of burners shall be such that there is no flame impingement on the tubes.
6. The thermal efficiency of a fired heater may be improved as economical by
a. Exchange of heat between flue gas and a process fluid
OR
b. Exchange of heat between flue gas and a utility stream
OR
c. Use flue gas to pre-heat combustion air.
The minimum allowable flue gas temperature shall be limited by the dew point of the acidic flue gasses that are corrosive in nature.
7. Air pre-heat systems shall be designed to obtain max. heat recovery, consistent with high availability and reasonable maintenance costs of heat recovery equipment.
8. Means for controlling the cold end temperatures shall be provided to limit flue gas corrosion.
9. Combustion air temperatures, along with fuels, burners and combustion conditions shall
be designed to achieve acceptable levels of NOx formation.
10. Purge steam facilities required for purging the firebox of any combustibles, should be approximately 3 volume changes in the firebox in a 5-minute period. The same philosophy to prevent blowing of condensate into the Firebox shall be adopted as mentioned for Snuffing steam. (When snuffing steam facilities are provided, the same may be utilized for purging).
e. Control and Instrumentation
Required instrumentation and control shall be provided including the following:
1. On-line oxygen analyzer shall be installed for all Boiler flue gas stacks.
2. Requirements described in the following SES shall be adhered to:
– SES-X01-S01
– SES-X01-S05
– SES-X01-S04
3. The burner control and manifold system shall be designed for ease of operation and proper control of the furnace and shall meet the following essential requirements.
a. Adequately sized headers to eliminate pressure drop problems.
b. Proper type of control valves.
c. Proper location of burner regulating valves for adjusting valve while observing the furnace.
d. Adequate drains, crossovers, purge points, etc to permit drainage and cleaning of the manifold system.
4. If shutdown initiating devices must be bypassed to start a unit, visual indication on the central panel board must be provided. Shutdown initiating conditions and set points shall be subject to SABIC’s approval.
f. Layout and Piping
1. The snuffing steam connection should ideally be individually valves and located at a safe distance of approx. 15 meters from the heater. A steam trap should be provided upstream of each valve and a 6mm weep hole (pointing away from the personnel) shall be provided at a low point between the valve and the heater for each individual lateral to prevent blowing condensate into the firebox. (Snuffing steam quantity adequate to sweep the entire firebox in one minute is required.
2. The location of the Fired heaters should preferably be upwind (based on the prevailing wind direction) of the process equipment to minimize the possibility of any vapor releases from the process equipment being ignited by the Fired heaters.
3. Tall structures such as Towers should be located as far away from the heater stacks as practical, to minimize the possibility of personnel being exposed to hot flue gasses while on elevated platforms or structures.
g. Valving and Isolation
Fuel supply block valves to furnaces and fired heaters shall be installed per the appropriate codes. Additionally, an isolation valve at grade located 15-m from the equipment shall be provided for rapid isolation in an emergency. This valve may serve multiple equipment in case furnaces are grouped together and isolation as a group is acceptable to SABIC.
5.11.6 Fuel Gas System
a. Design
1. The fuel gas header downstream of the fuel gas control valve should be adequately sized to permit equal distribution of gas to all burners. In order to maintain uniform distribution, the difference in pressure drop across two burners shall be no greater than 5%.
2. The amount of fuel oil re-circulated back to the tank should be approx 50-100% of the fuel consumption by the heater.
3. Burners shall be designed to have
a. The ability to handle fuels having a reasonable variation in heating value.
b. Provision for safe ignition and easy maintenance.
c. a reasonable turndown ratio between the min. and the max. firing rates.
d. Predictable flame pattern for all anticipated fuels and firing rates.
e. The ability to meet NOx emission requirements (Royal Commission Environmental Regulations).
f. Noise level as per SES S20-G01.
b. Control and Instrumentation
Required instrumentation and control shall be provided including the following:
1. Automatic control for maintaining the atomizing steam and fuel oil differential pressure shall be provided.
2. Pressure gauges shall be provided on the steam and oil lines for each burner.
3. Temperature and viscosity of the fuel oil shall be maintained by providing steam tracing and insulation.
c. Layout and Piping
1. The fuel gas piping should be arranged so that the piping is pitched to allow condensate in the piping to be drained and routed to a location safe distance away from the heater.
2. The individual take-offs from the gas header should be taken off the top of the header to minimize the possibility of routing of liquids to the gas burners.
3. The burner header shall preferably be located just above the peepholes with valve location such that it can be operated while observing the flame.
