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CNG 101
Compressed Natural Gas (CNG) is rapidly replacing traditional sources of vehicle fuel like gasoline and diesel.

CNG 101

Compressed Natural Gas (CNG) is rapidly replacing traditional sources of vehicle fuel like gasoline and diesel. This is not only because of its significantly lower cost but also because it is much more clean and safe to use. However, it is also much more difficult to handle and before deciding to switch to CNG it would be pertinent to take into account the operational and capital requirements for running a CNG fueling station.

Have a well thought out transition plan

Plan ahead and plan carefully in order to smoothly achieve the transition to CNG. One of the most important factors to consider would be the layout and design of your station including all the components within it. Compressors, in particular, need to be paid special attention to with regards to their size. A small compressor leads to painstakingly slow fueling or inadequate fueling.

Your plan will need to incorporate an analysis of fueling trends and patterns such as:

Remember to keep future expansion needs in mind when designing and constructing your CNG station so as to easily incorporate a growing CNG fleet. You will also need to determine which type of CNG station you want to operate. The three main types of stations run today are time-fill stations, cascaded fast-fill stations and buffer fast-fill stations. Let us look at each type in some detail to gain a better understanding of them.

1. Time-fill station: This type of fueling station is based on a simple and cost effective method that involves drying the gas before compressing and dispensing it to all vehicles at the same time through a manifold. This type of station offers many benefits in that there is no need for storage or cascading and it also enables you to save on man -power as drivers connect to the manifold and leave. This also saves on precious time that is often wasted on fueling.
However a time-fill station can only be used in instances when fleet vehicles are stationed at the facility for a long period of time. This limitation makes time-fill stations only feasible for certain types of vehicles that park overnight in a home base such as trash collection trucks and school buses.

2. Cascade Fast-Fill Station: These are much faster than time-fill stations primarily because they make use of vessels that can withstand more pressure than mere compressors alone. These high pressure vehicles are grouped together and set in an automated sequence or ‘cascade’ to fill a vehicle. Vehicles get filled relatively faster and are not required to dock at the facility for a long period of time as in the earlier case.

3. Buffer Fast-Fill Station: The main difference between buffer fast-fill stations and cascade fast-fill stations is that the former uses huge compressors to fill vehicles directly rather than fueling them from storage. These large compressors continue pumping even when there are no vehicles fueling, which leads to uninterrupted and fast flow upon resumption of fueling.


Some Essential Components


1.  Gas Compressors: These are the most essential components of a station, of which many styles and manufacturers exist. However, the basic concept underlying the design is the same; they contain pistons that rotate in cylinders. It is the packaging used to support the compressor that requires special attention as it varies in quality and functionality.

Some compressors are non lubricated and while this makes them simple to use and prevents oil leakage on to the vehicle, they expose their inner components such as rings and piston rod seals to wear and tear. Furthermore, they need to be run slower, which can affect the efficiency of your fueling.

The industry norm is to use air-cooled compressors, as they have remained durable over time.

CNG compressors generally create a lot of noise, so it is often required to enclose them acoustically. Though a properly manufactured enclosure is expensive, it would be worthwhile to invest in one as it provides the best noise control.

You should also inquire from your local utility company how much gas service pressure they offer. This is important to know because the higher the pressure offered, the lower the horsepower required to generate the same volume of flow per minute.

Industry standards in the U.S dictate that compressors operate with a discharge pressure of no more than 4500 PSIG. Contemporary stations have widely begun to make use of electric motors, which are reliable, easy to use and compact, to power the compressor.

2. Gas Dryers: A gas dryer is needed to lower the moisture levels in the gas. To make this cost effective, one tower dryer consisting of a manual system of regeneration can be used.

3. Gas storage: This is only required for fast-fill stations. Several types of storage vessels are available including small tubes, large tubes and even spheres. These vessels should be able to withstand a minimum design pressure of 5500 PSIG and should contain condensate drains.

4. Gas dispensers: Depending on their application, these are available in various types. You can consult the manufacturers for more details about these.


Some Useful Facts and Terminologies


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