By Steve Shupert
A winch is used to tension a rope, which then moves, lowers, or stabilizes an object. It is also used on smaller vehicles as a self-rescue tool, such as for pickup trucks and all-terrain vehicles (ATVs).
Many fire departments are installing winches on apparatus, typically using a square-tube receiver-style hitch and sometimes in multiple locations around the rig. This powerful and useful rigging tool has many uses, limitations, and potential dangers included in the advantages it brings to the scene. We will discuss these issues as well as rope inspection and other concerns.
When determining how you will use your winch, there are several important considerations you must keep in mind. First, winches don’t lift, they pull. Yes, you can elevate a pulley (snatch block), but you are risking fouling the winch line—they just aren’t made to lift or suspend an object. A winch is designed for pulling an object on a relatively horizontal plane. A rule of thumb is that anything pulled above or below 45° from horizontal is considered hoisting. Hoists use a different braking device than a winch. Most winches are made with dynamic brakes, meaning a gear system will automatically hold the load. Dynamic brakes use the winch gears for resistance, which is why they are unstable for lifting or suspending objects. If you were to use a winch to suspend a load, the load could easily slip, and the gears could become damaged, resulting in catastrophic failure.
So, a winch is not a hoist and should never be used as such. Hoisting requires an elevated anchor point; other options such as a recovery rotator, tripod, ladder truck, or crane are likely better options. Some confined space rescue crews carry hoists on their tripods. When moving people with a mechanical hoist or winch, carefully weigh your risk/benefit considerations. It is difficult to feel the load (human) bind up, which could result in an additional injury.
When selecting a winch, determine the largest load you would reasonably pull or stabilize. The average car weighs about 3,500 pounds. The working load limit (WLL)of a winch is a bit of a moving target. It is determined by the rating of the wire rope or synthetic rope. And, all winch ratings are determined by the tension developed by the first layer of rope on the drum. The first layer is the only layer that will provide a pull equal to the working load limit. The capacity of a winch decreases as more layers are wrapped on top of each other around the drum, changing the diameter of the drum. Each additional layer drops the WLL by approximately 10%. The capacity listed on the winch assumes pulling on the first layer of rope. This is similar to a high-pressure air bag’s capacity where the taller the bag grows, the less it can lift.
Before using the winch, check the vehicle, fluids, tires, brakes, etc. Check that the winch is powered up, that the line plays out smoothly and is in good working order, that there are no broken or loose parts, and that electrical connections are bright and tight.
As stated, WLL is determined by the rating of the wire rope or synthetic rope on the drum. It is important to consider other factors that will reduce a winch’s capability. Wire rope can be damaged by pinching, fraying, kinking, or corrosion. Hazards at the scene can cause damage. The same is true for synthetic rope. It is prudent to limit your pulls to a value significantly less than the winch’s WLL. Industry experts suggest that it is good to maintain a 4:1 safety factor for every pull. Using this factor, a 9,000-pound winch should be limited to a 2,250-pound pull. This is a big dip in capability; however, keep in mind that if you are stabilizing a vehicle, most of the car’s weight is transmitted straight to the ground, and unless the vehicle gets in a bind, you are not pulling the entire weight. If you are just holding the vehicle in place, the demand on the winch is much less. If you are pulling the car up a hill or out of a body of water (the car is now full of water for a bit), these added loads will need to be considered in the planning.
National Fire Protection Association (NFPA) 1901, Standard on Automotive Fire Apparatus, suggests a minimum of 75 feet of rope for each winch. You can load more rope, but in winch work, more rope is not necessarily better. Keep in mind that to achieve the maximum pull from your winch, you need to lay off enough rope to get to the first layer (the layer closest to the drum). You do not want to stretch out all the rope and load the rope termination at the end of its line coming out of the drum either—this is a sure way to break your winch. Always maintain four to five wraps of wire rope on your drum. The drum is meant to be loaded, not the very end of the rope. A drum with too much rope will mean that you may not be able to pay enough off before reaching your pull point and you will be winching on the upper layers of the drum. This will reduce your pulling power and reduce the efficiency of your winch motor. Apparatus placement is critical in winching operations to obtain maximum pull. Ideally, the apparatus is straight in line with the load, and the distance between the apparatus and the load leaves four to five wraps of wire rope on the drum.
