Oil Free Screw Compressor – What To Look For..

You will find a multitude of hydrogen compressor and pump technologies in use nowadays. Types of compressors consist of diaphragm, reciprocating piston, and centrifugal. Pumps for hydrogen applications include various kinds of positive displacement systems. Every membrane compressor and pump system operates using various ways, and each is utilized for specific factors and for particular marketplaces.

To introduce visitors for this topic, we asked a number of hydrogen compressor and pump producers to illustrate the systems found in hydrogen applications nowadays.


Hydrogen will be the simplest and a lot abundant element in the world. (See CGI, Feb. 2008, p. 52.) It is really an efficient, non-polluting, green energy. Growing hydrogen technologies require storage and the use of hydrogen at higher pressures.

Compressors are utilized to increase the pressure of gaseous hydrogen (H2). In general, nevertheless, liquids are not deemed compressible. Pumps therefore are used to raise the pressure of liquid hydrogen (LH2) in the use point by providing a constant stream. Limitations and last use back stress cause the pressure improve. LH2 at high-pressure will be converted to vapour as it passes through a vaporizer, and is utilized or stored in the raised stress. Gaseous compressors and fluid pumps are both used in hydrogen applications.

Even though basic principles of compressing and working are generic to the majority of fumes and liquids, there are distinctive distinctions and requirements, such as safety, when confronted with hydrogen. One of the biggest difficulties to utilizing hyrogen is its safe containment, because of its reduced molecular mass.


The three fundamental varieties of compressors – diaphragm, reciprocating piston, and centrifugal (also known as radial) – have various qualities that make them appropriate for utilization in different settings.

Diaphragm Compressors

“Diaphragm compressors,” advises Osama Al-Qasem with Pdc Machines Inc., “are the ideal choice for compressing gases without having incurring contamination from the procedure media or leakage of gasoline to background air.” H2 is remote from the mechanical areas of the compressor and through the environment by a set of 3 metallic diaphragms. These are generally clamped among two exactly contoured concave tooth decay in upper and lower plates. Three of the diaphragms are nested and take action together as one. The top diaphragm is in touch with the H2 and the bottom is in contact with the hydraulic oil. A 3-diaphragm set can be used to make sure there is no cross-toxic contamination between the hydraulic oil and also the H2 being compressed. The middle diaphragm, used for leak recognition, has lines scribed on edges. In case a leak grows inside the upper or lower diaphragm, or if the O-bands put on, the mass media will seep across the scribe outlines into an accumulator. When an accumulator pressure reaches a set restrict, the nitrogen compressor will instantly quit. “As static seals are used,” advises Al-Qasem, “there is not any seepage of fumes towards the environment, and no reason to purge or vent the crankcase.”

A engine-powered crankshaft linked to a piston movements a column of hydraulic fluid up and down. Compression occurs because the hydraulic liquid is pushed upward to fill up the lower oil-dish cavity, exerting a uniform force against the foot of the diaphragm set, deflecting it in to the H2-loaded gas-plate cavity above. The displacement in the diaphragm up against the gasoline-dish cavity compresses the H2, pushing it out the discharge check device. Since the piston, which moves the hydraulic liquid, strokes downwards, the diaphragm is drawn back down in to the lower cavity, the inlet check device opens up, and also the upper cavity fills with H2. The period is repeated.

The primary advantage to diaphragm compressors is there is not really the concern for seepage as with other compressors or pumps.

Stephen St. Martin of Gasoline & Air Techniques, Inc. reviews that “Diaphragm compressors are used to compress H2 in cylinder trans-filling and tube trailer offloading operations, and then for gas recovery from the vapor space of cryogenic storage vessels. Due to the high pressure capability, and inherently oil-totally free pressure, the diaphragm compressor can also be commonly used in car hydrogen fueling stations, in which demands of 10,000 psi and previously mentioned are utilized.”

The hydrogen fuel cell requires extremely-purity H2 to function correctly. “The diaphragm compressors,” based on Osama Al-Qasem, “are made to offer precisely this feature. Countless diaphragm compressors happen to be installed globally as part of the renewable energy system to find alternative sources for oil.” Al-Qasem states that 85 to 90 % with this marketplace needing diaphragm compressors were supplied by Pdc.

