A bit more about the throat bushing

[AngelM]

I would like you to explain to me a bit more about the throat bushing features.
How is fixed to the housing? I mean about the tolerances in the outer diameters.
Does The piece is held in position only by effect of the pressure difference between the seal chamber and the rear impeller or need to be fixed due external tolerances with regard to the housing?

What kind of material are usually used?

For a API PLAN 32 with water external fluid and a shaft of 50mm wich would be the appropiate clearance or it depends only on the different pressure?

 

[flexibox]

In the good old days the bush was pressed into the stuffing box by means of interference fit. the materials can vary depending on application and pump type, ie API or ANSI. with water you can use Phosphur Bronze and typical clearances API used to be 0.65mm diameteral clearance. If you have shaft deflection the Phosphur Bronze will not damage the shaft in the event of pick up. If you are using plan 32 then the tighter the better to keep the solids away but you should consider shaft deflection too. Other materials that have been used Carbon fixed bush and floating bush design, Hastelloy, Monel etc

 

[AngelM]

Depending on the housing shape, can you use an stationary part of graphite with O-ring or rubber cup (floating) if the diameter clearance is acceptable? Is there no problems of moving inwardly of the chamber, or the pressure difference make it not posible?

Which is the usual interference if you use bronze, for instance? because it has to be easy to install, I guess.

 

[flexibox]

do not rely on Oring because over time this will lose interference and come off. if you have a few thou (0.002")interference that should be fine. If you have a good lead (chamfer) you can press it in without any difficulty.