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01 February 2003

Portable technologies upgrade safety

Assembly lines-such as those in auto plants-with equipment, robots, and people in constant motion are fraught with potential dangers.

With these ever-present factory floor hazards, manufacturers face the challenge of protecting both employees and assets without sacrificing efficiency.

Addressing the need for increased safety and efficiency, the electronic revolution presents new portable technologies. These technologies offer safer working conditions without cutting into productivity and efficiency.

The new portable technologies include cabled and wireless tools to help manufacturers minimize mishaps and enhance protection against injury to employees and damage to machinery.

WALK THE 100-FOOT LINE

Traditional operator interface terminals mount on and in panels and suffer constraints because of that mounted location. Whether a problem occurs on one machine or an entire line, a single worker may need to walk hundreds of feet between machinery and a fixed panel device, monitoring the effect of any adjustments-a time-consuming job.

Even when two workers are monitoring the equipment and communicating critical information from separate locations, the operation is prone to logistical problems and communication breakdowns-misunderstandings resulting in potentially unsafe conditions.

In gated areas, this can be a dangerous practice when one employee is controlling the body-adjusting a limit switch or moving the device-and another employee is controlling the brain, the operator interface. Even a slight misunderstanding can result in an unsafe condition.

Today's portable human-machine interface (HMI) devices, however, are breaking the boundaries of traditional fixed-panel operator interfaces, allowing personnel to carry information and control directly to most locations in and around the machinery.

AN ACCIDENT HAS OCCURRED

Let's say an automobile manufacturer uses traditional HMI devices to monitor a typical cell application where welding robots are used. With robots working on automatic pilot, this gated area is dangerous to human workers and closed off to personnel.

Diagnostic tests indicate that this cell is not reaching its full production quota. Maintenance decides to investigate a particular robot. The robots are in a partially shutdown mode before Worker A enters the gated area and goes directly to the trouble spot.

Meanwhile, Worker B monitors the operator interface device, some distance away on the factory floor. Worker B yells suggestions for adjustments to Worker A across the already noisy factory floor.

Worker A makes the adjustments but has difficulty hearing all of the commands and cannot tell whether the adjustments are working. Suddenly, one of the robots strikes A in the back, and A goes down.

Time passes before Worker B realizes an accident has occurred and takes action to disable the cell.

With access to the operator interface information and direct contact with the machinery in question, one worker can accomplish the same task that used to take two people.

With the operator interface information in hand and access to the emergency stop (e-stop) and the enable switch on the portable HMI, one worker can walk into the semi-shutdown gated area.

With the enable switch on, the machinery will remain in its semi-shutdown state, reading that the status of the worker is OK. However, if the worker becomes injured, the enable switch immediately disables the moving equipment in the cell.

Portable HMI reduces the number of employees needed for equipment monitoring, dramatically reduces downtime, and helps ensure operator safety. If the unforeseen occurs, mitigating the worker's injury is possible.

REACT TO IMPENDING DANGER

The same automobile manufacturer operates a separate assembly plant, where cars move along a line from one area to the next.

Pieces of equipment cover large areas of the plant floor, making it difficult for maintenance personnel to access the entire line.

When performing advanced troubleshooting, a worker might carry a laptop around the entire assembly line, returning frequently to a panel-mounted device. Portable devices, such as cabled machine terminals or wireless tablets, offer solutions that result in increased efficiency and productivity.

A maintenance worker monitoring equipment with a portable HMI in a potentially hazardous environment could use a cabled device in its enabled state. If the device hit the floor as though it had dropped from the technician's hand or went down hard in his hand, the system would default to a safe state rather than continue to operate and potentially put the worker in more danger.

Another portability advantage is the ability to react to a coworker's impending danger. Upon seeing a coworker in trouble, a worker can utilize the device's e-stop to shut down machinery without having to search for the machine's stop button.

By using portable HMI devices, workers have gained control over their situation and their safety. Additionally, increased productivity and efficiency means that maintenance and troubleshooting are streamlined.

Panel-mounted operator interfaces, along with portable HMI devices, can enhance and optimize maintenance and troubleshooting, in addition to regular start and stop functions. These are the financial benefits:

• System downtime reduces because of faster machine setup and changeover times.
• Time-efficient troubleshooting and maintenance reduce costs and keep machinery running better over the long term.
• Human and mechanical resources realize enhanced safety.

Employees are a company's greatest resource. Portable and wireless tools keep them safe and increase company margin, too.

-Keith Kersten, Rockwell Automation