Are Piston & Rod Wear Rings Interchangeable?

Whitepapers On Whiteboard

Expert Level
Jesse Thomas
Jesse Thomas

Are Wear Rings Interchangeable

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Video Transcript

Wear Ring Diagram

Today we are going to talk about the differences between piston and rod wear rings.

What I’ve got up on the board – you can kind of imagine –on this side [left] we’ve got your piston groove. Where you have this piece of metal running inside of your cylinder.

And on this side [right], you’ve got your cylinder head where the rod is going to be sliding in here. If you know what a wear ring is, it supports your moving piece of hardware, here in the case of the piston, and stops it from banging the inside of your cylinder. How are you going to get this super rigid, tough material wear ring to fit into its groove when you’ve got this extra piece of metal, this lip, keeping it from falling off? You can’t just bump it in and slide it over because you have a larger diameter.

What’s the answer? You cut it.

There are three types of cuts. The butt, the step, and the angle cut. They are all essentially the same for the purposes of this discussion.

The same question over here.

How are you going to get this rigid rod wear ring inside when you’ve got the larger diameter for the wear ring OD and the smaller diameter where you’re going to have to allow the rod to slide through?

The answer again is to cut it.

What are the differences between these two? Are they interchangeable?

The answer is no.

PISTON WEAR RING: The fundamental difference is that the piston wear ring you’re going to want to stretch it and allow it to collapse into its groove to eliminate its gap as much as possible.

ROD WEAR RING: The opposite is true for the rod wear ring because you are going to want to crumple it into a smaller diameter and allow it to spring and expand to that larger diameter.

Let's go out to the shop and I'll show you.

Wear Rings Shop

We are out here at the mobile hydraulics training center where we train our salesmen and engineers on how to rebuild hydraulic cylinders.

What I’ve got on the bench are two cylinder head glands like you’d see on the back or front of a piston cylinder, as well as two pistons.

What I’m going to show you is how to install the rod vs the piston wear ring on each of these.

Installing the Rod Wear Ring

Rod Wear Install

Like we saw on the whiteboard, how do you get this larger diameter rigid wear ring through the lip into where it seats on the inside?

The answer is:

  • You crumple it up
  • You put it through
  • And allow it to expand

And that’s going to stay right where we want it because it’s forcing itself outwardly.

Installing the Rod Wear Ring

Piston Wear Install

The opposite is true on the piston. This time we don’t want to force itself out. That will just cause it to flop out without any warning. Instead, we want it to collapse inwardly. That’s why on the piston wear ring we have very little space initially.

  • We pull it apart
  • And allow it to collapse into its gland

This is on pretty tight, and it’s not going to fall out during assembly.