In this video, Product Manager Mike Fick shows you how to repair a 2” Lever-Operated Dump Valve. You can find the step-by-step instructions below.
How to Disassemble a Dump Valve
This is a Diaphragm Balanced Dump Valve. Later we’ll look at the differences when repairing a Piston Balanced version.
- Firstly, start by securing the valve in a vise.
- If you have an original hub design, you will need to remove the trunnion plug, loosen the stuffing box nut, loosen the set screw almost completely, and use a punch to remove the shaft.
- Remove the stuffing box assembly from the bonnet.
- Remove both square keys.
- If you have a new style hub design, there is no set screw, and so you will only need to remove the nut and washer and slide the hub off.
- Remove the follower, teflon packing, and packing ring from the stuffing box assembly. In addition, keep the follower as it is not included in the repair kit.
- If they didn’t come off already, remove the gaskets from both sides of the bonnet.
- If the shaft is bent, it may be necessary to cut it off, then tap the trunnion shaft out through the stuffing box.
- Remove the four bolts from the bonnet and remove the bonnet.
- Re-secure the body in the vise at a 90-degree angle.
- Use a large punch to tap out the cage assembly from the bottom through the top. Be careful to remove it in a controlled manner and not let it fall out, which could cause damage or injury.
- Remove the gasket from inside the body.
- Secure the cage assembly in the vise.
- Using a wrench to hold the stem in place, insert a punch or screwdriver into the trunnion hub eyelet to unscrew it from the cage.
- Remove the diaphragm and the plate.
- To disassemble the trunnion hub, remove the snap rings.
- Remove the links and pins from the stem nut and hub.
- Remove the o-ring from the cage and remove the cage from the stem.
- Place the stem in the vise and wrench loose the lock nut.
- Remove the seat disc and soft seat.
- Remove the ratio plug.
How to Inspect a Dump Valve for Damage
- Start by inspecting the ratio plug. If you see an excessive amount of corrosion or erosion, it will need to be replaced.
- Inspect the bottom surface of the cage. If you see an excessive amount of corrosion or erosion, or any damage that could create a leak path between the cage and seat, discard and replace. This one will need to be replaced.
- Inspect the main trunnion shaft. If it is bent, it needs to be replaced.
- Inspect the sealing surfaces on both sides of the bonnet for pits or other potential leak paths.
- Inspect the stem. Make sure the threads are intact the stem is not bent, and the communication hole is clear of debris.
- Inspect the stem nut, Make sure the threads are intact, there is no severe pitting, and the communication hole is clear of debris.
- On the valve body, inspect the threads on the inlet and outlet to make sure they are intact.
- Inspect the seat area where the gasket will sit. Check for severe washouts anywhere inside the valve.
- Clean the interior and exterior to make sure it’s free of all solvents, debris and fluids that may damage elastomers and affect o-rings and gasket seals.
- Run all the parts through a parts washer. If you don’t have one available, use a wire brush, degreaser, and the appropriate PPE to get them as clean as possible.
How to Assemble a Dump Valve
For this re-assembly, we’ll be using new components to walk through the process.
- Place the new o-ring onto cage.
- With the stem upside down in the vise, place the ratio plug onto the stem. In our newer models, the ratio plug comes standard in Delrin.
- Grease and assemble the new style seat from the repair kit. This replaces both the old seat disc and seat. The new seat is reversible, effectively doubling its life span. If one side is worn, flip the seat to use the other side.
- Thread on the lock nut, then flip the stem assembly and re-secure it into vise.
- Place the cage on the stem assembly, followed by the stem plate with the serrations facing outward.
- Attach the diaphragm.
- To build the trunnion hub stem nut assembly, attach the 2 links and pins and 4 new snap rings.
- Apply lock tight, and thread the not onto the stem.
- Grease the o-ring, the shoulder where the gasket will seal, and the gasket.
- Secure the body in the vise and insert the cage assembly with the hole facing the same direction as the valve connection. If needed, use a mallet until the cage seats. The diaphragm should be flush with the machined surface. Make sure the flat side of the hub assembly is on the bottom.
- While holding up hub assembly, place the bonnet on the body. For the standard assembly, the rounded side should face away from the inlet.
- Attach the four bonnet bolts in a criss-cross pattern to avoid misalignment.
New Style Plug, Shaft, and Stuffing Box
- Firstly, grease the shaft and insert the thicker end into the bonnet as shown.
- Slide the bushing into the trunnion plug, add the o-ring, then grease them both.
- Thread the trunnion plug into the bonnet and tighten with a wrench.
- To assemble the stuffing box, start by placing the teflon bushing on the shaft.
- Add the new o-ring, being careful to not cut the o-ring on the edge of the flat.
- Install the o-ring around the outside of the stuffing box, then apply grease.
- Slide the stuffing box onto the shaft and tighten with a wrench.
- Install the new hub with the arm attachment slot facing away from the bonnet. Attach the washer and nut and tighten until snug.
- Finally, complete the assembly by attaching the lever bar.
Old Style Plug, Shaft, and Stuffing Box
- If you’re reusing the old-style hub assembly, installation will look a little different starting from once you’ve bolted the bonnet to the body.
- Insert the shaft into the hub.
- Insert the shorter square key into the keyway in the shaft. Tap into place with a punch.
- Install the new gasket on the trunnion plug, making sure the it rests against the shoulder of the plug. Apply grease to the gasket and then tighten the plug with a wrench.
- Install the washer onto the shaft.
- Install the gasket onto the stuffing box and grease.
- Thread the stuffing box onto the bonnet.
- Install the packing ring with teflon packing, follower, and nut onto the shaft.
- Install the hub and the longer square key.
- Tighten the set screw until snug.
There are only a few parts that differentiate the Piston Balanced from the Diaphragm Balanced Dump Valve. We’ll look over those differences now.
- Once you remove the piston assembly from the body, secure it in a vise.
- Use a wrench to hold the stem in place.
- Insert a punch or screwdriver into the trunnion hub eyelet to unscrew it from the cage.
- Remove the piston with the o-ring and two back-ups, and remove the cylinder from the cage.
- Remove the two o-rings from the cylinder, and remove the piston seal retainer and the o-ring.
- Next, remove the o-ring from the cage.
- Finally, remove the cage from the stem.
- Flip the stem over and secure it in the vise to remove the nut, seat disc, and ratio plug.
- Inspect all the parts for excessive corrosion or erosion or any damage that could create a leak path.
- Inspect the stem. Make sure the threads are intact and the stem is not bent.
- To reassemble, repeat this process in reverse, greasing all of the new gaskets, o-rings, and backups as they are applied.
If you have further questions about the Dump Valve or any Kimray product, contact your local Kimray store or distributor.