Diaphragm compressors are great for high pressure applications. It is really not surprising that diaphragm compressors are best for hydrogen programs, particularly in the development in the emerging hydrogen economy. Osama Al-Qasem noted one unique and interesting growing “double-green” technology. Pdc has compressors being utilized along with wind turbines. The electrical power from wind turbines can be employed to supply a water electrolyzer to electrochemically split water into its elements, hydrogen and oxygen. One feature that makes the marriage of such two technologies this type of interesting match would be that the electrolyzer can run with adjustable energy enter, as windmills turn at varying speeds, based on the wind. Hydrogen thus produced is compressed and kept for later on use, either within a fixed energy cell to create electrical power if you have no wind, or to supply a hydrogen vehicle.

Hydrogen compressor programs are lots of. They consist of making use of solar energy to electrolyze water to create H2, which, like the windmill application, is then compressed and stored for later on use, either within a fixed fuel cell to create electrical power if you have no sunlight, or fuel a hydrogen car. Compressors are utilized at hydrogen fuel cell stations, including those for vehicles, buses, fork-lifts, scooters, and household re-fuelers for energy cell (FC) vehicles; for satisfying and off-launching H2 from pipe trailers, gas cylinders, and storage space tanks; for your compression of syngas from renewable resources; as well as for wind and solar technology. H2 compressors are utilized in these disparate applications as gasoline blending, recycling, and mixing, metal handling, hydrogenation of edible oils, specialty gasoline filtering, drift glass creation, and energy plant turbine chilling. Fumes for semiconductor, electronic devices and fiber optics manufacturing require compressors. They are also utilized for feedstock for chemical, petrochemical and pharmaceutic sectors, pressure boosting and storage of gases from on-website era systems, and then for energy back-up using hydrogen FC for telecom towers, as well as research and development.

Multiple-stage Reciprocating Piston Compressors

Multi-phase reciprocating piston compressors are commonly employed for pressure of H2 gasoline. Piston compressors work on a simple theory. Rick Turnquist, with RIX Sectors instructs, “The piston within a big cylinder pushes a fixed amount of gasoline right into a smaller sized cylinder, therefore resulting in a pressure improve. This is based on the best gas legislation, which in abbreviated type is: PV=nT (pressure x volume = Moles of gas by temperature). Thus as volume will go down, pressure increases (note after the last stage pressure improve needs through the back stress inside the user’s tank or piping).”

Turnquist continues to explain that “H2 compressors are like those employed to compress other fumes; however you can find occasionally design differences as a result of tiny molecular size of the H2. These may be: an exclusive valve design; special piston diamond ring components; overlapping piston ring design to lower seepage; lower compression proportions; or cylinder and head castings may need to be impregnated to avoid leakages due to casting porosity. Additionally, the grade of steel used in the compression finish elements may need to be altered.”

Hydrogen, like all fumes, is heated up by pressure. “Intercooling” of the gasoline is needed when utilizing multi-phase high pressure compressors.

The largest finish-customers of multi-phase reciprocating CNG compressor are refineries and chemical plants. Clients consist of such businesses as Air Products, Praxair, and Chevron Research. These compressors are also used lrnhbl some refueling programs, for syngas, pilot vegetation, and laboratory R&D.

Centrifugal Compressors

Centrifugal compressors are rarely used for hydrogen applications due to the molecule’s reduced molecular weight. However, centrifugal compressors are used in cryogenic H2 programs where stream is relatively higher and the pressure head preferred is fairly reduced. Barbers Nichols Inc. (BNI), designer and producer of specialty turbo-machinery, makes cryogenic H2 centrifugal compressors for 2 programs. Those two programs involve sub-cooling H2 by sketching down fluid boil-away gas pressure listed below atmospheric. Jeff Shull, with Barber Nichols, explains that “this produces a more dense fluid that can then be utilized within a rocket better (takes up much less space and reduces overall weight). BNI utilized four separate centrifugal phases (4 solitary stage machines each having a motor) to draw in down pressure to approximately 3 psia having an atmospheric stress electric outlet and runs to get a propellant densification test at NASA. BNI’s H2 cryogenic compressors use a motor and bearings operating at room heat with an overhung impeller over a hollow shaft to minimize heat enter to the fluid. No dynamic seals are employed so styles are hermetic. BNI also has supplied a number of H2 circulators in supercritical applications (supercritical H2 is much more like a fluid than a gasoline, however) for cryogenic cooling.”