Pump suction strainer dilemma

[Wkcoo]

Hi all, how do you resolve frequent seal failure / pump seizure due to particle presence in the product?

I am thinking about reducing mesh size of the pump suction strainer, but am worried about the operability (technicians would not be happy to clean the plugged strainer frequently).

A seal plan change to cyclone / filters is not well perceived as it is pricey and some say the cyclone will get clogged as well.

 

[TugboatEng]

Why make the question so vague? Is the product you're pumping top secret/classified or are you arguing against a solution and are trying to prove someone else wrong?

 

[1503-44]

Not to mention, that with no additional information, the solution is the obvious one.
Give maintenance some job security.

 

[JJPellin]

What sort of pump would seize up from particles in the pumpage?

Johnny Pellin

 

[TiCl4]

JJPellin - lobe pumps and other PD pumps with very tight tolerances will seize up from very small particles entering those tight tolerances, then rolling and binding the impeller. I've experienced this several times with lobe pumps stopping up during commissioning from grinding particles that probably didn't even measure 1mm in diameter (and this was after triple rinsing the associated equipment before starting the pump).

Also, if the particles are large and sticky and you are using a centrifugal pump, the particles can agglomerate around the impeller and continue growing until they contact the pump casing, at which point the pump seizes up.



There are lots of possibilities for solutions. Alas, the OP did not provide any necessary details for us to help him.

 

[Artisi]

Wkcoo, getting a seal manufacturer / supplier involved is usually the easiest way to get a good answer.

It is a capital mistake to theorise before one has data. Insensibly one begins to twist facts to suit theories, instead of theories to suit facts. (Sherlock Holmes - A Scandal in Bohemia.)

 

[Wkcoo]

my situation is similar to what TiCI4 describe. Centrifugal pump in oil and gas refinery setting.

Typical particles can be corrosion particles (can range from smaller than 1mm to as big as 3mm) in size, or some congealing service. The congealing is at least "solvable" in my unit by steam flushing the pump.

The pain point is definitely those particles. Mech seals failure are quite frequent(3-4 yrs on avg) seal face deep grooves, flush line plug, seal face crack etc, all sort of things happened.

In your industry typically what is the pump mtbf? And how do you all solve this kind of issue?

 

[TiCl4]

Wkcoo,

I don't work in O&G, so I don't have directly applicable experience. However, in the applications where seal failure was due to ingress of particles from the pumped liquid onto the process-side seal face (single mechanical seal arrangement), our MTBF was extended by introducing two things:

[ul]
[li]A restriction bushing on the process-side of the mechanical seal[/li]
[li]A clean liquid (water, in our case) flush in between the seal and the restriction bushing. Flow had to be sufficient (10-15 gallons per hour) to pressurize this interstitial space and prevent ingress of process fluid/particles.[/li]
[/ul]

With this arrangement, our MTBF for seals in that particular application went from 3 months to 15 months. The caveat for this, of course, is that you have to have a source of liquid that is both clean and permissible to dilute into your process-side fluid.

If that isn't a possibility, then you will likely just have to filter out the particles beforehand. If this is a toxic/flammable liquid, you may actually be better served, risk-wise, by accepting your 3-4 year replacement rather than having operators cleaning out filter baskets every week/month/whatever frequency.

 

[TugboatEng]

If you are planning to use a strainer there are 3 key factors. You know the particle size and that determines the mesh size. Next, you need to size the strainer for your flow/allowable pressure drop. Finally, you need to estimate the quantity of particles in the fluid and size the strainer to provide adequate service life. Using a duplex strainer will also save the hassle of shutting down to service. If the strainer size to meet your requirements becomes unreasonable, then start looking into self-cleaning options including cyclone separation.

The coagulation will be a problem for most types of strainers. Self-cleaning edge type may be of benefit in that case. Steam tracing in problem areas may help.

What seal face material are you running?

 

[lilliput1]

How about using filters in parallel valved manifold and differential pressure gauges so you can shut and replace one while the other is in service. Consult filter manufacturer to determine size and filtration capability.