Frequently Asked Questions
Hoists
Determine the maximum load to be lifted. If the load falls between standard rated capacities, always go with the higher capacity.
A manual hand chain hoist is much less expensive than an electric hoist. Manual hoists should be considered when speed is not important and when lifts are very infrequent. When lifting heavier loads you should consider the fact that in order to lift a 5 ton load by hand, you must pull over 200 feet of chain at 80 pounds of force to lift 1 foot. Manual hand chain hoist can be used for vertical lifting and where accurate positioning of the load is required. For example, installing and removing tools and dyes from machinery.
Manual lever hoists can be used in different positions, such as horizontal pulling and where accurate positioning of the load is required. Lever hoist provide excellent spotting capability. Thus they can be used in small tight areas. Lever hoists are versatile. Electric chain hoists are not made for side pulls much less a true pulling application but ratchet lever hoists can be used at any angle.
The main difference between Electric chain hoist and wire rope hoists is in the design of the lifting mechanism. When a wire rope hoist lifts, it wraps the rope around a grooved drum. A chain hoist lifts by pulling the chain through sprockets and depositing the chain into a chain container. Both types use similar motor, brakes, and controls.
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BENEFITS OF AN ELECTRIC CHAIN HOIST: |
BENEFITS OF A WIRE ROPE HOIST: |
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Reeving refers to the configuration of the wire rope, blocks and drum of the hoist. Reeving affects the headroom, lifting speed and capacity by increasing the hoist’s mechanical advantage. Reeving also determines if the hoist has lateral hook movement or true vertical lift. The three terms used in reeving are: single, double, and part. Single or double refers to the number of ropes coming from the drum. Part deals with the mechanical advantage gained by multiple reeving. For example, with a two part single reeving (2PS) the load is distributed over the two parts, and the mechanical advantage doubles the capacity of one part reeving but reduces by one half the lifting or lowering speed of the hook.
Some applications require that the load not move right or left of the hoist centerline while being lifted. This is called true vertical lift and requires that the hoist be double reeved. Double reeving also requires less headroom than single reeving.
Both chain and wire rope hoists are rated H-4 (heavy duty). Duty ratings are a better indicator of hoist durability than hoist type (chain or wire rope). Both types use similar motors, brakes and controls.
Adverse environments, Corrosive, explosive, high temperature, etc., should be considered in the purchase of your hoist. We recommend you contact one of our sales representatives if you have any concerns. Options such as epoxy paint, stainless or zinc chain and hooks, rain covers should be considered in harsh environments.
Overhead Cranes
Some manufacturers have recommended using top running end trucks without rail. This is a VERY BAD idea. Not only is there a potential safety hazard with this standard rolling tolerance for beams, makes it very difficult to install this properly. The safety issue is due to wheel loading on the outside flange of the beam. If the beam is not sized for wheel loading, the flange can bend down due to this load. You will typically spend more to size a beam properly for wheel loading than the rail would have cost.
Double girder cranes typically have the hoist and trolley riding on top of the cross girders. It is a wire rope hoist that is placed on top of the crane kit and has a H4 duty class. Double girder cranes can provide more lift, because the hoist is placed between the cross girders rather than under them. Therefore, the depth of the cross girder is gained in switching to double girders.
A crane kit is a package that can come with many options to suit your lifting needs. A basic crane kit comes with top and under running end trucks with options to add different features on them. Equipment that can come with a crane kit includes end trucks, hoists, festoon systems, remote control, bridge crane, and many more options.
ACI’s crane kits are a money saving concept for the build-it-yourself customer who has basic fabrication skills.
Variable drives are typically added to the bridge and trolley motions on all but the lowest cost cranes. A variable drive improves efficiency and safety. By allowing infinite speed control and ramping the speed up and down, the operator can move loads faster with no dangerous load swing. The very slow speeds available allow accurate positioning; where the faster speeds allow moving cranes with no load or small loads to move more quickly. A variable drive bridge and trolley can save over 50% of the movement time over a single or 2 speed crane. When programmed properly variable drives reduce brake wear. Variable drives lifts are becoming cost effective and improve reliability.
Other cranes (jib, gantry)
A jib crane has one fixed leg, a cantilevered boom that rotates around the fixed leg, and a hoist/trolley unit that traverses the boom and lifts loads for placement somewhere else. A jib crane is helpful in a high-repetition lift process where an overhead crane would be otherwise tied up. Jib cranes are typically one to two tons, but sometimes reach five ton capacity. The reach or span of the boom does not typically exceed ten feet. When calculating a jib crane reach, it’s important to consider end-approach, or how close the hoist/trolley unit can approach the ends of the boom space for the hoist/trolley machinery, which is typically 12″, must be accommodated at each end of the boom.