4. For fuel oil firing, the atomizing steam header shall be properly pitched, drained and tapped to avoid accumulations of condensate in the header.
5. Heavy fuel oil systems shall be re-circulating loop type systems.
6. A crossover from the steam line to the oil line should be provided for each burner as close to the steam and oil headers as possible, to permit purging of the oil line to the burner.
7. Pilot gas should be from a different source than the fuel gas. Every effort should be made to maximize the reliability of the pilot gas system.
5.11.7 Waste Water Collection, Treatment & Disposal
a. Design
1. The wastewater collection, treatment and disposal system shall be designed to prevent spread of hazardous materials into the environment, avoid hazards to personnel in working areas, avoid fire hazards, to avert contamination and pollution of the soil and ground-water.
2. Disposal systems for all waste streams shall meet all site standards and requirements, including the Royal Commission Environmental Regulations.
3. The following main wastewater systems shall be provided for each new process plant.
a. Oily wastewater system
b. Chemical sewer system
c. Storm-water sewer system
d. Sanitary waste water system
4. Wastewater discharge into the Royal Commission seawater canal shall only be permitted if it meets the criteria of the Royal Commission and is approved by the Royal Commission.
5. The oily water system shall be able to handle all material including hydrocarbons, process water, wastewater, firewater, and storm-water that is likely to be drained to the paved area in the Plant. Plant areas handling C4 (or lighter) hydrocarbons shall not normally be paved except where frequent maintenance is anticipated. For C5+ hydrocarbons or lube oil handling, the area shall be paved and curbed to prevent oil / oily wastewater runoff and consequent soil contamination.
6. The collection system shall consist of suitably designed funnels, floor drains, and catch basins. Paved plant areas shall be subdivided into smaller drainage areas with proper slopes, to handle surface runoff. Drains must handle all deluge water falling on the paved area without flooding. Drain lines from diked areas for storage tanks in C5 and heavier hydrocarbon service shall be provided with valves located outside the dike. The valve shall be normally kept closed.
7. The system shall be designed to accommodate the maximum flow rate, calculated from runoff from paved areas at the once in 5-year 15 minute rainstorm of 40mm/hr or 50% of the maximum firewater demand for the entire single fire risk area (SFRA). The SFRA is calculated at the rate of 10 Lpm/m2 or 100% discharge of contaminated steam condensate whichever is higher.
8. The oily water sewer system shall be designed as a flooded system with a slight slope to permit draining the entire system. All manholes shall be vented to the atmosphere at least three (3) meters above the manhole location and a minimum of 15 meters away from where personnel are likely to be present.
9. Minimum line size shall be 6-inch except in case of individual drain connections. Normal design practices, e.g. provision for cleaning, providing gas seals / vents at suitable locations, provision for future expansion, etc. shall be followed.
10. The oily water collection shall be through a Corrugated Plate Interceptor (CPI) separator. To accommodate oily wastewater collection in excess of the capacity of the CPI separator, a covered oily water surge pond is to be provided. Under normal conditions, oily wastewater collected in the Plant is directly routed to the CPI separator bypassing the surge pond so that the surge pond capacity is reserved.
11. The contents of the surge pond shall be pumped at a controlled rate to the CPI separator, when conditions allow and within the capacity limitations of the separator. When the collected water in the surge pond is not contaminated, the water may be discharged to the storm water system, subject to necessary approval being obtained.
12. The CPI separators shall be designed to remove all oil droplets larger than 60 microns in
diameter and a minimum of 80% of suspended solids. Two 100% CPI separator units are
to be provided assuming one unit can periodically be removed from service for cleaning.
13. An oil pit with a pump for pumping the oil skimming’s to a slope oil tank is to be provided.
Use of incineration capability shall be evaluated.
14. The effluent from the CPI separator is pumped to a retention pond. The retention pond is
to be sized to hold the effluent pending necessary treatment.
15. If the CPI separator effluent is not in compliance with the Royal Commission discharge
standards, as detected by the online analyzers, the wastewater is pumped back to the
Oily Water Surge Pond or to the inlet of the CPI separator for appropriate treatment.
16. If the effluent is in compliance with the discharge standards, it shall be pumped to the service retention pond to discharge into wastewater return header to the Royal Commission. The oily water surge pond and the retention pond shall be jointly sized to contain waste water generated over 96 hours of plant operation, or once in 10 years, 24 hour storm with 72mm of rain, whichever is greater. The oily water surge pond shall be four (4) times larger than the retention pond.
