Contamination of Plan 54

[REVenezuela]

Hello everyone,

I've experienced a couple of contamination issues on two pumps using Plan API 54 (Vacuum Resid service), one is OH3 and the other is a BB2 type pump.

I checked all the pressure trends and supply pressure doesn't seem to have dropped as to allow back flow to the seal oil tank so I haven't been able to understand how this could have happened. Eventually the contamination became worst and in both cases we had to shut down the pumps once the filter plugged with VR. I'm working with the manufacturer (JC) to try to understand the failure mechanism and root cause. The pump ran only for 11 days before the contamination was detected, within that period it was switched a couple of times when the sucrtion strainer plugged. Further inspection of the seal revealed cracks on the IB primary ring insert, clogging of the bellows / springs with VR (as expected) and chipping on the OD of the OB primary seals.

I know that a plugged suction strainer will create adverse conditions to the pump (cavitation, vibration, etc.) but what I'm trying to understand here is why the seal oil system got contaminated instead of dropping the tank level once the primary seal failed especially when the supply pressure never dropped as to allow back flow.

I'd appreciate if anyone out there has experienced this situation or has an explanation for this.

PS: Mechanical seals are JC Tandem arrangement 48RPRS / 48MPRS (BB2 pump) and JC 3609 Rotating Bellows (OH3 pump).

Thanks

 

[flexibox]

Do you have a P&ID of plan 54? This can mean anything.
If you have higher pressure in Plan 54 than seal chamber then you should alarm on low pressure in Plan54 before process fluid can enter the seal.
What is the delta P across inboard seals? Is Plan 54 fitted with pressure transmitters? When stop start is there any possibility that operations start the pumps without starting plan54 first? You need to check this. In this case you may run as a tandem seal which can contaminate the seal.

 

[HansBrinker]

Hi RE

Just some thoughts. Go over with operations, in as much detail as they'll stand, what is going on when they're starting the pump, swinging the pump, flushing out the pump, venting the pump. Don't rule out that your stuffing box may be seeing a lot higher pressure than you think. It'll stop working soon enough, but the bother of putting a pressure indicator on the stuffing box may be worth it to see what's going on. Don't be shocked to find out that despite all written rules and procedures, the night crew has not been venting properly and have had the suction closed during flooding from the sister pump's discharge. Talk to your seal rep about maybe jacking up the seal barrier fluid pressure. The negative effects of higher internal pressure may be worth the insurance of staying above higher than expected seal chamber/ stuffing pressures caused by who knows what shenanigans you may have a very hard time making go away/ having someone fess up to.