Question:
I am servicing a 4” Conbraco model 40-700. The first check on the mainline assembly is not passing and I want to change out the check rubbers and replace the seat. Can you tell me about this assembly and how to service the check valve?
Mark:
The Conbraco/Apollo 40-700 is a reduced pressure principle detector assembly that was made in 3” through 10” sizes. Production of this model began in 1993 and was discontinued in 2012. The body is made of ductile iron and has a blue epoxy coating. The bypass assembly used for this model is a ¾” 40-200 reduced pressure principle assembly. Only standard tools are needed to replace the check discs. However, a special tool is needed to remove the check seats.
Doug:
The access covers will have to be removed in order to service the check valves. The covers are o-ring sealed and secured by bolts. There is a slight spring load on the cover, but the check springs are completely contained. Slowly loosen the bolts about ½” until the spring tension is released. Once you verify that the pressure is off the cover, then go ahead and remove the bolts and cover
Mark:
This assembly utilizes center stem guided check valve assemblies. Once the cover has been removed, the checks can be lifted up and out of the seat and body. Be careful to not hit or nick the inside epoxy coating when removing the checks. The spring tension does not have to be released to replace the rubber disc. Unthread the retaining nut from the stem and remove the stainless disc retainer. The rubber disc is now free to be replaced.
Doug:
The check seat for the 40-700 is threaded into the body and sealed by an o-ring. A special tool is required to unthread the seat from the body. There are no seat tools in production at this time, but a tool can be made from 3” steel pipe. The pipe should be cut 10” in length with two slots on one end to match up to the seat guide supports. On the other end of the tool, drill holes through the pipe to facilitate a handle. Once the tool is complete, position it in the center of the seat and unscrew counter-clockwise. The new seat should be threaded into the body by hand. When hand snug, use the tool until the seat is fully tightened into place.