17. The accumulated sludge is periodically sent offsite for disposal. On generation, sample of the sludge shall be submitted to the Royal Commission Environmental Laboratory for waste classification. Sludge pumps shall be provided to pump the CPI sludge to a sludge tank where it shall be drummed and loaded onto trucks for disposal.
18. A local chemical sewer system is required where water-soluble chemicals are used. Plant areas that may be subjected to chemical waste spills shall be paved and curbed to prevent waste runoff and resultant soil contamination.
19. Drains from the handling equipment and piping including curbed area runoff are to be collected in local drain pits, and evacuated by a vacuum truck as needed. The drain pit shall have underground piping with isolation valve to oily sewer. The valve is to be normally closed and opened manually when the level is high due to rainwater. Depending on compatibility, location, etc., common local pots may be provided for various chemicals.
20. This system shall collect caustic rich drainage from all caustic equipment and piping, which shall include the Caustic Wash Tower, Caustic Removal Column, Spent Caustic Tank, etc. if installed. Drainage from around the equipment shall be collected through funnels into an underground piping network discharging into an underground caustic sump. Material from the underground caustic sump will be pumped to a spent caustic tank for subsequent treatment and disposal.
21. A storm water drainage system shall be provided to ensure rapid drain-off of rain and firewater from the process area, roads, roof drains and other uncontaminated areas. Drainage from uncontaminated areas will be separated from that from potentially contaminated areas. Uncontaminated storm water shall be discharged into the Royal Commission storm water drainage ditch. Contaminated storm water flow shall be routed to the oily sewer.
22. Flooded gravity flow system shall be used to collect and drain storm water from clean areas. A channel / ditch running around the plant areas and along roads shall be provided for this purpose. This channel / ditch shall be connected to the storm water ditch and also to the Royal Commission storm water drainage channel / ditch adjacent to the property limit.
23. Storm water channel / ditch design shall conform to SES C03-S01. Entire length shall be
covered with heavy-duty steel grating and appropriate road crossings shall be provided. Storm water channel shall be sized to handle the climatic conditions given in Basic Engineering Design Data. Guard posts painted with white and yellow bands shall be provided along roads at 5-meter intervals to prevent vehicles from being driven over the storm water grating.
24. In addition to the above requirement, the channel / ditch shall be sized to prevent overflows in case storm-water cannot be immediately discharged to the Royal Commission storm water sewer due to accidental contamination. Storm water that can be contaminated with flammable materials shall not be allowed to flow in open ditches or unsealed sewers. Sewer lines in these cases shall be laid straight between catch basins and manholes and between manholes.
25. Provision shall be made to allow water from normally contaminated curbed areas, pits, sumps, ponds, etc. to be discharged into the storm water channel. This shall be done after necessary checks / analysis and in case of excessive rainfall which cannot be handled by the various wastewater treatment facilities.
26. The sanitary wastewater does not require any pre-treatment and may be routed directly to the Royal Commission sanitary sewer network. The sanitary wastewater streams from control buildings, maintenance buildings and operator shelters shall be drained to lift stations. Lift stations shall be provided to transfer the wastewater to the existing sanitary waste system for transfer to the royal Commission Pump Station.
27. Fiberglass reinforced plastic (FRP) shall be used as the piping material for wastewater service.
28. All dike walls for wastewater service shall be suitably coated with chemically resistant material.
29. High venting arrangements shall be provided for wastewater pits to prevent fuming.
30. All new piping culverts shall have rainy water sump & drainage system to avoid water accumulation that leads to piping corrosion.
31. Soft-soil access tubes (made of PVC with cover) shall be installed near all underground pipelines to check soil resistivity and monitor the pipe corrosion condition.
d. Control and Instrumentation
Required instrumentation and control shall be provided including installation of online
analyzer for pH and TOC measurement for CPI Separator effluent.
5.11.8 Utility Station and Headers
1. Utility stations at grade will consist of LP steam, plant air, service water and LP nitrogen.
Each service drop will have its take off from the topside of the distribution headers and a
valve and check valve shall be put upstream of hose. A vent valve downstream of the
block valve will be provided to permit depressurizing the hose. All utility hoses will have
special fittings to provide positive segregation from all other utility station and services.
2. For Utility header laterals to users, provide block valves for all lines 1.5 inches and
smaller in branches from header.
3. Utility hose stations shall be strategically located throughout the process unit.
4. Utility stations shall consist of Service air, Service water, Nitrogen and Steam.
5. Each service drop will have its take-off from topside of the distribution headers and be
protected by a valve and check valve at the header connection. Refer to SES P01-E40
for details.
