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 Art from the future
Design error on relay's

This site has been establish to cover a test regarding some relay's that have been ordered from Terex Demag. The relay's was ment to replace some older relay's in the main circuit-switch box. In 2009 I did have some problems with a 97 Demag AC 665. All problems was then related to electrical fault's, and the problem's seem'd all to be located in the main relay cabinet. There are a great number of relay's in this cabinet, mainly two different designs. The one you see here is the relay that I will prove to have a weakness, if not just to say the problem is a regular fault in the design of the relay. I do not know if the problem has been detected by Terex Demag yet, but so far I have not seen any information regarding the relay's, and the 97 Demag AC 665 are still having minor problems.

The LUTZE RPE-6144 module with the two SCHRACK PT571024 relay's.      

On the picture above the relay's are turned the correct way. And the problem may not arise in this position. However on the Demag AC 665, the module has been turned with the text up side down. This may have to do with the construction of the modules, to ease the work on the small printed circuit board behind the two relay's. Any way, the relay's are mounted like this. Will that be a problem? Not so far. Lets see on some details.  
The LUTZE RPE-6144 module now turned up side down.                      www.mobilcrane.com 

When you look at the relay's above, you will see two orange lever's. The function of the lever's are to override the relay's manualy. This may be used when the system is checked for problems, or just to operate a part of the system manually. Do not operate any of the relay's manually if you are not qualified to do so. If you look close at the orange lever's, you will see two small pin's on each lever, one at each side. These pins seem to have only one purpose, and that's to indicate if the relay has been operated manually. The two pin's will then break. It may seem to be a small and insignificant detail that will not affect the electrical function.  

The LUTZE RPE-6144 with the two relay's manual activated.                www.mobilcrane.com

This is how the relay's look like if you override them with the small lever's. It is a common way to test out system's when you have a problem, and are working with the electrical system to find any fault's. Again, do not do this if you are not qualified. Incorrect activating of system's on a crane or any other equipment may cause seriously accident's, and may lead to personal injury or death.
The lever's close up. See the small pin on the right side.                     www.mobilcrane.com

See it now? Follow the arrow.                                                               www.mobilcrane.com

To solve my problem's on the Demag AC 665, I did change some of the relay-modules. And the problem's did seem to go away, but not quite. And the hard thing to understand, new problems took place where old problems did disappear. New problems on the new relay's. And the problems did seem to be only when the relay's was in the non-activated state. It was by checking the system on this crane I discover the weakness of the relay-modules from LUTZE, on the LUTZE RPE-6144 module with the two SCHRACK PT571024 relay's. 

The LUTZE RPE-6144 in non-activated state. It must create problem's. www.mobilcrane.com

The small pin are here blocking the lever from returning to neutral.     www.mobilcrane.com

This example is just one I have experienced. The two pin's may also create other situations, depending on how and where they do place oneself after break more or less from the lever. When the relay's are mounted this way, up side down, the small pin's may also end up inside the case, and make the space between the case and the contact clip too small.  

If you do use the LUTZE RPE-6144 module with the two SCHRACK PT571024 relay's in any application's, be sure to remove the two small pin's complete. This will prevent you from haveing the problems I have described here. And I still declare the LUTZE RPE-6144 module with the two SCHRACK PT571024 relay's to be unsuccessful, or just beeing a design error.

New 20090603   Rev. 20101121   www.mobilcrane.com bilde   

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