David_Emmerich
Lifetime Supporting Member
Safety Bypass Switch
I need your thoughts on this...
On this fine piece of equipment that I am rebuilding are two Elevators, each independent from each other. They are driven up and down w/ a 3hp 3 ph 440v motor, w/ a 90vdc brake on the motor. The motor, via a vee belt, turns a ball screw that has a 3ph, 440v spring set brake on it. This screw brake is held released unless I loose power, or the carrage overtravels up/down. Now there is one Fault condition that I have found that is causing me concern...mainly in how best to clear it. If the fuse or the CB feeding the 90vdc brake opens, the carrage drops to the bumper springs at the bottom...OK, its not a good thing, but the springs were put there by the OEM back in 1966. I am going to moniter the 120v power in the brake controler and set the screw brakes if it fails. But if the carriage does go all the way down, it trips the down overtravel LS, which prevents the screw brake from being released and the and drops out the MCR, which means the elevator motor can not run. Now if, Heven forbid, someone is caught, or for any reason, what would you do to be able to over-ride that LS and raise the elevator ? Right now, and as far as I know this is true for all of these machines { there are hundreds out there !} the only way is to put a 3 foot pipe wrench on the screw shaft {ouch} and lift the carriage up until the screw brake pulls in...after fixing the bown fuse / CB.
! Key switch to over-ride LS, locater inside PB panel ?...don't like key switches, but...
Some sort of switch inside PB panel to set a line of over- ride conditions in the AD 250-1 ?.... no safety controls should be in a PLC....
Come on folks, I'm in need of some Stelar ideas....
I put this on Ron site first 'cuse I don't think I should run it thru the PLC...Thanking one and all for your time and ideas.
David
beerchug
I need your thoughts on this...
On this fine piece of equipment that I am rebuilding are two Elevators, each independent from each other. They are driven up and down w/ a 3hp 3 ph 440v motor, w/ a 90vdc brake on the motor. The motor, via a vee belt, turns a ball screw that has a 3ph, 440v spring set brake on it. This screw brake is held released unless I loose power, or the carrage overtravels up/down. Now there is one Fault condition that I have found that is causing me concern...mainly in how best to clear it. If the fuse or the CB feeding the 90vdc brake opens, the carrage drops to the bumper springs at the bottom...OK, its not a good thing, but the springs were put there by the OEM back in 1966. I am going to moniter the 120v power in the brake controler and set the screw brakes if it fails. But if the carriage does go all the way down, it trips the down overtravel LS, which prevents the screw brake from being released and the and drops out the MCR, which means the elevator motor can not run. Now if, Heven forbid, someone is caught, or for any reason, what would you do to be able to over-ride that LS and raise the elevator ? Right now, and as far as I know this is true for all of these machines { there are hundreds out there !} the only way is to put a 3 foot pipe wrench on the screw shaft {ouch} and lift the carriage up until the screw brake pulls in...after fixing the bown fuse / CB.
! Key switch to over-ride LS, locater inside PB panel ?...don't like key switches, but...
Some sort of switch inside PB panel to set a line of over- ride conditions in the AD 250-1 ?.... no safety controls should be in a PLC....
Come on folks, I'm in need of some Stelar ideas....
I put this on Ron site first 'cuse I don't think I should run it thru the PLC...Thanking one and all for your time and ideas.
David
beerchug