1 A portable receiver tube/trailer hitch-mounted winch. (Photos by author.)
2 A nonportable bumper-mounted winch.
3 A downward look at the receiver for the tube/trailer hitch-mounted winch.
4 A manual clutch knob allowing the operator to play out rope by hand.
5 A winch wire rope with a slip hook. Do not do this. You stand a good chance of putting a kink in this rope, taking the winch out of service. Use a separate sling on the load/object to connect the slip hook.
When planning winch operations, it is essential to think about how the apparatus will be oriented with respect to the point of pull. If you will be using your winch to stabilize disabled vehicles, then it may be more likely your apparatus will be alongside the point of pull, and you will want a winch mounted on the side of your apparatus. Another important aspect of winching is to make sure the cable spools up on the winch drum evenly. This is best when winching in a straight line. If it is pulled at an angle, the cable will bunch up on one side of the drum and use more of the electric current powering the winch. This could result in damage to the motor, rope, or drum. Angled pulls may also induce side loads into the winch mount, which may result in apparatus damage.
Extend the length of the winch by adding slings (chain, wire, or synthetic). Remember to keep the additional slings in the extension of the same or greater capacity (WLL) as the winch itself. The system you put together will only be as strong as the weakest link. When pulling a load, it may get stuck. It’s tempting to jerk the load, forcing it to move. Do not do this, as the cable may break. Do not use the winch rope as the rigging connection to the load. You should use other slings to connect the load to the winch line. The most common rigging foul with winch lines is using the winch line as a choker—hooking the slip hook on the winch line around the load and back on itself. This can damage the winch line and require complete replacement. And, there is no good reason to throw your bunker coat over the tensioned line, which has potentially thousands of pounds of load on it to suppress flying rope, thinking it will help.
The vehicle that has the winch is essentially counterbalancing the pull of the load against itself. It must be “heavier” than the load—likely not an issue if the winch is mounted on a large fire apparatus. It could be a different story on a pickup truck or ATV. If the ground conditions are slick where your winch is, chock the tires, set the emergency brake, and set the transmission in park or reverse if a manual transmission. Don’t discount tying and anchoring the vehicle back to keep it from sliding while pulling the load.
SAE J706 RATED WINCH
The capability of a winch, at a minimum, only needs to match the working load limit of the rope on the drum. Some winches, however, are designed to meet the Society of Automotive Engineers (SAE) recommended practice SAE J706. This standard requires that the winch components withstand twice the winch WLL capacity. This means there is a 2:1 design factor on the winch, ensuring that the winch will easily outperform the rope that it is carrying. So, how does this match up with the 4:1 safety factor mentioned above? This SAE standard is about the construction of the winch itself. If you purchase an SAE J706-compliant winch and use the 4:1 safety factor when rigging, you should enjoy a long life with your winch.
6 12-VDC electric plugs for a tube receiver trailer hitch-mounted winch on a pickup truck.
ELECTRIC OR HYDRAULIC?
Winches can be powered by either an elecSynthetic does not store energy. If it breaks, it will not fly apart like wire.
- Metal wire has memory; it can kink and, once damaged, it must be replaced. Abrasion/heat/chemical hazards can damage synthetic.
- Wire is not as flexible as synthetic.
- Wire has good abrasion resistance. You will need to provide edge protection for synthetic rope.
- Wire ropes are resistant to heat. Some modern synthetics (such as Kevlar and aramid fibers) have excellent heat resistance too.
- Wire is more difficult and cumbersome to respool. Both need to stay under tension when respooling.
