The Regulations for Construction Projects require that an inspection and maintenance program be implemented to ensure that rigging equipment is kept in safe condition. Procedures must ensure that inspection and maintenance have not only been carried out but have been duly recorded.
Rigging operations often involve the use of various tools and devices such as jacks, rollers, hoists, and winches. Each has its own unique features, uses, and requirements for safe operation and maintenance.
The construction regulations also require that the manufacturer’s operating instructions for such tools and devices be available on site. The rigger must read and follow all of these instructions to operate and maintain the equipment properly. The rigger must also read any warning information which may be stamped, printed, tagged, or attached to the rigging device.
Jacks
While there are a great many types of jacks, the ratchet jack and heavy duty hydraulic jack are the two types most commonly used in construction.
Ratchet jacks are usually limited to capacities under 20 tons because of the physical effort required to raise such a load. They do, however, have a much longer travel than hydraulic jacks and can therefore lift loads higher without having to re-block. Most ratchet jacks have a foot lift or “toe” near the base to lift loads which are close to the ground. Lifts can be made from the “head” or the “toe” of the jack. These jacks are often called toe jacks or track jacks (Figure 1).
Do not use extensions or “cheaters” on the handles supplied with ratchet jacks. If cheaters are necessary the jack is overloaded.
Hydraulic jacks are very popular in construction because they are quite compact and can lift very heavy loads. They are readily available in capacities ranging from a few tons to 100 tons. Some specialty units have capacities up to 1,000 tons. Lift heights are usually limited to approximately 8 inches or less but some can go as high as 36 inches (Figure 2).
Hydraulic jacks are also available in low profile models that can be positioned under a load close to the ground (Figure 3). Also known as “button jacks”, these are useful for lifting a load high enough to get a regular jack in place.
Like ratchet jacks, hydraulic jacks are available with toe lifts (Figure 4).
The pumps powering hydraulic jacks may be contained in the jacks or be separate external power units. Separate units may be hand-operated or electrically powered, but the self-contained pumps are always hand-operated.
With all types of hydraulic jacks it is critical that no further force be applied after the ram has run its full travel. The resultant high pressure in the hydraulic fluid can damage the seals and, in the case of external power units, burst the hoses.
Most external power units are equipped, however, with pressure relief valves. At the factory one valve w ill be set at the absolute maxim um pressure while another will be adjustable to lower settings by the user. Make sure you are familiar with the operation of this safety feature.
Most hydraulic jacks can be fitted with a gauge on the housing or at the pump to monitor hydraulic pressure. When used with a given jack, the gauges can be calibrated to measure the approximate load on the unit.
Hoses connecting pumps to jacks require careful attention. Make sure they are free of kinks and cracks. Check the couplings, especially at the crimp. This area is prone to cracking and is often the weak link in the hose assembly. Threads should also be checked for damage, wear, cross-threading and tightness. Remember that these hoses have to withstand pressures up to 10,000 psi.
Don’t use hoses that are unnecessarily long. Shorter hoses will leave the area less congested and reduce the chance of accidental damage.
The handles on jacks or hand-operated pump units are designed so that the rated capacity and pressure can be obtained with little physical effort. Don’t use extensions or “cheaters” on the handles. Again, if the load can’t be raised with the handle supplied the jack is overloaded.
Jacks should only be used in a true vertical position for lifting. Otherwise side-loading can cause the piston to rub against the housing. If this happens, the piston will be scored and allow fluid to leak at the seal which may cause the jack to slip.
Be extremely careful when using hydraulic jacks in welding areas or around corrosive chemicals. Sparks or acids can cause pitting on the ram or damage hoses.
Hydraulic jacks are generally not equipped with check valves. But check valves can be installed in the hoses of an external pump and are recommended. Alternatively, some hydraulic jacks have retaining nuts that can be screwed against the housing to hold the load for a short time.
Jacks should never be used for long-term support of a load. Blocking is much more stable and safe. Whenever possible, the load should be progressively blocked as jacking proceeds. This will allow for the unexpected.
Always jack loads one end at a time. Never jack loads one side at a time as this will be far less stable than jacking the ends.
If it is necessary to work or even reach under a load on jacks, place safety blocking under the load as a precaution.
Make sure timbers used for blocking or cribbing are long enough to distribute the load over a large enough area and provide sufficient stability. Crib height should not exceed the length of timbers used.
All jacks should be thoroughly inspected periodically, depending on how they are used. For regular use at one location they shou ld be inspected every six m onths or more frequen tly if the lifts approach capacity. Jacks sent out for special jobs should be inspected when received and when returned. Jacks subjected to high loads or shock should be inspected immediately.
Because jack bases are relatively small, care must be taken to ensure that the floor or ground can withstand the high pressures often associated with jacking operations. Blocking or matting under the jacks will distribute the load over a greater area and reduce bearing pressure.
