Tech Stuff

Twin-post lifts: Safety and maintenance tips

Never rely on hydraulic pressure when resting a vehicle on a lift. Always lower the vehicle so the weight is on the safety locks!
<p>Never rely on hydraulic pressure when resting a vehicle on a lift. Always lower the vehicle so the weight is on the safety locks!</p>

In this article, we’ll address safety and convenience options specifically for commonly used twin-post lifts, with two primary focus points: shop safety and increased efficiency.

Information sources

The primary source for lift inspection, proper operation, lifting procedures, and annual training is the Automotive Lift Institute or ALI (www.autolift.org), an association of vehicle lift manufacturers. Lifting procedures vary depending upon the lift type being used.

Lifting points

When the lift is set correctly, and prior to a technician servicing the vehicle while on the lift, the weight of the vehicle should be maintained by the mechanical safety locks, rather than by hydraulic pressure. The hydraulic system should be used only for lifting and lowering, and not for vehicle support during service.

A two-post lift engages the vehicle frame or lifting points. It is absolutely critical that lift operators are able to reference the specific lifting points for every vehicle that is to be raised on a lift.

To help shop technicians determine manufacturer-specific lift points, lift manufacturers who are ALI members include a copy of the book Lifting Point Guide (LPG) with every lift they ship.

However, the book is updated each year, so it’s imperative that shop owners purchase a new, updated copy of the lifting guide annually. The guide covers 20 years of vehicle lift points. A five-year-old version of the guide is missing information on the last five years of vehicles. If you don’t have the current guide, you’ll end up playing guessing games with regard to lift points. Choosing the wrong lift points can pose a real safety risk, along with potential undercarriage damage.

Overhead hydraulic lines don’t necessarily need to be straight. They can be fabricated and bent to conform to a specific ceiling shape requirement as illustrated.
<p>Overhead hydraulic lines don&rsquo;t necessarily need to be straight. They can be fabricated and bent to conform to a specific ceiling shape requirement as illustrated.</p>

Consider vehicle weight

Another critical issue to consider is the weight of the vehicle and the capacity of the lift. Every brand of two-post lifts has four telescoping swing arms that actually support the vehicle. So, it’s vital to know the per-arm capacity (determined by dividing the total capacity of the lift by the four swing arms) so the arms will never be overloaded.

Let’s use the example of a one-ton work truck with a standard load of tool boxes or service equipment. The lift we have is a 10,000-lb. capacity lift, meaning a maximum load of 2,500 lbs. per swing arm is the most we should try to lift. The truck we use in this example might only weigh 9,000 lbs. However, after putting the truck on a scale, we determine the rear axle has a weight of 6,000 lbs., while the front axle has a weight of 3,000 lbs. This means our 9,000-lb. truck is overloading our 10,000-lb. capacity lift because the 2,500-lb.-rated rear arms are overloaded with 3,000 lbs. on them. Large work trucks are often much heavier at the rear than at the front. Lift capacity should be based on the actual weight of the truck.

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