1. SCOPE ……………………………………………………….
2. REFERENCES ……………………………………………………….
3. DEFINITIONS ……………………………………………………….
4. FLOW INSTRUMENTS ……………………………………………………….
4.1 General ……………………………………………………….
4.2 Types of Flow Instruments …………………………..
4.3 Differential Pressure Flow Transmitters
4.4 Magnetic Flow Meters …………………………..
4.5 Vortex Flow Meters …………………………..
4.6 Positive Displacement Flow Meters …………………………..
4.7 Ultrasonic Flow Meters …………………………..
4.8 Coriolis Mass Flow Meter …………………………..
4.9 Thermal Mass Flow Meters …………………………..
4.10 Turbine Flow Meters …………………………..
4.11 Variable Area Meters (Rotameters) …………………………..
4.12 Elbow Taps Flowmeters …………………………..
4.13 Flow Switches ……………………………………………………….
4.14 Flow Gauges and Flow Indicators …………………………..
5. INSPECTION AND TESTING …………………………..
6. REVISION HISTORY ……………………………………………………….
1. Scope
This standard establishes the minimum requirements for the design, materials, sizing and
selection of flow instruments.
2. References
Reference is made in this standard to the following documents. The latest issues, amendments
and supplements to these documents shall apply unless otherwise indicated.
SABIC Engineering Standards (SES)
R01-E01 Field Instrumentation Specification
R05-S01 Flow Elements
R11-C01 General Instrument Installation Criteria
American Gas Association (AGA)
7
Measurement of Gas by Turbine Meters
8
Compressibility Factors of Natural Gas and other related Hydrocarbon Gases
American Petroleum Institute (API)
MPMS 5.3
Measurement of Liquid Hydrocarbons by Turbine Meters
American Society of Mechanical Engineers (ASME)
B 31.3
Process Piping Code
Process Industry Practices (PIP)
PCEFL001
Flow Measurement Guidelines
Other References
ASME
Fluid Meters, Their Theory and Application
ASME
International Steam Tables for Industrial Use
3. Definitions
Coriolis Mass Flow Meter: Measures mass flow rate by determining the torque from radial
acceleration of the fluid.
Custody Transfer Flow Meter: A flow metering device used for accounting purposes.
Elbow Flow Meter: A pipe elbow with a pressure tap at both the inner and outer radius. Flow is
calculated by measurement of the pressure differential caused by differences in flow velocity
between the two flow paths.
Flow Transmitter: A device that senses the flow of liquids in a pipe and converts the sensor
output into electric signals, which can be transmitted to a remote indicator or controller.
Magnetic Flow Meter: Used for measuring average velocity of a conductive liquid using the
principle of electromagnetic induction.
Mass Flow Meter: Measures the rate of flow in a pipe, duct or channel in terms of mass per unit
time.
Orifice Plate: A disc or plate like member, with a sharp-edged hole in it, used in a pipe to
measure flow or reduce static pressure.
Positive Displacement Flow Meter: Flow meter design in which volumetric flow through the
meter is broken up into discrete quantities. Flow rate is determined from the number of these
quantities that pass through the meter per unit time.
Rangeability: The ratio of the maximum and minimum flow rates of a meter.
Reynolds Number: A dimensionless criterion of the nature of flow in pipes. It is proportional to
the ratio of dynamic forces to viscous forces: the product of diameter, velocity and density,
divided by absolute viscosity.
Rotameter: See variable area flow meter.
Thermal Mass Flow Meter: Determines flow rate from rate of dissipation of heat injected into a
flowing fluid stream. It measures either the change in temperature of some point downstream of
the heater, or the amount of thermal or electrical energy required to maintain the heater at a
constant temperature.
Turbine Flow Meter: Uses the rotation of a turbine type element to determine volumetric flow
rate.
Ultrasonic Flow Meter: Measuring flow rates across fluid streams by either Doppler effect
measurements or time of flight determination. In both types, displacement of the portion of the
flowing stream carrying the sound waves is determined and flow rate is calculated from the
effect on sound wave characteristics.
Variable Area Flow Meter: A variable-area, constant-head, indicating-type, rate-of-flow-volume
meter in which fluid flows upward through a tapered tube, lifting a shaped plummet to a position
where upward fluid force just balances the weight of the plummet.
Viscosity: Measure of the internal friction of a fluid or its resistance to flow.
Vortex Flow Meter: Measures flow by sensing the movement of vortices in a pipe or conduit.
