Page 5 of catalogue Diaphragm Compressors of Andreas Hofer Hochdrucktechnik GmbH

Hofer Diaphragm compressors

page 5 of 20

Fig. 2: Classification of Compressors as per their displacement motion and flow of medium [1]

The intensive efforts to avoid all above disadvantages and to meet steadily increasing environmental and accident prevention requirements resulted in the further development of the piston compressor to a diaphragm compressor (Fig. 2). This compressor design has no sliding components in the gas chambers which need to be lubricated. Only static sealings are used which guarantee, that absolutely no leakage appears. Due to this special design, • diaphragm compressors are hermetically sealed towards the outside. The whole compression chamber of the compressor is sealed by metallic, static sealings. Leakage rates of 10-4 mbar l/sec. are quite usual and are achieved without any special action; higher tightness of 10-8 mbar l/sec. can be obtained with special modifications in the design. These small leakage rates allow the diaphragm compressor to be used also for the "hot areas" in nuclear power Plants or for the compression of highly toxic gases. • diaphragm compressors are operating absolutely lubricant-free in their compression chamber, i.e. the process gas will not come into contact with any Lubricants, and the removal of used and contaminated oils and grease is deleted. Critical gases, such as oxygen and chlorine can be compressed to higher pressures without any problem. • contrary to other types of compressors, no abrasion occurs from Piston rings and stuffing boxes. No need to provide purging or buffer gas devices at the stuffing box sealings. The process gas leaves the compressor with exactly the same purity level, as prevails at the compressor inlet. If the gas enters the machine already in a certain high quality level, it can be used directly after the process as breathing air, doting gas for semi-conductors, or as hydrogen for the fuel cell technology. • the process gas will come into contact only with metallic materials. Depending on the type of gas and on process duties, different material qualities are at choice. When selecting the correct material, a high corrosion resistance and a long lifelength of the gas-contacted components can be achieved. The wide range of materials reaches from simple structural steel via stainless steel qualities up to high alloy special materials, such as Hastelloy.