Subsea Hydraulic Systems Design Text

[Dayundone]

Saw a previous string discussing hydraulic system design texts though the material that followed seemed to be of generic nature. I'm in the offshore oil and gas industry and looking to develop more knowledge in the subsea controls arena.

Umbilical lengths are getting longer and longer and I'm not happy with the shutin response times we're getting on some of these due to the subsea temperature variance, compressibility of the hydraulic fluid, and expansion of umbilical tubing. I'm sure there are more factors I'll discover as I get deeper into my research. I've done a few electrical systems per the customer's request though the price tags were considerably higher on these types of systems and quite frankly the operators were not comfortable with them. So if there are recommendations on optimizing and dummy proofing an electric system as well I'd definitely be interested.

Thanks.

 

[Dayundone]

NOTE: that should read "shutin recovery times" instead of "shutin response times". Thanks.

 

[AcesHighJoker]

While I cannot suggest any particular text to help you I can suggest a couple of solutions to control pressure more consistently on long conductor systems.

While studying pneumatics which is, obviously, compressible, discussion on efficiency was a common theme. By relocating valving as close to the actuator you can reduce the effect of swelling and contracting fluid conductors. In most cases locating them directly on the actuator is best.
To further reduce pressure dips and surging using an appropriately sized accumulator can help quell spikes quite well. Even one sized as small as a 3cuin one can sufficiently quiet the spikes in a 3/8 sized 3000psi conductor system.

I know its no where near a textbook but I hope this helps.

 

[budt]

Is it possible to move the pump and motor to the working depth and exchange the long hydraulic lines for electric ones? Electricity responds a lot faster than oil.

A VFD motor might work better also.

Also,I have used multi-viscosity oil in low temp startup circuits to help with viscosity problems. However this would be unnecessary if the pump was at depth, just use low viscosity oil.



Bud Trinkel, Fluid Power Consultant
HYDRA-PNEU CONSULTING

 

[13392017]

All,
Actually the subsea control system vendor have designed the system as what AcesHighJoker advice. Not only the valve, they already put some Hydraulic accumulator subsea. The intention is to maximize the response time.

The umbilical only supply the hydraulic pressure to Subsea Accumulator. There are a lot of valve in Subsea Control Module which will direct the hydraulic pressure from accumulator to respective function in the equipment. This module is attached to the equipment to be control, i.e subsea X-mas Tree, Subsea Manifold etc.

Recent development by Cameron (one of subsea control system vendor) has developed the system called CameronDC which utilize the electric system to actuated the valve in X-mas tree.

Regards,
RK

 

[matkenmd]

the best way currently is to multiplex down. accumulators provide fast hyd power on signal. there's not a lot of ways around this.
conventional discrete/hydraulic systems are limited by physical laws you've already mentioned.