Relief header location

Safety devices should be piped with a minimum of inlet pipe runs because excess pressure drop before a safety valve will affect its operation. For a minimum of discharge piping, relief valves are located high on a tower in open relief systems. In closed systems relief valves are located just above the relief header. 

Relief valve systems that are open to the atmosphere are located at the top of the tower closed systems are located a minimum distance above the relief header. Exhibit 10-55 shows a typical arrangement for both systems. 

Many relief headers must be located above the t< ... 

Pipe rack additions are shown in Exhibit 11-30. rea A shows a standard two-level pipe rack, as lanned. Because it is always possible for the pipe rack ) be expanded in the future, the area over the slumns must be kept free of piping and conduit. The iture expansion may include another new level (B), 1 air cooler (C), or a series of shell and tube exchang-rs (D). The preferred location of a relief header )Ove a pipe rack is illustrated in Exhibit 11-12. 

Relieving vapors from various pressure-relief and depressuring valves in the system must be collected in individual flare headers that should be appropriately located near each process area. Subheaders must be interconnected to a main flare header which feeds to a knock- out drum and disposal system. Condensates that are carried over by vapors are separated in the knock-out drum. The vapors that exit the vessel go to the flare stack where they are burned. 

In large facilities and offshore platforms where the escaping gases and liquids could present a source of pollution or ignition, it is common to route the relief valve discharges into a common header that discharges at a remote safe location. Often a vent scrubber is installed in this header to separate the bulk of the liquids and to minimize the possibility of liquid discharges to atmosphere. 

The main arterial system of a plant is yard piping. It is here that long process lines are located interconnecting distant equipment with lines entering and leaving the unit. Also located in the yard are utility headers supplying steam, air, gas, and water to process equipment. Here are located all relief and blow-down headers. Often instrument lines and electrical supply conduits are also supported on the yard steel. 

With the normal residual heat removal system in service when shutdown, the only over-pressure protection claimed by the fault schedule (Section 4.10.5.9 of Reference 6.13) is the normal residual heat removal system safety rehef valve (Section 19E.4.10.1 of Reference 6.1). This valve is located inside the containment on the suction header, and set to open at 35.5 bar (500 psig). The capacity of the relief valve is 3200 litres per minute (850gpm) (Section 4.10.5.10.6 of Reference 6.13). 

Disposal to Oily Water Sewer (OWS) A process oil water sewer system is a convenient location to direct oily waste from process systems including thermal relief outlets. The oily water system normally collects fluids and directs them to the local sump. If several lines connect into a common OWS header, care shoifld be taken to prevent backflow into another outlet source. In such cases, use of air gap, i.e., drainage into a collection funnel, has been advantageous. 

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