Simmer; Seat Leakage; Back Pressure Testing (Ms & Da) - Baker Hughes Consolidated 19000 Series Instruction Manual

XVI. Setting and Testing (Contd.)
back pressure conditions will cause a shorter blowdown than
when observed with no back pressure.
G. Simmer
If simmer causes erratic valve opening, refer to the Trouble
Shooting Guide in this manual.
H. Seat Leakage
1. Air
The air-leakage test shall be performed with all
connections and openings in the body and bonnet
pressure-tight. The cap, with the gasket which covers
the adjusting screw, must be installed. Test the valve for
leakage using an API test fixture. The API leakage test
procedure is described below:
a. Per API Standard 527 (ANSI B147.1-72), a standard
test fixture consists of a piece of tubing of .313"
(7.94 mm) x .035" (0.89 mm) wall, one end of which
is joined to an adapter on the valve outlet and the
other end of which is immersed .05" (12.7 mm)
below the surface of a reservoir of water.
b. The leakage rate for a valve with metal-to-metal
seats shall be determined with the valve mounted
vertically and using a standard test fixture, as
described above. The leakage rate, in bubbles per
minutes, shall be determined with the pressure at
the safety relief valve inlet held at 90 percent of the
set pressure, immediately after popping, for valves
set 51 psig (3.52 barg) and above. On valves set at
50 psig (3.45 barg) and below, test for leakage at 5
psig (0.34 barg) below the set pressure, immediately
after popping. The test pressure shall be applied for
a maximum of one minute.
c. The Tightness Standard is the leakage rate in
bubbles per minute and shall not exceed that
shown in Table 13 for metal seat valves or Table 14
for O-ring seat seal valves. A valve with a seat of
resilient material (i.e., an O-ring valve) shall show
no leakage at pressures less than those indicated in
Table 13 when the test medium is either air or water.
Table 13: Metal Seat Valve Leakage Rate
Max Leakage Rate
(Bubbles per
minute)
40
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Approximate Leakage Rate
ft 3 per 24 hr. (Liters per 24 hr.)
0.06 (16.99)
Table 14: O-Ring Seat Valve Leakage Rate
Set Pressure
psig
15 to 30 1.03 to 2.07
31 to 50 2.14 to 3.45
51 to 100 3.52 to 6.89
101 or greater 6.96 or greater
2. Water
When a metal-to-metal seat valve is tested using water
as the test medium, there shall be no leakage, as
determined by sight when the pressure is held at 90
percent of set pressure.
For O-ring seat seal valves use Table 13 to determine
the percentage of set pressure.
3. Steam
When a metal-to-metal seat valve is checked for
tightness using steam as the test medium (at 90 percent
of the set pressure), there shall be no visual or audible
leakage after the interior of the valve is allowed to dry
after popping. If there is no visual or audible leakage,
the valve is acceptable.
For O-ring seat seal valves use Table 14 to determine
the percentage of set pressure."
I. Back Pressure Testing
1. (MS & DA)
After the valve has been set for the correct opening
pressure, it must be back pressure tested. Testing can be
conducted by installing the cap (with gasket) and applying
air or nitrogen to the valve outlet. Test pressure should be 30
psig (2.07 barg) or the actual valve back pressure, whichever
is greater. Examine the base (1) to bonnet (6) joint for
leakage during back pressure testing:
Note: Leakage is best detected by application of a
liquid leak detector. The use of soap or household
detergent as a leak detector is not recommended,
as it may cover up leaks.
Repair of leaking valve joints may be attempted by tightening
the leaking joint while the valve is still on the stand. If this
does not stop the leak, disassemble and inspect the leaking
joint. The seating surfaces should be better than a 32 RMS
finish. The valve must be re-tested if disassembly is required.
After the valve set pressure has been adjusted, tighten the
Consolidated 19000 Series Safety Relief Valve Instruction Manual
Min. Leak Point
(% of Set
barg
Pressure)
90%
92%
94%
97%
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