There is a lot more to overhead and gantry crane safety than slinging loads.
By Ron Hyink and Greg Snapper
Chris Marsh contributed to this article. Chris Marsh is owner of Ogeechee Training Services in Statesboro, Ga., where he helps businesses come into compliance with OSHA regulations and provides them with employee risk management services.
Inspections, testing and maintenance often get overlooked in overhead and gantry crane operation. Though this amnesia is not specific to one industry – as is most noncompliance with regulations – precasters in particular have come to rely on these steely skeletal movers as they continue to tip the scales with the sheer enormity of their expanding product sizes. In the pursuit for bigger and better concrete products, all the safety and maintenance requirements before, during and after operation may get lost in the production shuffle. So in order to keep from losing those production workhorses, a little maintenance and occasional inspections go a long way. And besides, if your plant is located in the United States, OSHA requires it (29 CFR 1910.179). If your plant is not located in the United States, you can ensure a safer working environment for your employees by following these tips.
According to OSHA, overhead and gantry cranes are grouped together with other cranes, including wall cranes, storage bridge cranes, semigantry and others, because they all have trolleys and similar travel characteristics.
The crane’s rated load must be plainly marked on each side, and if it has more than one hoisting unit, each hoist must have its rated load marked on it or its load block. This marking must be clearly legible from the ground or floor. You can modify cranes, but they will need to be rerated, and they must be checked thoroughly for the new rated load by a qualified engineer or the equipment manufacturer.
Outdoor storage bridges must have automatic rail clamps as well as a wind indicating device to provide a visible or audible alarm to the bridge operator at a predetermined wind velocity.
A minimum clearance of 3 inches overhead and 2 inches laterally between the crane and any obstructions is required. Likewise, two parallel cranes need adequate clearance between the two bridges. Also, do not place passageways or walkways where personnel will be jeopardized by the crane’s movements.
Only designated personnel should operate a crane, and the operator should be specifically trained for the crane he or she will use.
Following the initial inspection on a new or altered crane, two basic types of inspection must be performed based on the intervals required. They are the “frequent” inspection and the “periodic” inspection. These intervals were determined by OSHA based on the nature of critical components of the crane and the degree of their exposure to wear, deterioration or malfunction.
Frequent inspections are performed at daily to monthly intervals:
- Daily inspect all operating mechanisms for proper operation.
- Daily inspect for deterioration or leakage in lines, tanks, valves, drain pumps and other parts of air or hydraulic systems.
- Daily inspect hoist chains, including end connections, for excessive wear, twist or distorted links interfering with proper function.
- Daily inspect hooks with deformations or cracks.
- Monthly inspect hooks with deformations or cracks, and then certify the inspection with the date of inspection, the signature of the person making the inspection, and the serial number or other identifier of the hook.
- Monthly inspections should be certified the same as hooks mentioned above.
Periodic inspections are performed at one- to 12-month intervals, and should be interpreted as a complete crane inspection. This could be done monthly along with the other monthly periodic inspections. Watch for the following problems during the periodic inspection:
- Deformed, cracked or corroded members
- Loose bolts or rivets
- Cracked or worn sheaves and drums
- Worn, cracked or distorted parts such as pins, bearings, shafts, gears, rollers, and locking and clamping devices
- Excessive wear on brake system parts, linings, pawls and ratchets
- Load, wind and other indicators over their full range for any significant inaccuracies
- Gasoline, diesel, electric or other power plants for improper performance or noncompliance with applicable safety requirements
- Excessive wear of chain drive sprockets and excessive chain stretch
- Electrical apparatus for signs of pitting or any deterioration of controller contractors, limit switches and pushbutton stations
Cranes that have been idle for more than one month but less than six months require an inspection equal to the frequent inspection criteria. Cranes that have not been used in more than six months require an inspection equal to both the frequent and periodic inspections. Standby cranes should be inspected at least semiannually.
Rope, which refers to wire rope, must be inspected at least once a month. A certification record, which includes the date of inspection, the signature of the person who performed the inspection and an identifier for the ropes, needs to be kept on file. Any deterioration resulting in appreciable loss of original strength must be carefully observed to determine whether further use would constitute a safety hazard.
Some of the conditions that could result in an appreciable loss of strength are:
- Reduction of rope diameter below nominal diameter due to loss of core support, internal or external corrosion, or wear of outside wires
- A number of broken outside wires and the distribution of the broken wires
- Worn outside wires
- Corroded or broken wires at end connections
- Corroded, cracked, bent, worn or improperly applied end connections
- Severe kinking, crushing, cutting or unstranding.
