API 53B for a MPP crude handling 1

[mikefzj80]

Hello Friends

I`m working in project to make a improvement for better result in the sealing system on a Multi Phase Pump twin Screw IDP, handling Gas + Crude Oil, actually we`re using double seal with API Plan 54, with a lot of problem with this plan, it is very complicated, and we need some more practical, our proposal is to change to 53B, the operation condition are follow:

Suction pressure: 7 bar
Discharge: 40
Barrier Fluid: Duralub 22
Barrier Fluid Pressure: 41
Temperature: Max 80ªC
Mechanical Seal: Chesterton 2XP80
4 seal per pump.

Is the 53B a good option for this operation?
Can we do a plan full automatic, with periodical check field?

We espect by your friendly comment

 

[flexibox]

API Plan 53B is a very good option for dual pressurized seals. Plan 54 can be troublesome! Before you commit to Plan 53B what is the seal chamber pressure in these pumps? Suction or Discharge as this will have an affect on the operating pressures. Also do you want an individual acummulator for each seal? This will monitor each seal and in the event of a seal failure you will identify which seal is leaking. If you use 1 common acummulator then you will not know which seal has failed. Also with this plan you need a cooling loop for each seal. costs is dependent on what level of automation you want Instrumentation is where the costs blow out.
If you have suction pressure in the seal chamber, then you may consider 10lt acummulators for each seal and a transmitter to monitor pressure with auto top up. for a make up unit, have a tank with a Haskel pump that stalls when pressure is reached. If you have discharge pressure in seal chamber then the operating pressure may be too high for the seal deign. I suspect you have discharge pressure hence the 41 bar barrier pressure. consult your local seal manufacturer for local advice.

 

[mikefzj80]

Thanks flexibox.

The Stuffing box pressure is 41-45 BAR, we would like to use individual 53B systems for each seal and the seals have individual monitors actually. Due to the high pressure in the seal chamber, Chesterton desing a enginnered solutions for this application, based on high pressure seals, only we´re commited to work in the plan 53 for use with this pump, but we want to be full sure and we´re so close to find it, now, is good to use a l0 lts accumulator??

thanks again !!

 

[flexibox]

OK if the box pressure is 45Bar Max then the precharge pressure must be around 46 bar. this means that if you use a 10 lt acummulator then the operating pressure will be approx 90bar with 5lt of fluid. if you use a 50lt acummulator then you can operate at 56bar using 9lt of barrier fluid. You need to have reasonable barrier fluid so you end up with a Working Volume and safety Volume. At 9lt you can split that into 7lt working volume and 2 lt safety volume meaning that when the volume drops due to seal leakage an alarm will come on (Via transmitter) and the system needs topping up. 2lt represents 48bar. the system should protect the seals from reverse pressure so you should trip pump at 47bar.
therefore you should get the seal leakage rates and use the 7lt to determine the topping up frequency. If this is suitable then you can use these numbers. you do not need an individual skid for each seal, you can mount 4 acummulators on one skid and use 1 top up unit, but you will need 4 cooling loops.
trust this helps

 

[mikefzj80]

Thanks a Lot Flexibox, I hope to send a picture soon of this project!!

 

[Airsporter1st]

Flexibox is talking good sense as usual.

The only point I would differ with him on is his use of the term 'precharge pressure' where actually, I would say 'minimum system pressure'. 'Precharge pressure' refers to the nitrogen pressure in the bladder when the system is depressurised and would normally be 0.9 x minimum system, pressure,
i.e. 0.9 x 46 = 41.4 barg in this case.

I also like the use of a haskell pump for auto top up. It requires the minimum of instrumentation and is simply set to stall out at the desired pressure by regulating the drive air pressure. The inherent hysterisis ensures that it is not operating continuously.

 

[Pumpsonly]

Please check again on the seal chamber pressure, Twin screw pump with timing gears has the seal chamber seeing suction pressure.