CNG stands for Compressed Natural Gas. It is a gaseous fuel and is a mixture of hydrocarbons, mainly methane, in the range of 89% to 90%.Due to its low density, it is compressed to a pressure of 200-250 Kg/cm² (g) to enhance the vehicle on-board storage capacity.
Yes, it is safe. The properties of CNG make it a safe fuel. It is lighter than air, so in case of a leak it just rises up and disperses into the atmosphere. Besides, a high auto-ignition temperature of 540 degrees centigrade as against petrol’s 360 degrees centigrade, makes it a safe fuel. Also, in case of a leak, if CNG’s concentration in the air is less than 5% or more than 15%, the gas will not burn even in the presence of a spark.
All spark-ignited engines can be converted to CNG, but a specially designed conversion kit is required for the purpose. The kit consists of a cylinder to be fixed in the boot of the car and other equipment to allow gas flow into the engine.
Yes, even after conversion to CNG, the vehicle continues to be fitted with the petrol carburettor and fuel tank. The vehicle can therefore run on dual fuel, either on CNG or petrol, whenever desired, simply by flicking a switch on the dashboard.
The cost of converting a vehicle to CNG depends on its type and make. Broadly, it varies between Rs 25,000 to Rs 55,000 (approximately).
CNG cylinders are manufactured from a special steel alloy and are seamless in construction. Their compact size allows them to easily fit even in a small car. An empty CNG cylinder with a 50 liter-water-carrying capacity weighs 48 kg (approximately), with a length of 835 mm and a diameter of 316 mm. The 50 liter capacity cylinder is the one most regularly used; cylinders with 45 liter, 55 liter, 60 liter and 65 liter capacity are used as well.
- What is the capacity of a cylinder, and mileage from one fill? How does one get to know the quantity of CNG left in the cylinder?
A cylinder with a 50 liter water-carrying capacity is capable of carrying approximately 9 kg of CNG. This is equivalent to 12.5 liters of petrol and will allow a run of about 150-160 kms to a medium sized 1300 CC car. An electronic fuel gauge fitted on the dashboard as part of the conversion kit indicates the quantity of CNG left in the cylinder.
CNG cylinders are designed and built in such a way so as to withstand high pressure. The maximum pressure in a CNG cylinder is up to 200 kg/cm2 (g) (about 2840 pounds per square inch (gauge) or psi[g]). CNG cylinders are safe as they are manufactured as per specific requirements and tested before use, in accordance with international specifications and standards, and are duly approved by the Chief Controller of Explosives. Moreover, they are provided with a pressure relief device (PRD) that consists of a fusible plug and a burst disc that ruptures in case of inadvertent high pressure and temperature.
The fuel bill on the basis of average running of vehicle is reduced by 50 percent approximately. The cost of installation of the kit is recovered within a year, given average distances covered in driving.
CNG kit is safe and simple. It gives years of trouble free operation. It doesn’t require frequent servicing. Just as for all other fuels, it is advised to have routine services. An authorized person should be consulted for service. As per Gas Cylinder Rules, 1981, the cylinder should undergo hydro-stretch testing every 5 years to check pressure tolerance.
Owing to CNG's distinct features, it does not contaminate or dilute crankcase oil, giving a new lease of life to the engine. The absence of any lead content in CNG helps avoid lead fouling of plugs, thereby enhancing plug life. One of the important benefits of CNG is that upon entering the engine in the form of a gas (and not as a spray or mist like other fuels), it doesn't disturb the presence of lubricating oil in the engine, and reduces chances of wear and tear.
CNG provides easy starting, reliable idling and smooth acceleration. The acceleration of a CNG vehicle is a bit slower, which is due to a power loss of 5-15%. This can be minimized by proper tuning on CNG like advancing the spark timing to take advantage of the high octane rating of the fuel.
Yes, a diesel vehicle can be converted to run on CNG, but the conversion cost is higher than the conversion of petrol vehicles.
CNG is an environment friendly fuel. The natural gas is mainly composed of methane and its exhaust emissions consist of water vapor and a negligible fraction of carbon monoxide. The absence of carbon and other particulates result in negligible amount of harmful elements in exhaust fumes.
CNG emits less carbon dioxide and other pollutants as compared to liquid fuels. Thus, CNG contributes in lowering air pollution, also helps in improving the Balance of Payments by acting as a substitute for imported liquid fuels, provides more business and job opportunities with the opening up of a new sector, and being competitively priced, it appeases motorists.