Oil Level Switch

I am looking for an oil level switch to go in a existing hydraulic pump tank. I need to sense low level of oil. It need a couple of NO and NC contacts. Can somebody recommend some thing reliable ????

Thanks

GO JETS

Please, think analoque level measure. You can estimate when some hydraulic pipe have broken. Also you can send message to operator, fill oil tank.

I customer wants low level so the press can be stopped if there is leak or a hose breaks

got to this link it will give you a overview of what you need.

http://www.womack-machine.com/index.html

Regards,
Tom

Look at http://gavazzi-automation.com/ac/Documentation.asp download the our product catlogue
look for VPA1MNA level sensor

Hello,


I work with Hydraulic systems and would also recomend using a analog level sensor if possible. Using a digital will only tell you when the tank is almost empty. If you use a analog you can sense if the level changes much over a seccond and the alarm/stop the system before you have oil all over the place in case of a broken hose.

Hydac has a Good analog sensor. Look at www.hydac.com

MrQ said:

Hello,


I work with Hydraulic systems and would also recomend using a analog level sensor if possible. Using a digital will only tell you when the tank is almost empty. If you use a analog you can sense if the level changes much over a seccond and the alarm/stop the system before you have oil all over the place in case of a broken hose.

Hydac has a Good analog sensor. Look at www.hydac.com

Click to expand...

Thank you for the link.

I have seen it 2 times in same day, pipe connection breakes down and there was 200 liter oil in the cable channel. There was only low-level-switch !
br. Seppo

Personally I'd still take the digital switch route rather than an analog sensor unless you can predict how much the tank level will change under normal operating conditions, for example we always take the digital route but have a warn level switch and a stop level switch as on a lot of or machinery we use a 5000L tank and a cylinder approximately 5ft diameter for clamping plus more cylinders for other functions which makes predicting the rate of level change quite unpredictable

Ok so presumably there is some other way to know if the piston is extended or retracted, and you want to prevent cavatating (possable pump damage etc). If so you have two options to us a simple level switch like this: http://www.omega.com/ppt/pptsc.asp?ref=LVK90&Nav=grek12.

Option 1. With the switch mounted near the top of the tank; When the piston is retracted, check the level.

Option 2. With the switch mounted near the bottom of the tank; When the piston is extended, check the level.

Either way you could easily use the switch to set an alarm and shut down the machine. Nothing fancy required.

Here is the drift I get
You are concerned with two issues
1. Emptying the tank and burning out the pump.
2. Sensing when you blow a line.

Both are good concerns.
1. Hydraulic pumps are not cheap. A float switch will go a long ways to prevent this from happening.
2. Line failure. My introduction to this was on a submarine. Blew a flex hose with mist all over -- oil mist plus electrical controllers = a very scary situation. After mist "condensed" we were wiping oil for hours. As mentioned this is a little tougher - how do you differentiate from normal demand (either flow or change in tank level) vs a leak?

Not sure how to go about it. For sure you would have to get very familiar with all your equipment and what their peak oil demands are.

Dan Bentler

Couldn't you put a pressure switch on the discharge side to detect a blown hose? Loss in pressure would cause pump to shut down.

Just a thought.

Ken

Thought of pressure switch. Same situation as that of level what is normal pressure decreasee vs decrease from blown hose? IF pressure switch was set below any pressure decrease from normal op then that would work. WOuld need time delay to allow pressure to build durning startup maybe
I think.

Dan

We have a customer that is required by their insurance company to have a low level shut off switch. A lot of times the tank is sized for heat dissipation (this company forbids heat exchangers), to that low level switch is actually pretty high in the tank.

As mentioned above, we put in a low level warning switch and an emergency shut down one.

We use an analog level sensor, plus a digital emergency low level sensor which will shut down the system. We also have a pressure switch on the output side of the pumps (after accumulator) that is disabled for five seconds during startup. This setup has given us the ability to monitor levels in the tank in real time. It has also saved some pumps and fluid by shutting down the system when there is trouble, and no one is watching.

Regards,
Charlie

There's another problem with installing a presure switch after a pump, on proportionally controlled/servo controlled hydraulic systems the pressure will not be constant after the pump (the only pressure you would expect to have constant would be pilot pressure) hence a pressure switch would be continualy switching based on the system demand. I've always found a good way to determine if a hose has split is (if the hoses are close to the powerpack) is to install a float switch in the powerpack drip tray if it's large enough that will cut the motor if the drip tray overspills (from a split hose). Albeit this will not detect a split hose anywhere else but i've always found that 90% of the time the hoses nearest to the powerpack are the one's to fail due mainly to hydraulic shock or (as we use a lot of internal gear pumps they fail regualr due to oil quality) from improper fitment i.e. rubbing hoses, badly made hoses (we make our own - says it all).

Anyways, Jimtech, Can you provide a little more info as to what capacity the tank is roughly, pressures involved and on they hydraulic control side if it's a fixed displacement pump(s) or variable displacement. Thanks

EDIT:- Just had a thought that may work, how about using flow sensors, one in the pressure line out from the powerpack and one in the tank line and monitoring the flowrates, outgoing versus return, when a movement occurs you would expect there to be flow in both lines at the same time (albeit with a slight delay) so detecting flow in the outgoing pressureline above a certain threshold with a very low flow in the tank line would probably indicate fluid is being lost.

Regards

Tom