When preparing for a rigging project, it’s important to have a detailed plan and make sure that every item and tool that might be needed is close at hand. Even more critical is a pre-flight check of each piece of equipment to make sure it is in good operating condition and beefy enough to handle the job. It is always good to keep in mind that your rigging equipment is only as strong as the weakest link.
During the pre-operation equipment evaluation, questions may arise as to the appropriateness of the gear you have. These concerns can usually be addressed by your splicer or a wire rope company representative who knows about rigging. Do not be afraid to call on them with questions.
With today’s high-tension lift systems and their accompanying large-diameter ropes, plate clamps are being widely used for rigging procedures and are becoming more prevalent than traditional fist-grip clamps. Plate clamps are used with block-and-tackle rigs for multi-line pulling systems, sometimes using as many as 10 part lines. Because of this, fist-grip clamps are not found in as many places as they were 10 years ago, though many ropes are still rigged with them.
| Clip size (in.) | Min. number | Spacing | Torque (ft-lbs) |
|---|---|---|---|
| 3/8 | 4 | 7 rope diameters | 45 |
| 1/2 | 6 | 7 rope diameters | 65 |
| 9/16 to 5/8 | 6 | 7 rope diameters | 130 |
| 3/4 | 6 | 7 rope diameters | 225 |
| 7/8 | 8 | 7 rope diameters | 225 |
| 1 | 10 | 7 rope diameters | 225 |
| 1 1/8 | 10 | 7 rope diameters | 360 |
| 1 1/4 | 12 | 7 rope diameters | 360 |
| 1 3/8 to 1 1/2 | 12 | 7 rope diameters | 500 |
If you do use fist-grip clamps for tying off before splicing, make sure the tie-off ropes are the same diameter as the haul rope and that you have at least the minimum number of clamps outlined in the chart; use the correct size and space and torque them properly. The minimum number of clamps listed are a result of tests I have performed while the spacing and torque values are those listed by the manufacturers of the fist-grip clamps.
A righthand-lay main haul rope should be tied off with a righthand-lay tie-off rope while a lefthand-lay haul rope should be tied off with a lefthand-lay tie-off rope. Make sure that in both cases ropes are the same diameter. If the ropes being tied off are lefthand-lay ropes, the ruddles will have to be ground out of the fist grips so they are smooth.
To my knowledge, lefthand-lay fist-grip clamps are not available. Tests have been run on clamps with ruddles ground flush and they indicate the clamp efficiency remained high. As a result, clamps with smoothed ruddles can be used on either righthand- or lefthand-lay ropes without any resulting damage to the ropes. Again, the key here is using the minimum number and correct size, spacing and torque values.
When the clamps are installed, I tighten and torque them three times. First, when they are installed, again as soon as the counterweight starts to move or the rope is under tension, and a third time when the pulling operation has been completed. If the haul rope is to remain under tension for a period of days or weeks, the clamps should be tightening periodically.
Whether you are using fist-grip or plate clamps, remember that as the haul rope is tensioned the diameter of the rope will shrink, loosening any type of clamps being used. This is why retightening should take place periodically as you tension the haul rope. Ropes will also contract due to temperature changes, causing the clamps to loosen.
Most of all, remember to use common sense when rigging haul ropes. Many ropes are damaged every year because of poor rigging procedures. Avoid that damage and don’t be too proud to ask an expert for help.
