Signaling Pressure in Hydraulic Lines

Here is a list of all the Gauge manufacturers that Hydraulics & Pneumatics magazine has. It might get you tosomeon who can help.

http://www.hydraulicspneumatics.com/Directory/DrawSpecs1.aspx

I have been in contact with a lot of industry people and haven't found anything. Speaking to manufacturers doesn't seem to accomplish a lot but waste my time.

I was hoping to find someone here with subject matter experience. I sincerely appreciate your time spent in reply. Thank you...

Why not turn on the safety lights whenever the HPU is on?

I work for an organization with a big HSE dept. that wants to move the human interface out of the equation. It has to be automated>

I don't think he meant 'manually'.

What drives/powers the HPU?...presuumably it has some electrical input or control which could be sensed to automatically run the light?

Presumably this pressure line drives things like pistons? Use a piston to hit a microswitch and light the lamp, a nice heavy return spring will switch it off when pressure drops. Forgive me if I'm talking out of my catly backside...just trying to help.

Del

(maybe get someone from the HSE dept to stand there with a red flag )

No, the HPU is all air and fluid. The problem is that the HPU connects through a wall into a test cell where a subsea component is waiuting to be tested. The signal device has to be in the hydraulic line at the component. It cannot have an air line running to it. And yeah, I'd like to have HSE standing there alright...thanks...

Right, as Del mentions below I was suggesting to hardwire the lights to the electric motor in the HPU. This is what we did with our 100,000 psi system.

I guess I don't understand the relevance of the 100 psi point.

There is no electric motor or anything electric on these HPU's. The relevance of 100PSI...that is an arbitrary set point I've given as an example which HSE wants to warn personnel in the immediate area, and also anyone who might want to do something to a piece of equipment that there is pressure present and beware. My company is taking part in a global inititive to establish best practices for high pressure testing as regards subsea wellhead components. I'm searching for the best way to accomplish the task of signaling when prsssure is present in a hydraulic line.

A pressure transducer and its controller. There are transducers that will handle the 30k pressure. The control would have a low pressure alarm setting.

http://www.omega.com/toc_asp/sectionSC.asp?section=B&book=pressure

I don't understand the difference between a pressure switch, a transducer, and a transmitter. I am trying to find a way to do away with anything controlled with a PLC. That is my problem.

Oh, this seems not to0 difficult to overcome. I may help with them. I know a little knowledge on the transmitters. cause we did some detect. and sales

The difference among these items is as follow,

transducer, or we call it as a sensor, which senses some physics quantity and change it into electric signal, this signal needs to modify to suit for next device use, ths is so called transmitter task. the signal was modified and amplified to a regular signal which can match a standard, say 1vpp or 4-20ma or other standards etc. now this siganl can be sent to microchip or a swticher which on /off to be contented to the result.

ok now you know all.

What I want to be aware of is can you put out the photo to show your hydraulic line, in order that I can understand and make more explain. because there are lots of kinds of transducers for selection

Simply put,

Pressure switch = on / off.

Transducer would allow you to actually measure the pressure, I don't think you need a transducer to simply turn a light on an off.

The switch would be your best bet, be sure its rated for tour HPU's system pressure.

A transducer will produce an analog signal that can be read as a pressure by the controller. The controller will allow you to set pressure for your alarm.

The problem that you will face with a switch in your system is the difference in your low alarm pressure and you high operating pressure. One that would be able to switch accurately at a pressure of 100 psi would not hold 30k psi. Thats about .3% accuracy.

One that would hold 30k psi would not be able to set that low. Look at the mechanics of a simple pressure gauge. There are gauges for different pressures. The bourbon tube has to be light enough to flex thru the pressure reading but durable enough to handle the pressure. One that was able to read 30k psi would not even move for 100 psi.

Your best use a transducer.

As Del suggested, a small diameter hydraulic cylinder that has two position sensors mounted on it. The most reliable would be a pair of single pole double throw switches that are activated by the physical movement of your new cylinder. The common feed wire would allow an amber light to glow when no pressure is present. ( Two lights if you use redundant switches for safety.) When pressure is applied, the piston of your cylinder is held in place until what ever pressure you decide upon compresses the internal spring. At that time your cylinder would move to the other end of it's travel, trip the switch (s) causing the red warning lights to turn on. As a safety in the event of the red lights not working, the fact that the amber light (s) went off will tell you the system is pressurized.

