How to Replace the Seals in a 1:1 Piston Separator Gauge Protector

Posted on Oct 03, 2018 by Kathy DeGlandon

How to Replace the Seals in a 1:1 Piston Separator

The 1:1 piston separator gauge protector (CD136) is fitted with seals that assist the gauge protector in sensing and transmitting pressure to a hydraulic pressure gauge. When the seals becomes worn or damaged, they will need to be replaced.  Using a replacement seal kit (CKT211-1), follow these steps to replace the seals in your 1:1 piston separator gauge protector.

What You Will Need: 

  • CKT211-1 Repair Kit for 1:1 Piston Separator (CD136)
  • Check Valve (CC102)
  • 3/8x3" Bolt (or longer to pull piston out of housing)
  • 5/8" Wrench
  • Dnetal Pick or Similar Tool
  • Snap Ring Pliers
  • O-Ring Grease 
  • Teflon Tape
  • CD136 Piston-Style Gauge Protector


Step 1. With 1:1 piston separator gauge protector in the upright position, remove the check valve from 1:1 piston separator housing with 5/8th wrench. Check valve must be removed in order to remove hammer union.

Step 2. After check valve is removed, remove hammer union from 1:1 piston separator housing by slipping hammer union over top of separator. Piston separator housing will be in the upright position. Set hammer union aside.

Step 3. After the check valve and hammer union are removed, turn over the piston separator housing to reveal the piston.  The check valve hole is located at the top of the housing, and the piston can only be viewed from the hole underneath the housing.

Step 4. Once the separator housing is turned upside down, remove snap ring located at the mouth of the housing. For best results, use snap ring pliers. The CKT211 comes with a replacement snap ring, and it should be replaced when the seals are replaced.

Step 5. Thread 3/8-16x3” (or longer) bolt into center of brass piston inside separator housing. Use this bolt to remove piston from housing. If more leverage is needed, then use a longer bolt. Bolt is only needed to pull the piston out of the housing and is not part of the regular, completed piston separator. If more leverage is needed, a longer bolt may be necessary.

Step 6. Once piston is removed and with bolt still in place, remove both seals from brass piston with dental pick or similar tool.  Clean all grease, lubricant, and debris from piston grooves. Be sure to remove all debris from piston. Failure to do so can damage seals.

Step 7. Using a rag or paper towel, clean out piston housing of all grease, debris, and foreign matter. Be sure to remove all debris from piston housing. Failure to do so can damage seals.

Step 8. Grease as much of interior of separator housing as possible with a silicone-based 0-ring grease.  Greasing the housing will ensure that the piston move freely inside the housing.

Step 9. With temporary bolt still on piston, use a dental pick or similar tool to replace seals on piston. For best results, replace the top-most then bottom-most seal.  Then, grease piston with silicon-based 0-Ring grease.  Temporary bolt will help to keep hands clear of grease.

Step 10. With temporary bolt still on piston, insert piston into bottom of separator housing. Sink piston all the way into the piston housing until it is in the top-most position. Doing so will assist in removing air from the piston housing and make pumping up with fluid easier. Unscrew temporary bolt and remove.

Step 11. Using snap ring pliers, replace snap ring before flipping the separator housing over to its upright position. Be sure to use new snap ring provided in CKT211-1 repair kit.

Step 12. Now that separator housing is right-side up, replace 1502 hammer union.

Step 13. Put Teflon tape on check valve thread. Using 5/8th wrench, replace check valve in check valve hole. Now that seals have been replaced, the piston separator will need to be recharged with hydraulic fluid.

Important Safety Notice

Proper service and repair is important to the safe and reliable operation of all Crown Oilfield Instrumentation equipment. The service procedures recommended by Crown Oilfield Instrumentation and described in the service guide are recommended methods of performing service operations. Some of these service operations require the use of tools specially designed for their purposes. These special tools should be used when and as recommended.

 It is important to note that some warnings against the use of specific service methods stated in the guide can damage the equipment or render them unsafe. It is also important to understand these warnings are not exclusive. Crown Oilfield Instrumentation could not possibly know, evaluate and advise service personnel of all conceivable methods in which service might be done or of the possible hazardous consequences which may occur. Accordingly, anyone who uses service procedures or tools, which are not recommended by Crown Oilfield Instrumentation, must first thoroughly satisfy himself that neither his safety nor equipment safety will be jeopardized by the method selected.