Plan 13 Flush for Solids removal 2

[mjpetrag]

I wanted to know if any here has put a plan 13 flush on a regular centrifugal pump (Goulds 3196 stx) to make sure solids did not pass into the pump seal. It seems like the centrifugal force will force solids to the outer casing wall and leave clean fluid in the center for the seal to clean itself with.

I've seen problems with plan 11's getting junked up with solids in the product and making the flush useless.

-Mike

 

[flexibox]

You need to be more specific about your solids. Normally on a typical application with this type of pump you will use API Plan 31 to remove solids not 13. Plan 13 is used on vertical turbine pumps where the seal chamber pressure is discharge pressure. If you use this plan on the Goulds pump you will have zero flow.
If you are currently using Plan 11 and this is getting blocked then you need to consider the following:
1 Do you have an orificae in the Plan 11? Is it getting blocked?
2 If there is no orifice what is the tubing diameter and is it getting blocked?
3 Does the product solidify when pump stops and this is why Plan 11 blocks?

Perhaps if you shed some more light on the application you may get a more specific response to help you.

PS: When using a cyclone separator ensure the solids SG is heavier than the product to be effective.

 

[mjpetrag]

Discharge is 37 psig and suction is 1 psig which gives me about 10 psig in the seal chamber from

Pchamber = Psuction + .25(Pdischarge-Psuction)

Now I realize that this is only an approximation, but...

I would have a 9 psid from the seal to the suction line.

I am aware of the plan 31, but don't really want to install it on this application.

The solids are mostly from hard chunks of solidified caustic and assorted salts that come in slugs from process upsets, so it's not under normal operating conditions.

I just wanted to know if anyone had any success with doing this on centrifugal pumps. I am aware that they are mostly used in vertical pumps, and haven't seen them on any regular 3196's ever. That's what turned the red light on.

-Mike

 

[mjpetrag]

http://www.mcnallyinstitute.com/15-html/15-05.htm

I believe this is a very credible source, but I wanted as many inputs as possible.

-Mike

 

[flexibox]

I would use a seal that has external spring design, Silicon Vs Silicon Carbide faces with EPDM elastomers. Run it dead ended with Plan 02 because I dont think that you will have a VP problem. If you have access to include intermitent Water quench (Plan 62) to wash the crystal build up then I would apply it because regardless of the piping plan you will have crystal build up that may lead to seal hang up and failure.
I think that if Plan 11 is blocking then plan 13 will too.

 

[JJPellin]

I have used a plan 13 in an attempt to reduce solids entering the seal chamber as you suggest. I have a few concerns about your approach. I would not recommend use of a rule of thumb (25% over suction) to estimate the seal chamber pressure. You need to get a realistic value for seal chamber pressure from the OEM or measure it in a running pump. The pump model you mentioned has an open face impeller with back pump-out vanes.

I stated that I have used this alternative. But, I was not able to perform a valid comparison to determine the amount of solids introduces with Plan 13 as compared to Plan 11. I chose this alternative based on the engineering principals involved. If the solids contained in your stream are heavier than the fluid and if the fluid is drawn down the back-side of the impeller against the centrifugal affect of the impeller it seems likely that some of the solids would be spun out and the remaining fluid would have a lower solids content than it would if it came off the outside of the volute at discharge pressure.

Depending on the exact nature of your stream, flexibox may very well be correct. You may plug up a plan 13 anyway. But, I have used this alternative and feel it has been successful in some services. I feel it is appropriate for you to use it.


Johnny Pellin