|Alatas Service||System Upgrade|
Our client’s crane had experienced substantial downtime over the years due to an outdated hoist control system. There had also been a few instances of dropped booms due to operator errors and the releasing of the drums clutches (frictions) before dogs being engaged to hold the drums.
In addition to the boom issues, wear had begun to show on the friction band brakes due to the band brakes needing to be partially engaged while lowering a heavy load.
Finally, if the band brakes were not engaged while lowering the drum, it would gain too much speed. This meant it could lead it to run away as there is no system installed to prevent over-speeding of the motor and draw works.
The Alatas team based in Seattle were able to solve all of these issues by installing a new control system with a PLC, new hoist motor and VFD drive system.
The new control system and PLC now provide interrupts and status inputs to the cab mounted HMI for safer operation. The control interrupts are listed below.
New Control Interrupts
The hoist will not operate if any of the following items are present during the PLC scan.
- Drive fault is present
- E-stop is depressed
- Failure of the 480vac power is detected (or if a phase is swapped)
- Hoist motor over-temperature is detected
- Hoist motor fan over temperature is detected
- Short circuit of the hoist resistors is detected
- Fault in the hoist DBU (Dynamic Braking Unit) is detected
- If the system pressure is not greater than 95psi you will not be able to engage a drum clutch (friction)
- If the drum clutch (friction) is not greater than 95psi you will not be able to release a dog
- If a drums dog is not engaged you will not be able to release drum clutch (friction)
- If an upper limit is reached (Aux A2B, Main A2B, or Boom upper limit) the hoist will no longer operate in the up direction (unless bypass switch is activated) Hoist will only allow down operation
The new motor and hoist VFD drive allows for smooth operation as well as a higher amount of control over all ranges of load weight.
The VFD along with the motors control interface only allows the drum to run at the input speed given to the drive through the joystick input from the operator.
This eliminates the issue of having a runaway load or boom while lowering. It completely eliminates the over-speed issue that the old motor and control system would allow.
Removal and Replacement of Hoist Motor and Controls
- Alatas remove existing electric motor
- Alatas remove existing drive
- Alatas remove exisitng joystick control
- Alatas remove all damaged cables/wires or cables/wires that will be replaced
- Vigor to supply crane support when required (1-2 Days)
- Vigor to dispose of removed components
- Installation of new components
- Vigor to supply crane support for component placement (1-2 Days)
- Alatas to install new drive
- Alatas to install new electric motor
- Alatas to install new joystick
- Alatas to run new cables / wires
- Alatas to connect all components accordingly
- Function Testing verification complete with load test
- Alatas to function test the crane once the installation has been completed
- Alatas to check design speeds and adjust accordingly
- Vigor to sign off on installation
- Alatas to perform load test – 100 Metric Tons