CONNECTIONS PRESSURE IN DOUBLE CATRIDGE

[AngelM]

Hello,

Please, In a double cartridge like the one of the attached file working with water to 40 bar, Can I put through the flush connections water to main pressure line (to 2/3 bar) mainly to lubricate the external seal or I would have to insert water to more pressure than the working one, let say 42 bar?

I think with 2-3 bar would be enough because due to the configuration of the seal faces the working pressure will help to thrust the internal rotary face over the stationary one, and the connections pressure will help to close and lubricate the exsternal seal.

Am I wright?

 

[flexibox]

Angelm
Your description is not clear. Where is the 40bar water? First thing you have to do is make sure the connections are located at the top so that the seal self vents as you must remove any air. Next this is you need to have water " IN" and water "Out" so you should have a flow through the seal to remove heat generated by seal. What is the shaft size and speed?
The water which we will refer to as barrier fluid must be supplied approx 1 to 2 bar above the chamber pressure. This will ensure a clean water fluid film between the faces. What is the seal chamber pressure? What are the seal face materials as this is also important if you are operating at high pressures. Make sure that the water is filtered and that you have flow through the seal.

Suggest that you send more duty conditions for us to better understand your application unless I have answered your question.

Happy New Year.

 

[AngelM]

Hello, sorry and forgiveness for not explaining well. My question is for the double cartridge attached in my first email.

This cartridge is for sealing water to 180ºC and 40 bar. The proposed faces are Graphite-Antimonium / SiC in the internal seal and graphite/SiC in the external one. Shaft size: 40mm.

I have a doubt about the value of the pressure needed through the connections. According to the drawing, I think the seal chamber pressure will be the one I put through the connections. My doubt is if I can insert in the seal chamber water to the main pressure water line, I mean to only 2 or 3 bar, and the seal will work correctly or I need to insert water to more pressure than the working pressure, I mean 41 or 42 bars?



At the beginning I plan to insert main water line because it is easier and I think the the internal seal will work well. Am I wrong?? Can that seal work well with a pressure below the working pressure (40bar) due to its configuration or I will have leakages in the internal seal? and why if it is?

Thanks for your comments

 

[flexibox]

You have it all wrong. The seal pressure should be min 42bar but I am not so sure that seal can handle the pressure. If you only put mains pressure the seal will operate in reverse pressure leading to failure. Also I think if you pressurize the chamber without higher pressure on the double seal, the graphite face may break as this will be internally pressurized. Check with supplier.
I think you have the wrong seal arrangement anyway. I would have a high duty single seal with API PLAN 23. This is the most common sealing arrangement for hot water applications.
I suggest that you get the seal supplier involved because it sounds like you have little to no experience and seal failures will cost you money!

 

[AngelM]

The water that comes form the cooler to the seal chamber should be to a higher pressure than the working pressure, then. Is it OK?
So the barrier fluid circuit should be pressurized.

How would you propose to install the cooler to be able to have more pressure in the barrier fluid? using a seal pot pressurized with compressed air and inside it a cooler, for instance?

Sorry but I do not have a lot of experience.

 

[Pumpsonly]

You need to read up API 682 or other mech. seal manual to have more meaningful discussion. Look up John Crane or Flowserve web site will give you a better idea.

 

[flexibox]

AngelM
I'm sorry to say that you need professional advice on site. If you do not have experience and get this wrong then someone may get injured in the event of a seal failure due to incorrect instalation. I suggest that you call in a reputable seal company to assist you.

 

[AngelM]

Ok. I will.

But according to your experience, could you give some details about the instalation needed? You talk about API PLAN 23. Ok, but , please give details about the type of barrier fluid, the pressure of the fluid, etc. Nothing to do with the main water line? Can I take advantage of having the line near the pump in some way ?


All this can help me.

I was wrong, the working pressure is 31 bar, not 40.

Thanks
AngelM

 

[flexibox]

Here is a link for API Plan 23.

http://www.ppcmechanicalseals.com/API/API-23.pdf

I have also attached a API Plan 53 which is used with dual pressurized seals.

What I am saying to you is I think that the double seal you have is the wrong seal for that application. I think that you should have a single seal with API Plan 23.

Plan23 does not require an external pressurization system and it is described in attached link.