Any rope that has not been used for a month or more due to shutdown or storage of a crane on which it is installed must be given a thorough inspection before it is used. The appointed person has to perform the inspection, and his or her approval is required before the rope can be put back into service. Once again, the inspection must be recorded to include the date of inspection, the signature of the person who performed the inspection, and an identifier for the rope that was inspected.
Handling the load
While attaching the load, the hoist chain or hoist rope cannot have kinks or twists and cannot be wrapped around the load. Attach slings or other approved devices to the load, and make sure the sling clears all obstacles.
Secure the load and make sure it’s properly balanced in the sling before lifting it more than a few inches. While hoisting, avoid sudden acceleration or deceleration of the load, and watch for any obstructions.
Do not use a crane as a side pull unless specifically authorized by a responsible person who has determined that the stability of the crane is not endangered and that various parts of the crane will not be overstressed.
If any employee is on the load or hook, do not move the crane, and never carry a load over people.
Whenever a load approaches the crane’s rated load capacity, the operator should test the brakes. Test the brakes by raising the load a few inches and applying the brakes. Do not lower the load below the point where less than two full wraps of rope remain on the hoisting drum.
When two or more cranes are used to lift a load, only one qualified person can be in charge of the operation to include positioning, rigging of the load and crane movement. The operator cannot leave the controls while the load is suspended, and he or she must sound a warning signal when approaching other personnel.
At the beginning of each shift, the crane operator should check the upper limit switch of each hoist with no load attached. Exercise extreme caution and run the block at slow speed into the limit. If the switch does not operate properly, notify the appointed person immediately. The hoist limit switch that controls the upper limit of travel of the load block should never be used as an operating control.
The employer must establish a preventive maintenance program for each crane based on the manufacturer’s recommendations.
Run the crane to be repaired to a location where it will not interfere with other cranes and operations in the area. Turn all controllers off, and shut off the main or emergency switch. Place warning or “Out of Order” signs on the crane and on the floor or hook where other employees can see them. If other cranes are in operation on the same runway, use rail stops or some other suitable means to prevent interference with the idle crane.
When making adjustments and repairs, any unsafe conditions disclosed by the inspection must be corrected before operating the crane again. After making the necessary adjustments and repairs, do not use the crane until all guards have been reinstalled, safety devices reactivated and maintenance equipment removed.
Adjustments or repairs must be performed only by designated, trained personnel. Examples of areas to adjust include:
- all operating mechanisms
- limit switches
- control systems
- power plant
Here are some other items you should monitor:
Cabs. All operating handles must be within convenient reach of the operator when facing the area to be served by the load hook or when facing the direction of travel. The cab should have at least 3 inches of clearance from all fixed structures within the crane’s area of movement. Steps, ladders or platforms accessing the cab cannot exceed 12 inches for each step.
Footwalks and Ladders. Footwalks must have at least 48 inches of headroom. The footwalk must be on the drive side along the entire length of the bridge of all cranes having the trolley running on top of the girders. Footwalks must have an antislip walking surface. Gantry cranes must have ladders or stairways extending from the ground to the footwalk or cab platform. The ladder must be fastened in place permanently and securely.
Stops, bumpers, rail sweeps and guards. Stops limit the trolley’s travel and must be fastened securely to resist the forces when contracted. Bridge bumpers must be able to stop the crane when it travels at 40 percent or more of its rated load speed. The trolley must have bumpers as well, unless it travels at a slow rate of speed or is not operated near the ends of bridge and trolley travel. When more than one trolley is operated on the same bridge, each must have bumpers on the adjacent ends. Bridge trucks must have sweeps that extend below the top of the rail and project in front of the truck wheels.
Also use guards on all exposed moving parts, such as gears, set screws, projecting keys, chains, chain sprockets and reciprocating components.
Brakes and electric equipment; hoisting equipment. The OSHA standards relating to these parts are very detailed and specific. The reason for this is because both are major elements of a crane’s safety and pose potential hazards to operators. Wiring and equipment shall comply with Subpart S of the OSHA standard covering general industry. You should be aware that newer cranes will comply with these standards when bought, but older cranes and cranes not having preventive maintenance preformed as recommended may begin having problems in these areas. The same holds true for sheaves and ropes. Failure in any of these areas can cause safety problems quickly.
The owner and operator of overhead and gantry cranes should remember that this machinery is potentially dangerous and should be well-maintained and operated in a safe manner at all times.
There are many regulations on this subject in the OSHA standards, and OSHA insists that all U.S. plants comply with them. Even if you are not bound by OSHA regulations, you would do well to follow the standards. The ultimate goal is to provide safe working conditions to all employees. And of course the employee also has an obligation to operate equipment safely and follow company rules.