Share your pump management policy

[hazel]

In our plant we switch the spare pump running every month. Most pumps are centrifigual and operated under low temperature about -40 degree C. The process fluid is methanol contained 40PPM H2S. Since the pupm mechanical seal fail easily, We want change the policy to switch pumps every half month.
Can someone give us your plant's policy?
We are appreciative your any experience or opinion.

 

[Atyrau]

Hazel,

This switching period seems a little extreme. I worked recently on a chemical plant where the main deaerator feed pumps were switched over every 6 months! The main factor here is the MTBF of the seals. It has always been my philosophy that pumps should be kept running for as long as possible, as starting and stopping is not good for the seal. If you know the MTBF, then plan switchovers accordingly.

 

[tothepoint]

I have to agree with Atyrau. Seals are delicate pieces of equipment and in many services frequent start/stop cycles can cause premature failure. Process fluids can solidify on the seal faces, O-rings can take a permanant set, and operators can get careless with proper start-up procedures.

 

[Paperpete]

I agree with previous and would like to add the following. The MTBF includes those units that failed early on. The actual life expectancy for the units still in operation at that time may very well be significantly longer. If you have many pumps of the same kind, running under similar conditions and if the seals are your main concern then I would encourage you to track the life of these seals. Of course if the failure of one of these seals causes severe problems then "going for broke" may not be a good idea. I would also suggest that you discuss this with a reputable mech seal manufacturer like Chesterton or Crane.

 

[unclesyd]

Pump seals should be high on a reliability check list of things to do. Most of our pumps were spared in place and wern't valved, not check valves, in until needed. We never ran a pump just for the sake of it. This went back to the stops and starts and in our case most pumps would have to be flushed after running due to the process.


First I would have someone, yourself, attend a good class or seminar dealing with pumps and seals.

When have you achieved a thorough understanding of the whys and wherefores get a program started to closely monitor the seals from receiving until they are in a basket.

It is of great importance to have some knowledgeable person around when a seal is changed or the pump is disassembled. I’ve seen many a seal killed during installation both in the shop and in the field. We had a pump shop and crew that handled all the chores dealing with seals and pumps.

As stated above get a good seal manufacturers representative involved. Make sure you get a knowledgeable one. This is where the additional time spent improving the basic knowledge comes in. Recently I’ve seen a decline in the technical ability of some representatives.

Here is good place to start.

http://www.mcnallyinstitute.com/index.html

Good Luck

 

[RotaryG]

What is going on? Pump seals themselves do NOT require frequent switching over. ie, one does not expecte the seals to fail just because the pumps were not operated, say, within the last few months.

Switching over is practiced by different companies for different reasons.

***** Most pumps are centrifugal and operated under low temperature about -40 degree C*****. I have seen seals of such pumps failing due to simple reasons DURING STARTUP. Are the pumps fitted with a) Proper vent connections so that prior to start-up the pump casings are vented (automatically) fully? b) Are the spare pumps provided with cold recycle line so that the working pump keeps the standby pump cool and full of liquid all the time?
c) Are the pump casings self-venting? or not? d) Are the seals experiencing 'hangover' and the elastomers are compatible with process fluid? e) What is the sealing arrangement? Single? Pusher type? Bellows? Double? f) What is the failure like?

More questions than answers, eh ?

If you are not careful, you may break the seals as frequently as you start the pumps !!