This article is about technical specification of Spacing requirement and process equipment arrangements in plant layout levels.
Spacing Requirements & Process Equipment Arrangements
Plot Plan Layouts
Plot plan layouts are essential in the design and construction of industrial plants and facilities. These plans are detailed drawings that show the location of all the equipment, structures, and infrastructure necessary for the operation of the facility. Plot plan layouts help ensure that the plant is constructed efficiently, with maximum use of space, and in a way that is safe for workers and the environment.
Spacing Recommendations
- See Tables 1-A and 2-A for minimum spacing for equipment from other equipment, piperacks, tanks, buildings.
- Any reductions from the recommended spacing in this Specification shall be subject to each of the following conditions:
- a. The reduction shall be analyzed by using consequence analysis.
- b. Adequate measures shall be provided to compensate for any increase in risk by providing additional safeguards such as fireproofing, automatic water spray systems, emergency shutdown systems, or additional fire fighting equipment.
- c. Each reduction shall be clearly identified on a drawing along with the proposed additional safeguards and shall be reviewed with Buyer and local loss prevention/safety departments, as applicable.
- The separation distances in this Specification are to be measured between the nearest surfaces of equipment, units, or devices listed or to the nearest edge of a roadway. Spacing required between two pieces of equipment or facilities having different minimum requirements shall be governed by the larger of the two requirements.
- The separation distances in this Specification are recommended minimum distances unless otherwise noted. Engineering judgment must be used to assure adequate access for fire fighting and maintenance when applying the recommendations and when spacing equipment designated as “no minimum” (NM).
Process Equipment Arrangements
- General
- A plot plan for process unit, or a group of process units, shall be arranged with due consideration for maintenance requirements. The following factors shall be considered:
- a. Process requirements
- b. Constructability
- c. Operability
- d. Safety
- e. Available plot area
- f. Relationship to adjacent units or to other facilities within the plant.
- g. Economy
- h. Future expandability
- i. Security
- j. Prevailing wind direction
- Plot Plan for a Single Process Unit
- The preferred plot plan arrangement for a single process unit usually results in a layout with all equipment at grade level. In the usual development:
- a. A pipe rack is placed along the center of the unit.
- b. Vessels, exchangers, and other equipment are placed on either side of the pipe rack.
- c. Pumps are located along the pipe rack.
- d. Air coolers are located on top of the pipe rack or at grade level.
- e. Fired heaters are located at one end of the plot in an isolated area, normally upwind, at a safe distance from hydrocarbon processing equipment.
This layout simplifies construction. The equipment is easily accessible for maintenance because all major equipment is along a plot edge. A maintenance accessway is available under the pipe rack to service pumps located along the pipe rack.
This layout usually produces a long, narrow plot with a lengthy pipe rack and long utility headers. This may add to piping, pipe rack, instrument, and electrical costs. In large units, however, the length may be offset. When equipment (especially exchangers) is below 15 m elevation, it usually can be maintained by a mobile crane. Above that elevation, trolley beams, trolleys, and pulling beams shall be provided for removal of tube bundles. by using an L-shaped, T-shaped, H-shaped, or a U-shaped plot arrangement.
Placing equipment in structures also decreases the plot area, thereby reducing pipe rack length and piping costs. These savings must be compared with the cost of the structures. Multilevel structures add to the initial cost and to the maintenance costs.
Plot Plan for Multiple Units
In many plants, several process units are grouped together to reduce investment and operating costs. The entire group of units may then be required to shut down when any one unit is down. One arrangement for such a group, especially when all heaters must discharge into a common stack, fixes all the heaters along one side of the plant, with the stack and group of heaters approximately centered on the plant edge.
The balance of the units are then arranged around the heaters. This arrangement provides a compact group of
units in the smallest plot area. If the heaters are not required to discharge into a common stack, or if there is intermediate tankage that will allow individual process units to operate independently, then a plant can be laid out as follows:
- Place a main pipe rack along the center of the area.
- On either side of this pipe rack, locate branch pipe racks at right angles to the main one.
- Arrange process units around the branch pipe racks, as described for a single process unit.
- Main pipe rack should be outside of process unit battery limits.