Sapag Safety Valves Series 8400/8500/8490/8590
Installation and Maintenance Instructions
Emerson reserves the right to change the contents without notice
page 6
The Test Bench
The quality and condition of the shop test bench is paramount to obtaining proper test results. The
test bench must be free of leaks and the test fluid must be clean. Solids or other foreign material
in the test medium will damage the seating surfaces of the pressure relief valve being tested.
The test pressure gage must be calibrated and have a range proper to the pressure level of the
valve setting. Set pressure should fall within the middle third of the dial range of the test gage.
The test bench provides an accurate and convenient facility for determining valve set pressure
and seat tightness. It does not duplicate all of the field conditions to which a pressure relief valve
will be exposed while in service. It is not practical to attempt to measure relieving capacity or
blowdown using a test bench.
Test Fluids - Set Pressure Test
The Test Fluid should be air or nitrogen for valves used on gas and vapor service and water for
valves used on liquid service. Valves for steam service should be tested on steam. It may be
necessary to make a correction to the adjusted set pressure to compensate for the difference in
temperature of the test fluids(see appropriate instruction).
Valve Operation
Sapag Series 8000 valves intended for compressible fluid service and tested with air or steam will
open with a sharp clear popping action at the set point. Valves for liquid service tested with water
are considered open when there is a continuous unbroken stream of liquid flowing from the valve.
Set Pressure Changes
Set pressure changes beyond the Sapag specified spring range will necessitate a change in the
valve spring assembly consisting of the spring and two fitted spring washers. The new spring and
washers must be obtained from Sapag and the valve must be reset and the nameplate restamped
by an authorized valve repair facility.
Set Pressure Adjustment
Before making any adjustments reduce the pressure under the valve seat to at least 10% below
the stamped opening pressure. This will prevent seat damage due to turning of the disc on the
nozzle seat and minimize the chance of an inadvertent valve opening. A strong (high) ring position
is necessary to obtain a good clean popping action of the valve on air or gas with the limited
volume available on the test bench.
a. (Not required for testing on liquid.) Remove the nozzle ring set screw and raise the nozzle ring
until it touches the disc holder, then back it down two (2) notches. Exercise care in counting
the number of notches moved so that the ring can be returned to its proper position following
testing.
Moving the notches on the nozzle ring to the left will lower the nozzle ring.
Replace the nozzle ring set screw before each set pressure test. The set screw must engage one
of the ring notches, being careful that it does not bear on the top of a tooth.
b. Remove the cap or lifting lever following the instruction for valve disassembly. (See paragraph
6)
c. Loosen the adjusting bolt nut and turn the adjusting bolt clockwise to increase set pressure or
counterclockwise to reduce set pressure.
d. Retighten the adjusting bolt nut following each adjustment.
e. Two or three consecutive valve openings at the same pressure are necessary to accurately verify
the opening pressure.
f. Once the set pressure has been established, lower the nozzle ring to the installed ring position
as indicated in Table 1 and replace the nozzle ring set screw as described above. Seal wire the
adjusting bolt and adjusting ring set screw with identifying seals.
Nozzle Ring Settings
The nozzle ring adjustment is made at the factory and resetting in service is seldom necessary.
Should it be necessary to change blowdown or reduce valve simmer, the nozzle ring may be
adjusted as follows: (See the next paragraph for P, Q, R and T OrificeType 8500/8590)
a) Remove the nozzle ring set screw and insert a screwdriver to engage the ring notches.
b) Turning the ring to the right raises the ring, thereby increasing blowdown. Turning the ring to
the left lowers the ring, thereby decreasing the blowdown.
c) Do not lower the nozzle ring to the point where the valve begins to have excessive simmer.
Raising of the ring will reduce simmer.
d) The nozzle ring should not be moved more than two notches before retesting. When making
adjustments, always keep count of the number of notches and the direction in which the nozzle
ring is moved. This will permit returning to the original setting in case of error.
CAUTION: Should any adjustments
be made while the valve is
installed on a pressurized system,
the valve should be gagged while
ring adjustments are made.
