What is CNG ?
Literally it is Compressed Natural Gas. Gas is pressurized to become liquid and then used as fuel in domestic and industrial establishments.

Is CNG Safe?
CNG has four big safety features that make it an inherently safer fuel than petrol, diesel, or LPG. It is lighter than air so if it leaks, it just rises up and dissipates into the atmosphere. Its self-ignition temperature of 700oC is much higher than that of petrol (455oC). CNG needs to mix with air within a small range of 4-14% by volume for combustion to take place. This is a far narrower range than for petrol. CNG cylinders are designed and built to withstand high pressure and are safer than ordinary petrol tanks.

What is involved in converting a vehicle to CNG?
A specially designed Conversion Kit is required consisting of cylinders to be fixed in the boot of the car with associated equipment to allow the gas to flow into the engine and all cars can be converted irrespective of make or model.

Can a car still run on petrol if it runs out of CNG?
When converting to CNG, the existing petrol carburetor and fuel tank is retained so that vehicle can still run on petrol, normally, just by turning a switch on the dashboard.

What is the cost of converting a vehicle to CNG?
The present cost of a good Conversion Kit in the market is between Rs. 24,000-30,000. This is for vehicles fitted with a single CNG cylinder (gas capacity equivalent to 15 liters of petrol).

How long does it take to convert to CNG?
On the spot, about 4-5 hours for complete conversion.

How much does CNG cost?
CNG price is fixed by operators with government control, and is presently being sold at Rs. 17.43/m3, whereas “Super” petrol costs Rs. 32.19/ltr. One fill of 50 wlc. cylinder with the capacity of 11.76m3 (Total 12.5m3 less 0.74m3 for temperature pressure factor) Rs. 205. The equivalent Petrol cost is Rs. 460.

What are the dimensions and weight of cylinder?
Cylinders are manufactured from a special steel alloy without any joints in a single piece. Their size is such that they easily fit even in small cars. Typically, an empty CNG cylinder (which has a volume capable of storing 15-liters of petrol) weighs roughly 50-60 Kg, and its dimensions are 840mm x 316mm.

What is the mileage from one fill and how does one know the quantity of remaining fuel in the cylinder?
A cylinder of 50-water liter capacity holds approximately 11.76-cubic meter of CNG that is in the range of 13-14 liters of petrol equivalence. A medium-sized car that is powered by a 1300 CC engine will have a mileage range of about 150-160 Km per cylinder. An electronic fuel gauge is mounted on the dashboard as part of the conversion, similar to a petrol fuel gauge that indicates the quantity left in the cylinder.

What about refueling?
There are private CNG stations and a few operated by the government across Pakistan. Number of stations is increasing with the rising demand of CNG. Filled in the cylinder fixed in the boot in a manner similar to filling petrol through a flexible drop hose.

What is the pressure in a cylinder and is refueling safe at such pressures?
CNG is filled in the cylinder up to a maximum pressure of 200 bars (about 3600 psig). These cylinders are safe and are manufactured to meet rigorous international specifications & standards. As a safety feature, all cylinders have a burst-disc option. In case of inadvertent high-pressure filling or fire, the disc ruptures and no excessive pressure beyond specified level remains inside the cylinder.

Is CNG cylinder/tank safe in an accident?
CNG has been categorized as the safest fuel. The unique manufacturing of the cylinder enables it to sustain high pressure and impact rendering it much safer in accidents than petrol.

How much will be the saving after conversion to CNG?
The average fuel bill will be reduced by as much as 55% due to better mileage, fuel efficiency, and cheaper fuel cost. Cost of converting a vehicle from petrol or diesel to CNG is “recovered” through savings in the first twelve months of CNG use.

Does CNG Kit require servicing?
The equipment is not complex and gives many trouble-free years of service. However, as for fuels, to maintain maximum efficiency it is advisable to have routine checks. An authorized person, preferably the technician who carried out the engine conversion, should be consulted. Moreover the cylinders should be checked and tested every 3-5 years for tolerance of pressure.

Does CNG have any harmful effect on the engine?
The life span of an engine actually increases when using CNG. The life of lubricating oil is extended considerably because CNG does not contaminate and dilute the crankcase oil. Absence of lead content in CNG eliminates the fouling of plugs by lead emissions. CNG enters the engine in the form of a gas whereas petrol or diesel enters in the form of spray-mist that washes off the lubricant oil from the top piston ring area thereby increasing the rate of wear of the engine.

Should petrol be used occasionally?
Occasional use of petrol will lubricate the engine mechanism. Most CNG users switch to petrol as per whim.

Can diesel vehicles be converted to CNG?
Yes. The conversion cost is slightly higher than for conversion of petrol vehicles.

Can an existing LPG vehicle run on CNG?
No. The two fuels are essentially different. Each requires a specific air-fuel ratio for proper combustion. Conversion from one form to the other is a complicated procedure. LPG cylinders and CNG cylinders are built entirely differently and calibrated to withstand differing ranges of pressure. The CNG tank is permanently fixed to the car whereas LPG cylinders or tanks can be removed and replaced.

Do CNG vehicles have better exhaust?
CNG is an environmentally friendly fuel. Natural gas is mainly composed of methane and its exhaust emission consists of water vapors and a small fraction of carbon monoxide. The absence of carbon particles results in relatively tamer and safer exhaust fumes.

Can CNG be filled in the car through a domestic commercial outlet?
No. Natural gas used in homes, industries and factories is supplied at low pressures. In order for a car to function on CNG the gas has to be compressed at very high pressures.