Purpose of Seal Water Line To Pump

[tnboy82]

As a piping estimator, I'm always interested in the purpose of equipment and general design in water and wastewater treatment plants. So this question is solely for my curiosity.

What is the purpose of a seal water line going into a pump casing? Does it fill some sort of diaphragm that seals in water? Does it ensure that the impeller cavity is completely full of water, so that air won't be trapped at start up?

Thanks for your time.

 

[Artisi]

Its purpose is basically to supply water to the shaft sealing system which will be either a mechanical seal or packing gland which require lubrication or cooling.

 

[JJPellin]

To expand on the point already made, the seal water is generally used to cool the seal or to displace the pump product which may have poor properties for use in a mechanical seal or packing. If the product is abrasive, for example, a cleaner stream of seal water might be used to fill the seal chamber so that the mechanical seal is running on this clean water rather than the abrasive process water. The water introduced as seal water usually leaks externally (for packing) or leaks internally into the product stream. So, for most cases, the flush water has to be compatible with the product stream. The cost of this flush also needs to be taken into account. Downgrading high-value ,clean water into a dirty stream can be very expensive. You could search for information related to an API Plan 32 seal flush system if you want more details.

Johnny Pellin

 

[pumpking]

A little more into hw it works is that the liquid comes from the high pressure part of the casing (caused by centrifugal energy) and into the lower pressure seal area thus unsuring a constant flow of liquid to flush or keep debris moving if present in the liquid. On larger pumps there are sometines orifice plates to ensure the pump is kept efficient and simply not recirculating within itself.

There is also new 'bell mouthed stuffing box' technology which eliminates the need as much for the flushing, and recirculates internally - clearly tappings and small pipework has smaller material thicknesses and so if priduct is corrosive, leakage can occur. it is referred to as API flushing plan 01

Ash Fenn

http://www.cdrpumps.co.uk

 

[tnboy82]

Thank you all for your answers, your time and insight is appreciated.