- Wire is more likely to “bird-nest” when respooling than synthetic.
- Damage from exposure to sunlight is not an issue with wire; it is with some synthetics.
- Aluminum rope will not corrode or rust. If using steel rope, you must lubricate. No such concerns for synthetic.
- Wire rope is much heavier than synthetic.
- Synthetic rope requires a minimum of 10 wraps on the drum as compared with four for wire.
- Synthetic is more expensive than wire.
You will find synthetic rope on cranes these days. Pound for pound, good old nylon 66 (rescue rope) is stronger than steel. Great advances have been made with synthetics. A ½-inch steel wire rope sling has a WLL of 5,600 pounds. A ½-inch static kernmantle rope has a WLL of 9,000 pounds. A ½-inch high modulus polyethylene (HMPE) rope sling has an average tensile strength of 34,000 pounds. This rope also has good abrasion resistance but melts at around 300°F. It tolerates cold well down to –190°F. The high-end temperature rating for chain and wire rope is 400°F for comparison.
I also recommend stretching the synthetic rope before putting it in service. Place a significant load on the rope so the fibers stretch and tighten up. This will help prevent the rope from binding up on the drum when it gets loose and then put under tension—another good reason to try and play out as much rope as possible every time you use the winch. Respool under tension to keep the winch ready to go.
REMOTE CONTROL
NPFA 1901 states that the hard-wired remote control allows the operator to be at least 12 feet from the winch or within an enclosed area. A wireless or tethered remote control allows the operator to more safely observe the scene during the pull.
SNATCH BLOCK/PULLEY
Using a snatch block is inevitable. But, you cannot take it for granted. The snatch block is designed to be used to change the angle of the rope (change of direction) so the pull is in better line with the apparatus and the object. But nothing is free. Just like the changing WLL as the rope on the spool changes diameter, changing the direction of pull adds load to the system. Use the size pulley recommended for your size/type of rope.
As the angle of deflection increases, the force exerted on the snatch block pulley also increases. An angle of deflection measuring 45° would produce a force on the snatch block pulley equal to 76% of the load’s weight. So in this example where the load weighs 1,000 pounds, that would be 760 pounds. As the angle increases, so does the extra loading. If using a 9,000-pound-WLL winch on moving a 9,000-pound load and you have rigged a change of direction pulley into the system, you have just exceeded the WLL of the winch because of the additional load caused by the angle of the rope. In this extreme application, your pulley needs to exceed a 9,000-pound WLL to maintain your safety factor because of this additional loading effect. This must not be discounted in planning the movement.
7 An ATV bumper-mounted winch. The assembly with the rollers is called a “Fairlead.” If the rope was synthetic, it would not have rollers, just a smooth metal plate. When operating, keep all body parts away from this area. Safety glasses and gloves are the minimum required PPE.
8 A winch with an HMPE synthetic rope with a smooth-edged Fairlead.
9 A hard wired remote control.
10 A snatch block.
11 A dynamometer/strain gauge used to measure tension.
STRAIN GAUGE
To take some of the guesswork out of these operations, you can install a strain gauge, which will read the amount of tension in the system. This will allow the operator to constantly monitor the amount of load and make adjustments as needed.
ROPE INSPECTION
A quick way to begin inspecting wire rope is the “rag and drag” method. Get a shop rag and drag it along the entire length of rope. If it snags up, you likely have broken wires. The minimum number of broken wires to take a rope out of service is relative to the diameter of the rope. Also look/feel for the following:
- Thin spots.
- Corrosion or electrical arcing.
- Shiny or skinned spots.
- Kinks/twists in the rope.
Any of these conditions and more can warrant replacing the rope.
Inspecting synthetic rope includes many of the same points, including frayed out jacket, melting/char, and chemical damage. The American Society of Mechanical Engineers B30.9 standard should be used for inspection criteria.
