Question:
I will be replacing the check discs on a 4” Febco model 850 DCA. Can you give me some ideas on how to repair this assembly and if there are any special tools I will need?
Mark:
Fortunately, there are no special tools required to repair the Febco model 850. The check valve covers are sealed with an o-ring and secured by bolts. This model has springs that are contained as a spring module. The spring module is positioned against the check cover and creates a very slight spring load when the cover is removed. Once the check valve cover has been removed, the first thing you will notice is that the spring assembly will fall down against the check valve body. Don’t be alarmed; the unit is not falling apart in front of you. One end of the spring assembly is held in place by a recess in the lid.
Doug:
The next step is to remove the check valve from the body. The check assembly is sealed by a gasket and secured by four threaded studs that mount through the body wall. On the exterior of the check valve body, you will notice four 7/16” lock nuts. Once the lock nuts are removed, then the seat assembly can be removed from the body with the check disc, arm assembly, and spring assembly still attached. Before the check assembly is removed, make sure you have a new seat gasket to replace the old one.
Mark:
Once the check assembly is out of the body, the seat, arm assembly, disc, and spring assembly can be serviced. The first step is to examine the seat and arm assembly carefully for any damage. Be sure to look for wear on the hinge pin as well. It is important to note that the seat and arm are considered one assembly and should both be replaced if there is any damage. Next, we can look at the spring assembly. The spring assembly attaches to the arm with a hinge pin. If the spring assembly is damaged or worn, it can be replaced separately. The last step will be to inspect or replace the check disc assembly.
Doug:
The check disc is vulcanized and cannot be inverted (flipped). The disc is attached to the arm assembly by a stud and a jam nut. Simply remove the nut and replace the disc if needed. Note that the disc will have some play where it attaches to the arm assembly. This play, or “wobble,” is essential so that the disc can seat correctly. Be careful not to over-tighten the stud to make it snug. When you reinstall the check valve assembly into the body, tighten the lock nuts back equally so the seat does not warp. As you reassemble the check cover, be aware that the spring assembly will have to be set back into the recess in the cover.
