Compressed Natural Gas

Micro-Design, Inc. has been a leader in the CNG industry since 1991 with over 300 CNG stations  deployed worldwide.  We are a certified distributor of GE Gemini compressors, it’s spare parts, as well as Bauer and Sauer compressors.  We’ve developed a unique solution for low inlet pressure applications using a screw compressor on the front end and a reciprocating compressor on the back end to provide the appropriate high pressure.  Our controls are compatible with any CNG application, easy to use and incorporate a proprietary web based monitoring system which can be integrated into a SCADA system.  MDi specializes in creating CNG station designs, sizing, equipment distribution, installation and commissioning.  We pride ourselves in our rock solid relationships industry wide, exceptional engineering and customer support.

Packaged Solutions

Micro-Design, Inc. offers complete CNG packaged solutions which comprise of CNG compressor skids , valve panels, dispensers, storage tanks, dryers, etc. MDi specializes in trailer mounted, engine drive CNG compressor packages eliminating the need for any external power.  The entire skid including controls, sensors, solenoids, etc. are powered by the CNG engine.  With inlet pressures of 5 psi to 3000 psi, capacities of 20 SCFM to 1500 SCFM can be obtained.

Small CNG Skid  CNG Skid   Small CNG Trailer   Large CNG Trailer   

Station Equipment

We can help you decide the best combinations of compressors, valve panels, storage tanks and dispensers for the station(s) you will need to keep your CNG fleet of vehicles running efficiently as possible.

1024px-FillingUpCNG-620x330Conventional or Standard

Standard, conventional or online stations are descriptions of similar types of CNG stations.  Fast­fill stations take natural gas from a pipeline, compress it and dispense it into various types of vehicles. MDi has designed standard CNG stations for bus fleets of all sizes, private fleets and a range of sizes for public filling.

DSC00007Mother Station

Mother stations are used to fill large volumes of CNG into mobile storage trailers.  A mother station will always be located near a natural gas pipeline.  Mobile storage allows transportation of natural gas to a site that does not have access to a natural gas pipeline.  Typical applications where mother stations are used to supply gas to: daughter CNG stations, industries and city gas distribution systems.

CNG Skid

DSC_0887Daughter Station

Daughter Stations are installed where a CNG fill station is desired but there is no natural gas pipeline. Natural gas is brought to the station by mobile storage where the CNG compressor quickly and efficiently moves the natural gas from the mobile storage to a ground storage.  The daughter station compressor can also be used to directly fill vehicles.

CNG Large Trailer  CNG Small Trailer


Time­fill Stations are used to fill vehicles over longer periods of time. Longer fill times can allow smaller and lower cost compression equipment. Vehicles are often filled overnight when the cost of electricity used for the compression equipment is lower. Centrally fueled fleets such as school buses, trash trucks and utility service vehicles are excellent candidates for time­fill systems.

Fill Post Brochure

DSC00003Combination Stations

Combination Stations combine the features of a Fast­fill Station, Mother Station and Time­fill Station. One of the most efficient combinations is to perform fast­fill dispensing operations during the daytime and trailer fill and/or time­fill during nighttime operation. This combination allows high utilization of the station compression capacity during daytime and nighttime.

CNG Small Skid   CNG Skid   CNG Small Trailer    CNG Large Trailer 


Size matters. We provide consultation to all of our customers around proper sizing of the CNG compressor packages based on their current and future needs. A small business, trying to go “Green” with 3­-5 CNG-powered vehicles needs something smaller, mobile and cost-effective. Whereas a municipality with a large CNG fleet of trucks, buses and automobiles needs a compressor package or packages that can provide enough CNG output to keep those vehicles on the road.

Small CNG Skid   CNG Skid   Small CNG Trailer   Large CNG Trailer


20130320_110323Valve Panels

Micro ­Design, Inc. designs and manufactures CNG Priority and Sequential valve panels. Only the highest quality and most durable fittings are used to connect stainless steel piping to control valves and solenoids that direct compressor gas appropriately to storage banks and/or dispensing systems. Each panel is custom-built and includes shutoff or isolation valves for all incoming and outgoing lines. All lines are labeled and high quality gauges are provided wherever necessary. The electrical wiring is housed in conduits and proper junction boxes are provided for customer connections. Certain models include overfill protection to prevent compressor from “dead heading” and damage.


MDi manufactures “state­ of­ the­ art”, stand-alone controllers that are capable of controlling compressors, motor or engine drives, priority/sequential valve panels, and CNG dispensers. Our controllers are designed to function as stand-alone controllers for a particular piece of equipment, or as controllers for an entire CNG compressor/dispenser system. The MDi SCADA system links controllers via MODBUS RTU protocol to a PC-based master controller. All controller parameters can be monitored remotely or locally on high resolution LCD screens.  Real time data and historical trending are available for planned maintenance and supervisory control.

All of MDi controllers are FM and CSA approved for Class 1 Division 2 Group C or D hazardous locations and also comply with NFPA 52.

20141018_124305Compressor Technologies

Micro-Design, Inc. was the first to market a unique CNG package designed for low inlet pressure applications (as low as 5psi). This revolutionary concept employs a rotary screw compressor on the inlet side, with a three or four stage reciprocating compressor to reach the desired discharge pressure. The reciprocating compressor uses a through-shaft design so that both compressors are driven by a common driver. This configuration eliminates complicated gear drive mechanisms and the need for multiple drives on the same skid. Customized controls operate both the compressors simultaneously and maintain proper gas flow obtaining high discharge pressures such as 4000 PSI (300 Bar) from inlet pressures that are as low as 2­3 PSI (1 Bar).

In addition to being a certified GE Gemini compressor distributor, MDi offers a variety of compressors that are electric motor drive or engine drive. The GE Gemini reciprocating compressor is truly balanced-opposed in that the opposing cylinders are mounted “in ­plane”, thus eliminating the vibration associated with the horizontal couple prevalent in other so-called balanced-opposed compressors.


Department of Transportation (DOT) vessels have an operating pressure of 3600 psig and are used for filling 3000 psig vehicles. Typically, these vessels are assembled in groups of 20, 40 or 60 vessels.

Small Vessel ASME can be provided for 4500­-5000 psig operating pressure (3600 psig vehicle fill pressure). These are typically provided in groups of 20.
Large Vessel ASME can be provided for either 3600 psig operating pressure (3000 psig vehicle fill pressure) or 4500­-5000 psig operating pressure (3600 psig vehicle fill pressure). Typically, these are large vessels with individual storage capacity of greater than 10,000 standard cubic feet.

Spheres are built to ASME Section VIII Division 2 design and fabrication standards. They are normally used for 4500­-5000 psig operating pressure (3600 psig vehicle fill pressure) although can be provided for other pressures.


Natural gas dryers remove water vapor prior to storing or using natural gas for a vehicle fuel. High water content can cause blockage of CNG in fueling systems and can contribute to corrosion in storage vessels and piping.

Dryers typically operate on the low pressure side of the compression process. The low pressure dryer uses molecular sieve adsorbent desiccants to remove water vapor to extremely low levels.

There are a number of standard drying technologies and we will help you select the most cost effective type for you.

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