Handling out of harm's way

Remote control of equipment by radio or infrared devices heightens safety and improves efficiency.

By Tom Feare, Senior Editor -- Modern Materials Handling, 3/1/2001

Should you remotely control a materials handling operation?

Take, for example, moving a load of molten steel or aluminum by overhead crane and then pouring that molten metal. Remote control can help avoid accidents in cases such as this one, according to Daniel J. Mihalcak, director of sales, Cattron-Theimeg.

There are numerous other industrial situations where the load isn't so inherently dangerous. But the load's size and weight can cause harm and damage should it accidentally be released or lowered too far.

With remote control, the crane operator can maneuver equipment from a distance. He or she also is physically removed from the area of greatest hazard: directly under the load.

An operator using a pendant, in contrast, often is underneath the load. And he or she is near to other loads passing overhead in a facility, all of which pose safety risks. There's also "a serious problem of operators tripping when they use pendants," adds Bob Beckmann, vice president of engineering, Telemotive.

Similarly, there are safety issues with a cab operator in an overhead crane. His or her view of the load may be obstructed from that vantage point. He or she must rely on hand signals from a second operator on the shop floor. Misinterpreted signals can result in accidents and serious injuries.

Remote control can also produce labor savings. In the man up, cab crane example just cited remote control can eliminate the need for two operators. In multi-shift facilities savings add up.

Transmission of radio signals or infrared light from controller to remote equipment receiving the signals or lightwaves is the technology behind this greater safety and productivity. The receiving unit translates radioed directions, for example, into motions of the equipment.

Safety is top priority

"Everything is driven by safety," says Mihalcak, "It's the number one key to using remote control." Remote control has been proven in all kinds of environments. "It works in dirty, rough, hazardous conditions," Mihalcak continues, where employers would rather not have their employees work.

Rather surprisingly, however, roughly four out of five overhead cranes and hoists for materials handling run without using remote control, according to Telemotive's Beckmann. "Almost any one of these cranes and hoists could benefit from the operator being untethered from pendant control," he argues.

Users erroneously ask, Beckmann says, "Why should I put $8,000 in controls on a $5,000 crane and hoist?" But today's reality is that radio controls are far less expensive than they once were. Spending as little as $2,000 may be all it takes to provide an added margin of safety to an operation.

Control Chief materials handling specialist Tim Flacco agrees that safety is paramount. But another chief advantage to remote control is making more efficient use of personnel, he says.

Operating an overhead crane, for example, in the typical, busy steel service center with a push-button pendant control "is a real headache," as Flacco suggests. Remote control of the crane is far easier, he maintains.

An operator equipped with a remote control device need not thread a pendant cord between and over obstructions along the path of movement. The operator with a remote has a wider range of movements relative to the overhead load's position compared to pendant control, Mihalcak notes.

Negotiating around obstacles on the shop floor is necessary with pendants because they "tie" the operator to following the crane or hoist's path. Pendant control, moreover, generally requires moving the load in a series of right-angled steps. And that also makes for inefficiency.

Cab-controlled cranes, as Cattron's Mihalcak observes, need at least one person on the shop floor hand signalling to the cab operator. With remote control there's a direct labor savings. Only one person's time is necessary to move the load.

There are maintenance issues to consider as well to the choice of remote control versus pendant control, as Control Chief's Flacco notes. Operators have a tendency, for example, to "hang" onto a pendant control. Eventually they disable it or pull it free. In some operations, the maintenance department "has to replace the pendant as often as once a week," this exec says.

Radio remote control can be installed "on just about all overhead cranes for about twice the cost of pendant control," as Flacco points out. Even so, there often is redundancy in control. Most cranes will have a push-button, hard-wired, backup control system. "Very few cranes just have radio control alone," he says.

Radio units predominate

Materials handling systems can be controlled remotely by radio frequency (RF) devices or by infrared units.

Today, RF control is by far the more prevalent type of remote system used in handling. Infrared systems are definitely in the minority in the U.S., says Telemotive's Beckmann. "Most of our infrared unit sales are to overseas customers."

Cattron's Mihalcak, whose firm sells both types of control, concurs. He says the domestic market is split heavily in favor of RF. About 98% of controls sold in the U.S. are radio devices and only 2% are infrared, he says.

With RF, the device need only achieve a radio link with the equipment it controls - but it needs to be a link as interference free as possible.

With infrared, however, remote operation is based on establishing line-of-sight signal communication between the control device and the controlled equipment and/or its infrared sensors. (In some systems, sensors relay the instruction from the control device to the motor or to the drive that moves the crane or other equipment.)

