Hydraulically Driven

Design Features

Hydraulically driven, dry-running HOFER piston compressors are designed for easy maintenance and allow for lubricant-free compression of non-corrosive gases, which are free from solid particles, such as hydrogen, helium, argon, nitrogen, carbon dioxide and ethylene. The maximum discharge pressure of the standard design is approx. 14.500 psi (1.000 bar). For higher working pressures up to 65.250 psi (4.500 bar), special designs are available. This compressor type is designed for easy maintenance. A piston packing can be replaced in approx. 10 to 30 minutes, depending on the compressor size.

Operating Principle

The special construction and design of the piston packing allows the compressor to operate  completely without the lubrication of these sealing elements at higher discharge  pressures, although under normal circumstances such a lubrication is absolutely  required. The gas piston gets the required sealing and sliding properties by the design of the packing structure with the materials specially developed for this purpose. The gas space and the gas to be compressed are kept free from undesirable lubricants. HOFER piston compressors of the TKH type series are preferably built in either a two-stage or one-stage double-acting design. The unit is driven by oil hydraulics. The hydraulic cylinder is positioned between the first and second stage. An electronically-controlled hydraulic pump  pressurizes the hydraulic cylinder on alternating sides. Proximity limit switches activate the stroke reversion. Mixing of both media is excluded due to the separation of the hydraulic and gas chamber and by use of double seals. HOFERHydraulicPistonCompressor The force required for gas compression is generated by the oil pressure and the  corresponding ratio of piston diameters. The capacity is regulated by the piston speed (number of strokes) through varying the flow rate of the pump. The stroke frequency, and thus the suction capacity of the compressor can be continuously regulated between 0% and 100% via a standard analogue signal. Upon request, instruments for gas and oil leak detection can be integrated at this point. This allows for continuous monitoring of the condition of gas- and oil-side seals.   The gas compressed in the different stages is cooled by the inter-stage and after-coolers, respectively. Here, the temperature difference is approx. 10 K in relation to the cooling water inlet temperature. Usually, the hydraulic unit is also connected to this cooling circuit.

Installation of HOFER piston compressors in hazardous areas

For the use of the compressors in hazardous areas, two alternatives can be supplied:

  1. Installation of the cylinder set in the hazardous area (zone 2 or 1) and installation of the hydraulic system in the non-hazardous area. The hydraulic oil unit is connected through a gastight wall.
  2. Installation of the cylinder set and the hydraulic unit in the non-hazardous area (zone 2).
Capacity, compression ratios, pressure stages The suction capacity of the compressor is determined by the suction pressure, the discharge pressure and the frequency of strokes. For different models please refer to the attached tables (other performance data upon request). The stated driving powers apply to the maximum operating data.


HOFER compressors of the TKH model series can be supplied either without accessories or as a complete, turn-key operational unit with all  necessary devices, fittings and instruments.

Acceptances and certifications

The standards and directives applicable in the European Community

  • Directive for Machinery 98/37/EG
  • Pressure Equipment Directive 97/23/EG
  • ATEX Directive 94/9/EG
  • Low Voltage Directive 93/68/EWG
as well as any other applicable standards are the basis of our construction and design. Compliance with the applicable directives is confirmed by the conformity declaration respectively the manufacturer's declaration and the CE marking of the compressor.

US standards:

For the American market, the applicable US regulations and standards are complied with. Prior to delivery, each HOFER piston compressor is subjected to a test run under operating conditions for several hours. Upon request, the customer can witness the test run.

Type Examples:

Piston Compressors hydraulically driven - Type selection

Two-stage dry-running piston compressor with hydraulic drive unit  TKH 52/36 - 200 - 50
Type of gas H2, He, Ar, N, CO2, C2H4
Suction pressure 7.250 psi (500 bar)
One-stage double-acting compressor TKH 28/28 - 80 - 100
Type of gas H2, He, Ar, N, CO2, C2H4
Suction pressure 14.500 psi (1.000 bar)
PDF Data Sheets: Hofer - Piston Compressors

PDF files require Adobe Reader 7 or later


Comments are closed.