Limit Stop Mechanism Being Tripped By Lower Block

b. Check Push Button Operation and Phasing.

WARNING

On three phase hoists it is possible to have “Reverse Phasing” causing the lower block to lower when the

ábutton is depressed. When this condition exists, the automatic limit stop switch is inoperative and hoist operation will be dangerous.

To properly check the phase of the hoist, follow the steps below:

(1)With “POWER OFF” operate all the push buttons and determine that they do not bind or stick in any position

When floating rod is raised, stop switch is actuated first and then the reversing switch is actuated (Figure 2-3). Stop switch stops hoist. Reversing switch lowers hook block in case of floating rod over-travel. If limit switch does not function in this manner, refer to trouble shooting chart Section Vl for possible remedy.

WARNING

If any push button binds or sticks in any position — DO NOT TURN POWER ON — determine the cause and correct the malfunction before operating.

(2)Temporarily connect hoist to power source.

(3)Operate á button briefly to determine direction of hook travel.

(4)If hook raises, phase is correct. Turn power off and make temporary connections permanent.

(5)If hook lowers, hoist is “Reverse Phased”. TURN POWER OFF and correct by interchanging any two leads at power source connection. Do not change internal wiring of hoist.

c.Check Limit Switch Operation.

(1)A block operated upper limit stop (Figure 2-2) is furnished as standard equipment. This limit stop is factory set to stop lower block in its high position and guard against over-travel and possible damage to hoist. (Note mounting position of floating lever for 3 and 5 ton hoists.) No adjustment can be made. Limit switch operation should be tested when hoist is installed. Move hook to a low position by depressing push button marked â . Now depress button marked á to raise hook. While hook is traveling upward, manually (or with an extension pole) raise limit stop mechanism (Figure 2-2).

11403

Figure 2-2. Limit Stop Mechanism

Being Tripped By Lower Block.

Figure 2-3. Electrical Compartment Cover Removed

Showing Limit Switch and Reversing Switch Arrangement.

WARNING

Do not attempt to make above test with hook in a high position near hoist.

(2)A screw-type upper and lower limit switch is provided optionally when both upper and lower limit stops are required (Figure 7-2). This switch is adjustable and must be adjusted, at time hoist is installed, to desired high and low limits of lower block travel. Refer to Section Vll.

d.Check Lower Block and Hoisting Cable. Depress â push button and run lower block to its lowest position. No less than two wraps shall remain on the drum with the loaded hook in its lowest position, unless hoist is equipped with a lower limit switch in which case no less than one and one half wraps shall remain on the drum. Also check to see that lower block and rope does not twist excessively. If it does twist to the extent that two ropes rub against each other, disengage rope from the frame anchor and twist rope four or five turns in a direction opposite to that which the block turns. Reconnect rope to anchor (Figure 2-4), holding firmly to eliminate rope twisting back to its original position. Operate hoist up and down a few times. If lower block still rotates, repeat process until twisting is corrected.

e.Lubricate Hoisting Cable. For longer cable life, it is recommended that the cable be lubricated at time of installation by applying a Chain and Cable Fluid as outlined in Section IV, paragraph 4-3.

Figure 2-4. Rope End Anchor.

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