API Plan 13

[CaracasEC]

Dear Experts,
We are planning to tap the Flush Out (FO) connection of the mechanical seal to the pipe upstream of the pump suction flange.
Is this permitted per API 682. Thanks in advance...

 

[flexibox]

I presume that you are currently running dead ended. Normally the seal gland plate should have connections so we will assume you do not have any. Secondly what type of pump do you have and what are you trying to achieve? Are you experiencing problems or do you just want to add circulation to the seal?

Do you have an API pump and seal?

 

[CaracasEC]

Hi Flexibox,
This is API 610 vs6 pump with and original seal plan of 53C and modifying it to plan to a 13 + 72 + 76. This is process related reason, not to contaminate the process in case of higher seal wear using pressurized arrangement. I cannot find a clause on the api 610 that tapping the plan 13 flush out connection from mechanical seal to the suction pipe not on the suction pump is prohibited. We have not yet commission the pumps however technology provider have mistakenly specify the plan 53C.

 

[flexibox]

Plan 52 is for a pressurised seal. You are going for a dry running back
up seal. Are you sure the mech seal gland plate can be modified to achieve plan 13? API does not tell you what you can or cannot physically do but you should consult your seal supplier to ensure what you are doing will satisfy the seal arrangement you have.

I am confused how you can jump from a 53C dual pressurised to a dry running back up seal. I am assuming that you are using the same seal!
If you already have a dry running seal design then why was the seal not supplied with the connections to suit? But to answer your question, if you know what you are doing then its ok to drill and tap the gland plate to achieve Plan13.

 

[CaracasEC]

Hi Flexibox,
I'm sorry if i confused you. The scope of modification work is a total replacement of the system (seal support system + mechanical seal). Plan 52 is unpressurized seal (it is using a buffer fuid) which has a process pressure greater than the buffer fluid pressure.

 

[flexibox]

Sorry
That was a typing error. Plan 52 should read plan 53

 

[CaracasEC]

Thanks flexibox...

 

[JJPellin]

We have done this several times. We routed the Plan 13 flush line to the feed drum, continuously sloped. This allows the seal chamber to remain fully vented, even when not running. Our pumps are often set to auto-start. We could not rely on oporators to vent the pumps prior to start-up.

There is no prohibition against this piping configuration. And, in some applications it has distinct advantages.

Johnny Pellin

 

[CaracasEC]

Hi JJPellin,
Thanks for the information. I am now on close coordination between the pump manufacturer and the seal vendor.As the pump vendor wants to tap the plan 13 to the pump 1st stage suction casing could be because of the balancing piston. I'll be posting the information on the final tapping point..cheers...

 

[Pumpsonly]

You did not mention what product your are pumping. As VS6 pumps are usually used for volatile liquid, low NPSHA application,
returning the Plan 13 directly back to the pump first stage can cause flashing and hence cavitation if your pump flow rate is low.

 

[CaracasEC]

Hi Pumps only,
The pump is a nine (9) stage vertical pump, product is ethylene, specific gravity is 0.452, viscosity is 0.07 (flashing hydrocarbon application), operating temp is -36,.3 deg C, flow rate is 66.3 m3/hr.