Jacks – Inspection
Whether ratchet or hydraulic, all jacks should be inspected before each shift or use. Check for:
• improper engagement or extreme wear of pawl and rack
• cracked or broken rack teeth
• cracked or damaged plunger
• leaking hydraulic fluid
• scored or damaged plunger
• swivel heads and caps that don’t function properly
• damaged or improperly assembled accessory equipment
CHAIN HOISTS
Chain hoists are useful because the load can be stopped and kept stationary at any point. Because of their slow rate of travel, chain hoists also allow precise vertical placement.
Chain hoists should be rigged so that there is a straight line between the upper and lower hooks. They are intended for use in a vertical or near vertical position only. If rigged at an angle, the upper hook can be damaged at the shank and the throat may open up. If the gear housing is resting against an object while under load it can be damaged or broken (Figure5 ).
Always make sure that the hoist is hanging freely.
Before using the hoist, inspect the chain for nicks, gouges, twists, and wear. Check the chain guide for wear. Hooks should be measured for signs of opening up. Ensure that the hooks swivel freely and are equipped with safety catches. If the hoist has been subjected to shock loads or dropped, it should be inspected thoroughly before being put back in service. Check the load brake by raising the load a couple of inches off the ground and watching for creep.
If the hoist chain requires replacement, follow the manufacturer’s recommendations. Different manufacturers use different pitches for their load chain. Chain intended for one brand of hoist will not mesh properly with the lift wheel of another brand and the hoist will not operate properly, if at all.
The load chain on chain hoists is case-hardened to reduce surface wear and is unsuitable for any other use. Load chain will stretch 3% before failing, whereas Grade 8 alloy chain will stretch at least 15%. Load chains are too brittle for any other application. Any load chain removed from a hoist should be destroyed by cutting it into short pieces. Never try to repair a load chain yourself. Welding will destroy the heat treatment of the chain entirely.
Electric Wire Rope Hoists, Electric Chain Hoists, Pendant Cranes
Electric wire rope and electric chain hoists may be suspended from a fixed point or a trolley. The trolley may be motorized but very often the hoist is moved by tugging gently on the pendant. These units can only move along a fixed straight line (beam).
Pendant cranes, on the other hand, trolley along a bridge (east-west) which travels on rails (north- south). Pendant cranes have greater capacity than the other hoists and usually have two or more parts of line.
Apart from these differences, the devices are quite similar in operating procedures and precautions. Hoist operators must adhere to the following points.
• Know and never exceed the working load limit of the hoisting equipment.
• Ensure that controls work properly without excessive play, delay or effort.
• Check pendant control cable for cuts, kinking, or signs of wear.
• Check hoist cables for fraying, kinking, crushing, and twisting between the cable and the drum.
• Look at the hoist drum for proper alignment and stacking of the cable.
• Inspect the hook for cracks, bending, or distortion, and the safety latch for proper operation.
• Don’t try to lengthen or repair the load chain or rope.
• Read and follow manufacturer’s instructions and all instructions and warnings on the hoist.
• Position the hoist directly over the load.
• After the hook is placed in the lifting ring, apply slight pressure to the hoist to ensure that the lifting ring is seated in the bottom of the hook and that the hook is properly aligned.
• Between lifts, check whether the rope is properly seated on the drum.
• Ensure that the intended path of travel is clear of people and obstructions and that the intended destination is ready to receive the load.
• Check brakes for excessive drift.
• Ensure proper clearance for movement.
• Position yourself on the pendant side of the hoist to get maximum clearance from the load and to prevent entanglement of cables.
• Avoid sudden starts, stops, or reverses.
• Raise the load only high enough to avoid obstructions.
• Do not hoist loads over workers; wait until the area is vacated.
• Be alert for any variation in hoist operation and any possible malfunction.
• Do not leave a load suspended in the air. If a short delay is unavoidable, lock the controls.
• Do not allow unqualified personnel to operate hoists.
• Never operate hoist to extreme limits of chain or rope.
• Avoid sharp contact between two hoists, between hoist and end post, and between hooks and hoist body.
• Never use the hoist rope or chain as a sling.
• Never use chain or rope as a ground for welding or touch a live welding electrode to the chain or rope.
• Avoid swinging the load or hook when travelling the hoist.
• Pull in a straight line so that neither hoist body, load chain nor rope is angled around anything. Some hoists are equipped with limit switches. Generally these devices stop the wind automatically at its maximum allowable up position, down position and travel limits (if rail-mounted). Check limit switches daily for correct operation.
Whenever the operator does not have a clear view of the load and its intended path of travel, a signaller must direct operations. Signals for pendant cranes differ from those for mobile and tower cranes since m achine m ovements are different (Figure 6 ). Make sure that everyone involved knows the signals required for pendant cranes.