6. Utility stations to be provided at all levels of Platforms in all the units.
7. Nitrogen line shall be sized large enough to enable equipment purging in a short time.
8. Spare connections on Utility headers shall be provided for future expansion as agreed
with the SABIC.
9. Utility systems shall be provided with block valves at the battery limit and in all process
and service connections as required for the anticipated operation and maintenance of the
plant.
10. Utility header block valves will be shown on the utility distribution P&ID and not on the
process P&ID. Valves shown on process P&IDs are located at the process end.
11. Spare connections with block valve on utility headers will be evaluated and provided for
future expansion as agreed with SABIC.
12. Instrument Air valves (1” minimum) will be located on the instrument air header within
Process and Utility every 6 meters, as a minimum. Instrument Air branch lines will be
taken from top of the header. Block valves are required for branch connections and will
be located at the header. Instrument air supply to an individual user should be ¾”
minimum. Instrument Air System design shall comply with X01-E01.
13. Plant Air branch lines will be taken from top of the header. Block valves are required for
branch connections and will be located at both the header and at the equipment.
14. Cooling water header branches 4” and larger require header block valve for isolation.
Cooling water connections to equipment require inlet and outlet valves for isolation.
Above ground cooling water supply and return branch lines will be connected to the top
of the headers. Branch lines may come off of the bottom of the header subject to SABIC
approval.
15. Service water branch lines will be taken from the top of the header. Isolation valves are
required for each equipment item. Location should be determined on a case by case
basis.
16. Steam branch lines will be connected to the top of the header. Block valves shall be
provided in the branch lines from the steam headers at and above the elevation of the
steam header and installed in such a manner that no pocket is formed where condensate
may collect.
17. In order to prevent air and any hydrocarbons entering the inert gas system, piping
carrying nitrogen or other inert gases shall have a block valve where a branch leaves the
main header. A check valve will be incorporated near the item of equipment served. The
valve arrangement from the equipment end will be block-bleed-check-block or blindbleed-check-block.
18. Provide one 6” spare valve for future tie-ins on each header and main sub header of the
in-unit flare headers.
19. Utility systems will be provided with block valves at the battery limit and in all process
and service connections as required for the anticipated operation and maintenance of the
plant.
20. Utilities such as steam and nitrogen will not normally be directly connected to the
process. Where required, the connection will be with double valve and vent with a
permanently installed slip blind. Where this is not practical, another option is to use a
block valve and a ¾” vent with a common swing elbow for connecting to the equipment
when required.
21. Two block valves with a bleeder valve between them or a single double-seated valve with body bleeder will be provided in piping connecting systems where cross contamination cannot be tolerated, or in piping where isolation blinds are not provided for safety during maintenance.
22. Check valves in Header take-off for all services drops such as air, nitrogen, service water
and steam.
23. Check valves shall be provided in purge or inert gas piping connected to process
equipment or lines.
5.11.9 Double Block & Bleed Valves
Use double block and bleed valves for the following:
a. Where stream cross contamination must be prevented.
b. Permanently piped steam out and nitrogen purge connections. Also use blind and check valves as appropriate.
c. Drains to the flare from equipment containing liquid light hydrocarbons.
d. Double block and bleed valves do not constitute positive isolation. Where positive isolation is required, isolation blinds shall be used.
e. VHP (Very High Pressure) steam and VHP BFW services.
f. Other high pressure services (e.g. pump out).
5.11.10 Maintenance Isolation Valves
Emergency Shutdowns Valves (ESV’s) shall not be used for any purpose other than safety
shutdown and isolation. They shall not be used for maintenance isolation purposes. Where
isolation valves are required for maintenance or regular operation these shall be additional
to the ESV.
5.11.11 Battery Limits Block Valves and Metering
All battery limit connections between process units and utilities facilities including offsite
facilities will be in accordance with guidelines in the following table.
Table 16 – Battery Limit And Header Block Valves
Note:
1. Battery limit block valves to be of fire safe construction for HC and oxygen service only.
2. Utility services will require a meter at battery limits for accounting purposes. Process flow stream crossing the Battery limit shall also be provided with a meter for accounting purposes. The meter for both Utilities and Process flow streams shall be provided within the Process Unit ISBL. Required accuracy will be determined by SABIC. The metering system shall comply with SES-R05-E20 and SES-R05-E21 (Custody transfer meter).
3. The above diagrams indicate import only. For export systems, additional valving is
required in ISBL.
5.11.12 Tie-In Requirement:
Contractor shall perform the site visits, as necessary to fully define and verify the tie-in requirements on SABIC existing facility.