Why Consider A Load Limiter?
SAF-LIFT LOAD LIMITER - VIDEO
Europe has already created the following IE60242-32 Standard:
18.104.22.168 Monitoring of command actions
Movement or action of a hoisting machine or part of a hoisting machine that can result in a hazardous situation shall be monitored. On manually controlled hoisting machines, operators can provide some of this monitoring. Conditions that cannot reasonably be expected to be monitored by the operator will require means which may include over-travel limiters, motor over-speed detection, mechanical overload detection or anti-collision devices.
Remove clamps A and B and attach to dead end of hoist wire rope. The upper (A) set of clamps will grip rope securely and the lower (B) will allow a sliding fit on the rope.
SAF-LIFT is factory adjusted to the correct rope tension to trip on overload.
ATTEMPTING TO ADJUST UNIT WITHOUT CONTACTING THE MANUFACTURER WILL VOID WARRANTY.
IMPORTANT. Check to ensure that there is no interference with the hoist upper limit switch and confirm the upper limit functions properly.
The switch is held closed during normal operation and is released to open contacts when the overload is reached. The normally open contacts of the switch are used and are usually connected in series with the hoist UP contractor coil. Different makes of hoists have variations in the wiring arrangement and the electrical connections must be made by a qualified technician familiar with hoisting equipment. In the case of a 2 speed or variable speed hoist, a relay may be required. If problems develop, consult your supplier for assistance.
DO NOT ADJUST SPRING TENSION BOLT OR SWITCH TRIP SCREW
THE UNIT IS FACTORY CALIBRATED
SAF-LIFT CRANE LOAD LIMITER – ACCURACY AND RELIABILITY
SAF-LIFT crane overload protection is designed and calibrated to trip consistently within 50 Lbs of the Maximum Rope Load. Accuracy “at the hook” depends on the hoist reeving. Maximum Rope Load per OSHA is the number of pounds seen on one turn of the rope (tons/parts of rope). For example, a 2 part double reeve hoist configuration (4 rope parts) will be accurate to within 200 Lbs at the hook.
Typically, SAF-LIFT crane overload protection is sized for 115% of the crane full load capacity. The additional 15% is built into each unit to minimize the possibility of nuisance trips. Common reasons for adding a nuisance factor:
- Weight of the wire rope continuously changes depending on the distance from the hoist drum to the bottom block.
- Temporary attachments like chains, slings, spreader beams.
- Sudden acceleration / sudden snatch including accelerating from low speed to high speed when operating near the crane capacity.
- Rigging practices in a 2 hoist lift with center of gravity considerations
SAF-LIFT crane overhead protection must trip within 50 Lbs of the rope load 3 times in succession in order to pass our inspection procedure. It is recommended that the device be tested to the same standard annually by a qualified crane inspector to verify that the unit remains within this tolerance. Some reasons why the field tests should be conducted regularly:
- Physical damage to the device (interference from double blocking etc).
- Changes to the hoist (Different rope diameter etc).
- Relocating the unit to a hoist that it was not designed for (different reeving / wire rope).
In most cases, recalibration can be done in the field during an annual inspection. If there is physical damage to a unit, we recommend that it be returned to the manufacturer for inspection and repair.