Flow meters discussion

[Southern Cross]

We're having a discussion at my workplace around calibration of flow meters that are used to measure out hazardous monomers into a process vessel. Note that it would require considerable work to remove them from the current pipework to get them tested away from where they currently reside. The downtime would be a major hit on our production schedule.

Calibrations have been performed, but the process has safety issues. A proposal has been made to take these off the calibration schedule and use monitoring of the end product test results to verify that there hasn't been any significant changes. SPC with hard limits? I have concerns with the proposal from a quality/ISO9001 perspective, but I fear I'm going to get overruled by the SHE management. Any thoughts on whether the verification process might substitute for calibration? Or a better approach? Would it pass inspection by an auditor?

 

[Sidney Vianna]

If my understanding is correct, stopping the calibration of such flow meters could have a significant negative impact on both process safety and product conformity. Even if the organization doesn’t have a certified occupational health & safety system in place, you would think process instrumentation that is safety critical HAS TO BE monitored/calibrated. Don’t you have planned plant shutdowns when such meters can be calibrated without compromising production? Can the meters calibration interval be extended based on history and stability? Can’t the meters be calibrated in house to minimize downtime?

 

[Southern Cross]

Sidney, thanks for the reply.

If my understanding is correct, stopping the calibration of such flow meters could have a significant negative impact on both process safety and product conformity.

That's correct.

you would think process instrumentation that is safety critical HAS TO BE monitored/calibrated

That's my take on this as well. Monitoring the final results of the product with SPC would come under verification (as I understand it), not calibration. Therefore my consideration is that an auditor wouldn't agree that this approach.

Don’t you have planned plant shutdowns when such meters can be calibrated

Yes we do.

Can the meters calibration interval be extended

The calibration interval is already 12 months. I'm reluctant to push it out further, but combined with a verification plan, it might be made to work.

Can’t the meters be calibrated in house

Yes, that's happening now. It's got some safety issues due to some pipework that wasn't ever designed with the thought of calibration in mind.

Any advice is appreciated.

 

[Randy]

Chemicals? Flow meters? Are you a member of the American Chemistry Council? If you are then you have to do either RC14001 or RCMS...No options. Most likely if you have to do RC14001 then this comes to mind.

9.1.1 General.....
.... The organization shall ensure that calibrated or verified monitoring and measurement equipment is
used and maintained, as appropriate.

Now if your not, depending on the chemicals and quantities involved (and if you're in the US) you've no option, you've got to meet the regulatory requirements OSHA Process Safety (29CFR 1910.119)....you have no option. There are places where your question about calibration might be governed, here are 2 that jump out.

1910.119(d)(3)(ii)
The employer shall document that equipment complies with recognized and generally accepted good engineering practices.

1910.119(d)(3)(iii)
For existing equipment designed and constructed in accordance with codes, standards, or practices that are no longer in general use, the employer shall determine and document that the equipment is designed, maintained, inspected, tested, and operating in a safe manner.


Check with your SHE guys

 

[John Predmore]

@Randy provided the language in the standard. If verification is an acceptable alternative to formal calibration, would be acceptable to do verification of flow rate on a periodic schedule? If you are dispensing a liquid into a vessel, can you collect a sample and verify flow rate using a volume/time or weight/time calculation? The other possibility would be if there is a positive displacement pump, the flow rate is the product of the displacement and the RPM. I am not a process chemist, but I try to be a problem-solver.

 

[Randy]

Everything is dependent on situation.

If the OEM specifies periodic "calibration"

If there is an actual regulatory mandate for "calibration"

If there is some type of engineering specification for "calibration"

Bottom line is that somewhere in the process something has to be "calibrated", there is no one size fits all including the "verification" method or tool

 

[John Broomfield]

In my experience developing management systems that conform to RC14001:

Critical flow meters are periodically (quarterly, semiannually or annually) verified on-site (traceable to a national measurement standard). Flow meters are only recalibrated or replaced if or when a meter fails verification.

* the interval depends on conditions of use and the under or over risks.

 

[outdoorsNW]

You said the pipework was not designed with calibration in mind and removal creates safety problems. Is it feasible to modify the pipework to make removing the flowmeter much easier and safer?

 

[Southern Cross]

Sorry for disappearing, but I'm based in Sydney Australia, so the time zone is different. As a result, we're not on RC14001 - but we do need to comply with ISO9001, ISO14001 & ISO45001. Thanks to all for your input.

If you are dispensing a liquid into a vessel, can you collect a sample and verify flow rate using a volume/time or weight/time calculation?
No. Immediately after the flow meters there is a manifold that combines the liquid monomers being pumped, then a high speed mixer, before the product is dumped into water with initiator and emulsified under agitation. The liquids are being turned into a polymer immediately on hitting the process vessel.

if there is a positive displacement pump, the flow rate is the product of the displacement and the RPM
Not sure exactly what kind of pumps we use, but I think if I was the auditor, I'd then be asking how we calibrate the RPM on the pump. Practically speaking, that's difficult too.

If the OEM specifies periodic "calibration"
Now that's something I hadn't considered, but I think it's highly important. And it's something I can use in my arguments.

Is it feasible to modify the pipework to make removing the flowmeter much easier and safer?
The engineers are considering that - but I can see there's a passing the buck mentality in operation. They would rather than I monitored the process through SPC than have to undertake the work, for what they see as little benefit.

* the interval depends on conditions of use and the under or over risks.
One of the points being made is that we make approx. 18 batches per week using these meters. If we calibrate once a year, that's likely to be unhelpful. If there are problems, we're likely to know about it within a week - unless any drift in measured flow is slow and consistent.

So the argument being made by the production management and engineers is that the process of calibration isn't that useful - regardless of what ISO9001 (for example) insists on. I disagree, I think it's a useful exercise. But the safety management is likely to want to force the issue.