There are a lot of do’s and don’ts and what if’s in this article. You must be able to accurately estimate the weight of your load and factor in any deductions. It is said that good judgment comes from experience, and experience comes from making mistakes. We cannot afford mistakes. Go out and train and read the manuals. Being a good firefighter is hard and sometimes complicated. That helps explain why there are too few of us.
Endnotes
1. Working load limit (WLL) refers to the maximum allowed weight that a particular piece of rigging can handle under normal conditions. For instance, a winch strap with a WLL of 6,000 pounds should not be used to secure any load above that weight, as it exceeds what it is rated for.
2. https://www.fama.org/wp-content/uploads/2018/03/TC034-FAMA-Buyers-Guide-Apparatus-Mounted-Winches-180327.pdf.
3. https://www.jm.com/en/blog/2015/february/too-hot-to-handle/.
4. https://www.ecmweb.com/content/article/20899136/the-hot-issue-of-motor-temperature-ratings.
5. https://www.samsonrope.com/docs/default-source/default-document-library/warning-insert.pdf.
6. https://www.samsonrope.com/docs/default-source/technical-bulletins/tb_how-cold-can-you-go_jun2009_web.pdf?sfvrsn=71695d0a_2#:~:text=The%20safe%20operation%20temperature%20for,C%20(%2D193%C2%B0F).
7. https://www.rocorescue.com/product/cmc-rescue-rope-static-pro-lifeline-1-2/.
9. https://www.columbusmckinnon.com/globalassets/catalogs—documents/cm-rigging-guide-cmrg-0419-low-res.pdf.
10. https://www.ropebook.com/information/angular-vector-forces/.
11. https://www.industrialsafetyproducts.com/dbi-sala-8300030-winch-with-60-galvanized-cable-7-aluminum-tripod/?gclid=CjwKCAjwmJeYBhAwEiwAXlg0AaPK1AmMA4ruF5cH9B1m-zbO6AQtEUgKN5I0Q7RTRvFyHCjLcmuNvRoCsIwQAvD_BwE.
12. https://www.youtube.com/watch?v=s7DdaFYhSIA.
13. https://www.osha.gov/laws-regs/regulations/standardnumber/1926/1926.1413.
14. https://www.assemblyspecialty.com/guide-to-wire-rope/wire-rope-inspection/basic-guidelines-of-wire-rope-inspection/.
15. https://www.mazzellacompanies.com/learning-center/how-to-inspect-a-synthetic-roundsling-to-asme-b30-9-standards/.
16. https://www.youtube.com/watch?v=iBqOrPQrByY.
17. https://atvhelper.com/can-a-winch-be-used-as-a-hoist-winch-vs-hoist/.
18. https://www.sae.org/standards/content/j706a_197004/.
19. Duty cycle: the on-off cycle of a machine including load and rest deenergized periods and how long operating vs. how long off (cool down) before restarting.
(https://absoffroad.com/winch-duty-cycle-explained-what-is-it-and-what-does-it-mean/).
20. As a high-pressure air bag inflates, it rounds in shape and loses surface contact with the object it is lifting. Since the air bag needs pounds per square inch of air to lift, as it loses square inches of contact, its overall capacity is decreased. The capacity of a high-pressure air bag is only considered accurate for the first few inches of lift.
21. As the battery voltage drains/dips below 12 VDC, it will draw more current to compensate. This contributes to the motor overheating.
22. https://www.liftingequipmentstore.com/product/mckissick-420-421-snatch-blocks.
STEVE SHUPERT is a lieutenant (ret.) from Miami Valley Fire District, Montgomery County, Ohio. He is rescue team manager and training officer for Ohio Task Force #1 US&R. He is a veteran of 11 federal deployments including WTC and Hurricane Katrina, a member of DHS/FEMA Rescue Sub Group, a certified rescue specialist, a structural collapse specialist instructor, and a heavy equipment rigging specialist instructor. Shupert is director of training for Crash Course Village, a 501C3 nonprofit organization.