4. Flow Instruments
4.1 General
4.1.1 Flow meter selection shall be based on the type of fluid being measured, accuracy,
rangeability, and reliability requirements. Refer to PIP PCEFL001 for the guidelines on
selecting flow measurements types for an application.
4.1.2 Differential pressure type flow instruments shall be provided unless process conditions
make such types undesirable. Use of other type of flow instruments shall require SABIC
approval.
4.1.3 Refer to SES-R01-E01 for general design guidelines and specification.
4.1.4 Pressure retaining parts of all in-line meters shall be fabricated with full penetration welds
and shall be in accordance with the ASME B31.3.
4.1.5 Flow meters should be sized such that the normal flow is 65 percent to 80 percent of
expected maximum.
4.1.6 Flow meter sizing calculations shall use temperature and pressure base condition of 15 deg
C and 1.013 Bara.
4.1.7 For in-line flow meters, the manufacturer’s sizing and calculation methods shall be used. All
flow calculation data shall be supplied to SABIC.
4.1.8 In-line flow meters shall have flanged ends suitable for piping service where they will be
installed. Other types of end connections shall be with SABIC approval.
4.1.9 In-line flow meters shall undergo hydrostatic test to 1.5 times the maximum operating
pressure.
4.1.10 The overall accuracy for flow meters in accounting and material balance applications shall
be better than +/-1 percent of rate.
4.1.11 If project requires, calibrated flow meters should be used, for high accuracy applications.
4.1.12 Installation of flow instruments shall conform to SES-R11-C01.
4.1.13 Flow switches shall not be used in applications where flow transmitters may be installed.
Installation of flow switches shall require SABIC approval.
4.1.14 Pneumatic flow instrumentation shall not be used.
4.2 Types of Flow Instruments
4.2.1 Flow measurement can be accomplished satisfactorily by a variety of instruments and
therefore selection of the instrument shall be based on the specific application.
4.2.2 This document outlines following types of transmitters, gauges and switches for flow
measurement in process plants.
a. Differential Pressure Flow Meters
b. Magnetic Flow Meters
c. Vortex Flow Meters
d. Positive Displacement Flow Meters
e. Ultrasonic Flow Meters
f. Coriolis Mass Flow meters
g. Thermal Mass Flow Meters
h. Turbine Flow Meters
i. Variable Area Flow meters
j. Elbow Taps Flow Meters
k. Flow Switches
l. Flow Gauges and Indicators
4.3 Differential Pressure Flow Transmitters
4.3.1 Wetted parts shall be 316 stainless steel, as a minimum, unless process conditions require
different material.
4.3.2 Refer to SES-R05-S01 for the design, material, sizing and selection of flow elements.
4.3.3 Differential pressure transmitter range shall be zero based to meet the requirements of start
up and unusual process conditions.
4.3.4 Square root calculation shall be done in only one device, preferably in control system.
4.3.5 Pressure and temperature compensation may be used to improve the accuracy of the flow
measurement. The compensation can be done with flow, pressure and temperature values
in the process control system or with a multivariable transmitter. For flow compensation,
AGA 8 equation for gas services and in case of steam services ASME steam tables should
be used.
4.4 Magnetic Flow Meters
4.4.1 Magnetic flow meters shall be used for flow measurement of dirty, slurry, highly corrosive
and difficult to meter fluids with conductivity of 5 microsiemens per cm or higher.
4.4.2 Use of magnetic flow meter for conductivity of fluids lower than 5 microsiemens per cm shall
require SABIC approval.
4.4.3 Flow meter liner and electrode material shall be compatible with process conditions.
4.4.4 Manufacturer shall be consulted for proper meter selection.
4.4.5 Electrodes shall be mounted in the horizontal plane and kept clean.
4.4.6 Self-cleaning electrode assemblies shall be used when specified.
4.4.7 In liquid application magnetic flow meters typical maximum velocity through the flow tube is
9 m/s and minimum velocity is 0.3 m/s. Magnetic flow meters should be used for liquid
velocity typically between 1.5-4.5 m/s. Velocity shall be limited to 1.5-3 m/s when metering
abrasive slurries, to minimize abrasion and damage to the liner.
4.4.8 Vacuum breakers may be required for some applications, to prevent collapse of the liner.
4.4.9 Use of an integral signal converter mounted on the transmitter usually results in a higher
performance and less costly installation. This is especially important when metering low
conductivity fluids. Corrosive atmosphere or electrical classification limitations may require
remote converter installation.
