Hi all, brand new to this forum, i am employed as a Fleet training co-ordinator for a municipality where we utilize standard tandem dump trucks, Vactor units, automated solid waste units, Cat and Volvo loaders, graders etc. all of these units due to their operating components have large hydraulic tanks. the solid Waste and vactor units in particular have many hydraulic components utilizing many hose to feed the components. at least a couple of times a year these units will break a hydraulic hose and some are large enough to drain the tank before the operator notices. Not only does this create a possible dry running pump, but environmental damage and posssible lawsuits (we had a motorcyclist go down after hitting hydraulic fluid left on the roadway) Has anyone ever heard of an electronic tank level indicator that would either shut the PTO off or send an alarm to the operator to shut down the unit? seems as though this would be pretty simple to do?? Your thoughts? Kaziff
I don't think you need to go electronic. All it would need is a simple float switch mounted in the tank. The switch contacts open when the float goes down below the horizontal. The output from the switch could easily be used to activate a light and/or audible warning device in the operator cab. Here's a photo of a typical switch. The contacts will be open in that position, with the float in the horizontal position the contacts will close.
Could you use a electric gate valve along with that float switch?
i believe this might work Nige, have you ever used the float for this application? overworked, would a gate valve shut off fluid to the pto pump? might damage the pump? Thanks for your help guys! Kaziff
You would have to wire it in to kill engine also to prevent pump damage.
Yair . . . I don't believe that is a good idea . . . an engine shutdown at the wrong place at the right time could have worse consequences than an oil trail. Cheers.
I agree. you can't take control away from the operator/driver by shutting down the engine in a circumstance where he could probably be in danger. Kaz, the switch in the photo is used on pretty much all our machines to monitor hydraulic tank and engine oil pan levels, that's why I posted the picture of that particular switch - because I know it works............
For the purpose of preventing a spill on most hydraulic equipment a tank float wouldn't do very much good. On anything with cylinders what level would you put the float at, with all cylinders retracted or extended? My boom truck has around 400 litres in the tank when the boom is in the cradle and less than 100 litres when all out, that's 300 litres on the ground before the float would cut out. A 100 litre spill is reportable to the ministry of environment.good maintenance and alert well trained operators ultimately are the only good answer. In 30 plus year of running backhoes, excavators, boom trucks and all kinds of farm machinery I've never needed more than half a pail of oil to top up after a break.
Just to soften my previous reply the low level switch would be valuable to prevent damage to your equipment . Regards Glen
Velocity checks in some of the hydraulic lines would help........ they snap shut when flow exceeds design spec. Takes some engineering, but well worth it in some situations.
Not to be a jerk on this subject but maybe the best thing is to improve your maintenance program to have hoses inspected at scheduled times and when replacing one always be careful about the routing and that all hold downs are installed. Too often when working on a machine that came from another location I find missing hold downs, some people can be in too big a rush to get a machine back online.
Good point about shutdown safety, I was only looking at it from preventing a pump failure.
Hi all, Kaziff again, the guy who started this discussion, thanks for all the great response. i would agree that a switch shutting down the engine would be a bad idea, and i see some referrence to lack of maintenance or inspections of the units. We are a municipality with Gravel trucks, Vactors, hydraulic sweepers, hiabs, automated solid waste units, loaders etc. We have a NSC certified shop which hires certified heavy duty and automotive mechanics who do a gopod job of repairing reported defects and regular maintenence. Most of our units while in use retain nearly a full tank of hydraulic fluid (unlike the crane operator who uses most fluid on a full lift ,if a crane blows a hose, do the cylinders not lock keeping the fluids in the cylinders?) The day i started this discussion, our vactor had blown the main feed hose to the pump, under pressure and empyied the tank on the street while the operators were at the front of the unit flushing a sewer line. Today, the NEW repaired hose blew off from it's crimped end with the same result, 45 gallons of hydraulic oil running down the street. not sure how better maintenance would have prevented this? keep in mind, this hose runs under the unit and can not be seen unless underneath the pump with a flashlight. Can anyone see any harm in using the tank switch which would kill the PTO when the tank drops below it's normal in-use level? Kaziff
If the hose that came off was the inlet to the pump I am having a problem understanding how killing the PTO would stop the spill. Unles there is another pump pushing the oil to the one that the hose came off. I would be investigating why a new crimped hose failed, wrong hose for fitting? Wrong setting on crimp machine? Something causing excess pressure in the tank? New hoses should not fail. Not trying to be a jerk but would like to know the cause of the failure for a new hose assembly.
I like the idea of being able to kill the PTO via a tank level switch. However those switches are not designed to carry a large current, so you might end up with the level switch controlling a relay that kicks the PTO out. KSH, maybe I'm wrong but I get the impression the hose that failed is probably the one between the pump and the "business end" of the machine. I'd be looking at, in no particular order:- 1. System pressure settings on that specific machine and previous maintenance history. Any valves replaced or adjusted recently..?. 2. Hose fabrication process & tooling is up to the job. 3. Replacing critical hoses on a "before failure" basis, probably at the same time as a hydraulic oil change. 4. Personnel competency, whether it's an external shop or the equipment maintenance team that builds the hoses.
If it is an air operated pto you will need a relay going to and electric/pneumatic valve to kill the air Sent from my SAMSUNG-SGH-I317 using Tapatalk
I thought about what I wrote later and maybe when the OP said main feed he was saying the "feed" to what ever the pump was powering. I was originally thinking of the "main feed to pump" as the suction line to pump. Different people can use descriptions that can cause confusion, can't tell you how many times I had people refer to a hydraulic motor or control valve as a pump! On a system where a pump is just running hydraulic motors the oil level in tank would stay fairly constant so I can see a float switch being of some help. On a machine with cylinders not so much. I hate to think how much oil would spray out of the system of a 773G before level got low enough in hydraulic tank to set off alarms. Or a 350L excavator when drive hose fails in a mud hole, wait I do know the mess that made
almost as big a mess as a 375 that the drive hose blows in the mud/slop I might now where some new "oil sands" might be at
One almost nice thing about this failure was it was a low spot and as oil floats on water and we had an ample supply of oil only absorbent pads there was almost 100% containment of the spill