ISO BUTYL BENZENE SEAL LEAKAGE

[shyamshins]

Dear members

This is an agitator seal handling ISO BUTYL BENZENE at 50kg/cm2 while design press. is 45kg/cm2. This seal is operating since last 10 yrs. but has started to fail within last 8 months. It has failed 3 times within a gap of 4 months repeatedly.

Liquid handled is ISO BUTYL BENZENE. Stationary face is of silicon carbide which has deposits on face except the area where carbon (Rotary face) comes in contact with Stationary silicon carbide face, is it because oil they are using has developed sludge in tank as they are using API PLAN 54?

Rotary carbon face is of antimony impregnated. It has pitting marks at it I.D. of which I have attached photographs, is it because this agitator is operating at 50 kg/cm2 more than designed press. and operators are not keeping flushing fluid press. 2kg more than operating press.? is this causing carbon face to move up axially and touch sleeve? can this be the reason pitting marks are developed as operator is complaining that oil goes inside reactor and they have to refill there flushing tank.

O rings for rotary and stationary face are made of VITON and I have observed that they get hardened. Also they are pilled off from inside diameter which is same for rotary and stationary o ring.

Anti rotation pin of Silicon carbide face comes out from back of face and this face has deposits for which I have attached photographs.

Flushing fluid used is SAE 40 oil and they use thermenol oil in outer housing where I have found black sludge accumulated why is this sludge formed?temp. of flushing fluid when it enters seal is 32 degree celcius and at outlet is 34 degree celcius. Temp. in agitator is 200 degree celcius.

[highlight #A40000]CAN SOMEONE HELP ME ISSOLVING THIS SEAL PROBLEM AS THERE ARE 3NOS. OF SEAL AND THEY ARE FAILING WITH A GAP OF 3 MONTHS.[/highlight]

 

[shyamshins]

ISO BUTLY SEAL DRWG.

 

[shyamshins]

ISO BUTYL BENZENE PHOTOS

 

[shyamshins]

ISO BUTYL BENZENE SEAL

 

[shyamshins]

ISO BUTYL BENZENE SEAL FAILURE

 

[shyamshins]

ISO BUTYL BENZENE SEAL FAILURE.

 

[shyamshins]

ISO BUTYL BENZENE SEAL FAILURE

 

[flexibox]

If you had 10 years without problems then something has changed! Do you have new operators? Looking at the photos I think the oil viscosity is too high, I would use an ISO Grade 10 oil. What is the purpose of the thermenol oil? Is this in the cooling jacket to remove heat or heating the jacket?

If oil needs to be topped up then I assume that the barrier pressure is always maintained above the agitator pressure? Can you confirm this? There should be no sludge in the tank.

I would increase the Delta P from 2 bar to 5 bar and change the barrier fluid. Check the oring compatibility I don't have access at the moment but sounds like they are chemical attack on process side.

 

[shyamshins]

Sir,
Purpose of Thermenol oil in outer housing is to cool barrier fluid which is circulated at 2kg/cm2 this is used to dissipate heat of barrier fluid.

Barrier fluid pressure is always maintained 2kg/cm2 above agitator pressure, but sometimes operator operates agitator at 55 or 60kg/cm2
which is well above designed press.(designed press. is 45kg/cm2) CAN THIS BE THE REASON FOR O RINGS FAILURE?
Also they do not raise barrier fluid press to 52 or 62kg/cm2 when they operate agitator at 50 0r 60kg/cm2.

 

[flexibox]

In one sentence you say the barrier pressure is always 2 bar above the agitator pressure and in another sentence you say the operator does not increase the barrier pressure when 50bar and 60bar!

The barrier pressure must be set to cover the maximum pressure seen in the agitator so if it is 60 bar then operate barrier pressure at 65bar.

Viton has a published max temp of 203C I think that the oring is exposed to high temperature and this is the problem. Change to a perfluoroelastomer.

Change oil to an synthetic oil. Royal purple is good quality barrier fluid.

I think the seals are exposed to reverse pressure and this may explain the sludge build up and you need to check the pressure limits of your seal design if it can handle this pressure.

Good luck.

 

[shyamshins]

Flexibox,
Thanks for your reply.
Can you pls. tell me why carbon face is pitting from I.D. and not its face? (where carbon and Silicon carbide contacts each other)
This carbon face Material of construction is Anitimony carbon, is this MOC suitable for Iso butyl benzene? I have attached Pitted carbon faces photos in previous mails.

 

[flexibox]

Check this out

http://www.stle.org/assets/document/The_Effect_of_Oil_Type.pdf

http://mechanicalseals.info/index.p...l-seals-troubleshooting-blitering-part-9.html

http://www.fluidsealing.com/sealingsense/Dec04.pdf

 

[shyamshins]

Thank you,

Flexibox.

 

[shyamshins]

Flexibox,

Now again I attended above mentioned seal which failed.

After dismantling I observed following points:-

A) Sleeve was having brown deposits of Oil on face where compression unit(Outboard / Inboard) fits.Compression unit fittement is indicated in drwg. in trailing mails.
B) I/B seal ring (Antimony Carbon) found pitted at I.D. same as mentioned in trailing mail photographs.O ring(Viton) material gets removed at the face where O ring contacts carbon face but O ring is not attacked on its I.D. where working fluid is in contact.

Does these brown deposits on sleeve indicates (Mentioned in Point A) that oil which is used as barrier fluid is not cooled properly through condenser?

Does these O ring from which material is removed as mentioned in point B also indicate that carbon face is overheated as O ring material is not removed from I.D.? This pitting occurs only at I.D. below carbon face.Do we need to change Oil grade as we are using SAE 40 oil?

Pls. help.

 

[shyamshins]

Flexibox,

Should agitator be 100% filled with process fluid,then pressurized and then operated? is this proper procedure of operating reactor?

Can this be the reason of seal Failure?

 

[flexibox]

Sorry about delay have had issues

With dual pressurised seals you must always pressurise seal first then you pressurise the agitator or pump then start up. You must always remember that the seal MUST be vented. If you have air trapped then you will most likely experience problems.
If you fail to do this then you can experience seal problems but this should generally occur on start up.