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Fig. 1: Pipelines from a cooling water treatment system in an industrial plant. Source: Aquatherm.

Complete Vacuum Supply with MINK Claw Vacuum Technology


Aquatherm is the leading worldwide manufacturer of PP-R (polypropylene random copolymer) pipe systems for plant engineering and building services. At their headquarters in Attendorn and their subsidiary plant in Radeberg, Aquatherm annually manufacturers 38,000,000 meters of pipe and over 40 million molded parts like fittings for pipeline construction.

At their Attendorn site, Aquatherm relies on MINK claw vacuum technology from Busch Vacuum Solutions for material feed from their external silos to the extrusion lines, as well as for degassing molten material in the screw sections of the extruder, and exclusively uses MINK vacuum pumps throughout the entire production process.

About Aquatherm

Aquatherm is the leading worldwide manufacturer of plastic pipeline systems made from PP-R (Fig. 1). Areas of application include potable water applications, heating systems, fire sprinkler systems, air-conditioning and refrigeration technology, as well as surface heating and cooling systems. The product range comprises more than 17,000 articles in seven product lines. Aquatherm products are found in a wide variety of buildings and ships all over the world. These include the Elb Philharmonic Hall in Hamburg; the Crane Houses in Cologne; the Mall of Berlin; the European Patent Office in The Hague; the Agbar Tower in Barcelona; various Olympic sites in Athens, Beijing, Sydney, and Vancouver; numerous top hotels and resorts, including the international chains of Hyatt, Hilton and Marriott, the Blue Waters Apartments in Dubai and the Dubai Frame, as well as AIDA cruise ships.

To ensure worldwide product availability and provide local services, Aquatherm works closely with long-standing partners in over 70 countries around the world. The company employs more than 600 people in Germany, Italy, the UK, US, and Canada. The company manufactures exclusively at their headquarters in Attendorn and in Radeberg, both in Germany. Today the family company, which was founded in 1973, is managed by the second generation.

About the installation

Over 20 years ago, Aquatherm began switching from vacuum generation with conventional oil-lubricated vacuum pumps for material feed to using MINK claw vacuum technology, a new technology in those days. The advantages at the time were as obvious to management as they are today: MINK claw vacuum pumps operate without operating fluids and thus provide completely dry compression of intake air. The moving parts within MINK vacuum pumps do not come into contact with each other. So there is no resulting friction that would make lubrication of the parts necessary. No friction also means no wear. For Markus Korth, who is responsible for maintenance, this means he does not need to replace spare parts or worry about work associated with operating fluids like oil. Because Aquatherm runs a three-shift operation seven days a week, the vacuum supply needs to operate reliably almost around the clock. This is why an internal maintenance team annually changes gear oil in the vacuum pumps as a preventive measure.

Today, Aquatherm uses a total of 29 MINK claw vacuum pumps for material feed, supplying a total of 22 material feed circuits with vacuum. All vacuum pumps (Fig. 2) are located in a machine room and are easily accessible. Over the past 20 years, the number of MINK claw vacuum pumps has grown parallel to Aquatherm's success and the associated production increase.
This vacuum technology provides a further benefit: Claw vacuum technology has the highest efficiency factor of all mechanical vacuum pumps. By eliminating internal friction and thus the need for operating fluids, MINK claw vacuum pumps are extremely energy efficient. The only change at Aquatherm since the first MINK vacuum pumps were delivered 20 years ago, is that the IE1 motors have been exchanged for today's standard motors in energy efficiency class IE3.

About the degassing process

PP-R is delivered to Aquatherm as a raw material in pellet form and then processed to create a master batch using additives, stabilizers and pigments in compounding extruders.

The polyolefin-based thermoplastic PP-R is excellently suited for use in potable water and heating installations due to its high heat and extraction stability. When used in potable water installations, its absolute corrosion resistance is of great significance for hygienic reasons. The pipeline systems are also used for industrial applications in pressure and vacuum lines.

At ten of the 19 extruders (Fig. 3) the molten PP-R is degassed using the MINK claw vacuum pump. A standing filter from Busch directly attached to the extruder prevents water vapor, residual monomers, and other by-products and degradation products resulting from chemical reactions, temperature load, and shear stress in the molten material from entering the vacuum pump, potentially leading to splitting.
For over 17 years Aquatherm has also been using MINK claw vacuum pumps for degassing molten material. The ten extruders that need to be degassed are each connected in parallel to two MINK claw vacuum pumps in constant operation. Both of these vacuum pumps are also set up in a separate machine room. For safety purposes, an inlet filter is installed directly on the vacuum pump's gas inlet. However, if any cracking occurs inside the vacuum pump, which can happen on occasion, two vacuum pumps are available as a reserve and can be immediately switched in. Contaminated or cracked vacuum pumps can be easily dismantled, cleaned and reassembled by the maintenance team. They are immediately operational after that. Maintenance Manager Markus Korth says:
Our maintenance staff is able to dismantle MINK claw vacuum pumps in 20 minutes.
Maintenance effort and thus maintenance costs are significantly lower than the previously used liquid ring vacuum pumps. These use water as an operating fluid, which needed to be checked on a daily basis and replenished, if necessary. Furthermore, the entire water circulation system required regular cleaning. Correct disposal of the operating water also took additional time and produced further costs. After about 20 years of using MINK claw vacuum technology, the team at Aquatherm is very satisfied. The high degree of operational safety and reliability as well as the high economic efficiency – thanks to energy-efficient operation and low maintenance costs – speak for themselves.