shaft seals

[ian600]

Hello ,

I am seeking to quantify the correct loading for length packing . Specifically I refer to the technique known as “ live loading” where a standard compression spring energises rings of length packing to create a shaft seal . This technique can be used in both reciprocating and rotary applications . What is the correct loading ? Does it vary according to conditions ? eg packing type / surface speed etc

I’m keen to discuss the matter with anyone who knows…

 

[pumpking]

For small centrifugal pumps (up to about 6" we used to use the theory of about 10 drips per minute of liquid - it is important that there is some dripping to ensure that the gland packing is lubricated along its diameter and doesnt burn the shaft. Overtightening only causes excessive wear of both packing and ultimately shaft.

Not sure if this helps ??

Ash Fenn

http://www.cdrpumps.co.uk

 

[Artisi]

The correct loading is as pointed out by pumpking - a load sufficient to seal the shaft but also to allow a small leakage for packing/ shaft lubrication.

You have virtually answered your own question - it will depend on packing type and pressure you are sealing against.
The problem I see with this type of arragement when first installed it may well have the correct load, but as the packing compresses and wears overtime the spring force will reduce and leakage will increase.

 

[JJPellin]

I don't recall ever seeing live loaded braided packing in a pump. I have seen live loaded structured packing in a couple of reciprocating pumps. This technique is most common in my industry in control valves. I don't have the answer to your question. But someone with expertise in control valve packing might know.

Johnny Pellin