Recommended Installation Practices; Mounting Position; Inlet Piping - Baker Hughes Consolidated 19000 Series Instruction Manual

XI. Recommended Installation Practices
Mount safety relief valves
in a vertical, upright
position only.
Do not mount valve at
the end of pipe through
which there is normally
noflowornearelbows,
tees, bends, etc.
Heed all service
manual warnings. Read
installation instructions
before installing valve(s).
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Baker Hughes
A. Mounting Position
Mount SRVs in a vertical (upright) position (in accordance with API RP 530). Installing a
safety relief valve in any position other than vertical (±1 degree) will adversely affect its
operation as a result of the induced misalignment of moving parts.
A stop valve may be placed between the pressure vessel and its relief valve only as
permitted by code regulations. If a stop valve is located between the pressure vessel and
SRV, the stop valve port area should equal or exceed the nominal internal area associated
with the pipe size of the SRV inlet. The pressure drop from the vessel to the SRV shall not
exceed three (3) percent of the valve's set pressure, when flowing at full capacity.
The threaded inlet and outlet ports and sealing faces of the valve and all connecting
piping must be free from dirt, sediment and scale.
In the case of screwed/portable valves, use caution to avoid unscrewing bonnet from the
base; if a pipe wrench is used to install or remove the base, ensure that the wrench is
placed on the flats of the base and not on the bonnet. If the bonnet/ base joint is broken,
the valve should be retested to ensure proper set pressure and function of the valve.
Position SRVs for easy access and/or removal so that servicing can be properly
performed. Ensure sufficient working space is provided around and above the valve.
B. Inlet Piping
The inlet piping (see Figure 7) to the valve should be short and directly from the vessel
or equipment being protected. The radius of the connection to the vessel should permit
smooth flow to the valve. Avoid sharp corners. If this is not practical, then the inlet should
be at least one additional pipe diameter larger.
The pressure drop from the vessel to the valve shall not exceed three (3) percent
of valve set pressure when the valve is allowing full capacity flow. The inlet piping
should never be smaller in diameter than the inlet connection of the valve. Excessive
pressure drop in gas, vapor, or flashing-liquid service at the inlet of the SRV will cause
the extremely rapid opening and closing of the valve, which is known as "chattering."
Chattering will result in lowered capacity and damage to the seating surfaces. The most
desirable installation is that in which the nominal size of the inlet piping is the same as,
or greater than, the nominal size of the valve inlet flange and in which the length does
not exceed the face-to-face dimensions of a standard tee of the required pressure class.
Do not locate SRV inlets where excessive turbulence is present, such as near elbows,
tees, bends, orifice plates or throttling valves.
Section VIII of the ASME Boiler and Pressure Vessel Code requires the inlet connection
design to consider stress conditions during valve operation, caused by external loading,
vibration, and loads due to thermal expansion of the discharge piping.
The determination of reaction forces during valve discharge is the responsibility of the
vessel and/or piping designer. Baker Hughes publishes certain technical information
about reaction forces under various fluid flow conditions, but assumes no liability for the
calculations and design of the inlet piping.
External loading, by poorly designed discharge piping and support systems, and forced
alignment of discharge piping can cause excessive stresses and distortions in the valve
as well as the inlet piping. The stresses in the valve may cause a malfunction or leak.
Therefore, discharge piping must be independently supported and carefully aligned.
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