overriding a safety curtain?!?

[muttleydoo]

It has been mentioned many times in this post about being well covered legally when doing modifications to power press safety devices. I'm not sure about the legislation in the USA but in the UK we're bound to conforming to the machine directive and CE marking legislation.

If a power press has been CE marked then an 'in-house' risk assessment after modifications is just not adequate. The press must be inspected by a government appointed specialist who must inspect the press before re-qualifying the press safe for use.


It will certainly be of interest to the company’s insurers who would probably insist on an inspection by their appointed engineers before they would allow it to be used under the terms of the liability policy.

Just some food for thought!

 

[vettedrivr]

Nobody has ever been caught in a press so far. This was my supervisors hypothetical scenario. I tried arguements using logic but they fell on deaf ears. I was surprised we didn't install meteor shields as well because "It could happen". As long as I have my piece of signed paper I guess they get what they want.

 

[WrongWay]

I had posted this as an intial reaction to the work order I had read before heading home for the day. After investigating this is a better snapshot.
The press which is a vertical hydraulic cylinder (8 tons) with two horizontal hydraulic cylinders (2 tons). the cycle actuates the two clamping cylinders to hold the part and then the vertical. There are only three outputs in the plc program.
1) advance ram
2) advance clamps
3) turn on hydraulic pump
The solenoids are spring loaded so when the light curtain is tripped the solenoids are de-energized, the pump remains on so the cylinders cycle back to home position.
This press was made in 2006 and I just reviewed an email from the maker who states that this is done for safety.
I guess this may start some more discussion as to whether or not the cylinders should stop instantly along with the hydraulic pump.
I am leaning toward Mr. Oklahoma's suggestion of a 3 position, open center SV, adding the necessary control outputs, and killing the pump when the light curtain is broken? No saying thats what I'm doing yet, the discussion will continue.
Also, there is a new quality engineer that is asking for this feature. Apparently we have never tried to verify that the part was actually held(clamped) in the exact center position before the ram cycled. So they would like to hold in the clamped position for measurements.

 

[iant]

Nobody has ever been caught in a press so far. This was my supervisors hypothetical scenario. I tried arguements using logic but they fell on deaf ears. I was surprised we didn't install meteor shields as well because "It could happen". As long as I have my piece of signed paper I guess they get what they want.

This is the usual quote of an IDIOT.
You can tell him that from me as a quote - tell him to look at this post.
MR SUPERVISOR _ YOU ARE A DANGEROUS IDIOT _ IN AMERICA PEOPLE SHOOT PEOPLE _LIVE LONG AN PROSPER.
as no one has been killed, no one can????.
If I drive through 10 red lights and never have an accident does that mean I am a safe driver.

It is a fact that Mechanical presses Mame and Kill people.
This is not rubbush - why is ther so many regulations.
In Australia there are specific regulations for this.
I was the direct contact with our australian Occupational Health and Safety Authority (now called workcover)
Working at Toyota Australia Press Plant for 16years. And for the past 30 yrs they have not had a press accident yet, But those guards are well setup.
Toyota Aus. has gone from manually loaded machines to fully automatic in the early 90's.
The guarding is majority Captive key. with Light curtain access during die change operation.
Die space access is with Scotch Block - connected to the main motor through captive key -
Instruction to use this correctly is precise - loss of employement is the choice.

Please Note I left Toyota in 97 - But their guarding levels have only got better.


But your idiot is living with rose colored glasses. if it is not safe it is only a matter of when it happens.
I hope it is not you or onr of your friends.

 

[iant]

I had posted this as an intial reaction to the work order I had read before heading home for the day. After investigating this is a better snapshot.
The press which is a vertical hydraulic cylinder (8 tons) with two horizontal hydraulic cylinders (2 tons). the cycle actuates the two clamping cylinders to hold the part and then the vertical. There are only three outputs in the plc program.
1) advance ram
2) advance clamps
3) turn on hydraulic pump
The solenoids are spring loaded so when the light curtain is tripped the solenoids are de-energized, the pump remains on so the cylinders cycle back to home position.
This press was made in 2006 and I just reviewed an email from the maker who states that this is done for safety.
I guess this may start some more discussion as to whether or not the cylinders should stop instantly along with the hydraulic pump.
I am leaning toward Mr. Oklahoma's suggestion of a 3 position, open center SV, adding the necessary control outputs, and killing the pump when the light curtain is broken? No saying thats what I'm doing yet, the discussion will continue.
Also, there is a new quality engineer that is asking for this feature. Apparently we have never tried to verify that the part was actually held(clamped) in the exact center position before the ram cycled. So they would like to hold in the clamped position for measurements.

Valve control for safety systems.
- Simple question - If the valve spool jams in one direction how do you stop.

Both Machanical and Hydraulic presses either are fitted with Dual Poppet and or Monitored valving.
Older machinery can be retroffitted.

the stop time of presses can also be monitored.
1800 ton Mechanical 'A' Class press with a light curtain.
Needs to stop within 200 Mili seconds @ 90 degs
1 mtr. Oppening
(this is by approved calculation method)
that tabluates to 75mm movement.
this is achievable and repeatable.

 

[geoplc]

Link Electric designs such a control for each specific application, keeping in mind that limited control of bypass keys is maintained and falls with your companys responsibility. The ckt reliability and liability though will lie in their hands. Their ckts include redundant force guided contact relays throughout along with bypass annunciators to alert anyone in the area that the light curtain is bypassed. We have this incorporated throughout our plant on many presses (up to 2000ton) with every specific control designed by Link.

 

[iant]

hi Geoplc,
Over here that is manditory

 

[iant]

That was my responsibility While I was at Toyota.
Also this is the sort of work i am still is doing,
But with many other types of machinery.