Handle with care

When a lift truck falls off a dock, overturns or simply runs out of juice in the middle of a critical pick, it’s a black eye (or worse) for both operations and maintenance. But the costs of such high-profile events may pale in comparison to everyday waste due to breakdowns, damage to equipment, product and the facility, and repetitive injuries.

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“Maintenance is always coming to me saying operators are tearing up their equipment,” says Annette McDaniels, instructor of safety at Toyota Forklifts of Atlanta (www.atlantaforklifts.com).

“They don’t realize how operator safety can reduce maintenance costs.” At a facility where operators are trained once per year, “We see zero incidents and no unplanned downtime,” McDaniels says. “At another plant where we just recently became involved, the managements has, how shall I say it, a ‘let’s go’ attitude, and they have incredible downtime.”

Training remains key to safe, productive operations, but lift truck technology, ergonomics and dock equipment have come a long way in the past few years.

This side up

Lift truck manufacturers have drawn on the latest sensor, microprocessor and servo technologies to build in life- and property-saving features. While not available (or needed) for every application, a quick tour tells a lot about lift truck dynamics.

Trained operators know not to transport elevated loads, but some raised motion is inevitable when picking and placing. Electronic controls can limit truck speeds and mast angles based on current operating conditions, and even lock rear suspension to improve stability when needed.

Some trucks limit speed according to turning radius. “CurveControl is a proactive system for lateral stability in cornering,” says Jason Dunigan, product manager, Jungheinrich (www.jungheinrich.com). “It controls the speed according to the turning radius – as the wheel angle increases, the truck automatically slows. It’s done electronically through the programmable controller on the unit.”

Toyota offers two patented systems: System of Active Stability (SAS) and Active Mast Control (AMC). Starting in 1999, the systems have been integrated into all the company’s internal combustion and electric sit-down counterbalanced models. “Operator safety training remains the first line of defense in reducing forklift related incidents,” says Martin Boyd, national product planning manager, Toyota Material Handling, U.S.A. (www.tmhu.com). “However, it is known all too well in the lift truck industry that errors in operator judgment, as minimal as they may seem, often lead to accidents. Toyota’s SAS and AMC technologies were designed specifically to reduce the likelihood of accidents during these ‘errors in judgment’ scenarios.”

SAS (Figure 1) senses mast height, load weight, vehicle speed and yaw rate (angular acceleration); conditions that play a significant role in lateral lift truck stability. “Should the operator mistakenly place the lift truck in an unsafe condition which may lead to potential lateral overturn, SAS instantly interprets those conditions and locks a hydraulic cylinder on the rear steer axle, changing the lift truck’s stability footprint from triangular in shape to rectangular, thereby increasing lateral stability and substantially reducing the likelihood of a lateral overturn,” Boyd says.

AMC, which is standard equipment on the company’s three-wheel electric models and an integral part of SAS on the four-wheel sit-down IC and electric models, senses mast height and load; conditions that play a significant role in longitudinal stability. A forward tilt angle controller automatically overrides the operator’s manual control, and limits forward tilt to decrease the likelihood of a forward tip-over or spilled load. A rear tilt speed control automatically governs the mast’s reverse tilt speed to reduce the likelihood of a rearward tip-over or spilled load.

Sophisticated electronics also support more pedestrian features, such as operator-specific speed and acceleration limits, collision detection and safety-related convenience features. “The controller determines the maximum acceleration rate and top speed, and can be set up to limit them differently for the individual driver codes the operators use to log onto the machine,” says Dunigan.

Operators know the truck is tracking who’s driving it and if it has hit something, so they tend to be more careful.

Controllers, variable-speed drives and AC motors allow precise maneuvers and automatic safety features. For example, a “snail” button on Jungheinrich trucks engages a creep mode for controlled maneuvers in tight places. The parking brake is automatically set when the operator leaves the machine, and also on inclines – you can take your foot off the brake and it will stay put. Speed is controlled on downhill inclines, Dunigan says, “If you take your foot off the gas, it won’t speed up.”

Lift trucks are durable equipment with high initial costs and long service lives, so much of the existing fleet doesn’t have the latest safety features, but most trucks have or can be fitted with basics like governors and operator interlocks. For many applications, those appear to satisfy users.

“We buy our trucks refurbished and they don’t have stability control,” says Doug Jones, facilities manager, Yarde Metals, Southington, Conn. “Ours are fitted with standard safety gear and governed at 7 mph maximum speed. We’re experimenting with a device that stops the truck -- if an operator hits something, he has to go get a supervisor with a key to turn it back on.”