By 1926 the capacities of the small institute workshop were no longer sufficient for the ever increasing number of orders. Thanks to the support of Professor Fischer, Andreas Hofer was able to construct his first own factory building in Werdener Weg, which is close to the Institute. (Gallery 4)

From now on, Andreas Hofer concentrates his development activities on the high-pressure area. Thanks to modern, high-quality products, such as the turbo-stirrer for 200 atü (1929) and compressors with four and five stages (1928 and 1931), HOFER established a worldwide reputation as a high-pressure expert, which the company still lives up to today. The first high-pressure valves and system components were already part of the product portfolio at this time. (Gallery 5)

In the following years, Andreas Hofer develops into a successful entrepreneur who can now devote himself to his preferences for fast cars (Gallery 6) and flying (Gallery 7). He can not realize his vision of visiting his international customers with his own plane. He died of cancer in 1932 and left his wife Elsa Hofer a successful company and a name that is still associated with high-quality high-pressure technology today.

After the death of her husband, Elsa Hofer takes over the management of the company in 1932. The technical department is now headed by Walter Baensch. Andreas Hofer had already brought the innovative engineer to Mülheim in 1931 to pass on his technical knowledge and corporate philosophy to him.

In the medium term, the two children of Elsa and Andreas Hofer are planned to succeed him in the management of the company. While son Rudolf starts studying mechanical engineering, daughter Charlotte starts a commercial apprenticeship at HOFER. 

After the National Socialists came to power in 1933, HOFER is able to continue to work unhindered at first and can continue to demonstrate technical achievements even under Walter Baensch. In 1938, Baensch applied for a patent for a new technique of regulating the delivery rate of liquid pumps and in 1939 for a new piston compressor.

With the outbreak of the Second World War in 1939, HOFER is also shaken by major changes. At first, the formerly international sales market is reduced to the territory of the German Reich. From 1939 onwards, the German Research Foundation became the central client. Despite the increasing difficulties in the procurement of materials from 1940 onwards, HOFER succeeds in maintaining its own quality standards even during the war years.

The death of Rudolf Hofer is much more serious. The planned successor for the technical area falls in 1941 on the Eastern Front. At the end of the war in 1945, the company faces an uncertain future.

The HOFER company survives the Second World War without major damage. Although the American troops are very interested in the design drawings of the Mülheim-based company, Elsa Hofer has them falsified by her engineers as a precaution. The captured documents are therefore worthless for the Americans.

HOFER resumes operations shortly after the end of the war. Elsa Hofer (Gallery 8) and Walter Baensch continue to divide the commercial and technical areas among themselves. At the same time, daughter Charlotte is introduced to the company management. For the deceased son Rudolf, a suitable successor is found in Dr.-Ing. Werner Köttnitz in 1946. He is responsible above all for important innovations in the electrical engineering area.

At the same time, Walter Baensch attracts attention with innovations in the compressor sector. In 1950 he develops the first HOFER high-pressure piston pump (new patent specification). One year later, Werner Köttnitz also receives his first patent: a process for operating electromagnetic stirring devices in closed pressure vessels. Within a few years HOFER is able to win back its international customer base thanks to modern compressors (Gallery 9), well-known quality and presentations at international trade fair (video 1 and 2).

At the beginning of the 1960s, the economic miracle also reaches its peak at HOFER. The factory building on Zeppelinstraße (formerly Werdener Weg) now employs over 100 people. In order to be able to offer management, production, sales and development sufficient development opportunities, work begins in 1963 on a new company headquarters. By 1966, a modern factory building is erected in the Friedrich-Freye-Straße, which has sufficient expansion possibilities (Gallery 10).

The development department continues to produce significant innovations in these years. In 1962 the first glandless valves were presented. Shortly afterwards, HOFER takes on a technology that is about to become an outstanding part of the product range. In 1963 Hans Georg Bergendahl patents a new type of sealing ring for diaphragm compressors. In the following years HOFER develops into one of the world's most important specialists in this field. A status which the company has maintained until today.

In 1966, shortly after moving to the new factory buildings, Elsa Hofer dies. She led the company through ups and downs for over 40 years.

1966 Werner and Charlotte Köttnitz, the second generation of the family, take over the management of the company. With a competent development team and a good feeling for new markets, Werner Köttnitz continues the HOFER success story.

Already in the first decade under new management, important innovations are developed in all three product fields. In addition to new reciprocating compressors, it is above all the high-quality diaphragm compressors that ensure that HOFER is also licensed for projects in the highly sensitive nuclear power sector in 1970.