4.4.10 The allowable length of the signal cable between the transmitter and a remote converter
depends upon the fluid conductivity, flowmeter size and type. Length of up to 30 m is
commonly available.
4.4.11 Magnetic flow meters should not be used where thermal shocks are anticipated.
4.4.12 If the process piping is non-conductive, grounding rings resistant to process fluid corrosion
shall be used at both ends of the flow meter.
4.5 Vortex Flow Meters
4.5.1 Vortex flow meters feature high accuracy and wide rangeability, and require little or no
maintenance. Their wide range of applications includes low viscosity, clean, non-abrasive
liquids, steam and gases up to 204 deg C.
4.5.2 Vortex meters are not suitable for slurries and high viscosity fluids.
4.5.3 Vortex meters shall be used up to 8 inches of meter size.
4.5.4 Selection of vortex meter sizes shall be as per manufacturer’s recommendation. Vendor
shall submit sizing calculations.
4.5.5 Meter body shall match pipe line specifications.
4.5.6 Vortex meters have low flow cut-off. This can have drastic effect in closed-loop control or
mass balance applications. Sizing should therefore consider minimum flow rates as well as
maximum. The minimum value of the pipe Reynolds number at the lowest expected flow
should exceed 10,000 for liquids and 50,000 for gases. Below these values the vortex meter
may not generate a reliable flow signal.
4.5.7 Flow direction shall be permanently marked on the meter body.
4.5.8 Vortex flow meter internal diameter shall be matched as closely as possible to the adjoining
process pipe internal diameter.
4.5.9 Welds on mounting flanges should be ground smooth. Gaskets should be selected to
ensure that no part of the gasket protrudes into the flowing stream.
4.5.10 The vortex meter output shall be either pulse or HART. It shall be digitally integrated into the
control system.
4.5.11 Vortex flow meter design shall permit the replacement of vortex sensor without depressurizing
the
line.
4.5.12 Vortex meters are available in wafer and flanged connections style. The flanged
connections should be preferred over wafer connections.
4.5.13 Calibration of vortex flow meter should be done by using a fluid or gas similar or identical to
the process fluid.
4.6 Positive Displacement Flow Meters
4.6.1 Positive displacement (PD) flow meters accuracy should be 1 to 5 percent or better, over a
rangeability of 5:1.
4.6.2 Liquid positive displacement meters can be used for custody transfer if other meters
capable of operating in the service conditions do not meet accuracy or rangeability
requirements.
4.6.3 The PD meter is suitable for high viscosity fluids. These meters are particularly suited for
measuring fluids for blending and batching operations.
4.6.4 PD meters have high pressure drop and have moving parts requiring frequent maintenance.
4.6.5 The meter should not be used for dirty, non-lubricating or abrasive fluids.
4.6.6 Temperature compensation should be considered, when necessary.
4.6.7 Inlet and outlet ports shall be clearly marked to indicate proper flow direction.
4.6.8 Liquid meters are unaffected by turbulence or other abnormal flow distribution.
4.6.9 Recommended flow rate ranges should not be exceeded if the rated accuracy is to be
maintained. Errors increase rapidly below minimum flow rates because slip becomes an
increasingly significant factor. Flow surges may cause permanent damage. Care shall be
exercised when putting meters in service to avoid over speeding due to flushing, blowing, or
steaming-outlines.
4.6.10 Fluctuating flow rates can cause serious errors in wet test meters due to surging of the seal
liquid. Accuracy is highly dependent upon maintaining the seal liquid at the proper level.
4.6.11 Manufacturer’s recommendations should be followed for viscosity and flow rate limitations.
4.6.12 Meters should be calibrated with liquids having physical characteristics similar to those of
the liquids to be metered. For maximum accuracy, meters should be calibrated at pressures
and temperatures comparable to the service conditions to eliminate errors due to
dimensional changes.
4.6.13 If temperature can rise where meters are isolated by upstream and downstream valves,
relief valves should be installed to prevent fracture of the cases or damage to the internals
due to overpressure.
4.6.14 To avoid breaking or distorting pistons and vanes, liquid meters should not be subjected to
water hammer.
4.6.15 Meters in line sizes 1 inch and above shall be flanged body style.
4.7 Ultrasonic Flow Meters
4.7.1 The ultrasonic flow meter shall only be used where process conditions preclude the use of
other metering methods. Clamp on type ultrasonic flow meters can measure liquid velocity
in a pipeline without intruding into the flow stream.
