Hydraulic Circuit Fluid Temperature 3

[nathinder]

My manager has shown me this circuit its for a welding station for my revision. Its a circuit hes ran for many years thats never had problems but all of a sudden the oil tank is very hot on inspection and the system seems to be losing its ability to work. Hes asked me why and what improvements can be done? I have never done hydraulics before so just learning. Many of the findings in theory state its due to filters clogging over time or leak but the oil level in the tank is fine and theres no contamination so that makes me believe that the filters are not clogged and theres no leakage.

The cylinder (item 10 )operated and holds the pressure to 100 bar for 15 mins and the relief valve is set to 130 bar. Pressure switch (item 11) is set at 100 bar. when pressure is required the PLC energises item 6 and when pressure has reached 100 bar the PLC signals item 6 to unload the pump.

I am assuming that the increase of temperature is a result of an increase in pressure due to heat not being able to dissipate in the system. Is it possibly because the switch has failed to indicate the pressure has increased from 100bar and as such the PLC has not activated the 2 position directional control valve (item 6) to unload the system and due to the oil not being able to flow anywhere as a result of the non return valve (item 7) the system is just wasting oil.

The pump is a fixed displacement gear pump that is displacing at 2.5lt/min.

Item 1 is a strainer and item 4 is a pressure filter with by-pas which opens at 1 bar. Item 8 is a accumulator. Item 5 is a 2 stage pressure relieve valve.

Any thoughts on what could of caused this heat increase?

 

[nathinder]

This is a case study provided by my manager to help me learn hydraulics and understand. I think he just wants general reasons as to why the oil reservoir is overheating in the current circuit as shown. He simply just gave me this circuit and said the system has worked for many years but one morning he came and the oil reservoir was so hot he wasn't able to touch it (this is not the normal state) and asked me what are the possible causes of the problem? Then he mentioned to suggest any improvements to the circuit that might protect against the in the future but do not suggest major hydraulic changes since the circuit is standard unloading circuit that has worked well for many years.

The only other info given was as stated above
the cylinder (10) is of a clamping station that holds nominal pressure of 100 bar for approx 15 min then off for 2 mins while welded piece is removed and recharged with unwelded pieces. The relief valve (5) is set to 130 bar. When pressure is required the PLC energises Item 6 and when the correct clamp pressure has been achieved, the pressure switch detects system pressure as correct and sends a signal by the PLC to valve 6 to unload the pump. Also during the 15 mins welding, if pressure switch (11) sees a pressure drop below the 100 bar, valve 6 is re-energised until the correct pressure is regained.

He said that the oil level is fine and regular oil sample checks show no issues of contamination. The system sees to be losing its capability to work no other information.

He said to come back to me with the possible causes of the problem.

Which i think everyone has stated it can be a multiple set of things which i need to list to him.

Thanks

 

[Stick.]

"Trust, but verify" is extremely important when you're troubleshooting. From the way your posts have been written, it sounds like you've done a lot of trusting, but no verifying. You really need to go out to this machine, watch it run and start checking things for yourself. For instance, is valve 5 actually set to 130 bar, or is it maybe only set to 110 bar? During the 15 minute clamp time, what does each pressure gauge read? Does the accumulator have to be recharged during the 15 minutes? If so, how often? Can you tell where the heat is being generated (which component is the hottest)? Have you talked to anyone else besides your boss that might be able to confirm or maybe counter your boss's description (maybe it's always run like this and your boss has only just noticed it)? When your boss says that oil samples show no issues of contamination, what does that mean exactly and when was the last sample taken?

This isn't a problem that is easily solved at your desk, go out to the machine and poke around a bit. If you're too new/inexperienced to do this safely by yourself, get a list of things you want to check (you have enough info in this thread to make a pretty good list) and find someone who can help you out. If there are any good maintenance people at your company, I'd recommend making friends and seeing if they can help you out.

 

[3DDave]

Stick - the machine does not exist. It was to test if the OP knew about hydraulics.