Fire Sensor for Hydraulic System

The FM inspectors (on our invitation) have paid us a visit and generally liked what they saw but they recommended that we install some heat sensors above our hydraulic equipment to detect a flame and shut down the pumps. I'll tie it into the estop string but also monitor its status with the PLC so we can alarm the fault.

Any recommendations?

This sounds like non-sense.

I would ask here
http://forums.hydraulicspneumatics.com/groupee
I doubt oil will catch fire before a lot of other things will. I have never seen a fire detector just for hydraulic systems and most of mine have been in saw mills. Oh yeah, why bother? The saw dust will catch fire before the oil does, if it ever does.

This has been a thing here in the UK.

Believe it is due to pin prick holes developing in pipes and escaping oil being in mist form. This is then a highly combustable situation ( so I am told ).
We used to fit an auto extinguisher above oil filled transformers.
Very simple glass activation. Heat broke glass, extinguisher went off.
As to the monitoring system why not tie into your fire alarm system .

Peter Nachtwey said:

I would ask here
http://forums.hydraulicspneumatics.com/groupee
I doubt oil will catch fire before a lot of other things will. I have never seen a fire detector just for hydraulic systems and most of mine have been in saw mills. Oh yeah, why bother? The saw dust will catch fire before the oil does, if it ever does.

Click to expand...

Although I agree with Peter I have been through the same thing with an Insurance Company that wanted not only heat sensors but Fire Suppression over top of all of the HPU's. Funny thing is in a steel plant there is almost nothing to burn and everything else is supposed to be burning!

Our solution was to change oil. Ecosafe is water glycol based. It is fire resistant and bidodegradeable. Made the insurance people and the environmental guy happy and seems like pretty good oil. We had it in service for a couple of years before I left with no ill effect. Also the company was great to do business with, I highly recommend them. Changing oils in a system, especially to a water based needs to be done carefully and methodically. A rep from the company came down with each changeout and worked with the maintencance guys.

http://www.americanchemtech.com/fire_resistant.html

Sorry can't help with a temp sensor though.

Greetings Peter, thanks for the link, I'll register and ask.

It may sound like nonsense, but Factory Mutual and FM approval are a big deal and that is what they are asking for - a heat sensor - and now our safety officer is all fired up (pun intended) to get some installed.

From what I understand these are simple, a eutectic band holds a pair of contacts closed, the eutectic melts at a specified temperature and the contacts open - works pretty much the same way a fire sprinkler works.

Its standard in marine/offshore.

This is a valid issue. A small leak in a oil hydraulic system can spray oil very much like the oil burner that heats your house and it does not take much to ignite that spray. There is a real possibility that this condition could burn for a long time before hoses melted or it ran out of oil.

Two people said fires were caused by small leaks.

So why not detect the leaks? How can leaks go undetected unless there is absolutely no one around to hear the noise or see the mess? Are people really so careless that they would walk right by a hydraulic mess or the leak makes without thinking there is something wrong?

There are numerous ways to do this, from simple (plastic tubing that melts and releases its trapped air pressure, indicating a fire) to the complicated (UV/IR flame detectors).
Theres also the little wax bulbs that are used on deluge systems that achieve the same thing (wax melts, air pressure released, water follows shortly after!)

I dont think I would try to detect the HEAT as much as the actual flame. I've done a bunch of fire&gas offshore and its usually a combo of UV/IR flame detection and single point/Line of sight gas detectors.
I'm sure something along these lines would be adequate.

We have used Fenwal Series 27100, 28000 Vertical DETECT-A-FIRE® Units when asked by customers for FM compliance.

I have attached a PDF manual.

In my natural gas compressor station, we use gas detection, UV/IR flame sensors, Multi-IR sensors, and heat detectors (Fenwal, 225 deg F)mounted on the ceiling.

Our older flame detectors were just UV detectors. In the last 30+ years, each of the 3 or 4 fires we had were detected by the heat detectors first. The reason being that smoke from a fire obscured the UV radiation that the flame sensor is monitoring.

Our later flame sensors were UV/IR combo sensors, but they also still needed to "see" UV radiation from the flame. I think the idea was that the sensors needed to be immune to false triggers from things like lightning flashes and such, so the IR portion was added to better discriminate for flame characteristics. No fires since they were installed. $3000 each.

Our current sensors are Multi-IR (no UV portion)@ $3500 each. There are still situations in which a UV detector is desirable, but ours is not one of them.

We refuse to do away with the Fenwal heat detectors at $150 per. They have been proven to work and are still manufactured. We use the NC sensors in series for fail-safe design.

http://www.fenwalcontrols.com/utcfs/Templates/Pages/Template-54/0,8063,pageId%3D1045%26siteId%3D375,00.html

Depending on the kind of eqipment the hydraulics are either in a seperate pump room, enclosed doghouse, or in a pit under the press so a flame could go for several minutes before it would be noticed. These are huge 13000 ton presses and the oil is under pressures up to 18,000 psi, (thats not a typo) so a pin hole leak can spray large amounts of oil mist very quickly. We've never had a fire and there aren't any likely ignitions sources in the area. That doesn't matter to the safety officer and when he orders it we do it.

Thanks for the tip on Fenwall.

Steve, I like the tube idea - it has the advantage that the tube can be snaked around multiple points.

I also found a cable that has a low melting point insulation, when the insulation melts the wires connect. http://www.lineardetection.com/linear_heat.htm

And there are these guys, I would need several sensors but they are inexpensive. http://www.thermotechheatdetectors.com/

We use a product called protecto wire on our coal handling equipment and transformers. It has two wires seperated by an insulator. When the insulator melts, the connection is completed. There are some length limitations, but is easy to install, and available in different temperature ranges. If you pay attention to the distances when installing, the available head end unit can even give you an idea where the closest melting point was observed.

Peter Nachtwey said:

So why not detect the leaks? How can leaks go undetected unless there is absolutely no one around to hear the noise or see the mess? Are people really so careless that they would walk right by a hydraulic mess or the leak makes without thinking there is something wrong?

Click to expand...

With respect to "normal" hydraulic system leaks - people ignore them all the time.
With respect to ruptures they leave to avoid getting wet with oil or not breathing oil mist.
Have seen several ruptures - twice on submarine where most of engine room was fog of 2190 TEP - also in industry. Amazing how much oil a pump can pump all over the floor in a matter of seconds. These were only on 3,000 psi systems - I would not want to se one on 16Kpsi.

Seems to me that the FM guy is going to inspect whatever system / control / alarm / detector you install. So I would ask him what he wants you to put in.

Dan Bentler

Our FM guy also wanted heat detectors in our hydraulic pump room. the pump room used to feed our entire plant running mainly motors for conveyors etc. We got the detectors from our alarm company that services our plant and tied them into the alarm system and cut power to the pumps when tripped.
Also had to install flow monitors on the pressure side of the pipes to sense a major increase in flow if we broke a pipe in the plant. After all this was done we quit using the system and went AC Drives on the equipment that that was hydraulic. I don't undrestand why it was hydraulic in the first place as our plant is a food processing plant.