Photoelectric sensors - the benefits are obvious

Supplier: SICK Sensor Intelligence By: Roland Hackenjos, Product Manager for Industrial Sensors, SICK AG, Waldkirch
16 April, 2018

During peak production periods, well over one million glass bottles per day are made on the container glass production line that uses machines manufactured by Heye International.

Detecting and counting the bottles in the high-speed flow is not the only challenge, faced by the SICK WL12G-3 photoelectric sensors that are in use in the plant, they also have to withstand the extreme operating conditions. As a result of the bottle temperature of over 600 °C and the radiant heat, the sensors and reflectors alongside the conveyor become very hot.

The ClearSens WL12G-3 photoelectric sensor for transparent products and the high-temperature SW50 reflector come from SICK’s range of heavy-duty sensors. These both form part of the heat-resistant and highly available “best-in-glass” system solution at Heye International. They meet high standards and fulfil users’ requirements for reliable operation under the toughest conditions. However, when different types of critical operating conditions are combined, the challenge becomes serious. In Heye International’s container glass production machines, the sensors have to withstand high ambient temperatures, significant mechanical stresses, soot particles, glass dust, and tiny particles of oil and water vapour in the air and the effects of chemicals such as hydrochloric acid.

Heye International: “We are Glass People”

With its slogan “We are Glass People”, Heye International GmbH from Obernkirchen in Germany underlines its leading global position in the field of services and systems for the container glass industry. The company, which has been part of the international Ardagh Group since 2003, manufactures machines and equipment for the efficient production of container glass under its HiPERFORM brand. Its HiSHIELD testing and inspection systems can be used with a wide variety of hollow glass containers, while its specialist HiTRUST services include project management and planning, designing and constructing new production facilities and improving the efficiency of existing processes. As a supplier of high-performance machinery and production optimisation and project management services, the company’s objective is to make glass the most successful packaging material in the world.

Highest stresses at the “hot end”

HiPERFORM machines are used at what is called, the “hot end” of container glass production. During peak periods, the machines can make more than one million bottles a day over three shifts at the fluid glass melt, which has a temperature of more than 1,000 °C. When the bottles are transported in a continuous flow to the next stage of production, they are still at temperatures of up to 650 °C. This heats the air in the production area to over 120 °C. The operating conditions of the sensors that count the bottles and monitor the flow are made even more difficult by contaminants and moisture in the air and the heavy vibration of the machines.

“Best-in-glass” – the ClearSens WL12G-3 photoelectric sensor for transparent materials

With these challenges in mind, the employees of the product development and production maintenance departments at Heye International evaluated several different sensor alternatives. Non-optical systems proved to be unsuitable because of their inadequate operating distance, inappropriate size, poor detection results and slow response times. There were also problems with optical sensors. Through-beam photoelectric sensors were rejected because they involve twice the amount of assembly and installation work for the senders and receivers. Photoelectric proximity sensors failed primarily as a result of their operating distance and the critical hot surface of the glass bottles.

The “best-in-glass” solution proved to be the ClearSens WL12G-3 photoelectric sensor for transparent materials from SICK, combined with the SW50 high-temperature reflector. The sensor’s metal housing, which has an enclosure rating up to IP 67, makes it highly mechanically rugged and resistant to a range of aggressive chemicals. It has a maximum safe operating ambient temperature of +60 °C. However, in long-term use at Heye International, installed behind a heat shield, it can withstand more than +80 °C. With a sensing range in this application of two meters, this auto-collimation sensor guarantees to provide an impressively reliable detection function and, at the same time, has high operating reserves, for example, if a coating builds up on the sensor lens. This is made from scratch-proof PMMA (acrylic glass), which is resistant to chemicals and ageing. The switching frequency of the photoelectric retro-reflective sensor is 1,500 hertz, which ensures that the individual bottles in the transport flow are detected and counted reliably. This is where the reflector comes in. It is installed on the other side of the flow of bottles from the sensor, where the temperatures are also high. Standard plastic reflectors would melt and become deformed after only a short time because of the intense heat. This does not present a problem for the SW50 high-temperature reflectors from SICK. They have a pane of borosilicate glass mounted in an anodised aluminium frame which allows them to withstand temperatures up to 300 °C over long periods. As a result of their past experiences, the team at Heye International also put a great deal of importance on the ease of use of the sensor. The bottle and container glass machines are in operation around the clock. For this reason, it is essential that the sensors can be operated during the third shift when there is no maintenance engineer available.

The portfolio of heavy-duty sensors – the “survivors”

The system solution consisting of the WL12G-3 photoelectric retro-reflective sensor and the SW50 high-temperature reflector that is in use at Heye International is only one of a whole range of options for reliably automating processes using sensors under the toughest conditions. When moisture is a problem, the photoelectric sensors from the W4 Inox product family are the ideal solution, for example in wet or damp areas in the food processing industry or filling and packaging machines. The W12-3 product family produces impressive results in applications where sensors come into contact with greases, oils, coolants and lubricants.  For example, when processing and packaging animal and vegetable fats, using machine tools or manufacturing sheet metal in a steel mill where the air has a high oil content. In areas where sensors need to be highly mechanically rugged, the first choice is the W24-2 product family from SICK. These sensors have zinc die-cast housings that make them a tough, long-lasting and reliable detection solution, even in challenging environments where heavy items such as steel coils and railway rails are being handled. In cases where optoelectronic sensors are not the best answer, SICK’s portfolio of heavy-duty products also offers other highly effective alternatives, such as the IMB product family of inductive sensors. They are shock and vibration-resistant, have a corrosion-resistant stainless-steel housing and can withstand constant spraying with or immersion in water, permanent contact with aggressive cutting oils and cooling lubricants and temperatures ranging from -40 °C to 100 °C.

Heavy-duty sensors from SICK function reliably under the toughest conditions and not only in the bottle and container glass production plants manufactured by Heye International. They ensure the highest possible levels of availability for machinery and processes.