QUESTION:
I am working on a 4” Apollo RP4A. Can you tell me about this assembly? How do I replace the check valve discs and service the RV?
MARK:
The Apollo RP4A is a reduced pressure principle assembly for which production began in 2008. The body is made of stainless steel and no special tools are needed to repair this assembly. This unit has a single access cover for both checks which is sealed by an o-ring and has no spring load. The first thing you will notice is that the access cover is secured by a v-band clamp. To remove the clamp, simply loosen the lock nut until the latch can be disengaged from the t-bolt. The band can now be taken off and the cover can be removed by lifting it from the body. A flathead screwdriver can help to pry it from the body as well. Once the cover has been removed, you will be able to service the check modules.
DOUG:
When servicing the check valves, it is important to know that the first check assembly must be removed before the second check valve can be removed. The check modules for this assembly are secured by retainers and sealed by an o-ring. Each retainer consists of a stainless steel retaining ring and a spring clip. To remove the spring clip simply pinch the clip ears together and pull it straight out of the body. The stainless steel retaining ring will come out when the module is removed. The check module can now be pulled straight out of the body.
MARK:
Both the first and second check modules require the same service procedures. The spring tension is contained so the seat and rubber disc can be easily inspected. It is important to not remove any hardware from the spring side of the module. There are four lock nuts located on the retaining plate on the back of the check valve that must be removed. Once these are removed, the disc retainer can be separated from the module. The rubber check disc is located in the retainer and is ready to be inspected or replaced. The check seat is part of the check valve module and cannot be removed. If the seat is damaged, the complete check module will need to be replaced. To reinstall the module, be sure to first replace and lubricate the check o-ring. The check module will push straight into the body, and the stainless retaining ring will rest against the module. Now the spring clip can be installed. The best way to do this is to insert the end of the clip into the body groove first. Then pinch the ears together as you insert the rest of the clip. The clip will snap into place when it is fully seated.
DOUG:
To service the RV, the sensing line will need to be removed. The RV cover is secured by a v-band clamp and sealed by the diaphragm. Once the clamp is removed the cover will pull away from the body. Remove the RV module by grasping the diaphragm plate and pulling straight out of the body. To change the disc, simply remove the retaining bolt and washer. To replace the diaphragm, hold the diaphragm washer firmly and remove the retaining bolt (be aware that the module is spring loaded). Once the retaining bolt is removed, the stem, bushing and spring are free and ready to inspect. There is an o-ring on the stem that should be replaced if it is worn. Reassemble the RV in reverse order and push the module straight into the body. Make sure the outer edge (bead) of the diaphragm fits into the groove on the body before replacing the cover.
