External gear pump - thrust plate design

[MRSSPOCK]

Does anyone have any input regarding thrust plate design with respect to external gear pumps?

There doesn't seem to be much information available.

I can only guess what is trying to be achieved by the geometry of the seal tracks, on images viewed online.

Thanks

 

[hydtools]

I suspect that the design specifics are company intellectual property. Generally, the design provides a pressure bias to keep the plates forced against the gears to reduce leakage, increase efficiency. It also allows greater dimensional tolerance for the gear chamber depth and gear width.

Ted

 

[hydtools]

And the plates provide replaceable wear surfaces for pump repair.

Ted

 

[MRSSPOCK]

Thanks hydtools, for confirming my assumptions.

I assume the various seals with multiple tangs are only to help keep the seal correctly positioned?

I also assume that the plates with holes drilled are lubrication channels?

Would those assumptions be correct?

One other query, why does the outer seal not need an anti extrusion plastic backup ring?

Is it because at the central location, (where they have the backup ring), that the low and high pressure are so closely located to one another, i.e. just the width of the seal, whereas at the outer seal, there is quite a lot of face to face flange contact before full exposure to full atmospheric pressure is encountered?

Thanks again

 

[hydtools]

The holes communicate pressure to the seal side of the plate in order to load the plate against the gears.
The outer or housing face seal requires no anti-extrusion backup seal because there is zero clearence between the mating faces. There is no extrusion gap into which the seal could be forced.

Ted

 

[MRSSPOCK]

Thanks again.

Now I've got it.

I hadn't been considering the wear plates thickness variation which could permit extrusion.

So one more question, although it is maybe silly.

Can you think of a way to get a few unique backup rings made at a reasonable price?

Would 3D printing be an option?

Would you have any idea what material would be required.

The fluid would just be regular hydraulic oil, if there is such a thing.

 

[hydtools]

You could try here:

http://www.allsealsinc.com/rubber.html

I don't know what a reasonable price would be.
The material could be what Parker calls "hard rubber".

Ted

 

[MRSSPOCK]

Dead on hydtools.

I rang them and they said they a have a few methods for creating odd ball profiles.

I can't imagine they will be cost effective, but once I know what I want, they said they will gladly quote for even a small batch.

Until then .....

Thanks