Diaphragm compressors are the preferred choice when contamination-free and leak-tight gas compression is required. Diaphragm compression achieves its high purity compression by isolating the pulsating hydraulic fluid from the process gas with a set of triple metallic diaphragms and a set of static seals. The reciprocating piston moves a column of high pressure hydraulic oil through a fixed cavity, which allows the diaphragms to compress and pump the process media.

PDC utilizes the latest technology in cavity contour design, diaphragm processing technology and metallurgical design to provide the longest lasting diaphragm life in the industry.

The typical markets for diaphragm compressors include:
• The industrial gases industry including transfilling, cylinder and tube trailer filling stations, and gas distribution markets such as helium, hydrogen, nitrogen, and argon among others.
• The specialty gases industry including electronics gases (silane, specialty gas blends), calibration gases among others.
• The alternative energy sectors including the hydrogen energy sectors, compressed natural gas applications and biogas industries.

PDC leads the industry in diaphragm life and our typical client reports between 6000 and 8000 hours of operating life from PDC machines diaphragms.

Low operating temperatures
Diaphragm compressors are well-suited for applications ranging from vacuum to pressure as high as 60,000 psig [4136 BARG]. Diaphragm compression is very unique in that compression application that could require three to five stages on traditional types of compressors, in diaphragm compressors can be done in one to two stages.

“Diaphragm compression is very unique in that compression application that could require three to five stages on traditional types of compressors can be done in one to two stages”

This is due to heat being dissipated in the mass of the large surface area of the compressor head assembly(s), the presence of pulsing oil and integral cooling of the compressor heads. Typically, diaphragm compression can run 20-60% cooler on outlet temperatures than other types of compression technology. This inherent advantage enables downstream cost benefits including lower operating and maintenance costs. PDC compressors run a compression cycle that is more isentropic than adiabatic and this enables – in certain applications – compression ratios as high as 100:1.

High efficiency and low-power
From an efficiency perspective, diaphragm compressors provide outstanding results.

Due to horizontally opposed crankcase designs, PDC compressors, for example,
can achieve up to 33% brake horsepower reduction in running power, as opposed to traditional in-line opposed designs with high suction pressures.

Volumetric efficiencies run between 87% and 94% depending on the compressor size, and isentropic efficiencies upwards of 90%. This all correlates to maximizing the return on the capex spent with low power requirements and high efficiencies.

Integral hydraulic lube oil system
With all PDC compressors, automatic priming pumps are included as a standard, eliminating the priming problems typically associated with gravity-fed lube oil pumps or hand crank devices. This automatic system works in tandem with an automatic injection pump assembly which injects a fixed volume of oil into the compressor head assemblies during each suction stroke.

This injection pump acts as a compensation pump device, compensating for the following:
• Normal oil leakages past the high pressure oil piston
• Compressibility of the oil under high pressure
• Providing for over-pump to ensure the diaphragm makes a complete sweep of the process cavity, enabling full efficiency during each compression stroke.

Safety features
Standard diaphragm or seal failure leak detection systems are provided on all PDC diaphragm compressors. This interlock stops the compressor upon a failure of either a process or oil side diaphragm or seal.
Due to the inherent nature of diaphragm compressors, there is no possibility of leakage of the process media to the atmosphere, the crankcase or into the hydraulic oil. This enables the compression of pyrophoric, explosive, radioactive and other hazardous gases, without the need to purge crankcases or manage gas leakage past the main seals.

Authored by, Kareem Afzal