LyondellBasell - Improving safety in a flash

At LyondellBasell in Geleen, they process plastic waste. Especially in the summer, this attracts many flies. Those flies also activate a safety light curtain along the conveyor belt of a production line, causing that line to be shut down. This leads to a lot of unnecessary downtime.

For a solution, itsme called on partner Leuze, manufacturer of, among other things, light curtains.

 

LyondellBasell (LYB) in Geleen is a mechanical recycling company that processes plastic waste. “It arrives here in pre-sorted bales,” says Marco Caenen, maintenance leader Electrical. “The bales go through a shredder and the plastic is then purified and separated by color. It is then extruded (melted and pressed into a new shape, ed.) with additives into our end product.”

The factory has a production capacity of 35,000 tons per year and produces high-density polyethylene (HDPE) and polypropylene (PP) polymers on two lines. These serve in pellet form as a high-quality raw material for, among other things, packaging, suitcases, and children's toys.

Flies on the light curtain

A problem occurred during the receipt of the bales, Caenen explains. “A forklift with a bale clamp places the bales on a conveyor belt. After that, a light curtain is activated so that operators can no longer access it when the belt starts moving to transport the bales to the shredder.” The light curtain in question consisted of a light curtain: a large number of emitted light beams, each of which falls on a receiver. The curtain serves to protect operators working at a machine or line. If one or more light beams are interrupted because an operator moves wholly or partially through the curtain, they are no longer ‘seen’ by the receiver side. That is the trigger to shut down the relevant machine or line (emergency stop).

“The line kept dropping out countless times and that caused us an enormous amount of production downtime”

Especially in the summer, the problem arose that flies were attracted to the waste, Caenen reports. “Those flies would also land on the light curtain and it was so sensitive that the line went down countless times. That caused us an enormous amount of production downtime.” That downtime was unnecessary every time, because it was not caused by an operator getting dangerously close to the conveyor. Caenen first tried to solve the problem with a large fan under the curtain that was supposed to drive the flies away.

However, that did not provide sufficient relief, so he started looking for a solution with an improved light curtain. He contacted Frank Aussems, account manager at itsme, which has been supplying LYB with electrical engineering materials and supporting it with industrial automation for many years.

Aussems, in turn, approached Raymond Leerintveld, technical account manager at Leuze, a partner of itsme and manufacturer of, among other things, optical sensors and safety components.

Lesson Learned

A safety light curtain can be compared to an invisible fence around a machine, explains Leerintveld. “As soon as an operator reaches through the light curtain or walks through it, the machine is brought to a safe stop. At LYB, however, the problem was different: flies were frequently passing through the light curtain or landing on it, causing unnecessary machine stoppages. LYB was using a light curtain from another manufacturer. We were able to supply a new light curtain that had already proven successful in solving a similar issue for another customer. A standard light curtain detects an interruption in approximately 7 milliseconds. Our light curtain uses a so-called double-scan function: after the initial detection, it checks again a fraction of a second later to determine whether the obstruction is still present. Only if it is does the system stop the machine. In most cases, a fly has already moved away by the time of the second scan. As a result, the response time increases to approximately 12 milliseconds. This difference is so small that it has no impact on operator safety, but it makes a significant difference in practice. Unnecessary machine stops are virtually eliminated, meaning operators no longer have to repeatedly reset the production line, significantly improving production continuity. This allowed us to resolve LYB’s problem quickly. Equally important, safety has improved. Alarms that are triggered unnecessarily too often can lead to frustration and increase the risk that operators will look for unsafe ways to bypass the safety system.”

“For safety it makes no difference, for the continuity of production it does”

Last year, a new light curtain was installed along each of the two lines in the factory. In addition to a less sensitive setting, they also provide better protection against contamination by flies. All of this to Caenen's satisfaction. “The fans are gone; we don't need them anymore. We hardly have any failures anymore, maybe three times in a complete shift, instead of every five minutes. We also only clean the light sensors once a week now, as a preventive measure, whereas before we were cleaning them almost daily.” As far as he is concerned, the problem has been solved. “We no longer need any improvements or modifications to our light curtains. But if we run into problems with light sensors or the like again in the future, at least we know where we can ask for advice and find a party that can think along with us.” Aussems picks up on that. “For itsme, this was naturally also a good learning experience. Recycling is becoming increasingly common, and then flies can become an issue more often. If this starts happening with other customers, we may have a solution for them.”

Connector and advisor

Aussems speaks on behalf of itsme of a great collaboration with LYB and Leuze. “Marco approached me about this problem, and then I asked Raymond to come along to take a look at the customer's site. In that way, I acted as the connector and Raymond provided the technical advice.” That is something Leuze does more often, says Leerintveld. “In addition to standard products, we have a great many special products. For every application, we can often offer something. That may be a special, customer-specific solution; in any case, we always think along to find the best solution. That's how itsme knows to find us, and conversely, we know how to find itsme when we encounter a problem out in the field. That way, we always complement each other well.”

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