Control Chief's Flacco notes how this line-of-sight requirement can become a plus for safety: A control will not function and the crane won't move when the operator's view of the equipment or his/her ability to see its sensors is obstructed. The operator's ability to see and assess the situation is essential, Flacco says.

With infrared, the transmitter need not be aimed directly at the equipment or its sensors. This feature gives the operator flexibility in positioning himself. If equipment or sensors are out of view, however, the system won't operate.

Infrared technology "is the best way to go," Flacco suggests, in those situations where there are a large number of remotely controlled cranes.

With radio devices and multiple cranes controlled, "an operator might grab the wrong transmitter by mistake," he says, and start running the wrong crane. Infrared control, in such a situation, "makes handling more operator-proof. Even the smartest guy can make a mistake," he says.

Two types of RF control

RF remote control is achieved by two kinds of radio technology: narrow-band and spread spectrum systems. Narrow-band RF is the older, more conventional method of controlling materials handling equipment remotely. In newer spread spectrum systems, essentially the same RF signal is spread out over a wider frequency band.

To further complicate matters, narrow-band RF is further divided into low-power and high-power applications. Low-power systems require no license from the Federal Communications Commission (FCC), as Cattron's Mihalcak explains. Their operating range, however, is limited to 200 to 300 ft. Opting for a high-power system means getting an FCC license. (Suppliers can assist in the licensing process.) But these licensed applications have the advantage that they work over longer ranges, Mihalcak says. Overhead cranes with long runs and short haul railroad locomotives, for example, can be remotely run readily from distances of up to 2,500 ft, he says. Telemotive's Beckmann says some of his firm's systems will control remotely at up to a mile from the RF device.

With an FCC-licensed system, moreover, "you have secure, safe remote control. You're protected from radio interference from other systems," Mihalcak adds.

Through its regulatory power the FCC has divided up narrow-band RF into more radio frequencies which are closer together. That increases the channels available to users, he also observes.

Use of spread-spectrum RF requires no FCC license. The technology also offers other benefits. One advantage is the capability to control multiple pieces of equipment on a single frequency without cross-talk interference, says Control Chief's Flacco. Another plus is two-way communication between the remote RF unit and the crane or other machinery under control. With spread spectrum a crane, for example, will be equipped with a transceiver that can both transmit and receive RF signals. In this way the operator can obtain diagnostic and operational data on the crane.

Smaller controls

Advances in electronics and circuitry over the last 10 to 20 years have made remote control devices smaller and less expensive, the suppliers say. The same capabilities that pack so much into today's electronic gadgets-a cellular phone or perhaps a TV that one slips into a shirt pocket-have impacted design of remote control systems.

Controls that 15 or more years ago fit only into a cabinet measuring 10 ft by 3 ft by 8 in., Mihalcak says, now are packed onto a single, small board device.

Miniaturization is important, agrees Flacco. The object is to reduce the control unit to a size that's comfortable for the operator to hold or carry it - depending upon whether it's a hand-held unit or it's a belly box. "But at the same time we want the remote to be durable, to hold up in a materials handling environment. We want it to still be running 10 years from now."

Most new remote devices rely on digital technology now rather than the analog circuitry of older systems. More features are standard on digital RF units now that once were options on analog devices, Mihalcak says.

"Reliability of remote systems has always been good," adds Telemotive's Beckmann. "Now, however, we do more complicated things with our systems. They have more features. And we still maintain high reliability."

Digital technology also has slashed the costs of remote systems dramatically from the far, far higher expenses of analog control. Systems relying on digital RF can be installed for as little as $1,500 to $2,000, Cattron's Mihalcak says. Multiply those figures by ten, he adds, and you get the range of costs of the old, analog RF systems of 15 years ago. These old, lower-end systems ran $15,000 to $20,000 and that's without factoring in for inflation since the 1980s.

Control Chief's Flacco suggests users will pay similar costs for his firm's new systems. A remote device providing two-speed, all motion control costs about $2,000. Controlling a heavy-duty overhead crane runs about $6,000 and up, he estimates.

Complex installations, however, may push up the price tag to $30,000, says Mihalcak. And some very specialized systems have cost the end user around $100,000.

Costs will vary, of course, depending upon the complexity of the equipment controlled as well as the number of motions and speeds to be managed by the device. Also, off-the-shelf devices may work for some applications. Or the user may need a custom system.

Levers or joysticks?