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Potash salt has been extracted at the Neuhof-Ellers mine for over 100 years

Water

Majestic mountain and long line

The task at hand was to pump saltwater from a mine spoil heap into a river 63 kilometers away, incorporating high-efficiency leak detection. The Siwa Leak smart water solution reliably localizes unwanted water leakage.

The K+S KALI group is part of the international K+S AG concern (formerly Kali und Salz AG). The company runs a potash salt mine at Neuhof-Ellers in the Fliedetal valley, near Fulda, Germany, that has been in operation for over 100 years. The site employs some 720 people in mining and finishing processes. The products are used primarily for manufacturing fertilizer and also in other industrial manufacturing sectors.

All mines produce spoil waste. In this case, it is composed mainly of rock salt that has built up to create an imposingly tall heap directly adjacent to the mine. Nicknamed “Monte Kali” by the locals, it’s the highest elevation in the flat landscape and visible from far and wide.

The outdoor salt mound is sluiced by rain, creating some 700,000 cubic meters of saltwater per year. For many decades, the water was pumped off and stored in a deep plate-dolomite layer as a means of protecting the environment, particularly the groundwater. As the capacity of the rock was gradually exhausted, new disposal methods had to be found. The existing mining license included permission for the construction of a long-distance pipeline to discharge the saltwater into the Werra River. After reviewing alternative options and obtaining approval for the pipeline's routing, the project finally began in 2012.

The Fulda pumping station at the spoil heap – the start of the saltwater's journey to the Werra River

Expertise as key criterion

The TÜV technical inspectorate body stipulated that the line should be built in compliance with the technical standards for long-distance pipelines. “That also included precision leak detection and localization”, says Christoph Hachfeld, the K+S KALI GmbH project engineer. He goes on: “That requirement was also a key factor in the choice of supplier for the pipeline control system.”

Following an extensive selection procedure, Siemens emerged as the ideal partner for the project. First of all, the company already had comprehensive expertise in pipeline outfitting, and the project team was also greatly impressed by the Siwa Leak leak detection system. In addition, Siemens was not an unknown quantity to K+S KALI. The Siemens Simatic PCS 7 process control system had already been in operation at its plant in Neuhof for some years.

As a result, Siemens was appointed as the general contractor to supply the complete pipeline leak monitoring technology. And for the first time, K+S KALI installed Sitrans measuring devices to record operating parameters like flow rate, pressure, and temperature.

Mastering a complex medium

The TÜV stipulations were demanding: The detected water loss in operation of the pump had to be less than 1% of the maximum flow; while in standby mode, no more than 4 liters of water per hour was allowed to seep through undetected.

The complete pipeline is divided into 14 segments, with a slide valve and air-bleed station between segments. The pressures in the various segments are anything but homogeneous: Altitude differences and temperature fluctuations along the pipeline are among the factors that influence the measurement results. Therefore, an algorithm had to be devised to take into account all those parameters.

“The problem was the fact that saltwater behaves very differently from normal drinking water,” explains Siemens Project Manager Matthias Rüttiger. This is because of the dissolved salt crystals in the water, which react to fluctuations in temperature completely differently from water, producing unpredictable changes in water pressure. Heavy rainfall also has a major impact on the salt content of the water. The control system had to be capable of allowing for all these factors.

The trouble-free operation of the system pleases both Project Managers: Christoph Hachfeld (K+S KALI GmbH, left) and Matthias Rüttiger (Siemens, right)

The problem was the fact that saltwater behaves very differently from normal drinking water.
Matthias Rüttiger, Siemens Project Manager

Fast detection, precise localization

Working with K+S KALI and TÜV, Siemens devised an entirely new leak detection algorithm. It was tested in a wide variety of different conditions and pipeline operating modes in order to guarantee the reliable detection of leaks while at the same time eliminating false alarms.

The result was more than satisfactory: Siwa Leak not only met the TÜV requirements, it exceeded them. When the pump is running, the system responds at just half the maximum permissible water leakage if the pipeline is leaking at any point. In standby mode, it’s even able to detect leakage at rates of just 1.45 l/h.

But it’s not enough to just reliably detect water loss: It’s also important to determine the exact location of the leak so as to provide a fast, targeted repair. It’s helpful that the pipeline is divided into 14 segments that can be individually blocked off by means of slide valves. This means that very closely targeted measurements can be performed, and leaks can be localized to within a few hundred meters. Then conventional devices such as acoustic leak detectors can be used to scan for the exact location of the leak.

Complete solution with added benefits

Of course, a 63-kilometer pipeline with 12 external stations doesn’t just need an efficient leak detection system; it also needs an automation system that provides reliable operation, control, and monitoring from a central control room. The Siwa Leak system is based on Simatic PCS 7, which had already been successfully employed at the Neuhof plant. Additionally, Sitrans measuring devices were installed to record necessary data like flow rate, pressure, and temperature. The new process instrumentation is designed to operate optimally with PCS 7 which comes with preinstalled safety features such as the Safety Matrix, and covers the entire plant’s functionality with no need for additional hardware or software. It even provides extended archiving with a reporting function.

For K+S KALI, PCS 7 was the key to fast engineering and commissioning. Integrating all the functions in just one system also makes system maintenance much easier, which results in substantial cost benefits throughout the plant’s lifecycle.

All in all, the 63-kilometer saltwater pipeline between Neuhof and Hattorf is an example of how even tough challenges can be mastered when all the stakeholders involved work collaboratively. “Of course, a project of this scale doesn’t always run completely smoothly,” project engineer Hachfeld sums up,“ but we were all working together to the same end. The cooperation was outstanding.”

Picture credits: K+S Aktiengesellschaft