Machine Safety

How to keep machines operating during stoppages and power disruptions

Zoned safety and uninterruptible power supplies for control power offer enhanced machines control during stoppages and power disruptions

By Mike Johnson and Enrico De Carolis October 2, 2020
Courtesy: Emerson

As packaging line machinery has become more sophisticated, it has also become more complex. This increased complexity, coupled with a high number of interactions between operators and machines, increases the potential for safety incidents.

For example, in the packaging world, production lines may stop for manual loading 10 to 30 times per shift, each time necessitating some form of interaction that exposes operators to possible risk and increases the potential for a safety incident.

Guarding against these risks isn’t easy. When changes are made to improve a machine’s safety, operations can become even more complex or more restrictive. These safety measures often incorporate time-consuming procedures to stop machine operation, isolate energy, resolve issues and restart processes, which translate into lost production time. Frustrated by these disruptions, operators may look to bypass safety measures to keep the line moving and meet throughput expectations, exposing them to unnecessary risk.

The consequences can be significant. An operation can experience damage to equipment, unforeseen costs, loss of productivity from shutdowns, injury to its personnel and even loss of life. A recent study by the Occupational Safety and Health Administration (OSHA) reveals manufacturing accounted for 26% of all reported hospitalizations and 57% of all reported amputations — the highest proportions for all industries.

Clearly, safeguarding people and assets remains a challenge for end users and original equipment manufacturers (OEMs) that must account for a seemingly infinite number of variables, including machine complexity, operator interactions, workplace culture and individual attitudes. Despite these challenges, improving safety within a packaging operation is possible.

By implementing the right technologies, OEMs and end users can create safer manufacturing environments that reduce risk to operators without compromising productivity. Specifically, innovative technologies such as zoned safety and uninterruptible control power solutions offer enhanced control of machines during stoppages and power disruptions. Providing operators with enhanced functional safety systems on their machinery helps minimize the impact of these events on operations and results in more predictable machines that improve operator safety.

Zones ensure safe operator interactions

When operators interact with machines, they can be exposed to increased risk. If something goes wrong, they can be hurt or damage can occur, which causes production to come to a grinding halt. This especially holds true for pneumatic control sections of machines in a packaging operation. Traditionally, ensuring operator safety of these machines has required employing discrete safety circuits with redundant dump valves, designed for lockout/tagout (LO/TO) applications, that shut off air supply, dump air and disable machine operation.

In addition to wasting energy by repeatedly dumping all the compressed air in the whole machine and forcing operators to wait for extended periods as entire systems restart, this approach adds significant complexity and unnecessary cost to the machine design because it requires complicated control structures to be in place and more expensive components. Without these control structures, the sudden reintroduction of air into a pneumatic system can cause unintended motion of components, increasing the risk of damage to the machinery itself or cause the machinery to drop products resulting in spills, lost product and scrap. To avoid this damage and maintain their expected output, operators may allow some machinery to remain live at times when it shouldn’t be active, inadvertently exposing themselves and their operations to increased risk.

Zoned safety technology offers a better approach to machine safety during manual interactions while meeting the requirements of the Machinery Directive and ISO 13849-1 (see Figure 1).

Figure 1: Zoned safety technology offers a better approach to machine safety during manual interactions while meeting the requirements of the Machinery Directive and ISO 13849-1. Courtesy: Emerson

Figure 1: Zoned safety technology offers a better approach to machine safety during manual interactions while meeting the requirements of the Machinery Directive and ISO 13849-1. Courtesy: Emerson

Zoned safety technology simplifies the design of a redundant pneumatic safety circuit with a single manifold system that can be configured to shut down air and power to only the group of valves that controls the machine’s specific motion in the operator’s vicinity while the rest of the machine remains in operation. This ensures operator safety and allows the rest of the machine to keep producing even though these safety circuits are enabled. Multiple independent safety circuits and standard valve functions can easily and cost effectively be designed into a single pneumatic valve manifold. This reduces complexity and the number of safety system components by up to 35% while allowing multiple and independent safety functions such as stop motion, return home, exhaust air, unclamp, remain clamped, and so on.

For equipment owners and operators, zoned safety manifolds simplify operations and reduce cost while optimizing machine safety and improving productivity.

Intelligent shutdowns and restarts

Power disruptions represent another critical area of concern when it comes to ensuring the safety of a packaging operation’s people and assets. For operators who rely on electronically driven automated packaging systems, power disruptions can occur with little or no warning, and the sudden machine stops that result from these disruptions can be dangerous, time consuming and costly. In addition to potentially exposing operators on a packaging line to unsafe conditions, these stops can lead to damaged equipment, ruined product, material pileups and product backorders.

These disruptions can be caused by a wide range of power issues, including voltage sags and surges, brownouts, power interruptions and low- and high-frequency voltage transients; no facilities are immune. Compounding the problem are aging plant electrical systems that provide power to advanced machinery with electronic control systems, which are highly sophisticated but also highly susceptible to the impacts of a disruption. Simply put, damaged control systems can plunge a line into a state of chaos, causing machines to act unpredictably, with components crashing into each other, products breaking and operators caught in the crossfire.

Preventing this chaos — and the threats it poses to an operation’s safety and productivity – requires maintaining critical, electronic-based plant equipment during a disruption. Uninterruptible power supplies (UPS) offer a means of achieving this by allowing machines to keep their field power supplies, programmable logic controllers (PLCs) and communications devices functioning during an unexpected outage (see Figure 2).

Figure 2: Uninterruptible power supplies (UPS) help protect electronic equipment such as field power supplies, programmable logic controllers (PLCs) and communications devices safe during a power disruption. Courtesy: Emerson

Figure 2: Uninterruptible power supplies (UPS) help protect electronic equipment such as field power supplies, programmable logic controllers (PLCs) and communications devices safe during a power disruption. Courtesy: Emerson

In the event of a power disturbance, a UPS provides immediate backup ac power so that processes can continue or be intelligently shut down without causing unsafe conditions. These units also enable operators to safely control the restart of power without accidental re-energization of circuits before it is safe to do so. With the ability to provide status updates of the UPS while it’s running, these power supplies help operators prevent equipment issues that can lead to potential hazards.

Outfitted with UPS technology, packaging lines can operate reliably and continuously and help operators stay safe.

The right thing to do

Ensuring machine and operator safety in today’s increasingly complex packaging lines will remain a growing challenge, especially as operations seek to maintain production standards and meet customer expectations. Those expectations along with the subsequent pressure felt by operators to keep the line moving aren’t going anywhere. Still, manufacturing companies must ensure the safety and health of their employees who are engaged in the installation, operation, adjustment and maintenance of production equipment. It’s simply the right thing to do, and technologies that offer enhanced control of machine interruptions make it possible.


Mike Johnson and Enrico De Carolis
Author Bio: Mike Johnson is vice president of marketing at Emerson Automation Solutions. Enrico De Carolis is vice president of global technology at Emerson ASCO Numatics.