Emerson Fisher HP & EH Instruction Manual download pdf (Page 14)

Instruction Manual

D100392X012

EH Valves NPS 8 through 14

July 2014

5. After lapping, again disassemble as necessary, clean the seating surfaces, reassemble, and test for shutoff. Repeat

the lapping procedure if necessary.

Trim Replacement

After all trim maintenance has been completed, reassemble the valve by following the numbered steps below. Be

certain that all gasketed surfaces are clean. Key numbers referenced in this procedure are shown in figure 12 for the

EHD valve and in figure 14 for the EHT valve.

CAUTION

Thoroughly clean the seat ring (key 6), the seat ring cap screws (key 7), and the cap screw threads in the valve body with a

good-quality degreaser. Unless the valve is to be used for oxygen service, thoroughly lubricate the cap screw threads and

the underside of the cap screw heads with one of the lubricants (or equivalent) shown in table 7.

Failure to lubricate as described may cause galling and improper seat ring gasket or O-ring (key 12) loading which may

result in leakage.

WARNING

If the control valve is to be used for oxygen service, use the lubrication procedure above, but substitute a lubricant that has

been approved for oxygen service. Use of unapproved lubricants creates a fire or explosion hazard.

1. Install either the seat ring gasket or the O-ring (key 12). Place the O-ring in the O-ring groove in the seat ring before

installing the seat ring in the valve body. Install the seat ring (key 6) and secure it with the seat ring cap screws (key

7). Torque the hex socket head c ap screws in a criss-cross pattern with no more than 20 NSm(15lbfSft) of torque.

When all are tightened to 20 NSm(15lbfS ft),increasethetorque20NSm(15lbfS ft) without exceeding the torque

valuespecifiedintable7,andrepeatthecrisscrosspattern. Repeat until all cap screws are tightened to the torque

value specified in table 7. Repeat the final torque and if any cap screw still turns, tighten every cap screw again.

2. Install one of the cage gaskets (key 11) between the valve body and cage (key 2), and install the cage.

3. If the cage used has multiple sizes of windows, attempt to orient the largest window toward the valve body web (a

shelf-like projection of the casting into the flow cavity). As an alternate reference, orient the largest window toward

the process outlet for a flow-down and toward the process inlet for a flow-up valve.

4. Inspect the valve plug stem threads for any sharp edges that m ight cut the packing. Use a whetstone or emery cloth

to smooth the threads if necessary.

5. To install the piston rings or seal ring (key 8), proceed as appropriate:

For an EHD valve, if installing a new piston ring, the replacement piston ring will arrive in one piece. Use a vise with

smooth or taped jaws to break this replacement piston ring into halves. Place the new ring in the vise so that the jaws

compress the ring into an oval. Slowly compress the ring until the ring snaps on both sides. If one side snaps first, do

not try to tear or cut the other side. Instead, keep compressing until the other side snaps.

Remove any protective tape or c overing from the valve plug and stem assembly, and set i t on a protective surface.

Then place the piston ring in the piston ring groove with the fractured ends matched.

For an EHT valve, install the seal ring (key 8) onto the valve plug (key 3). Install the ring with the open side facing the

seat ring end of the valve plug for a flow-down application (view B of figure 14) or with the open side facing the valve

stem end of the valve plug for a flow-up application. Slide the backup ring (key 9) onto the valve plug. Secure with the

retaining ring (key 10). For an EHT valve with a Whisper Trim Level D cage, install the piston ring (key 30, figure 14)

using the procedure given in the EHD instructions immediately preceding this paragraph.

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Emerson Fisher HP & EH Instruction Manual Page 14

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