In addition, the third field, plant construction, is completely repositioned at the beginning of the 1970s. The "block system" developed by HOFER enables a quick and uncomplicated design of compressor systems. The systems tailored to customer requirements in Mülheim are characterised in particular by an individual and weld-free combination of the individual components. 

The first catalogues and information sheets are developed, which are intended to inform customers about the advantages of the Mülheim products and the latest developments. 

Thanks to continuous development, HOFER remained on the road to success in the 1980s. In the meantime, the company is able to manufacture compressors with a pressure of up to 3,000 bar and is further  expanding its block system. After the patenting of a high-speed electromagnetic lifting stirring device in closed pressure vessels and the registration of a utility model for glandless valves at the end of the 1970s, two further utility models for level sensors and a gas and liquid measuring device followed in 1982.

In 1985, the establishment of the latest series of multi-stage hydraulically-driven piston compressors is a remarkable progress by which HOFER enhances various gases tob e compressed without contamination. In the same year one of the first models of this kind, the TKH for argon, has been delivered.  Under Werner Köttnitz HOFER succeeds in entering a new market with the first delivery of a compressor to China.

In addition to the traditional piston compressors, the technically sophisticated diaphragm compressors in particular continue to gain importance. Thanks to HOFER's good reputation and high quality, Werner Köttnitz manages to receive the order from the European Space Agency for the development of compressors to refuel the rocket Ariane 5, at the end of his career.

Finally, in 1989, Werner Köttnitz hands over the management of the company to his son Andreas.

In 1989 Werner Köttnitz hands over the management of the company to his son Andreas and his wife Isabelle. Within just a few years they succeed in developing the first contacts with the natural gas industry, which were still made by Werner Köttnitz, into an important sales market. Once again, it is the high-quality diaphragm compressors that give HOFER access to new sales markets. (Gallery 11). At the beginning of the 1990s, HOFER supplies its hydraulically-driven piston and diaphragm compressors to customers all over the world and in a wide range of industries. 

In parallel with these successes, Andreas Köttnitz is once again attempting to put the increasingly unprofitable autoclave division back on the road to success with the development of the ecoKlav. But an unexpected drop in orders forces the management to take drastic measures in 1997. From then on, HOFER concentrates on its three core competences diaphragm compressor (MKZ), hydraulically-driven piston compressor (TKH) and system engineering. All other areas are removed from the portfolio.

Nevertheless, at the end of 1997 HOFER is about to be sold to the NEUMAN & ESSER GROUP. However, shortly before the contract is signed, the old company building can be sold at a profit and the revenues used to build a new building at its current location.

In 1998 and 1999, the new company building is constructed in Ruhrorter Strasse, while production continues at the old location. During this time, a significant increase in income of orders is recorded. The modern diaphragm and hydraulic piston compressors remain successful products whose quality can convince customers in the long term. In particular, the ability to develop customer-specific solutions is paving the way of recurring success (Gallery 12).

With new self-confidence, well-known quality and a modern appearance, HOFER is successfully opening up the emerging market of solar energy at the turn of the millennium.

When Andreas Köttnitz reaches retirement age in 2015, he sets out to find a successor. As there is no one available in his own family, he turns to another family business. Once again he contacts NEUMAN & ESSER and the successor generation Stefanie and Alexander, who have taken over the management of the company GROUP since 2008. At the end of 2015, Andreas Hofer Hochdrucktechnik GmbH becomes a 100 percent subsidiary of the NEUMAN & ESSER GROUP.

Shortly before the retirement of Andreas Köttnitz, the continued existence of Andreas Hofer Hochdrucktechnik GmbH is threatened. One of HOFER's largest customers is planning a takeover and is impending to terminate the business relationship as an alternative. To prevent the closure of the Mülheim site, Andreas Köttnitz contacts Klaus Peters. Despite the failure of the first negotiations on the takeover of HOFER by the NEUMAN & ESSER GROUP, the contact with Klaus Peters was remembered positively. On November 5, 2015, the NEUMAN & ESSER GROUP finally takes over Andreas Hofer Hochdrucktechnik GmbH.

Under the joint management of the Managing Partner Alexander Peters and Dr. Klaus Hoff, Technical Managing Director Compressors, the NEUMAN & ESSER GROUP expands its product portfolio from January 1, 2016. After several innovations, including the integration of HOFER diaphragm compressors into the KO³ software, have been successfully implemented at the Mülheim site, Dr. Hoff returned to Übach-Palenberg. As of July 1, 2018, Jörg Strizek took over the management together with Alexander Peters, and Oliver Spanner became Head of Technology. 

