CNG Vehicle refuelling solutions - Refuelling Station Design
CompAir is the world leader in the design, manufacture and installation of ready-to-run CNG Refuelling stations.
From years of experience CompAir have realised the importance of getting it right at the design stage and forming close relationships with the customers and our agents is very important.
CompAir gets involved very early on in the project life cycle and as such understands the customer’s requirements fully and can therefore provide a station that exceeds all the customers expectations.
A typical CNG refuelling station project plan will look like this:
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What type of station do I need?
This will depend on many factors including the types of vehicles being filled, when they are filled, how much fuel they need at each fill, the size limitation of the site, and the budget available, to name but a few.
An important issue is whether the station is for private use or for public refuelling as this may determine the types of dispensers and the point of sale equipment as well as the filling method (fast fill or time fill).
Fast Fill is where the vehicle is filled from a stored volume of gas that has previously been filled by the compressor. The speed of fill is comparable to petrol or diesel and is typically found on public forecourts.
This is the only suitable method of refuelling public vehicles or where cash payment is made, i.e. the quantity of gas put into each vehicle has to be known.
Time Fill is where the vehicle is filled straight from the compressor without the need for extensive storage cylinders at the refuelling station. This method requires the vehicles to be parked up for some length of time, typically overnight, and is therefore suited to depot based refuelling like buses. The quantity of fuel dispensed into each vehicle is not easily monitored and therefore this method cannot be used for public refuelling.
Compressor selection
The size of compressor will depend on the quantity of gas required each hour and the overall gas requirement each day.
The filling pattern and operating hours of the site are also important factors to bear in mind.
Essentially you need to make sure that at any given time the vehicle trying to fill should be able to get a full (normally) 200 bar fill.
This is a carefully worked out equation balanced between the size of the compressor and the size of the storage.
Ideally you want the compressor (or compressors) to be running between 12 and 20 hours per day, this way you will maximise the gas compressed, and hence better your financial returns, but also give yourself time to take the compressors off-line for essential servicing or maintenance.
Dispenser selection
Another important decision needs to be made on the type and quantity of CNG dispensers.
There are two main types, electronic and manual.
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Electronic dispensers are the more sophisticated and have the ability to be pressure and temperature compensated, that is they can dispense a very accurate quantity of gas no matter what the operation or ambient weather conditions. |
They also have the advantage of being “locked out” until some form of access card or point of sale equipment authorises it to be used.
Electronic dispensers tend to be fully automatic in operation and are always found on public forecourts and large CNG stations.
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Manual dispensers are much simpler and have little or no electronics inside them, instead they just rely on manual operation and simple manual valves. There is usually no means of monitoring or recording the quantity of gas dispensed and therefore these are mostly suited to small private stations such as CNG Forklifts or private car users. |
The quantity of dispensers required will very much depend on the base parameters of the station.
This includes the number of vehicles using it per hour, the size of each fill, the type of vehicle using the station (cars, buses etc.) and the size of the refuelling station (compressor, storage, gas pressure)
If for example it takes 5 minutes to fill a car (including time to attach and detach the filling hose) then you can only fill a maximum of 12 cars per hour on each hose.
If you have 500 cars filling at a refuelling station then you will be need two hoses, i.e. 12 cars per hour for 24 hours = 288 cars per hose (12x24) per day, therefore need two hoses.
In practice you will in this instance probably have two twin-hose dispensers (4 hoses in total) so that congestion at the pumps is keep to a minimum.
Storage selection
The design and specification of the storage cylinders is very much dependent on which country you will be operating in as each country has its own codes of practice and rules.
When sizing the storage you will need to know how much gas is required and what compression top-up you will have from the compressors.
Safety and Hazardous Areas
Whenever you design a CNG refuelling station you must take into account the local and international rules that are applicable in that region or country.
These will relate to the design, installation and operation of CNG refuelling stations and may differ from country to country.
In all cases you will need to do some sort of hazardous area analysis and a series of Risk Assessments, all of which will ensure that the equipment is installed and used in a safe manner.
Careful consideration needs to be given to the specifying of components within the hazardous area (the area defined as that which might contain a hazardous environment).
Hazardous areas may have to be approximated at an early stage in a project to allow electrical equipment to be specified and other potential sources of ignition to be located. However, a definitive drawing should be produced prior to operation of the filling station and should be based on the appropriate standards for that region.
When embarking on a gas station project you would need to take many other legal and allied considerations into account, such as Consultation with appropriate enforcement bodies, legislative Law and Acts, Codes of Practices, and also the competency of the people designing, installing and operating the gas stations.
CompAir have extensive knowledge and experience in this field and would be able to assist in all these areas of responsibility.
In relation to the compressor and associated equipment, CompAir has invested heavily in ensuring its equipment is as safe as practically possible.
All CompAir stations have many safety protection devices including:
- Inlet Solenoid Valves
- Inlet Non-Return Valves
- Inlet Pulsation Vessels
- High & Low Pressure Switches
- Gas Inlet Filter
- Auto Drain Solenoid Valves
- Blow Down Vessel Return lines
- Gas Tight Oil Filler
- Vent Stack Manifold
- Compressor Delivery Non-Return Valve
- Starter Control Panel Pressure Switch
- Exd Marshalling Box
- IS Marshalling Box
- Acoustic and explosion proof enclosures
Aftermarket
Once the gas station has been commissioned you will need to then concentrate on its continual safe and trouble-free operation.
The most important thing at this stage is to ensure that you are have full service coverage and that you are regularly servicing the compressor and associated equipment to the schedules as lay down by the manufacturers.
Some of these will be to satisfy the Written scheme of Examination (a requirement to periodically inspect and test pressure equipment) and some will be to satisfy the manufacturers warranty.
In all cases you need to insist on the use of genuine spare parts.
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CompAir have an extensive and worldwide coverage of trained service engineers and full spares availability, as well as many service centres and manufacturing facilities strategically located around the world. CompAir can offer extended warranties and long term service contracts as well as servicing and supply of genuine spare parts. |