Hydraulic oil mist detector

The Plant Safety Officer wants an oil mist detector installed in an unattended hydraulic pump house to detect when a fine spray high pressure (we operate at pressures > 1kilobar) oil leak exists that saturates the air with a fine oil fog. (We call it atomized oil spray, though its not really that fine.) This kind of fine oil fog happens when there is a hairline crack in a manifold or fitting. They are rare, but PSO wants it and what he wants he generally gets. Because its so fine PSO is concerned about an explosion hazard. Real threat or not, PSO doesn't want us to find out the hard way.

We already monitor tank level for an unexpected rate of change for major leak checking. That method would not likely find one of these fine spray leaks.

Does anyone know of any kind of sensor that might be used?

Have seen a couple flex hose on 3,000 psi breaks. Most impressive on submarine back in shaft alley where the hydraulic pump controllers are. Completely fogged shaft alley. We wondered about ignition of oil spray also.

Think I would give some thought to moving as much electrical as possible out of there. Mostly to protect the insulation on windings and circuit boards from oil. Relays of course would stay well lubed - darn oil gets into everything.

14,000 psi - really? That is about the pressure range of diesel engine injectors so maybe the question of the mist ability to ignite is a good one. It is also at the bottom of the water jet cutter range - a pin hole could really inject or cut someone.

To share some industrial hygiene experience. I woulod not just stick an instrument in there because
1. Waste of money
2. IF wrong instrument it give a false sense of safety (like smoke detector with no battery)
3. Calibration issues (something to consider even if you get the RIGHT instrument).

Been a few years but I believe their is a mist standard. You might want to look into American Conferance of Governmental Hygienists (ACGIH) documentation of Threshold LImit Values (TLV). They give full explanatin of how and why the TLV was written.

Think I would have a lab evaluate the question first and have them determine an airbornce concentration of mist that will ignite and give the upper and lower flammable concetrations.

Most people scratch their heads on this question - I am now. I think a good starter comparison is the nuisance dust standard (OR the mist standard??) which is emplaced mostly for clarity of vision (hard to see across factory when air is full of dust).

There are instruments made generally using scattered light to detect airborne concentrations of dust. These may be able to be used in your situation.

Baccarach, MSA, are some instrument manufacturers I would talk with.

Grainger bought out Rice Safety in Seattle to get their foot thru the safety business door. Check with your local Grainger to see if they have an industrial hygienist to consult.

YOur state safety group should have a consultant who may be able to help (unless you are an OSHA state then it would be OSHA - at least it is free)

After that the yellow pages for "safety or industrial hygiene"

Dan Bentler

Sticking 'oil mist detector' in to Google brings up 60,000 hits. Mostly to do with ship board and engine room systems but I don't think the sales people would mind if you are a 'landlubber'.

Bryan

in the cranckshaft of big motors (marine and generators) they are always used. if the pressures are very high please check the blow line to open air, it should have a antimist device mounted. Or a nitrogenline on the tank to prevent oxygen in this tank.

Did a Google search and found interesting article at
http://www.oilmist.com/bilbao-paper.pdf

Thought was good info.

Dan Bentler

I found the same. Now I know what the instrument is called - a nephelometer.

Nephelometer sounds kinda kinky. But we do have hot oil mist so maybe appropriate?

Dan Bentler

It looks very similar to a light-based particulate smoke detector. How can it tell the difference? Possibly via the absorbed spectra of the oil? Could a smoke detector-type device work for this application?

-rpoet

yes any device that looks at the light change will work however it will get dirty inside so impossible to use. when the airflow is through a pipe it will work good.

rpoet said:

It looks very similar to a light-based particulate smoke detector. How can it tell the difference? Possibly via the absorbed spectra of the oil? Could a smoke detector-type device work for this application? -rpoet

Click to expand...

Worked with instrumentation using light to detect airborne "contaminants". Light sources included visible UV IR etc.

One of the problems with these as with any instrument is false positive or negative and error from other "chemicals"

Could smoke detector work for this maybe
Accurately -- doubtful.
Reliably -- more doubtful - not engineered for your environment.

Dan Bentler