22 |
Baker Hughes
© 2020 Baker Hughes Company. All rights reserved.
c. If the valve opens at a pressure below the
recorded set pressure, allow the valve to close
and the boiler pressure to reduce to 85 percent
of set pressure. Increase the compression on
the spring by turning the compression screw
clockwise 1/6th of a turn. Tighten the adjusting
screw lock nut and replace the cap and lifting
lever assembly. Retest the valve as described in
Step 6. If the valve continues to open below the
required set pressure, calculate how many turns
to move the adjusting screw to cause the valve
to open at the correct set pressure. Adjust as
necessary.
d. If the valve opens and closes rapidly, (called
“chattering”) hold the valve open to prevent
damage to the valve. Reduce the fire in the
boiler and allow the boiler pressure to reduce to
approximately 85 percent of the set pressure.
Gag the valve, and reset the adjusting rings
according to presetting instructions, (see Section
XIV.C).
e. If the valve indicates simmer at a pressure
greater than 1 percent of the set pressure of the
valve, allow the valve to reseat and the boiler
pressure to reduce to 85 percent of set pressure.
Gag the valve to prevent accidental lifting
while making adjustments. Remove the lower
adjusting ring pin and raise the lower adjusting
ring. As viewed through the ring pin hole, move
the adjusting ring from left to right one or two
notches. Remove the gag, retest and note when
simmer occurs and repeat as necessary.
Note: The lower adjusting ring should be adjusted
to the notch that provides a minimum of
simmer and does not interfere with the
blowdown of the valve.
f. If the valve “pops” open then drops out of lift, like
it was going to close, but remains open at a very
low lift, this is called a “hang up” and indicates
that the position of the lower adjusting ring is
interfering with the blowdown of the valve. To
correct a hang up, gag the valve, remove the
lower ring pin and lower the adjusting ring one
Note: Baker Hughes recommends that the maximum operating pressure never exceeds 94 percent of the
set pressure of the 1511 series safety valve.
Table 9
ASME Boiler and
Pressure Vessel
Code Section and
Symbol
CODE SYMBOL
STAMP
ASME Section I
Set Pressure Tolerance (The valve must
“POP” open within the range indicated
below.)
Blowdown Requirements
If valve set pressure is less than or equal to
70 psig (4.83 barg):
±2 psig (±0.14 barg)
After opening, the valve must reclose
within a range of 98 percent to 96
percent, however, if the valve set
pressure is 100 psig (6.9 barg) or less
the valve must reclose within a range of
2 to 4 psig (0.14 to 0.28 barg) below set
pressure.
If valve set pressure is 71 psig (4.9 barg)
up to and including 300 psig (20.68 barg):
±3 percent of set pressure
If valve set pressure is 301 psig (20.75
barg) up to and including 1000 psig (68.95
barg):
±10 psig (±0.69 barg)
If valve set pressure is 1001 psig (69.02
barg) or greater
±1 percent of set pressure
CODE SYMBOL
STAMP
ASME Section VIII
If valve set pressure is less than or equal to
70 psig (4.83 barg):
±2 psig (±0.14 barg)
After opening the valve must reclose
before the system pressure returns to
normal operating pressure.
If valve set pressure is 71 psig (4.9 barg) or
greater
±3 percent of set pressure
UV
V
XIV. Setting and Testing (Cont’d)