You would have a self contained safety warning system that would only need 1 connection to the pressure design. Thank you Del.

Is there any simple P&ID you have? Kindly published it.

I need to see this, before given you an advice.

Eren

We use HPU's in many different configurations. Just imagine a stick of 3/8" high pressure stainless tubing. That is what I'm working with. The problem with a cylinder controlled device is this: imagine, for example, a wall with 10 Haskel pumps of various configurations mounted. These are different combinations of low pressure/high volume pumps, or high pressure/low volume pump set ups. (I can't explain why it is configured in such fashion except to say that a sub-sea wellhead has many different types of configurations and each type requires a different type of pressure test. We have to have the ability to pressure up a large component very fast (low pressure/high volume), and to be able to pressure to around 30K PSI (high pressure/low volume) which requires combinations of pumps to efficiently handle the task at hand. Some of our components go through testing of one million pressurizations, with a valve being stroked between each cycle.) The combinations of pumps would make it a problem to use cylinder controlled signals. Let me ask you...what do you think of this solution proposed by an electrical engineer:

__________________________

by KILGORE TROUT:

Tap into the system and pipe to a solenoid valve that is parallel with a check valve that will dump back to the system. Beyond the solenoid valve have a pressure switch that will make when the unsafe pressure is reached (100 psi), it will turn on the warning light and close the solenoid and keep the pressure from building to level that will damage the pressure sensor switch--When the pressure in the system falls below 100 psi the check valve will open and the switch will open and bleed the pressure off, then, turn the warning light off.

The size and design of the valves can be worked out to handle the 30K pressure and you will be able to use any pressure rated switch.

Possibly?--Hope this helps.

____________________________

This sounds like the solution we have been looking for. Does anyone see any problem with this? Thank you so much for your time and energy in helping me solve this difficult problem. It is difficult because all of the solutions we have come up with so far cause other problems that are not acceptable for a variety of reasons. Anyway, thank you so much for your help.

Hello ThomasLenBrown:

Do you want to check pressures (hi/low etc) in each of the 10 Haskel pumps, or just the one with the highest max pressure?

http://www.nov.com/Products.aspx?Puid=QvFN1nIv1se9oD&nodeId=8ZKGRGJ6MUECNN90CBZW%2BL5DSCM%3D-QPKN1NIV1SE9OD

Check this link please.... This type of equipment is tried and true for many years for many applications in the Drilling Field of operations.

Hello Tim in Mexico:

did you send me this so I could see what the thread originator was after Tim?

DB1011A-SERIES 4:1 Debooster

Sorry you guys think every thing in/out 150%... I made a mistake in replying on the wrong tab becouse someone was in my office with a brand new emergency at the time, nothing more... I'll be more careful in the future. OOPS

Hello Tim in Mexico:

No problems my friend. I forgot some people have to work for a living!

Take care..............

Here is one other option I'd like to submit for review. What about using a pressure limiting valve and a pressure switch. Ashcroft makes a ChemQuip Pressure Limiting Valve which will limit the amount of pressure that would flow to the pressure switch. That would enable me to use a pressure switch in the operating range of 30K PSI. The problem with using a pressure switch is that none are rated for that level of pressure. I'm thinking this may solve that problem.

I can visualize a system that would clamp around a specific piece of tubing and would be able to detect the stretch of that tube. That sensor could be used to trigger your lights. Where I have seen this is still not coming to me. It could have been a refrigeration system.

I did a google search of strain gauges. There are products there that will do exactly what you want.

"The use of a pressure transmitter involves having a PLC and just doesn't seem the way to go.

Understand that you have to comply with API codes for Class 1, Zone 1, 2 opperations for any contact system added to a wellhead. The use of intrensic safey barriers, pressure transmitters and PLC's will be needed where the API code applies.

Good luck!

Paul Williamson

Sr rig mechanic, Weatherford Drilling International