In many countries the regulations stipulate that only designated personnel are permitted to operate a crane. In the USA the Occupational Safety & Health Administration (OSHA) defines designated as ‘selected or assigned by the employer or the employer’s representative as being qualified to perform specific duties’.

Because the term ‘qualified’ is not itself defined, OSHA would interpret ‘qualified’ in light of operator-qualified provisions of industry standards such as ANSI B.30.2.

Many times we look at the big crane rigs as being dangerous and forget to consider the small shop overhead crane in the same light. Overhead cranes are at least as dangerous as any other piece of heavy equipment.

Owners and employees too often take bridge cranes for granted. They think of them as an easy type of equipment to operate. Without realising it, they are behind the controls without performing a complete pre-operational inspection or realising the dangers that are involved with a heavy load or even the personnel in the area.

A lot of the time we forget about the small details when it comes to operating electric overhead travelling (EOT) cranes. It is not paying attention to details that will get us in trouble.

Precautions

First of all, be fully familiar with the manufacturer’s manual that came with the crane. If one does not exist, call the manufacturer and provide the make of crane, rated capacity and serial number (ID) if it applies.

One of the first steps when approaching the bridge crane is a walk-around inspection. This will give you the opportunity to identify any problem, large or small, that could affect the safe lifting capability of your crane.

Foundations

Take a look around the bottom of a rail supporting structure. If you find that the concrete or grout is crumbling at the base area, or if it appears to be leaning, inform your supervisor and seek professional help from an engineer. This is the foundation of your rail and it must support the rail and full rated capacity of the crane. Permanent concrete shall rest on a footing below the frost line. This structure takes a lot of punishment due to starts and stops of the equipment with heavy loads.

Crane runways

Once you board the crane stand on each end and look down the rail to check for abnormalities, such as missing J-bolts. You may also see an excessive amount of steel build up in a certain spot of the runway. These steel shavings are from the wheels of the crane and several things will cause this. If the crane has just been overhauled it is be possible that a wheel was installed in reverse. Keep in mind that the sides of the wheels will have different heights.

One other item that no one ever thinks about is the type of landfill that the building is sitting on. If there is no problem in the morning, and then come the afternoon the wheels are squeaking or the crane is skewing, maybe the building is sitting on a tide-affected area. At high tide the building may rise and fall with extreme action, causing the rails to become out of line and bind the wheels. Over a period of time, this will wear the sides of the flanges or may even cause bearing problems. In addition, keep in mind that a means shall be provided to limit the drop of a bridge to one inch (25mm) in the case of a bearing, wheel or axle breakage.

Electrical equipment

Some older cranes are still using exposed third rails. These conductors are attached below the rail on the girders by insulators. If the operator accidentally brushes up against or touches this component, it means certain injury and possibly instant death.

Falls and pinch points

Over the years I have been a witness to several falls which resulted in major injuries. If you need to climb up on a working crane, let the operator know and ask permission to board. This will prevent any misunderstanding between the operator and the person who needs to board. I have seen people climb aboard these cranes without informing the operator. If the operator moves the crane and there is someone between the end of the crane and a wall, the results are unforgiving.

Hoist limit switch

A major cause of two-blocking on a bridge crane is the failure of the upper limit switch. I have witnessed operators who have become so engrossed in watching the load, hook block and signalman that they forgot about the distance between the top of the hook block and the hoist drum. A failure can cause severe damage to the wire rope or, worse yet, the wire rope parting and dropping the load.

I have also seen operators who rely on this limit switch to stop the hoist action as though it was a working switch. Do not rely on this mechanism as part of your operational function. It is a safety device only.

The correct way to use this device is as follows: first of all, at the beginning of each shift, the operator ought to check this switch for proper operation. You should hoist the hook block just below the weight of the switch, then stop, and proceed with caution until the switch engages and automatically disconnects the hoist motor. Never take your eyes off this movement.

If it does not stop within the proper clearance bring the controller back to the natural position instantly. A qualified person must repair a failure in this area.

Travel brakes and crane skewing

Applying bridge brakes too severely will result in a lot of grief, with one end of the bridge crane moving ahead of the other – in other words skewing.

The two things that will cause a bridge to skew are sudden starts and sudden stops with a heavy load.

The operator must use slow and steady pressure when applying these brakes. Stopping too fast will also cause the wheel to skid and make it hard to position the crane over a load correctly.

If the skew is not corrected, it will lead to peeling of the wheel flanges, wheel bearing problems and further damage.

Avoiding load swing

Another common accident is a collision caused by a swinging load. Stopping a load from swinging takes experience. Here are some tips to prevent the load swinging:

• Always keep the hook directly over the centre of balance of the load to be picked.

• To find the centre of balance, take the slack out of the hoist ropes and, with small increments in the hoist mode, start to lift the load, at the same time watching the attitude (direction of pull) of the hook block.

• If the hook block wants to pull to the right, for example, adjust the bridge to the right and then readjust the hook block (out or in) at the same time.

• Once you have made what you think will be a straight lift, slowly continue the hoist mode while keeping your trolley directly over the centre of the load at all times.

• Once the load is in the air, and as you start to travel, the load will have a tendency to stay behind the crane.

Wait for the load to catch up under the gantry and slowly pick up your speed if travelling over some distance. Be sure that you keep the load directly under your trolley at all times. You may have to adjust the speed in small increments several times to perform this using your momentum. Bear in mind that a load swing can exert a pulling force on the structure and may exacerbate any undetected damage that may have been caused to the components of the crane.

There is no real substitute for good operator training. And training is very inexpensive compared to the cost of an accident. H