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LASS Anti Surge Control in PCS7

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The company
Linde Gas is part of the Linde Group. With over 600 branches and sixty thousand employees in more than one hundred countries, the Linde Group is a major player in the supply of industrial gases. In the Netherlands, Linde Gas has two production sites, in Rotterdam and IJmuiden. The Linde Gas site in IJmuiden is known as one of the largest air separation plants in Europe.

The contractor
Arnold de Laat is plant manager IJmuiden at Linde Gas Benelux. The IJmuiden plant mainly produces oxygen and nitrogen. The main customers for the gases are steel producer Tata Steel and the Gasunie.

An important part of the air separation process is the compressors. Compressors are devices used to compress a gas such as air or nitrogen to a desired pressure. For example, a compressor sucks in air from the environment, after which the air in the compressor is brought to pressure. In the case of Linde Gas IJmuiden, a large number of large compressors are involved. The product compressors are supplied with gas from the factory and are connected to the pipelines that transport the gases to the customers. Arnold: “Production of Linde Gas continues 24/7; the gases must be delivered 24/7. Stability, reliability and continuity of our processes are extremely important.”

The assignment
Linde Gas was commissioned to supply two product compressors. The question for CoNet was: implement the LASS functionality in the existing DCS system Siemens PCS7 version 7.1.

Arnold: “When you order a compressor, the control is included in the scope of delivery. These controls do not have extensive possibilities. This limits the functioning of the machine. This is a well-known problem at Linde Gas; it applies to almost all compressors in IJmuiden as well as on the other sites. Linde’s dependence of the manufacturer bothered Linde even at a global level, partly because of the cost of the regulations and because of the need to hire specialists for commissioning. That is why, a few years ago, Linde Gas developed the so-called Linde Anti Surge System, or LASS.”

“LASS is an amazingly beautiful piece of software that is as simple as it is intelligent”, says Mathieu Smit of CoNet enthusiastically. “In LASS, several pieces of process parameters are measured and regulated. For example, LASS allows the compressor to operate closer to the surge line. Due to its dynamic character – for example independent measuring ranges can be configured for the suction and pressure sides of the compressor – LASS is much more accurate than the system supplied.”

The project was scheduled to last three months. This deadline was met with flying colours, partly thanks to the perfect collaboration between the technicians of CoNet and Linde Gas. “It was a Dream Team,” says Mathieu. “The team consisted of a process technologist and project manager for Linde Gas, a project manager and engineer for CoNet and, of course, the technicians for Linde Gas. The men knew exactly what they had in common, which made the project run smoothly from start to finish.”

The approach
CoNet follows almost the same schedule for each project. After taking stock of the wishes of Linde Gas,” says Mathieu, we started programming in a virtual environment. We then invited the customer to test the system in this virtual environment. After approval, the first compressor was claimed for maintenance and adjustment of the instrumentation. The product-to-product time was one week. In that week we first installed the instrumentation and outputs, then we programmed the software, and then two more test days followed while the machine was running. All that went perfectly. After three months – we had programmed this period to correct any imperfections, which by the way did not happen – we set up the second compressor in the same way.”

The result
“We are absolutely satisfied with the result,” says Arnold. “Ease of use has been improved many times and energy efficiency has also increased. The operator has a wider operating range and more insight into what is happening inside the machine. The machine now automatically adapts to the different pressure levels, which saves energy. All in all, pipeline pressure is much more stable and our customers are also reaping the benefits.”