Question:
I have a 4” Apollo DCDA 4A that needs service. I am not familiar with this unit. What is the best way to remove the check valves from the body? Can the check discs be replaced?
Mark:
The Apollo DCDA 4A began production in 2008 and is a double check detector assembly (DCDA). The body is made of stainless steel and no special tools are needed to repair the 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 removed by lifting it from the body. A flat head screwdriver can help to pry it from the body. Once the cover has been removed, you will be able to service the check modules.
Doug:
It is important to remember that the first check valve must be removed before the second check valve can be removed. The check modules for this assembly are each secured by a retainer and sealed by an o-ring. Each retainer consists of a stainless steel spacer 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 spacer will come out when the check 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 procedure. 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 retaining plate 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.
Doug:
Once the check valve module is reassembled, it can be installed into the body. Be sure to replace and lubricate the check o-ring. The check module will push straight into the body bore. Once the stainless spacer ring is placed against the check module, 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.
