Reprinted with permission of Public Works Magazine, November 1993
Whether it is the city, county, or state level, government agencies are always trying to find cost-effective solutions to equipment needs. Before investing tens of thousands of dollars in a new product, purchasing decisions have to be carefully researched, and each product’s advantages and disadvantages carefully weighed.
For government motor pools, an important purchasing decision is choosing a vehicle lift. This device represents a substantial investment – a decision the motor pool will live with for 20, 30 or 40 years. There are three basic systems for under-vehicle maintenance: service pits, in-ground lifts, and above ground lifts.
Service pits. A service pit is not a lift system, but simply a way of accessing the vehicle’s underside from a pit beneath it. Requiring an excavation 6 to 8 feet deep, the pit requires minimal maintenance. However, special care must be taken during construction to meet OHSA regulations. With the combination of fuels and sparks in a restricted area, OSHA requires an extensive ventilation system and explosion-proof wiring on electrical equipment to minimize any fire threat. Water encountered during excavation or during the pit’s use means requiring a drainage system. The service pit must have three means of escape. Also, a service pit does not permit tire removal.
In-ground lifts. Among true lift systems, the in-ground lift has been the industry standard for years. This system usually has one, two, or three posts that raise the vehicle either by one its wheels or chassis. A fully hydraulic or combination hydraulic/air compression system provides lift power.
Like the service pit, an in-ground lift needs an excavated area – usually a 4 ft square 6 to 8 ft. deep. Digging an installation site is costly, especially in areas of shallow bedrock. Although below-ground lifts are normally less expensive than their above-ground counterparts, excavation costs can result in cost parity. Being underground though, in-ground lifts are subject to damage by electrolysis, corrosion, and high water tables. While fiberglass insulation can prevent some problems, an in-ground lift repair often begins with a backhoe clearing an access to the piston. Because of its hard-to-reach under ground location, maintenance can be costly and time consuming.
An in-ground lift with one lifting cylinder also creates a significant obstruction under the car. Since the cylinder is directly beneath the vehicle, movement around the vehicle is hampered and under-car-access is restricted. A one-post system usually leaves a 1-in. clearance between the lift and the car. As a result, some repairs, especially exhaust and transmission work, are difficult, if not impossible to perform.
Because in-ground lifts require excavation, they fall under the jurisdiction of state and Federal regulatory agencies. The EPA is increasingly concerned with underground leakage of oil and other pollutants. They recently announced a plan to check in-ground lifts for leakage and to require a “soak-up” area surrounding leaking sites.
Above-ground lifts. Working to overcome some shortcomings of other systems, above-ground lifts have become more popular with constant refinement. As a result, they now compare favorably with other systems, and depending on the situation, can be the better choice, both in practical and economical terms. An above ground system does not require excavation work, only a concrete floor 4 in. deep rated at 4,000 psi. Because the posts are located on either side of the vehicle, there is little to obstruct the working area beneath the vehicle. There is also room for transmission jacks, engine hoists, and large tool boxes. Floor space is better used; and when a repair on a particular vehicle is delayed, it can be raised overhead, clearing the way for another vehicle underneath.
Several design changes eliminated many problems associated with above-ground lifts. For example, the twin posts of automotive lifts were originally located near the vehicle’s centerline. This prevented opening the doors an made switching from under-the-car to under-the-dash servicing impossible without removing the vehicle from the lift. The introduction of asymmetric design solved this problem. The posts can now be set away from the vehicle’s center, offset arms supporting the vehicle safely and securely. For heavier fleet vehicles, the posts are set far apart for easy door access. Another former problem was vehicle clearance. Some above-ground lifts now have only a 3-1/2″ arm height, which can accommodate almost any vehicle.
Until recently, a twin-post design, whether above-or in-ground, had to equalize hydraulic pressure between the two beams by using protrusive floor plates and overhead chains or cables. Floor plates obstruct the space beneath the vehicle, while fixed overhead chains or cable restrict the height of vehicles to be lifted. By using adjustable hydraulic tubes to equalize the posts’ hydraulics, the garage ceiling is the only factor limiting the vehicle height. On some lifts, adjustable hydraulic tubes can be lowered to 10 ft. 6 in., allowing them to fit almost any garage ceiling. If ceiling height is still a problem, several above-ground lift manufacturers offer an underground hydraulic line option.
An above-ground system should include several safety features. A direct drive or chain-driven system provides maximum safety since chains are stronger than cables, which fray, stretch, and require periodic adjustments. A chain’s longevity also required by cable or mechanical screw type lifts. An “all-heights” mechanical locking system with hydraulic back ups is another important safety feature. Twin-post, above-ground lifts are designed to lift different weights from 6,000 to 30,000 lbs. For motor pools that service large vehicles weighing more than 15 tons, such as fire engines, salt trucks, and earth moving equipment, ramp-style above-ground lifts have the advantages over their twin-post counterpart. The biggest lifts can handle up to 120,000 lbs., and if necessary, can be made to fit any wheelbase and track width.
Government motor pools can find many advantages to using an above-ground lift system. With free under car access, installation ease, low maintenance, clear-floor design, and ability to accommodate low vehicle clearance the above-ground lift is increasing in popularity.