Full, Straight Flow Though Pilot-Operated Solenoid Valve

Most any effect you may see as a result of a bend or any obstruction in a pipe will dissipate after about 10X the diameter in pipe length. I.E. if pipe is 1" DIA you lose most effects in terms of pressure and turbulence in 10" of length. In the event that axial swirl is an issue you can place a straightener in the pipe. This would take the form of a perforated plate or a bundle of small short tubes within the pipe. If you would like to see examples or possibly even buy off-the-shelf solutions for these issues simply Google relevant terms in the context of natural gas pipe line equipment. If the scale is off you can at least see the concept and adapt.

Thanks for that input. I should have given a bit more background. The fluid in question is liquid N2O (supplying large hybrid rockets), which is quite viscous and must not be allowed to turn to gas in the system. (hence no eddies). The 90deg bend results in layout and piping problems in an already crowded system - hence the search for a straight flow-path. The pilot operation is needed for fast emergency shutdown. The solenoids are safety shut-off valves.

I'm the guest who responded this morning. My name is Max. I have so many questions but let me first say that a quarter turn ball valve is the obvious choice for a straight through application. When the valve is open you have the same diameter all the way through. You should be able to find one in any diameter, pressure range and temp range you might need. They are among the most reliable valve types. Remote actuation (pilot) methods are limited only by your imagination as a quarter turn ball valve may be actuated via electric solenoid, screw motor, pneumatic, hydraulic, and mechanical linkages connected to any of the afore mentioned. A ball valve is also among the fastest operating, depending on the actuation method, since you indicated use as emergency shut-off. It can be set up as normally open, normally closed or push/pull depending on what failure mode you want to build into your system.

Hi Max, Again thanks for the input and interest. It's great to have some external thought. We use 1/4 turn ball-valves in the main throttles and also in the start-up throttles, for the reasons you outline. The main-throttles can't be used as safeties, as a backfire can disrupt them and the linkages. The safeties have to be further back up line. The start-ups are on a ganged up pneumatic arrangement - with an extra closing spring for safety. On the main oxidiser lines this is too cumbersome for the required layout of four (or six) main throttles in line with the rockets. Even this arrangement does not close fast enough for our safety requirements - even .1sec is much too slow! The solenoid valves are purely safety shut-offs. They are in the line for instant killing of the rockets - they don't actually have anything to do with the running of the car. We already have a running four-rocket car with systems that have been developed over a four-year period. If you e-mail me, I can send you pics and schematics - to make things clear. The problem with ball valves is the high-torque and slow operating speed when used as safeties. Hence the inclusion of the pilot-operated solenoid valves - as soon as they're de-energised the line pressure shuts them. This allows for a 'dead-man' pedal for shut down in a crash situation. As this is a manned rocket (and I'm the idiot getting in her) instantaneous shut-down is vital. Dick Keller used wafer valves in Blue Flame (very low torque) but they aren't really suitable for the cryogenic liquid N20.........plus he only had to layout one rocket system. So we're in search of an instantaneous shut-down system that is fail-safe. There are, I'm sure other answers - we haven't come up with them yet, hence the search. cbc1250@hotmail.com

Why not consider a squib operated valve? Perhaps a gate valve. Squibs are reliable, inexpensive, and pack a large punch in a short time. A shotgun shell or airbag actuator, for example, performs all its work in fractions of a millisecond.

The specification makes me think that you will most probably not find the right valve available from the shelf and will be obliged to design one. For estimations some other parameters must be made available: pressure drop [MPa], flow[l/min], temperature [min..max], maximal dimensions, ducts before and after diameters, dimensions of flanges, viscosity of fluid (dynamic and cinematic), density....

Most important is the closing time which you mention only as "instant" and unfortunately it is not the same if instant means 50ms or only 5 ms.

You should also look at airborne systems where similar conditions could be present.

I think I could suggest a solution but cannot say anything before an estimation which can be only made knowing above details. Please use private channel and do not give your mail on open discussions it is too dangerous.

Well, lot's of response - that's helpful! Squibs - hard to see putting six of them in the system - and how to make it fail-safe, though the operating speed is attractive. Design and build your own valves is (and has been looking like) the most probable course. Aerospace may have one ready to use - so that's definitely worth investigating. When you consider just how many feet/second 350mph is, you can see that something like (or less than) 5msec is where we need to be. Still hoping for an off-the shelf solution, though! We do have all the design parameters,

Please see: http://s959.photobucket.com/home/CarolynneK This is what we're doing

Very cool. I'll catch up with you on Monday. You need to do a video introducing everyone on the teem and a history of your progress.

Don't know what size valve you need, but try something like this ...

http://www.betavalve.com/piston.asp

betavalve eh? Very Interesting! I'll e-mail them tomorrow to get operating speeds. !/2" BSP nominal. there's so much video been done. We've come a long way and have developed some very novel and useful technology. I'll give you all a paper in the next few days. Thanks so much for the input! Don't stop now!!!

see www.laffin-gas.com, www.myspace.com/laffingasrocket www.youtube.com/laffingastv

I have been trouble shooting our hydraulic pressure and flow issues for a while in an oilfield (my job) application. You find a huge selection of direct acting pilot relief valves and more at sunhydraulics.com. They work great and can handle flow up to at least 30 gpm and 6000 psi. We use 4 of these valves with pressures from 200 to 6000psi. Upstream is a positive displacement pump (7gpm), pumping 13m hydraulic fluid.

Jordan Valve makes a short-stroke regulating valve with orifice plates having several parallel slits. The distance between full open and full closed is 1/2 the distance between the slits in the plate. They are available in a variety of materials, but I don't know if cryogenically suitable. Flow is straight through.

Well. Looked at those. Jordan too bulky and not appropriate, Sun can't handle N20 (wrong seals)... still waiting for a response on the other. If this was easy -I wouldn't have asked for help!! Never mind -it must be out there somewhere.