Emerson YARWA 151 Series Manual

YARWAY PROCESS THERMOSTATIC STEAM TRAPS

SerieS 151

How to install repair capsules in Series 151 steam traps

Full pipe size of
equipment outlet

¾” Min. for 151
1” Min for 151H

Series 151-A (Angle) Series 151-I (In-Line)

SPECIFICATION

ANSI Class 300

Maximum Operating Pressure: 300 psig (21 bar)
Maximum Operating Temperature: 500F (260C)
Minimum differential: 1 psi (.07 bar)
Maximum test pressure: 740 psig (51 bar)

Nominal Capacity

100 psi (7 bar) near saturation temperature.
Series 151: 4500 lb/hr (2040 kg/hr).
Series 151H: 8500 lb/hr (3850 kg/hr).

End Connections

¾”, 1” NPT-ANSI B1.20.1
¾”, 1” Socketwelding-ANSI B16.11

OPERATION

Series 151 steam traps are designed for use
in process heat exchange applications. A filled
thermal element actuates the pilot valve. The
main valve/cage assembly is actuated by fluid
dynamics. Discharge is basically cyclic in
nature and occurs near steam temperature.
The pilot valve can discharge condensate
continuously, but will close when dry steam
reaches the trap.

INSTALLATION

Before installing the trap, blow out the piping
thoroughly to remove loose scale and dirt. Use
pipe dope or tape sparingly when attaching the
trap to the pipe.
Observe the pressure limitations and flow
direction shown on the trap label. Install the
trap in an accessible location for inspection
and maintenance, below the equipment being
drained (see Fig. 1).

20" min

921 Strainer

Isolated valves

(Gate or Ball)

FIGURE 1
Recommended installation

Position

The trap may be installed as shown in Fig. 1
with discharge downward or with bonnet on the
side. For freezeproof installation, it should be
positioned vertically or on its side. Make certain
that the arrow on the body agrees with the
direction of flow.

Discharge piping

To avoid excessive back pressures, discharge
piping should be amply sized. For short
discharge lines, (up to equivalent length of 10
ft.) use pipe equal to trap size. If several traps
discharge to a common return line or manifold,
size the line to prevent buildup of excessive
back pressure during the simultaneous
discharge of all traps. All piping and fittings
downstream of 151H traps must be 1” or
larger.

Series 151 - A trap

Union

Test valve
(Gate or Ball)

STRAINER

Series 151 traps have built-in screen. Install a
separate Yarway series 921 Wye strainer with
blowdown valve.

WARNING

Hot discharge from this product may cause severe
burns. Discharge must be piped away or directed
so that persons in the vicinity are not endangered.
This product must be isolated, vented and cool to
the touch before repairing or inspecting.

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VCIOM-05067-EN17/01

YARWAY PROCESS THERMOSTATIC STEAM TRAPS

SerieS 151

MAINTENANCE

Reassembly

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.

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.*

Trap remains
open and
is blowing
steam; is not
shutting off.*

*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.

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.

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.

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