4.7.2 Use of ultrasonic meters shall be approved by SABIC.
4.7.3 Ultrasonic flow meters shall be Doppler type with clamp on design.
4.7.4 Clamp on type Ultrasonic meters shall not be used on the lined pipes or pipe with sonically
opaque coatings
4.7.5 The Doppler flowmeter requires a liquid flowing medium containing significant quantities of
suspended solids or entrained gas. Reading using entrained gas are not reliable unless the
degree of entrainment is closely controlled. Solid concentration requirements vary
depending upon particle size and characteristics.
4.7.6 Transducer location shall be carefully selected to avoid turbulence in the pipe.
4.7.7 Transducer type and configuration shall be determined based on the application
requirement.
4.7.8 Piping geometry and installation accuracy is vital for the accurate flow measurement by
ultrasonic flow meters.
4.7.9 Accurate information on the fluid, flow rates and piping details should be furnished to the
vendor and their recommendations for the application suitability, selection, straight run
requirements and installation shall be followed.
4.8 Coriolis Mass Flow Meter
4.8.1 Coriolis mass flow meter shall be used for high accuracy application such as custody
transfer, for gas and liquid application. Refer to SES-R05-E20 and SES-R05-E21 for
custody transfer meters.
4.8.2 The meter shall be sized so the maximum full scale flow rate is above 66 percent of the
meter range, unless pressure drop considerations require a larger meter.
4.8.3 Integral transmitter on the sensor body should be preferred. For remote transmitters, the
sensor to transmitter wiring shall meet area classification requirements.
4.8.4 Coriolis flow meters shall be sized for the desired accuracy at normal and maximum flow
rate without exceeding the permissible pressure drop at the maximum flow rate.
4.8.5 Consideration must be given to the stress related corrosion caused by the vibrating meter
tubes.
4.8.6 Secondary containment should be considered when using coriolis meters for measuring
highly corrosive or hazardous materials.
4.9 Thermal Mass Flow Meters
4.9.1 Thermal mass flow meter shall only be applied in applications where the fluid thermal
conductivity is well known. Change in thermal conductivity shall cause the shift in sensor
response resulting in large measurement error.
4.9.2 Use of thermal mass flow meters shall be approved by SABIC.
4.9.3 Thermal mass flow meters do not require pressure and temperature compensation and
provide an accurate linear output with wide rangeability.
4.9.4 Thermal mass flow meters are used for low flow rates of clean gases. Thermal mass flow
meters are available with integral control valves for use as complete self-contained flow
controllers.
4.9.5 Thermal mass flow meter may be used on corrosive process streams if proper wetted
materials are specified.
4.9.6 Insertion type thermal mass flow meters shall be mounted in the horizontal pipelines, since
thermally induced currents will cause errors at low flow rates if mounted in vertical lines.
4.9.7 Insertion type thermal mass flow meters probe shall be specified with retractable probe
assembly to facilitate removal for cleaning while line is in service.
4.9.8 Calibration of thermal mass flow meter shall be done with a gas having thermal conductivity
similar to the process gas to be measured.
4.10 Turbine Flow Meters
4.10.1 Turbine meters should be used for +/- 0.25 percent of accuracy, 10:1 rangeability, and for
clean fluids. It is commonly used to prove other meters.
4.10.2 The turbine meter is not suitable for high viscosity liquids.
4.10.3 Turbine meters shall not be used for pulsating flow conditions.
4.10.4 Design, calibration and installation of turbine flow meters shall conform to API MPMS 5.3 for
liquid and AGA-7 for gas flow measurement.
4.10.5 Temperature compensation should be considered when necessary.
4.10.6 Turbine meter inside diameter shall be matched as closely as possible to the adjoining pipe
ID. Gasket shall not protrude and obstruct free flow of fluid in line.
4.10.7 Turbine meters shall be marked to indicate proper flow direction.
4.10.8 Turbine meters 1 inch and above shall be flanged.
4.10.9 Turbine meter bearing type and material of construction shall be compatible with the
process conditions.
4.10.10 Gas turbine meters shall have rotor module removable from top of meter through a special
flange or through bore of meter for meters larger than 3 inches.
4.10.11 Piston-type, positive-displacement pumps shall not be used in series with turbine
flowmeters.
4.10.12 Turbine meters shall be integrated digitally to the control system. Frequency to current
conversion is not preferred choice.
4.10.13 Turbine meter can be damaged by over speeding (over 150 percent) or by hydraulic shock.
4.10.14 If turbine meters use in liquid application are purged with gas, ensure that the rotor shall not
be run over speed. They shall not be purged with steam.
