Question:
I am servicing a 4” Apollo Model RP4AN. Can you tell me about this assembly, and how to replace the check valve discs and the relief valve’s rubber parts?
Mark:
The Apollo RP4AN is an “N” shaped reduced pressure principle assembly. Production of this assembly began in 2008. The body of the 4” size is made of stainless steel and no special tools are needed to repair this assembly. This unit has separate access covers for each check. The covers are sealed by an o-ring and there is no spring load during removal. The first thing you will notice is that each 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 flat head screw driver can help pry it from the body if needed. Each of the check modules for this assembly are secured by a retainer and sealed by an o-ring. The check retainer/spacer is made of black plastic and resembles a cage. Once the check cover has been removed, simply lift the retainer out of the body. The check module can now be pulled straight out of the body by the wire handle.
Doug:
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 remember 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 disc 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.
Mark:
Once the check module is reassembled, it can be installed into the valve body. Be sure to inspect and lubricate the check o-ring. The check module will push straight into the body. The plastic retainer/spacer is then set down over the check module. Please note that the retainer does not fit tightly in the body and is held in place by the cover. Replace the V band clamp and tighten the lock nut.
Doug:
To service the relief valve, 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 can be inspected. 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.
