Pressure Not Building Up

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MAINTENANCE@SANKAR.COM Member Join Date: Mar 2008 Posts: 5	Pressure Not Building Up 03/17/2008 2:45 AM
	our 400 ton hydraulic press H type with PLC based electrical control is having a working pressure of 320 kg/cm2 is not building up the required pressure.request for expeert advice.
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PWSlack Guru Join Date: Jan 2007 Location: In the bothy, 7 chains down the line from Dodman's Lane level crossing, in the nation formerly known as Great Britain. Kettle's on. Posts: 32175 Good Answers: 839	#1 Re: pressure not building up 03/17/2008 5:46 AM
	Blockages or leaks in the hydraulic lines and pumps? __________________ "Did you get my e-mail?" - "The biggest problem in communication is the illusion that it has taken place" - George Bernard Shaw, 1856
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Labyguy Guru Join Date: Dec 2006 Location: Charlotte, NC USA Posts: 791 Good Answers: 17	#2 Re: Pressure Not Building Up 03/17/2008 11:55 AM
	There is a leak somewhere. I wouldn't think there would be a blockage as a blockage would build up pressure, just not where you need it. If there is not any hydraulic fluid on the floor, then the leak must be internal, an over pressure relief valve may be stuck open, I've seen that before. __________________ Be careful of what you wish for .....
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Solrac Commentator Join Date: May 2007 Posts: 56	#3 Re: Pressure Not Building Up 03/17/2008 11:59 PM
	How do you know that the pressure is not building up? I assume that the PLC controls the actuation of the press, and as such requires a reading of 320 kg/cm2 before actuation. Of course looking for leaks would be the first step, but if no leaks are found, then check the pressure sensor - it might be faulty.
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Anonymous Poster	#4 Re: Pressure Not Building Up 03/18/2008 12:03 AM
	pls check relief valve pressure, if this is opening early then the desired value then this would lead to not maintaining the required pressure. By the way the working pressure of your press is decided by the system relief valve or other safety valve. Kindly see the circiut of your press and find out the relief valves available. You might get some clue for your problem. regards Brijesh
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The Mechanic Power-User Join Date: Feb 2008 Location: Mid-West USA Posts: 498 Good Answers: 28	#5 Re: Pressure Not Building Up 03/18/2008 8:01 AM
	Start with the easy stuff first. Did your problem come on gradually or all at once? If gradual it could be the filter. Have you noticed any new noises in the system? If so a plugged filter could be causing the pump shaft seal to suck in air. A sticky control spool or relief valve could also show up intermittently at first then fail completely. Internal leaks caused by failing seals in cylinders and valves, as well as a pump failing, appears at higher pressures first and the ability to build pressure drops over time. Sudden failure could be the result of debris in the system cutting seals, contaminating valve seals, and ultimately damaging the pump. Keep in mind that the debris could be coming from the pump. When was the last time the hydraulic oil and filters were changed??? First - Check the filter and relief valve(s) Second - verify pump pressure at the pump. If using a pressure / flow meter compare the flow to the spec sheet for the pump. This may indicate a blockage in the suction line if the filter appeared ok. Third - Start checking all remaining valves in the system including the solenoids that control them. Starting at the pump since you have verified it to be good.
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Grochy Power-User Join Date: Jan 2008 Posts: 127 Good Answers: 5	#6 Re: Pressure Not Building Up 03/18/2008 5:19 PM
	We have had similar problems to this on a press and traced it back to 2 seperate problems one was a dirty relief valve in the main valve block and the other was a manually adjustable pressure valve on the side of the press that someone had adjusted out.That said if the pressure control is an electrically operated propotional valve controlled by the plc you may need to check the plc is getting a true reading from transducer etc and is actually going into the Pressure side of the bend as some presses free fall until the mute point is reached then perform the bend operation
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bwire Guru Join Date: Dec 2007 Location: Upper Mid-west USA Posts: 7498 Good Answers: 97	#7 Re: Pressure Not Building Up 03/18/2008 10:27 PM
	Have you bled air from system or cylinder? __________________ If death came with a warning there would be a whole lot less of it.
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Anonymous Poster (1); bwire (1); Grochy (1); Labyguy (1); PWSlack (1); Solrac (1); The Mechanic (1)

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