Pipe racks elevation

Install critical power, control, instrument, and alarm wiring and pneumatic tubing outside the fire-exposed envelope. Cable trays and conduit banks should be routed underground or on the upper levels of elevated pipe racks at least 30 feet above the ground and outside the drainage path of hydrocarbon spills. Install fire proofing of critical systems and equipment if they are inside the fire-exposed envelope. 

Pipe racks (Fig. 6-4) are an elevated collection of pipes that transport utilities as well as raw material, product, and waste streams from one part of the plant to another. They may also be used to transfer information to and from control centers. Placing all the pipes together simplifies their construction and, later, the location of problems. Nothing should be located under pipe racks, since if leaks occur they may damage equipment. 

Finned-tube, air-cooled heat exchangers are usually placed in elevated locations, often above pipe racks. Finned-tube heat exchangers that are fan-... 

Fig. 9-9. Section through typical outdoor overhead pipe rack showing arrangement of north-south runs at two elevations and east-west runs at an intermediate elevation. Reprinted with permission from The M, W. Kellogg Co., Design of Piping Sy ms," 2d ed., John Wiley tfc Sons, Inc., New York, 1956.)...

High work Work on scaffolds, platforms, pipe racks, or elevated equipment. 

The bottom support elevation of the main pipe rad< is dictated by the maintenance and piping clearance beneath the pipe rack, with additional levels spaced at 6-ft (1,800-mm) intervals. On projects with very large diameter piping, increasing this dimension to suit clearance requirements should be considered when pipe direaion is changed. External clearances (e.g, over main roads or intersections with off-.site pipe racks) need close attention. Exhibit 3-20 shows a typical pipe rack elevation. 

Pipe racks within vertically structured or housed facilities cannot be defined as easily as for inline arrangements, because the equipment is usually located on several levels. The venical units are usually fed by conventional pipe racks at established elevations entering the structure at a designated area. Once inside the structure, piping should be routed in an orderly manner according to economic, constructibility, and support requirements. Exhibit 3-22 displays a typical process structure. 

This chapter explains what is required to finalize the pipe rack width, number of levels and elevations, and bent spacing and addresses pipe flexibility and access and maintenance concerns for each item located within the pipe rack area. 

After the bent spacing, rack width, and number of levels are established, the elevation of the levels must be set. As discussed in Chapter 2, the plant layout designer must know the minimum clearances to set the elevations. Plant roads, type of mobile equipment, and equipment located beneath the pipe rack can influence the pipe rack elevation. Usually, space is allowed below the pipe rack for equipment, with a minimum clearance of 10 ft (3,050 mm). 

Exhibit 11-14 shows a typical arrangement for a hose station. Battery limit valving for a single-level pipe rack is shown in Exhibit 11-15. The valves are staggered on either side of the catwalk, and handwheel extension stems are furnished when necessary to facilitate operation. Exhibit 11-16 also displays a single-level rack. Here, however, an elevation change is required between the process unit and the off-site pipe rack. This design has the block valves installed in the vertical portion of the line, which allows for relative ease of operation. 

Exhibit 11-17 illustrates a two-level process unit pipe rack the elevation change to the off-site area is either above or below the process unit pipe rack. 

When complex equipment (e.g., a converter and fractionator in a fluid catalytic cracking unit) is designed, a stair structure with a vertical pipe rack must be located between both vessels, as shown in Exhibit 12-26. Although elevators are often used, diem approval must be obtained before they are included. The optimum layout includes arranging the vessel platforms for easy access from the structure. Clearance between the vessel and structure platforms must accommodate die growth of the vessels, which should be calculated to satisfy safety concerns. This structure eliminates the... 

Another responsibility of the plant layout designer is to establish the location of the instrument cable trays and analyzer houses. Both items are coordinated with the instrument engineer during the early phase of the job. The main instrument cable runs are located either in elevated trays, generally in the pipe rack, or below ground in cable trenches. These requirements are dis-cu.ssed in Chapters 11 (Pipe Racks) and 13 (Underground Piping). 

Monitors 6E and 8E are elevated and can cover the air coolers over the pipe rack as well as the pipe rack itself. 

Elevated piping or pipe racks (a horizontal lifeline system is recommended for elevated piperacks)... 

The location of the pipe in the rack is selected to minimize the congestion and eliminate line crossing. If a process line connects two nozzles which are elevated higher than the piperack, then the upper level of the rack is used. Similarly, if the nozzles are both below the piperack, then the lower level rack is used. Other cases in which one nozzle is below and the other above use the least congested part of the piperack. Lines with valves are more easily accessed from the upper level, but require an access platform. 

Figure 12 shows the plan and elevation views of a process unit piping (9). A dmm is supported off the piperack. Heat exchangers are located far enough back from the support columns so that they are accessible and their shell covers can be removed. Pumps are located underneath the piperack, but sufficient room is provided for maintenance equipment to access the motors and to remove the pump if necessary. The motor is always oriented away from the process equipment and located on that side of the piperack. Instmment valve drops are shown supported from the columns. The instmment trays themselves mn on the outside of the support columns. Flat turns are only made from the outside position of the piperack. Nozzle-to-nozzle pipe mns are made whenever possible. Larger lines are located on the outside of the piperack. Connections to nozzles above the rack are made from the top... 

Figure 7-57. This is a typical elevation for yard piping intersection. Notice that the 14-foot elevation of the lateral rack permits turning up or down at the intersection.

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