3 replies to this topic

[GTE]

All

hope all is well for everyone.

 

I am writing a specification for a power plant.

 

"Mechanical sealing system shall be used on all pumps".

 

Do you believe it is an over specification for the plant? YES or NO.

May you please justify your answer.

Many thanks in anticipation for your help.

Regards,

GTE.  

 

[RAM1975]

No it will not be overspecification,however it will be zero discharge to environment.

[GTE]

I need to get clarification about the mechanical seal.

one of our contractor on a project seems to be willing to provide mechanical sealing only for oil pumps, high temperature water pumps, CEPs and BFPs. 

does somebody knows what is behind this request. what other pumps are they referring to? and what would be the cost involved in requesting mechanical seal for all the pump.

 

And please if you feel that this question is already answer somewhere please direct towards the answer. incidentally I checked before, but you never know.

Many thanks in anticipation,

Regards,

GTE

[GTE]

Hi 

doing some parallel research somebody has replied this to me. so I share their answer for the future reference of somebody else.

 

"I suspect the answer (and the answer to most things) is that it is about money. Typically, a mechanical seal (and it ancillaries) will be more expensive than gland packing, so I am assuming that the contractors want to know what to allow for, so that they are on a level playing field.

 

The contractor’s comment has some logic to it – you do not want leakage of fluids that are either hot or flammable/ dirty and for the CEPs, you would want a mechanical seal to ensure that you do not pull air into the pump under vacuum.

 

Having said that, you are correct, the decision on whether to use a mechanical seal is a detail issue and does not need to made right at the beginning of the project.

 

Gland packing is cheaper and (usually) simpler to maintain. It requires a certain amount of leakage to operate, so requires a safe place to drain away to – we (#####) supplied a number of pumps to a power plant in ##### a few years back and the closed cooling water pumps had gland packing specified with a drainage system that went back to a nearby place. Unfortunately, the cooling water was a water/ glycol mix (anti-freeze) and would have done the lake water no good, so we retrofitted mechanical seals at a later date. For small, general service water pumps, gland packing is fine.

 

For very small pumps, where the cost of the mechanical seal is a matter of pounds, some manufacturers will only fit mechanical seals, because the cost of changing standard parts lists and drawings is more than the supplying the seal. "