University of Extrication: Skills Update: Winch Operations—Part 1

Topic: Winch Skills Update

Objective: Review winch skills and competences

Task: The rescue team shall establish winch skills and competencies that can be used when responding to incidents with a vehicle that has a rescue winch.

There are a few essential skills and competencies that rescue personnel should possess if they respond to incidents that require the use of a rescue winch. This University of Extrication Skills Update explains these fundamental winch skills and competencies so personnel can better their knowledge of the winch and its components, operate it in a safer manner, and be more efficient and effective when deploying the winch at a rescue scene.

The rescue winch line

A winch unit used by vehicle rescue personnel typically contains 100 feet or more of steel cable, properly referred to as wire rope. The most common design of wire rope found on rescue vehicle winches, the 6 x 19 Class Improved Plow Steel core wire rope, consists of six steel wire strands wrapped around a steel core. The 6 x 19 designation means that there are six strands of wire that are braided together to form the actual winch line, with each strand consisting of 19 thinner wires.

The six or more steel strands of the winch line could be wrapped around an internal steel core or a synthetic fiber core, or the entire line could be synthetic rope instead of steel. Synthetic rope does not rust or corrode, and if it fails under a load, it does not whip around as dramatically as a steel line will. The rope, however, is more fragile than steel so it has to be carefully protected during use. For purposes of this discussion, we will continue to assume that we are dealing with steel wire rope as the line on the winch.

The diameter of the actual winch line has to be matched to the diameter of the drum of the winch unit. Manufacturers typically match the diameter of the wire rope to the diameter of the cable drum at a 1:8 ratio. What this ratio means is that if the wire rope on the winch is 3/8 inches in diameter (0.375 inches), a common size line for a rescue winch, the diameter of the drum of the winch should be 8 times that size or at least 3 inches in diameter.

Care and maintenance

Winch line care and maintenance is an important undertaking and one that is many times neglected by rescue personnel. As such, rescuers must wear proper PPE, especially good work gloves and eye protection. Maintenance begins by pulling all of the line out from the winch drum and cleaning of the entire length with a stiff wire brush or compressed air. This is also an opportunity to check the connection that attaches the wire rope to the drum of the winch to ensure that it is tight and secure as well as to closely inspect the hook on the lead end of the winch line.

After cleaning, the entire line should be inspected for physical damage—cuts, crushing, bends, kinks, heat damage, corrosion, localized abrasion, or severe stretching. Stretching can be seen by looking for a noticeable reduction in the diameter of the wire rope at one spot, an area that appears thinner than the rest of the line. Approximately 6 inches of stretch per 100 feet of length is normal in a 6 x 19 stranded steel wire rope. More than that is a tipoff that the wire rope might be deteriorating and should be replaced. During care and maintenance work, any condition that causes doubt about the integrity or condition of the winch or the winch line itself is a reason to seek repair or replacement.

Once cleaned and inspected, the winch unit, winch line and any components can be lubricated with a material permitted by the winch manufacturer, typically dry graphite or a Teflon-like lubricant. These lubricants protect the wire rope from rust and corrosion plus allow the wires and small strands to move internally as the wire rope turns around the drum or moves through a snatch block. It is better to not apply too much lubricant material; light applications applied more frequently are preferred. The lubricant should be a brand that is free from acids and alkalines, resists oxidation, and is able to penetrate between the small strands of the wire rope. Also, if accessories such as a snatch block are in the tool inventory, these can be lubricated as well.

Working load limit

Each type of winch line, whether steel or synthetic, is tested by the manufacturer and then given both a minimum and a maximum tensile strength rating. The minimum number is referred to as the working load limit (WLL). This is the number that rescuers need to be aware of when working with the winch. The WLL should not be exceeded during any use of the winch.

Testing in a controlled laboratory setting yields the load at which brand new wire rope will fail when subjected to a steadily increasing pull in a straight line. That failure point is called the breaking strength or ultimate load. It can be a high number. The ultimate load number is then divided by 5 to determine the actual WLL of the line. A 5:1 safety factor ratio is common within the industry. Rescuer’s use of the winch should keep line loads at or below this WLL, essentially only 20 percent of the breaking strength of the line when it was brand new from the manufacturer.

First layer power output

At a rescue incident where the winch will be placed into service, a calculation must be made as to what potential loads will be applied to the winch line. Our goal is to stay below the WLL of the line. Part of this competency also requires that the winch crew be aware of what is called “first layer” winch power-output rating. This first layer consideration references the reality that the build-up of layers of wire rope wrapped and stacked onto the drum of a winch influences the actual pulling power of the winch. All ratings advertised by winch manufacturers, such as 8,000 or 9,000 pounds of pulling power, are all calculated at “first layer” when only one full layer of wire rope is wrapped around the drum of the winch.

All winch manufacturers caution users to maintain a minimum of five wraps around the drum of the winch to assure that the end of the winch line does not actually pull completely off the winch drum. Be careful when working at first layer that you don’t take too much line off the drum.

Rescuers should think of every winch as actually having not one power rating but a range of power output based on the layers of wire rope around the drum. Why the power output of a winch changes is because each layer of wire rope added to the drum fattens the diameter of the winch drum and thus changes the pulling power of the winch. The power output of a winch actually decreases every time another layer of wire rope builds up on the winch drum. A WARN-brand winch for example, with 125 feet of 3/8-inch 6 x 19 wire rope, is rated at 8,000 pounds. If you break down the power rating range for that particular winch per layer, you would get:

1^st layer 8,000 pounds (which is the labeled rated capacity of the winch)

2nd layer 6,700 pounds (a 27 percent loss from the 1^st layer)

3rd layer 5,700 pounds (a 15 percent loss from the 2^nd layer)

4th layer 5,000 pounds (a 13 percent loss from the 3^rd layer)

5th layer 4,500 pounds (a 10 percent loss from 4^th layer and 44 percent less than the labeled rating)

The speed at which the winch line moves is called the line pulling speed and is expressed in feet/minute. Similar to the variation in winch pulling power, line speed also changes as more layers are added around the drum of the winch. For example, at first layer, the winch line take-up speed is actually the slowest. As layers stack onto the drum of the winch, more cable is pulled in with each revolution of the drum resulting in a faster line take-up speed. As we near a full drum, the take-up line speed may be almost double the speed when working off the first layer. This is yet another basic competency that crews operating winch units must be knowledgeable about.

In Part 2 of this Skills Update, we will focus on winch rigging at incident scenes to be most effective and safe. This article will also provide a brief winch skills training checklist to assist departments with their winch training efforts.