Manufacturing Equipment Pressure Gages Calibration Requirements

[ScottK]

Re: Pressure Gages Calibration

How do you bend metal? You apply pressure...I'd say they would need to be calibrated.

It's probable that the force per unit area on the metal is not what's being measured.
Likely, what's being measured is the pressure in hydraulic or pneumatic lines which are typically not quality critical measurements. It shows you if the press is operating properly, not if the part it's making is good. I'm sure the variation in the pressure required is so wide as to make it useless process monitoring and just a target for the setup guys to check and to indicate if there are any leaks in the lines.

I've worked in machining, coating, and molding, all of which had hydraulic lines with gauges, and they were never calibrated.

In fact the only pressure gauge I've ever had to calibrate is one used measure static pressure in a vessel to show the saftey margins are being met.

But, you never know - in some applications pressure may be a process indicator for metal bending.

 

[Boscoeee]

Hello everyone.

Durring a recent aoutdit i have been qriten up by an auditor for not calibrated preasure gages on our manufacturing equipment.My question is do the have to be calibrated?

Thank You.

Do you have a calibration status on the pressure gages?

The requirement is to be able to establish the calibration status of the equipment, you decide what needs to be calibrated based on need and what is acceptable industry standard.

IMHO, if you decide not calibrate a pressure gage, then it should be labeled as such!

 

[Hershal]

Hello everyone.

Durring a recent aoutdit i have been qriten up by an auditor for not calibrated preasure gages on our manufacturing equipment.My question is do the have to be calibrated?

Thank You.

This has a very simple solution:

If the pressure gage tells you something you need to know to complete your task, calibrate it. If it does not need to be calibrated, remove it from the machine and system.

 

[ScottK]

This has a very simple solution:

If the pressure gage tells you something you need to know to complete your task, calibrate it. If it does not need to be calibrated, remove it from the machine and system.

what if the gauge an indication of the status of the system and not necessarily related to product conformity?

Now -I'm assuming ISO9001.....
ISO9001 7.6 is all about providing evidence of the conformity of the product.

An injection molding machine for bottle caps might have several pressure gauges, none of which are used to monitor the conformity of the product.
So they don't need to be calibrated. But they can't be removed because they do monitor the machine.

An ISO9001 registered injection molding shop with a lot of lines that makes low margin, high volume parts would go broke in calibration costs.

 

[Hershal]

What do the gages tell you?

If they have no effect on the product, then why have them installed? If they tell you about the machine, then I suspect they tell you whether the machine is working within parameters; therefore the indication does have an effect on machine performance and as a result product quality. Therefore they need to be calibrated.

 

[ScottK]

What do the gages tell you?

If they have no effect on the product, then why have them installed? If they tell you about the machine, then I suspect they tell you whether the machine is working within parameters; therefore the indication does have an effect on machine performance and as a result product quality. Therefore they need to be calibrated.

Yes - logically that makes sense and is likley a best practice.

But it's not what the ISO9001 standard requires. It's the first paragraph of 7.6: "...evidence of conformity of product to the determined requirements."

Hydraulic line pressure isn't going to prove that that required dimension A is Xmm. It will tell you if the machine is capable of getting there, but that's not what the standard requires.

 

[BradM]

Re: Pressure Gages Calibration

Quote from the Report

"Pressure gages on forming machines are not calibrated or identified as not requiring calibration"

This interests me. How did the auditor determine these gauges needed to be calibrated? If the auditor saw the gauges and did not see a calibration sticker, then, I would question the finding. If however, the readings were relevant to the process, then they should be calibrated. Did you get any kind of objective evidence from the auditor regarding this finding?

Well gages in question are part of a bending machine. The reading is taken form the gage by the operator as reference only. Is there a standard that would call out that the gages need to be calibrated. And if yes taking apart the machine each time the gage needs to be calibrated would be insane.

You should not have to take it apart. There are probably air hoses running to the gauges. You can go disconnect the hoses, and simulate the pressure into the gauges.

As far as labeling gauges for reference only, I have just seem to find it easier for me (and others) to always label indicating/measuring devices. Not saying that's the law; it's just always been the easiest with me.

 

[bobdoering]

Re: Pressure Gages Calibration

This interests me. How did the auditor determine these gauges needed to be calibrated? If the auditor saw the gauges and did not see a calibration sticker, then, I would question the finding.

Actually, it would be a good call by the auditor. I have had customer auditors ask the same question, and what was even more embarrassing was there were little green stickers on the gage that seem to imply where the pressure should be, and it wasn't. The audit questions is simple "How do you know if that gage is providing adequate feedback about the process?" If you can state the you can remove the gage, because it has nothing to do with the process (even PM), then that may justify no calibration (and no inclusion in the FMEA).

On the other hand, if it has any influence on the process and its control, the answer is simple. Not only should it be calibrated, it should show up in the FMEA and/or control plan.

As far as labeling gauges for reference only, I have just seem to find it easier for me (and others) to always label indicating/measuring devices. Not saying that's the law; it's just always been the easiest with me.

Yes, otherwise it looks like the gage was overlooked...which is not really a good thing.

 

[BradM]

Re: Pressure Gages Calibration

Actually, it would be a good call by the auditor. I have had customer auditors ask the same question, and what was even more embarrassing was there were little green stickers on the gage that seem to imply where the pressure should be, and it wasn't. The audit questions is simple "How do you know if that gage is providing adequate feedback about the process?" If you can state the you can remove the gage, because it has nothing to do with the process (even PM), then that may justify no calibration (and no inclusion in the FMEA).

On the other hand, if it has any influence on the process and its control, the answer is simple. Not only should it be calibrated, it should show up in the FMEA and/or control plan.

I pretty much agree. I'm just unclear as to why the auditor just summarily wrote up an instrument. It could be important; it may not.

Injection molding machines have 106 gauges on them, most all of them are just used for maintenance. So I'm still unclear if the auditor just saw an uncalibrated gauge and started writing, the auditor found a clear nonconformity within their QMS regarding the gauge(s), or if the auditor may have process knowledge, and knows the gauge is relevant to the process.

 

[Marc]

Re: Pressure Gages Calibration

<snip> Yes, otherwise it looks like the gage was overlooked...which is not really a good thing.

I have long advocated against labeling each gage that does not need to be calibrated. Looks don't mean a thing. Gages which have to be calibrated should be on a recall list. If the person responsible for the machine can not explain which gages have to be calibrated, and why, and which do not have to be calibrated (and exactly why they don't have to be calibrated), that person has no business being involved with the machine.

If one uses the type of 'label everything' model, one would have to label every uncontrolled document 'Uncontrolled' in some way (as an example) which is a total waste of time.