When using load charts, the operator must know how to calculate all of the variables. "There are tables to calculate deductions to the load chart based on the sail area of the load," says Schiller.
You must also consider environmental conditions. "Rain can cause ground conditions to change, which may decrease the crane's stability," says LaMar. "Wind will affect load control and can increase stress on the boom. Even though a crane manufacturer may state an upper wind speed limit, the operator is responsible for determining how safe it is to work under any wind conditions. Low temperatures may affect the structure of the crane and the manufacturer should be consulted."
Common sense says you want to keep as many people clear of crane operations as possible.
"The swing area around the crane should be barricaded," says LaMar. "When loads will be lifted over areas where workers are, they need to be warned and a clear travel route established. All workers need to receive safety training with regard to crane operations, and must be required to wear the proper personal protective equipment (PPE)."
Also pay attention to the surroundings. "The simplest thing is don't put yourself under the load," says Schiller.
"In addition, what makes for good crane operation, makes for safe ground operation," Schiller points out. This means ensuring correct support of the crane, correct positioning, working within the chart, correct configuration and proper crane maintenance.
The first step in preventing electrocution is to try to avoid power lines. "Select a site as far away from the power line as possible," says LaMar. "Whenever a crane is working where it is possible for it to come in contact with a power line, a spotter should be assigned to monitor the crane and alert the operator via some type of audio device (horn) when he is coming close to the lines. Proximity alarms are sometimes used to warn the operator, but they should not be solely relied on."
The legislated clearances for power lines are:
- 50 KV - 10 ft. of clearance
- 50 to 200 KV - 15 ft. of clearance
- 200 to 350 KV - 20 ft. of clearance
"But in many cases, the operator is not aware of how many volts a power line is carrying," says LaMar. "Some power company managers suggest staying 20 ft. away from them." Whenever working over power lines, he advises contacting the power company.
The use of the latest technologies, such as insulated links, can also protect ground crew and operators. According to Schiller, insulated links can be provided between the hook and the rigging and for use on the tag lines. "Rubber gloves and rubber boots are also supplied for the folks on the ground," he says. "The insulated link will protect the crane and also protect the people handling the tag lines because they are also going to be insulated."
When a crane does hit a power line, it is important for the operator to stay in the cab. "It's the nature of a crane that when the boom hits, electricity travels on the outside surfaces of metal. So the operator inside a cab is somewhat protected," says Schiller. The problems arise when operators step out of the cab and onto the earth where they ground themselves.
Don't rely on aides alone
"Manufacturers are providing fairly sophisticated computer systems that monitor various aspects of the crane during loading and lifting, and will stop the machine when it reaches its upper limit," LaMar notes. "But these are operator aides and should not be solely relied on. Also, these limit controls can be overridden. It's the [duty] of the operator to operate the crane responsibly."
The Load Moment Indicator (LMI) helps the operator identify the exact load on the crane at any given time. But it is not a substitute for a knowledge of the basics. "The crane remains simple in its basic concept," says Schiller. "It is simply a temporary structure from which you are lifting a load. It needs to have sufficient ballast to compensate for what it is trying to lift."
LMI systems help the operator figure out what the crane can lift and how far it can lift it. "But this information is also contained in the paper load charts," says Schiller. As such, if the LMI fails, it is still possible to conduct safe lifts. However, he adds, "The regulations are now written such that if the LMI system fails, it needs to be repaired as soon as practical."