Best Mech. seal solution for Thermic Oil, 300¦C

[AngelM]

Hello guys,

I would like you to help me to choose the best solution for this application:

Fluid: Thermic Oil
Temperature: 300ºC
Stuffing box pressure: 6 bar
RPM: 1800
shaft: 55mm

Which would be the best lubrication API PLAN?

 

[flexibox]

Normally when pumping heat transfer oil with low VP I have always used API Plan 02 & 62 (LP steam or N2) you should use a high temperature metal bellows seal with silicon vs carbon. Plan 02 is dead ended seal chamber with Plan 62 to prevent coking.

 

[AngelM]

Then what it looks clear is the use of a metal bellow seal with faces Graphite-antimonium/SiC (I think).
External seal (single cartridge) or internal seal?
If we use internal seal we should include the connections in the stuffing box in some way but with a cartridge we already have it. Is it correct?

The quench fluid can be water?

As the pressure in the quench would be less than 1 bar (or so) the natural leakage would be from the product to the quench fluid. But without using a reservoir, how is it posible to know when the seal fails?

 

[flexibox]

A cartridge seal will have all the connections. You should have a safety bush (disaster bush) in the seal design. Water cannot be used on this service. It must be steam or N2. If you need to contain the leakage in the event of a seal failure then you need to change to AP
I plan 02/52 but this can be costly.
Speak to your local seal representative.

 

[AngelM]

Why it's better to use steam than water? Too much thermal shock.

If I use a main water line for the quench, I should increase the temperature before going into the cartridge, right?

 

[flexibox]

if you use water on 300C product the water will flash off as it enters the quench area and for this reason it is not recommended. you will hear it falshing off. Steam will not do this and has been industry standard for many years

 

[AngelM]

To profit the water main line (very common in industries) I can heat the water before entering the cartridge) to get steam, that steam goes into the quench connection and after the drain line the steam is cooled to use the water for other applications.

What do you think? Otherwise, another alternative?

 

[flexibox]

As mentioned previously, providing you inject steam or N2 it's ok. If you have water, then you run the risk of potential problems.

 

[AngelM]

OK flexibox.
Thank you for your help in advanced.

Could you explain to me the potencial problems that can happen if using water?
I mean, the liquid flash off when entering the quenching area and becomes steam.
What is the main difference between using steam or water that becomes steam when entering?

Thank you for your help.

 

[bk19702]

If the water vaporizies upon entering the seal gland, the change from liquid to vapor instantaneously occurs right beneath the seal faces - you will pop the faces open as a result or worse if the reaction is violent enough. As stated - hot, dry steam or N2 are the only acceptable quench mediums for this service, unless you transition away from a single seal and go to a dual configuration.

 

[AngelM]

With PLAN 62, I need some way to know if leakage is produced. If the seal fails, the oil will mix with the steam, so I would have to install some device in the outer connection to check that. Is it correct? What can I install?

Another thing. Is The thermic Oil to that temperature good enough to lubricate the faces?

 

[bk19702]

A single seal with a steam quench will have connections on the gland in addition to a throttle bushing; the steam will get injected between the seal faces and the throttle bushing through an inlet, then drain freely through the second connection in this area (one will be labeled 'quench' or 'Q', one labeled 'Drain' or 'D', most likely).

Typically, the drain is freely pipied to atmosphere. If you can't tolerate any leakage to atmosphere, you can route leakage to a collection device, labeled API Plan 65A or B; not to be confused with Plan 75 which is for dual seals. If you want to go lower tech, you can run a Plan 66A or B, which involves an additional port between the seal faces and throttle bushing where a pressure sensing device is mounted (gauge or transmitter). The area between the sensing port and quench area is either separated by a bushing (Plan 66A) or an orifice fitting is included in the connection (Plan 66B). The purpose of the last two plans is to provide restriction for leakage of the primary seal enough so that pressure will be detectable in order to provide an indication of increased primary seal leakage.

These are just some suggestions. Whoever is your preferred seal vendor should be able to provide you with some guidance as well.

 

[AngelM]

I can not find information about PLAN 66 A or B. Can you send me something?