2
YARWAY
PROCESS THERMOSTATIC STEAM TRAPS
SerieS 151
MAINTENANCE
Inspect the trap and clean the strainer screen
during the first month of operation. Inspect and
clean the trap every 6 to12 months.
Inspect the trap and clean the screen
Close the valve ahead of the trap and close the
downstream valve. Allow the trap to cool and
slowly open the test valve. Sudden opening of
the test or strainer valve can cause damage to
the filled thermal element. Open the strainer
blowdown slowly. Loosen the bonnet. The
strainer screen fits tightly on the bonnet screen
guide. Remove the bonnet and screen to expose
the working parts of the trap.
Caution
Be certain the pressure in the trap is relieved
before removing the bonnet.
Clean the trap
Inspect the following parts for wear or oxide
deposit: the seat (4), the outside surface of the
cage (3) and the inside bore of the bonnet (2).
Do not remove the seat unless it is damaged.
Clean dirt or oxides from inspected parts using
a commercial solvent. Do not scrape surfaces
and do not use emery paper or other abrasive
material.
If internals are damaged or worn, renewal
kits are available from your local distributor. A
renewal kit consists of a seat (4), seat gasket
(5), preassembled cage assembly (3), bonnet
gasket (8) and strainer screens (6). Bonnets (2)
are available separately.
Reassembly
Lubricate the bonnet (2) threads and both sides
of the bonnet gasket (8) with Loctite Stainless
Steel PST sealant or equivalent. Place the
screen on the bonnet screen guide. Place
the cage assembly (3) in the body. Thread the
bonnet into the body making sure that the cage
enters the bonnet and the screen fits properly.
Recommended bonnet torque: 150-160 ft-lb
(203-217 Nm).
Installation of renewal kit
Remove the old seat. Clean gasketing surfaces
in the body to remove dirt. Use a new seat
gasket (5). Lubricate the seat (4) threads with
suitable high temperature lubricant such
as Loctite Stainless Steel PST sealant or
equivalent. Thread the seat (4) into the body.
Recommended seat torque: 60-65 ft-lb (81-88
Nm). Install cage assembly (3), screen (6) and
gaskets (5)(8) in accordance with reassembly
instructions.
Start-up
Slowly open the isolating valve ahead of the
trap. This allows the filled thermal element
to warm up and minimize water hammer and
shock. Slowly open the downstream line valve.
Close the test valve.
TROUBLESHOOTING
Problem
Potential Remedy
Trap remains
closed or
provides
inadequate
drainage.*
a. Check the upstream and downstream isolation and check valves to assure they are open.
b. Check the strainer for clogging. Blow down the separate strainer and clean the screen
within the trap.
c. Dirt or oxide deposits. Clean the trap internal cage plugged with dirt. Replace cage.
d. Poor Installation-the trap is too hot. Be certain the trap is installed bellow equipment
being drained, using uninsulated piping to condense untrapped steam and provide
sufficient subcooling to open the main valve.
e. Trap may be undersized. Check requirements against trap rating.
CAUTION: Follow the maintenance instructions when attempting to disassemble and service
the trap.
Trap remains
open and
is blowing
steam; is not
shutting off.*
a. Dirt on the seat of the cage and/or pilot valve, or oxide deposits between the cage and the
bonnet. Clean the trap.
b. Damaged or worn pilot. Replace the cage with a new repair kit.
c. Condensate load is too low. Pilot capacity is adequate to remove condensate. Trap is not
full open, just operating on pilot flow only. The trap is not faulty.
CAUTION: Follow the maintenance instructions when attempting to disassemble and service
the trap.
*Dirt can lodge between the bonnet and cage. This unlikely event could result in the cage remaining open or
closed. Disassemble and remove dirt. Check to be sure screen is in place and undamaged.