The most common applications for jibs are individual workstations; e.g., machine tools, welding/fabrication stations, and some small assembly stations. They are also often used in simple loading / unloading operations where it is not necessary to spot a load precisely. Jib cranes most often handle lighter loads at lower duty cycles than their bridge and gantry crane counterparts. A “classic” application for jibs is to outfit an assembly floor with a series of jibs at individual workstations, which are then supported by an overhead crane to lift / carry full assemblies. The hook coverage is limited to the boom length. The hook operates along a boom which rotates about a fixed point.
A gantry crane is similar to a bridge crane, but typically has legs at either end of the bridge girders, which are then mounted with end trucks at the bottom of the legs to move the gantry along ground-level tracks. Gantry cranes are more frequently found outdoors where no raised runway is present. Also, small non-powered gantry cranes are used in light duty applications such as small machine shops or automobile garages. These gantry cranes typically do not have a fixed path, but rather have rubber tires.
A gantry crane is more cost effective if you:
- are currently in a leased facility and don’t want to make a major investment in a bridge crane runway structure
- may be planning to move the crane in the near future and want to take your entire investment with you.
- require a crane system that moves loads between the exterior and interior of your building
- need a long runway structure where runway steel and foundation costs are prohibitive
Pendants
To help determine which pendant you are looking, here are some steps that should be taken:
- Determine the number of switches (button holes) required.
- Select switches (include light inserts if required).
- Calculate the number of conductors required.
- Determine outer diameter of cable.
- Select appropriate bushing to fit over cable. Cable bushing consists of waterproof packing which protects the electric cable.
- Select options, i.e. buzzers, blind rubber, key switch, etc.
Remotes are used in situations where being tethered to the crane is inconvenient. In applications where the operator must walk around an object to assure proper positioning, such as truck repair facilities, remotes allow one operator to do the work of two people. In facilities that move long items the remote allows the operator to balance the end of the load eliminating the need for an extra person. With improved reliability, added safety features, and lower cost remotes are an option we are seeing on increasing numbers of cranes. We sell many brands of remotes. All work well but there is a tremendous difference in the durability of the hand held unit (transmitter). The least costly will work well in environments where they will take little abuse. The most costly are designed to work in harsh environment. When pricing this option, be certain you are being quoted the same brand and model. With Independent festooned pendants, remote controls are becoming more reliable and less costly, therefore independent festoons are not used very often. An independent festoon for the pendant allows the operator to stand anywhere along the length of the crane when operating, not just next to the hoist. The pendant cable runs on a second separate festoon track. This is important when rotating long items or if the operator must lift from a pit or truck or walk in a crowded area.
Maintained pushbutton pendant – This type of pendant is often used in conditions that require long distance and where accurate positioning is a concern. Once pressing the button, the current continues to provide power to your equipment until it is pressed again causing it to stop. Momentary pushbutton pendant – This type of pendant is often used in conditions that require accurate positioning within a short distance. A person must continue to press and hold the button to provide power to the equipment. Once the button is released, the power will stop.
Lifting magnets
Permanent magnets are basically permanently magnetized material. The magnet can hold on to certain weight depending upon its capacity. Electromagnets depend on electricity to charge the magnet and to firmly hold the material to be lifted. These magnets need a permanent power source to work, which means that a power failure could lead to major problems.
Lifting magnets are primarily used in industrial applications to lift and move various types of heavy machinery from place to place. They are used to move a variety of ferrous metals such as small bundles of rod or scrap up to large blocks of metal. A positive feature of these magnets, compared to conventional cranes and hooks, is that the magnet does not do any damage to the material that is being handled.
Each unit is equipped with a handle assembly for easy separation from the ferrous object. To use, simply attach the magnet to the desired ferrous object, that is wide enough to incorporate the handle assembly, and begin lifting.
Lifting accessories
To determine which beam clamp is right for your lifting needs, you must have the approximate weight and flange width of your objects. The flange width is simple, you must measure how wide the object is so that the clamp could adjust tightly for lift. Once you collect the weight, choose the closest clamp which is listed as metric ton (Note: 1 ton = 2,200 lbs).
Shackles are recommended for permanent or long term installations and where the load may slide on the shackle pin causing the pin to rotate. Screw pin shackles can be used in any application where a round pin shackle is used. In addition, screw pin shackles can be used for applications involving side-loading circumstances.
Both are thermoplastic polymers, they can be used in similar applications and both contain aromatic chemicals in their plastic structure. Nylon is totally synthetic, but polyester can be made from plants. Polyester slings have become very valuable especially in applications that subject the sling to acid conditions. Whereas, nylon slings is highly resistant to alkalies, but should not be used in acid conditions. Also, polyester slings are excellent where headroom is limited because of the webbing’s low stretch characteristics. Polyester can be used in temperatures up to 200 F.
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