MKS HPS Two-Stage Manual De Servicio página 16

Chapter Two: Servicing an HPS Products Two-Stage Valve Disassembly of the main valve
To soak the valve, 1) remove the bypass valve (see pg.4 on bypass valves). 2) Prepare a bath of
warm deionized water. 3) Immerse the valve to the body flange. Do not allow water inside of the
bellows since it is very difficult to remove (even with baking), it can damage the stem guide bearing,
and it can rust the spring.
It may be necessary to soak the valve for up to one hour before the buildup will loosen enough to
allow the assembly to be pulled out.
Once the internal assembly is removed, three O-rings will be visible: the actuator cap seal, bonnet
seal, and the nosepiece seal.
To replace the actuator cap seal and the bonnet seal, sit the O-ring in the groove.
Remove the nosepiece O-ring only if a new replacement is available. To remove the old O-ring, 1)
insert a sharp pointed tool, such as a machinist's scribe, obliquely into the ring. The sharp point must
not pass through the seal, or the groove surface will be damaged. 2) Lift the seal out with the scribe.
3) To replace the seal, position the nosepiece so that the groove faces upward. The bottom of the
groove and surfaces of the new O-ring should be clean and free of scratches. If necessary, a suitable
solvent may be used to clean the groove. Particulate contamination may be blown off with dry
nitrogen. 4) Place the proper O-ring on top of the groove. 5) Place your thumbs on the O-ring at
points 180 degrees apart, and push the O-ring into the groove. Do not twist the O-ring while pushing
in. 6) Continue to push in opposing intermediate points, until the ring is uniformly in place.
Internal rebuild assembly kits are available. Disassembling the internal assembly is hazardous and
not recommended. A new kit easily slides into the cleaned valve body.
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