High temperature in API 53B Mech Seal

[zipped]

Hi Frnds
This is an issue related to a double mechanical seal of an agitator.
We observed a sudden high buffer fluid temperature which rose up to 103 deg C.
Within 25 mins it went from 56 to 103 deg C and came back to 50 deg C.
After 2 hours we observed, high seal oil differential pressure of 5.2 bars g. It got normal with in 10 mins.
One operator also observed that seal system safety valve was also popping for few mins.
It was also observed some black particles in buffer fluid with change in color.
Now after 3 days, seal is performing well.

Details:-
vessel pressure: 7 bars
Vessel fluid: HDPE slurry
Buffer Fluid: Shell Ondina 909
Seal Plan: API 53B (back to back)with jacketed cooling water. Special seal having bearing (greased) attached to it.

Can you help for the sudden high temperature and seal differential pressure rise.

 

[Pumpsonly]

YOu did not mention about the vessel temp. It seems to be the vessel pressure is higher than your barrier fluid pressure and the HDPE slurry is getting into the barrier fluid.

What you mean by high seal oil differential pressure of 5.2 BarG?

For Plan 53B, the seal oil/ barrier fluid must always be higher than the vessel pressure.

 

[zipped]

Vessel temp is around 75-80 deg C.
There is a sight glass in the seal. We can see how much it is leaking. We didn't observe any slurry in it.
Seal oil differential pressure is difference of seal oil pressure & vessel pressure. This differential pressure is generally maintained around 1.5 to 2 bars g.
As this is a Plan 53B, with an accumulator. It always maintain pressure more than vessel pressure. Chances of slurry getting into seal is rare.
What I think is, if there is any obstruction to the cooling water flow, the seal oil temperature will increase. But it was observed that CW was continuously kept open.
As this seal is accommodated with a bearing, some problem with bearing may also cause this temperature rise.
This is what i suspect.

 

[flexibox]

have you checked to ensure that the seal is fully vented and that there is no ait traps that will cause seals to run hot. the the PRV was popping then check the P&ID a see if there is an isolation valve downstream of the accumulator. if this is closed then it may be the cause!

 

[QPAini]

Dear Guys,
I have lots of Plan 53B system intalled into my plant, it had has experiance seem to be look like the same were question are loaded,

trough my experiences may it help.
1. Check N2 Pressure must not more than 80% from stuffing box pressure while ran.
2. Vent proper while you fill barrier fluid into the system.
3. Ensure pumpingring in seal system in correct angle, because it's make me mad due to pumping ring design are unsatisfied to reduce temprature by barrier fluid circulation.
Analizing taking place, comparation are done, from Eagle burggman to the Jhon crane mechanical seal, i suggest Jhon Crane Manufacture is better then Eagle seal were I had no problem with mechanical seal and barrier fluid temprature.

 

[Airsporter1st]

QPAini - your first 3 points are perfectly valid, but the fact is that just as you are asserting that John Crane manufacture is better than Eagle Burgmann, somewhere on the other side of the world, someone else is asserting that Eagle Burgmann is better than John Crane! (And I don't work for either of them.)

Fact is, as my old boss used to say, "a mechanical seal is a round thing with a hole in the middle"..... All seal manufacturers produce perfectly sound designs using basically the same materials and engineering principles.

It is more often than not the type of seal chosen, the environment, the system, the process,the equipment in which the seal is installed or the operation of seal or system which is at fault.

To the point in question, I have experienced this type of phenomena previously. It may be due to air or water in the barrier fluid, or a loss of cooling or a pressure reversal from the vessel. Generally with a 53B the temperature excursion will be accompanied by a pressure excursion because of thermal expansion of the barrier oil. If the pressure excursion comes first, this is usually a sign that the vessel pressure has increased above barrier pressure (or that barrrier pressure has dropped below vessel pressure).