MAINTENANCE – DISMANTLING
1) Remove the cap.
2) Before removing the adjusting bolt, take a measurement from the top
of the adjusting bolt to the top of the cylinder as a reference for
resetting the valve later.
3) Loosen the adjusting bolt nut and turn the adjusting bolt counter-
clockwise to completely remove the load on the spring. Unless this is
done, unnecessary damage to the seat or misalignment of the trim
parts may occur when the valve is reassembled.
4) On Series 800 valves remove the set screw and gasket.
5) Unscrew the cylinder from the base. Lift the cylinder from the base
making sure that the guide remains on the base.
NOTE:Iftheguideisnotremovedwiththebase,inverttheentirevalve
and remove the base. Then remove the guide, disc holder and disc
insert.
6) Remove the spindle, spring and spring washers.
7) Invert the base/guide/disc assembly and remove the base.
8) Remove the disc holder assembly.
– Metal Seated Valves
The disc insert is not attached to the disc holder so use care when
removing this assembly.
– O-Ring Seated Valves
Remove the disc insert by inserting a drive pin or similar tool into the hole
in the disc holder and press out the disc insert. Remove the O-ring with a
suitable tool. Be careful not to damage the O-ring groove.
CLEANING
The followinginstructionsaregeneralguidelines.Certainapplicationsmay
require the use of special cleaning procedures.
1) After the valve has been completely dismantled, the seats on both the
nozzle andthe disc insertshould beexamined to determinehow badly
they are damaged, ifat all. Any severe damage maymake it advisable
to replace the parts.
2) External parts, such as the cylinder and cap, can be cleaned by
immersion in a bath such as a hot oakite solution or equivalent.
3) Internal parts, except O-rings, can be cleaned using acetone, dena-
tured alcohol or any other suitable solvent. Mechanical cleaning of
internalparts, exceptseats,can beperformedusingfinesandpaperor
emery cloth.
LAPPING OF SEATS –METAL SEATED VALVES ONLY
Many different methods exist for lapping valve seats but certain essential
steps are required for satisfactory results. Extreme care should be taken
throughout to make certain that the seats are kept perfectly flat. The
following procedure is suggested for lapping bases and disc inserts:
1) Never lap the disc against the base. Lap each part separately
against a cast-iron lapping block of proper size. These blocks hold the
lapping compound in their surface pores and must be recharged
frequently.
2) Check the lapping block frequently on a good lapping block
reconditioner to make certain that it is perfectly flat.
3) If considerablelappingis required, spread athincoat of medium coarse
lapping compound on the block. After lapping with this, lap again with
a medium grade compound. Unless much lapping is called for, the first
stepmaybe omitted. Next, lapagainusing a finegradecompound. Lap
theblock against theseat. Do not rotatetheblock continuously, but use
an oscillating motion as in grinding automobile valves.
4) When the seat is flat and all nicks and marks have disappeared,
remove all compound from the lapping block and seat. Apply polish-
ing compound to another block and lap the seat with this. As the
lapping nears completion, only the compound left in the pores of the
block should be present. This should give a very smooth finish. If
scratches appear, the cause is probably dirty lapping compound.
These scratches should be removed by using a compound free from
foreign matter.
5) After wiping off all compounds, the valve is ready for assembly.
TESTING
Testing should be performed by trained personnel using the applicable
test procedure. Follow these guidelines for performance of the set
pressure test.
– Test Fluids – Set Pressure Test
The test fluid should be air or nitrogen for valves used on gas and vapor
service andwaterforvalvesusedonliquidservice.Note:Series800valves
are for gas and vapor service only. Valves for steam service should be
tested on steam. When steam testing is not possible, valves for steam
service may betestedonairornitrogen.Insuchcasesitmaybenecessary
to make a correction to the adjusted set pressure to compensate for the
difference in temperature of the test fluids.
– Temperature Correction
When a valve is set on air or water at room temperature and then used at
a higher service temperature, the cold differential set pressure shall be
corrected to exceed the set pressure using the following temperature
correction:
OPERATINGTEMPERATURE %PRESSURE
Degrees F Degrees C INCREASE
0 to +150F -18 to +66C NONE
+151 to +600F +66 to +316C 1%
+601 to +750F +316 to +399C 2%
– Valve Operation
Valvesintendedforcompressiblefluidserviceandtestedonair,nitrogenor
steam will open with a sharp, clear popping action at the set point.
Valves for liquid service tested with water are considered open at the first
continuous unbroken stream of liquid flowing through the valve. Sometimes
itis helpfulto installa shortpieceofpipeinthevalveoutlettodetermine the
opening on water.
SET PRESSURE CHANGES
Set pressure changes beyond the Crosby specified spring range will
necessitate a change in the valve spring assembly consisting of the spring
and two washers.
The new spring and washers must be obtained from
Crosby and the valve must be reset and the nameplate restamped by
an authorized repair facility.
SET PRESSUREADJUSTMENT
Before making any adjustments reduce the pressure under the valve seat
to at least 25% below the stamped opening pressure. This will prevent
seat damage due to turning of the disc insert on the nozzle seat and
minimize the chance of an inadvertent opening.
BLOWDOWN ADJUSTMENT – SERIES 800(GasandVapor
Service only)
The adjusting ring is set at the factory and resetting in service is seldom
necessary. Should it be necessary to change blowdown the ring may be
adjusted as follows:
Caution: Should any adjustments be made while the valve is
installed on a pressurized system, the valve should be gagged
while ring adjustment is made.
Remove the set screw and insert a screwdriver to engage the ring notches.
Turning the ring to the right raises the ring, thereby decreasing the
blowdown. Turning the ring to theleft lowers the ring, therebyincreasing
the blowdown.
The adjusting 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 ring is moved. This will permit
returning to the original setting in case of error.
