Pressure gauge calibrators - recommendations?

[Ingenuity]

I need to regularly calibrate 10,000 psi pressure gauges (hydraulic stressing applications).

I want to do this now in-house and want to know if anyone has experience with RALSTON or FLUKE pressure gauge calibrators with their respective manual hydraulic pumps.

Specifically, I am looking at RALSTON FieldLab calibrator.

I would send the calibrator back for yearly NIST-traceable calibration.

Thanks in advance.

 

[EdStainless]

We had an older Ralston dead weight tester. It worked well.
We only did about 100 gauges a year (and it was in a lab) and so we sent it back every 2 years.

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P.E. Metallurgy, consulting work welcomed

 

[Ingenuity]

Thanks Ed for the feedback.

I was impressed with the limited research I did on Ralston equipment, and made in the USA is always nice.

In my case we shall be using more in a field setting.

 

[danw2]

Beamex had been really making a nice package for field calibrators the past decade or so with what seemed to be an emphasis on the record keeping.

I have not used one, just have seen the blurbs and a white paper or two.

 

[hydtools]

Using a deadweight tester in the field would require paying attention to leveling the tester so that the weight supporting piston does not drag against its cylinder. I have used one like the Ralston.

Ted

 

[Ingenuity]

Just to clarify, the unit I am proposing is not a deadweight tester. The system I am thinking of getting uses a hand hydraulic pump:

The reported accuracy is 0.02% of FS for 0 to 2,000 psi range, and 0.1% of reading for 2,000-10,000 psi range.

Any input on such a setup?

 

[catserveng]

What kind of tolerance/accuracy are you looking for? The small hand pump calibrators are great, but getting them up to 10,000 PSI several times can be quite a bit of exercise.

CAT dealer I worked at needed to add a calibration procedures in shop for higher pressure sensors and gauges, we used a Fluke 743 that we already had, and added a Fluke 750P31 10,000psig pressure module, for a pump we used either OTC or Enerpac hand pumps we already had on hand for porta power rams and other tools. We added a needle valve on the output of the pump that gave us some fine adjustment, and found the larger pumps with longer handles used less effort and made finer adjustment of pressure easier.

Not sure if this would meet your needs, but may. You may also consider renting a couple different calibrators and seeing which one meets you needs best before spending the money to get a new one. Transcat has quite bit of tooling available for rent and in some cases also has free or low cost demo equipment.

MikeL

 

[itsmoked]

That looks almost as bulky as a deadweight tester.

The deadweight tester we had came in a stout metal housing where the tester was built into the base. You carried it like a small suitcase setting it where you wanted to use it and flipped a few latches and the top came off with the carrying handle. Everything was there and ready to go.

Deadweight testers are beautiful fundamental physics. Someone will be calibrating those gauge type ones with a deadweight one. They don't go out of calibration. You don't need to have them calibrated unless the laws of physics change. They're easy to use. They're obvious.

You should re-consider.

Example Brochure

Keith Cress
kcress -

http://www.flaminsystems.com

 

[hydtools]

The force due to gravity is pretty reliable.

Ted

 

[itsmoked]

True dat! But, there is actually gravity variation all over the surface of the planet and these testers come with a table you can use to correct for it if you need even higher accuracy.

Keith Cress
kcress -

http://www.flaminsystems.com

 

[Ingenuity]

Thanks for the continued discussion with some great information.

Our calibration setup is in our workshop - so not a lab setup, but certainly better than a field setup.

A deadweight tester would be indeed 'perfect' but they are pricey, for up to 10,000 psi pressures they run over US$10k. So about 3 times the price of a pressure gauge calibrator like the Ralston setup.

To catserveng good point - we also have numerous hydraulic hand pumps - Power Team and Enerpac type, with 10,000 psi capacity, that we could dedicate one to a calibration-only setup.

Some other relevant information too: Each 6 months - after we get the pressure gauge calibrated - we then calibrate the hydraulic jack stressing system - pump, jack/ram, hoses & gauge - with a calibrated center-hole load cell that is also traceable to NIST. Our load cell has a reported accuracy of 1% of Full Scale (50 kips capacity, so 1% is 500 lb). 500 lb on the ram/jack represents approx 80 psi of gauge pressure. We typically read only to 100 psi gauge increments in the field.

Given that this is a construction application/setup, maybe a dead-weight tester is overkill? Thoughts?

 

[btrueblood]

With electronic strain gage items like the pressure calibrator and load cell, you will want to get them recalibrated yearly at least. Strain gages have drift issues over time. As Keith said, deadweight testers really don't go out of calibration (ok, the cylinder walls might wear over many, many thousands of calibrations and very slightly affect the pressure, but that is just a change to the area term in the calibration equations, and away you go again).

 

[danw2]

The calibration check reports I've done for clients always include the calibration device, its traceability to NIST and the date the calibrator was last calibrated. Since I'm not a metrologist, I don't get all nervous and upset when the calibrator's calibration certificate is 1 year and 1 day old, but the paper pushers on the customer end do. "Your calibrator is not calibrated ! ! ! The cert's expired ! ! !

There is something magical about the 1 year expiration date of a cal cert, as if the floating ball re-sizes itself or the chamber wall expands at exactly one year after the unit was calibrated, just like Cinderella's experience at midnight.

So, yeah, there is the reality of how little a deadweight drifts, but there's also the reality of the perception of the sacredness of validity of a calibration cert for one year, exactly one year.

If it were me, I'd go electronic. It's a secondary standard but your customers are not demanding a primary standard (deadweight).

 

[itsmoked]

Didn't realize that deadweights cost so much. We bought ours on ebay which has a lot of them.

If indeed you must get everything calibrated every year.. a gauge or transducer based calibrator may actually make more sense as they'd likely be easier to ship back and forth to a calibration lab.

Keith Cress
kcress -

http://www.flaminsystems.com

 

[EdStainless]

For your work the pressure gauge unit will be fine.
The only issue is the temperature issues, in very hot or cold applications the TempCo corrections can get a little iffy.
The gages that we used in the plant had a 18 month cal requirement, the certs and stickers all said 18 months. But our procedure said to re-cal at 12-16 months.

= = = = = = = = = = = = = = = = = = = =
P.E. Metallurgy, consulting work welcomed

 

[Ingenuity]

I did check out eBay too - considerably less cost but not too many to choose from at the 10,000 psi range.

I really appreciate all the input and comments from everyone. Thank you.