This is a bad example to use. I know for a fact that ball check valves are not used to regulate steam pressure. Instead diaphragm operated valves are used, either spring adjusted pressure or pnuematic controlled. The regulator valve is not set at one simple point and left there, the valve has to be able to adjust to varying pressures and demands.
A ball and spring type valve can be used to regulate pressure in a system, but it regulates the presure up stream of the valve not down stream. Where this is commonly used is in hydraulic control systems. It operates just like a MBC. You adjust a nut on top to control the spring pressure and when it is exceeded the valve opens to relieve pressure, once the line pressure upstream of the valve is less than the spring pressure the ball reseats. Some cars use this same way to control oil pressure from the oil pump.

100% correct!

You can use this method to see if the valve is a source of restriction, however sometimes the amount of restriction may be less than 1 psid. I work with numerous fluid systems and seeing a restriction from one point to another is not always simple as it sounds. I have piping systems that are 4" in dia and numerous valves and bemds ar in the system as well as flanges. If you read the pressure in one point of the system and read the pressure at another point in the system you will possibly get the same reading. Most gages do not read accurate enough. The best way to conduct this test would be to use a gage calibration unit, however these are pretty expensive and hard to come by. Even gages in engineering plants are allowed to be off by a certain %.

No pedigree here. I am a highschool flunky. I am a Chief in the Navy that operates boilers for a living. No classroom or fancy college books just real life experience. I have to figure out what is wrong when the Engineers screw everything up. :lol:

all you engineers!! :rolleyes:

:lol:

I am not an Engineer I am a Steam Plant Operator.

O.K. you and I were doing allright until this statement. Let's examine your "expertise".
If we were talking about a sealed system, regardless of volume, you are correct in that once both sides of the valve reached equilibrium, the valve would "check". Wherein our case we have an open nozzle, the downstream side will never be equal to the upstream side and, therefore, the valve will never close. At least not until the upstream pressure falls below 20#. You refer to the spring pressure as "pressure drop". Wrong! Pressure drop is a function of frictional losses as a medium passes through an orifice or restriction. It is certainly not a function of the spring value. The valve will open when the pressure exerted on the ball reaches and exceeds 20#. The valve opening and closing has nothing to do with "pressure drop". You say you have no need to open your Crane, but if you've forgotten the difference between line pressure, pressure drop and flow coefficients for valves perhaps it's time to "crack" the books.

Whoosh,

I have outline the test set up, please pass it on to you Sr Engineer and confirm is a good enough for the a rough indication before I spend more time on a more refined test rig.

http://www.aquamist.co.uk/forum/gallery/EVO/test.gif

As a matter of interest, what is his view on this topic?

it's going to boil down to the checkvalve design. If it's a straight through design like Richard has shown, where the back of the ball sees the pressure of the fluid downstream of the seat, it's gonna cause a pressure drop equal to spring pressure.

I see where you guys are coming from, and agree with you, IF you're refering to a design other than the way it's drawn. But if it's a check valve like Richard has drawn, it will check at the spring pressure and cause that same amount of pressure drop.

Picture a spring loaded diaphragm valve (simple regulator with no reference) with the backside of the diaphragm vented to atmosphere. Then yes, the upstream and downstream pressure across the valve can be very close, all that matters is the pressure pushing up against the diaphragm and in the pipe, and pressure drop will be minimal. This is similar to a fuel pressure regulator, only the reference for the backside of that diaphragm is manifold pressure, not atmospere. But that's not what is drawn. Follow me? Like someone already said, I suck at explaining this.

Slowcar, any idea what the design of the check valve you're testing is?

I will draw one, give me 30 minutes

we're still doing allright, don't get bent. :lol:

Look at the picture Richard posted. The orfice size around the ball/seat will change based on flow. More flow, the orifice gets bigger, less flow and the orifice gets smaller. Yes, the orifice is causing the pressure drop, not the spring, but the spring is in charge of the orifice size. So yes, the spring pressure can be said to be in "control" of the pressure drop. I think you're thinking of a typical piping check valve, which isn't what Richard has represented.

security at work is tight like a solenoid valve...i cant upload anything to the web

the checkvalve is an in-line swagelok CP series - will have a x-section pic and pressure Vs. flow diagram posted when i get home

The downstream pressure gauge needs to be past the "variable restrictor". I'm assuming that the variable restrictor equates to spray nozzle. This is why I suggested that the nozzle be fitted into a sealed pipe that would replicate an upper I/C pipe. By having the gauge at this point it will give you a true value of the required pump pressure required to achieve a desired nozzle pressure and, hence, a proper flow pattern at the nozzle face. If you duplicate what you have drawn and include the changes I have suggested, we both are certain you will get the results you are looking for.
It's actually a "her". I have discussed everything I have posted here with her. By nature and by company mandate, each persons work is QAQC'd prior to going out of the office. I gotta tell ya...she's on my side on this one.

Abner, I have found your videos, I will render them to a more a manageable file size and put up a viewable link on our web space. :)