Hydraulic Press Controls

The company I work for uses a dozen or so hydraulic presses in the range of 300 tons. The controls on these things date back to the mid 80’s. They use Modicon controllers, have two buttons to begin the pressing operation but don’t really conform to two handed control. Meaning the buttons aren’t spaced far enough apart and there is no anti-tie down mechanism. So we are looking at retrofitting these things with new PLC’s, light curtains, safety controllers and Touch Screens.

So here’s my question. I’ve been doing some research and getting up to speed on ANSI Standards B11.2 and B11.19 as well as OSHA 1910 laws. 6.3.3 of B11.2 calls for Control Reliability and recommends using two programmable controllers in the control system. I can see the advantages of this however I am planning on using a PILZ PNOZ Multi Safety controller on the press. These things have independent processors from 3 different vendors. The E-Stops and Light Curtain will be wired into this thing and the Relays it will be switching will be wired back to provide feedback to the controller so it knows the state of those relays. Using a system like this is it necessary to use redundant microcontrollers for the control system?

On a side note, this project has gotten the hair up on some of the managers claiming we can’t do anything to the presses without the consent of the original manufacturers because of liability issues. Now I see there point in one aspect but in another if someone gets hurt on these things who is really liable? The original Press manufacturer who made these things 20 years ago, or us for not having them up to OSHA standards.

Anybody do press controls for a living? What’s your take on this?

The modifications to older presses to make them conform to current standards frequently requires more than a control upgrade. Enderle Engineering [email protected] does these upgrades, both on the control side and the hydraulic side. Contact name is Gordon. We have worked with him on many projects and he will not steer you wrong. His phone number is (248) 375-1010

On the redundant plc's, we have built a number of controls which use either dual plc's with the outputs split between them, or a single processor with two outputs (separate cards) required to activate the critical valves on the press.

Remember, the person who is most responsible for the safety of the machine is the one operating the machine!

BC

While you're upgrading don't forget ANSI/SPI 151.1-1997. There are a lot of new requirements called for that can make an upgrade quite expensive. I can't say too much about light curtains and such, as most of my time was spent around 1500-3000 ton presses.

Mike

glaverty,

Here is some information that should be relevant as to what you are looking for.

The first is a product that we designed in conjunction with the company that sells it, specifically for Press safety. It is ideal for retrofits. Our customer's (KTI Technologies) information can be found at the bottom of the page. They too specialize in safety and have done retrofits of existing presses. They do offer other safety related products.

http://www.entertron.com/cm1805as.htm

The second link discusses the use of multiple products to accomplish what you are specifically looking to do.

http://www.entertron.com/einl/app5.htm

With regards to the issue of modifying the current press, I would believe that so long as you work with someone who knows what they are doing, there shouldn't be a problem. You may want to contact the OEM of the presses, to make certain you have all current documentation for the equipment. You are not specifically changing the operation of the press, but rather installing or upgrading the safety of the press, that at the time was compliant under current regulations. However, those regulations have changed.

For anyone who isn't aware, I am employed by Entertron, the manufacturer / marketer of the products mentioned in this response.

Hope this helps.

God Bless,

Thanks for the replies guys, I have a guy coming in today whose company specialize in this kind of thing, just wanted to get some other opinions on the matter.