As part of the NEUMAN & ESSER GROUP, Andreas Hofer Hochdrucktechnik GmbH knows a strong partner at its side. Thus, since its foundation, HOFER has always succeeded in being an innovative company for high-pressure technology with premium quality. Using the latest technology, HOFER offers innovative solutions for the compression of toxic, abrasive and expensive gases. The high-quality products are designed and assembled in Mülheim according to specific customer requirements and put to the test under load on the own test bench. The integration into the NEA GROUP offers HOFER new opportunities in the fields of development, sales and service. Thus, the Sales & Application Centers of the NEA GROUP take over the customer service for new machines and the NEAC Compressor Service Centers take over the support of the installed plants worldwide.

Since 2015, HOFER has been able to rely on the NEUMAN & ESSER GROUP's Central Technology Department at its headquarters in Übach-Palenberg. A joint development team operates an independent R&D/design and standardization department for all compressor business areas. The central division Technology is constantly working on the improvement of all products and technologies. A central component of this improvement is the KO³ design program, which can be used to design and implement individual customer requirements. In 2016 the technology of HOFER diaphragm compressors was integrated into KO³. In close cooperation between Übach-Palenberg and Mülheim, the quality control criteria are constantly being redefined and updated.

The central product of Andreas Hofer Hochdrucktechnik GmbH is the diaphragm compressor (MKZ). Special features of these HOFER compressors are the long service life of the membrane and the high quality standards. Continuous further development of the complex diaphragm compressor technology always offers new application possibilities. For processes with relatively small gas quantities but very high pressure, which do not allow any contamination in the downstream application, the diaphragm compressor is the ideal solution. Especially when working with toxic or explosive gases, HOFER diaphragm compressors are characterised by their hermetic sealing and constructional details.

The first HOFER piston compressors were already developed by company founder Andreas Hofer. Today, the HOFER portfolio also includes hydraulically driven TKH piston compressors. These are used for special applications. Solid-free gases such as hydrogen, helium, argon, nitrogen, carbon dioxide and ethylene are compressed without lubricants. In hot isostatic presses (HIP), metallic components are improved to high mechanical strength by sintering under high argon inert gas pressure of up to 4,200 bar.

The fittings construction as an independent HOFER product group is very successful, too. In the past two years, the NEUMAN & ESSER GROUP has made high investments in the fittings and valve construction. Today, entire valve panels can be built. The HOFER test stand with the most modern control system is designed for test pressures of up to 4,000 bar in order to fully test safety valves including bursting discs. The extensive HOFER fittings range includes particularly robust and durable valves and piping elements and is approved for use in zone 1.

The extensive pipeline and fittings programme "Block System" includes shut-off and check valves, connecting parts, reducers, adapters and nozzles. The system for technical gases guarantees maximum stability even under vibrations and shocks and enables very user-friendly handling. The valves are mounted without axial pipe movement and retain their original clamping force even after repeated installation and removal. HOFER safety valves have been characterised by maximum safety and reliability since the company was founded. HOFER safety valves can be used for almost all gases, vapours and liquids. 

HOFER compressors have been used for hydrogen compression for many decades. Diaphragm and hydraulically driven compressors from Mülheim are used in various areas. In addition to hydrogen filling stations, the transport and storage of "green hydrogen" are also among the applications of the compressors. HOFER compressors are now used in the mobility with hydrogen refuelling of cars, buses, trains and submarines.

Further potential can be exploited by integrating them into the NEA GROUP. One of these is the area of digitalisation, which is in great demand, especially among operators of hydrogen filling stations. This demand is mainly aimed at the remote monitoring of important plant components for a low-maintenance plant availability.  

As part of the NEUMAN & ESSER GROUP, Andreas Hofer Hochdrucktechnik GmbH lives the NEA philosophy. In this philosophy, social aspects and sustainability play an important role. The employees, the team idea as well as the "we" are in focus. Common values such as communication at eye level, mutual appreciation and openness for the ideas of others shape the NEA philosophy. The intensive exchange between the central functions of the headquarters in Übach-Palenberg and HOFER also enables a common understanding of the company philosophy and goals at the working level. With the integration into the NEA GROUP, the Mülheim-based company has become a training company, too.