4.10.15 Turbine meters for gas application shall not be purged with liquid or steam.
4.11 Variable Area Meters (Rotameters)
4.11.1 Variable area flow meter may be used for local indication of small volumetric flows for
chemicals, chlorinators, instrument purging, small rates to analyzers and small rates on air
streams.
4.11.2 In general, variable area flow meter should be used for local indication of low flow rates in
line sizes less than 2 inches where integral orifices are not practical and the process fluid is
clean.
4.11.3 Rotameter accuracies vary depending upon the type of meter, the scale length, and the
calibration procedure.
4.11.4 Variable area flow meter accuracy should be 2 percent or better over a rangeability of 5:1.
4.11.5 Variable area flow meter sizing shall be done in accordance with manufacturer’s literature,
however, proper compensations shall be applied to correct for liquids other than water or
gases other than air. Normal flow should fall in the 50-60 percent of the maximum range.
4.11.6 Straightening vanes, or straight runs of pipe upstream or downstream of the meter, are not
required.
4.11.7 Meter factor and the design conditions shall be permanently engraved on the meter
nameplate.
4.11.8 Rotameters with metal metering tubes are used where conditions preclude the use of glass
metering tubes.
4.11.9 Metal tube type rotameter’s material for the float and tapered tube shall be 316 stainless
steel, as a minimum, unless process conditions require different material.
4.11.10 Glass tube meters shall be used only in air, inert gas and water services at temperatures of
60 deg C or below, and pressures 6.5 Barg or below. SABIC approval shall be required for
use of glass tube meters in other services.
4.11.11 Variable area flow meter in pulsating fluids flow measurement service shall be equipped
with pulsation dampener.
4.11.12 Hydraulic and thermal shock shall be avoided when using meters with glass metering tubes.
4.11.13 Variable area meters shall be armoured for all hazardous services.
4.11.14 Variable area meters end connections and rating shall be in accordance with the piping
specifications.
4.11.15 Scales for variable area meters shall be direct reading in Standard Cubic Meter per Hour
(SCMH) of air for gas or air service or Gallons per Hour (GPH) of water for liquid service.
4.11.16 For purge rotameter applications, a check valve shall be installed on the outlet of the meter
to prevent back flow. Needle valve shall be installed on the inlet side for manual flow control.
4.11.17 Purge rotameter shall be equipped with integral flow controller to compensate for the
change in purge fluid or upstream pressure variations.
4.11.18 For local flow rate indication of larger line sizes, the shunt rotameter, a combination of orifice
plate and rotameter may be used.
4.11.19 Meters employing floats with magnetic extensions shall not be used for fluids containing
magnetic particles. The particles will accumulate at the poles of the magnets, resulting in
increased friction or sticking.
4.12 Elbow Taps Flowmeters
4.12.1 Elbow flowmeters can be considered for noncritical flow measurement. SABIC approval
shall be required for using elbow taps flowmeter.
4.12.2 An elbow that is un-calibrated but carefully tapped, measured and located according to the
criteria set forth is subject to about +/- 4 percent error; refer to ASME Fluid Meters, Their
Theory and Application.
4.12.3 The elbow chosen for metering preferably should be long radius. The minimum pipe size
recommended is 1 ½ NPS.
4.12.4 The pressure taps shall be located 45 degree from the elbow inlet and in the plane of the
elbow centreline.
4.12.5 Data is not available on the effect of straightening vanes or non-uniform flow in elbow
flowmeters.
4.13 Flow Switches
4.13.1 Flow switches shall not be used without prior approval from SABIC.
4.13.2 Flow switches are not preferred for the critical process services and shall be used only for
non critical applications in utility lines.
4.13.3 Flow switches shall be the flapper types with a micro-switch, the moving magnet type with a
reed relay, or any other similarly suitable type.
4.13.4 Minimum process connection size for flow switch shall be 1 inch NPT.
4.14 Flow Gauges and Flow Indicators
4.14.1 Local flow indicators shall be bellows type fixed range differential pressure gauges.
4.14.2 Flow gauges with glass windows shall be used in only utility and non-critical services, such
as fluid purge or lube oil system.
4.14.3 Flow gauges shall have impact resistant safety glass.
5. Inspection and Testing
Vendor shall submit the following documents for the purchasers review, approval and records,
where applicable and as specified:
a. Sizing calculation
b. Calibration report
c. Hydrostatic test report
d. Material certificate
e. Dimensional drawings