Wharton 7.5 Ton Overhead Crane 1

[clarkgrizwald]

Does anyone have any circuit diagrams for the above crane?
The crane is over 40 years old, and has long travel,cross travel, and fast and slow hoist. The problem is the slow lower function is not working,the thrustor energises but the brake and lower contactors do not energise.
Thanks

 

[Walden]

Is this Stacreep: An AEI/BTH system of controlled hoisting?

 

[clarkgrizwald]

The slow hoist /lower controls are located in a seperate panel on the cross travel. They consist of a creep hoist contactor, a creep lower contactor,a thrustor contactor, and a brake contactor,also located in the panel is a 415v/110v transformer which supplies the brake contactor.
When the slow hoist button is pressed on the pendant controller, the thrustor contactor energises followed by the brake and creep hoist contactors, and the hoist operates on creep.
On pressing the slow lower button, only the thrustor operates, the brake contactor does not energise as there is no 415v supply to the primary of the brake coil transformer, the creep lower contactor also remains de-energised.
Thanks

 

[Walden]

This does sound like the old Stacreep system from AEI / BTH and I sold some to Wharton Cranes.

The controlled motor, be it hoist or travel, is a slip ring motor and on the lowest speed the rotor frequency is fed through a transformer to the brake thrustor motor. A simple AC motor operates the thrustor, on the brake mechanism, and as the input frequency changes, so does its speed and, hence, the pressure on the brake drum.

If we consider the hoist motor. As the load descends quickly, the frequency on the sliprings decreases: the thrustor motor slows and the brake is applied more heavily, slowing the hoist motor. The hoist motor speed soon reaches an equilibrium, which can be adjusted by the various springs on the brake.

The transformer in the crab control panel converts the rotor volts to the thrustor motor voltage.

This controlled speed operates on the first step only: after the first step, conventional rotor resistance control is used. The thrustor motor is then connected to the mains supply and lifts the brake mechanism clear of the brake drum.

I haven’t worked on a Stacreep system since the late 1960’s, but I have typical circuit diagrams somewhere – contact me!

 

[clarkgrizwald]

Thanks mpyke,
It would be great if you could supply me with some drawings of the Stacreep system, as we have no drawings of this crane at all.
The fault has existed for some time, so there is no hurry, and we are going to be busy for the next couple of months anyway.
Thanks again.

 

[Walden]

Post your business address and I'll send you what you want.

 

[clarkgrizwald]

Thanks mpyke,
My address is:
William Auld
Turbine Group
Hunterston Power Station
West Kilbride
Ayrshire
KA23 9QJ

 

[Walden]

OK, give me a few days

 

[clarkgrizwald]

Thanks mpyke. The drawings arrived on Tuesday. It may be some time before we can get back to this crane, as we are very busy at the moment.
Thank you once again
clarkgrizwald