May 7, 2008
Compressed Natural Gas (CNG) is a substitute for gasoline (petrol), diesel, or propane fuel. It is considered to be an environmentally “clean” alternative to those fuels and it is much safer than other motor fuels in the event of a fuel spill: natural gas is lighter than air, so it disperses quickly when leaked or spilled. It is made by compressing natural gas (which is mainly composed of methane (CH4)),to less than 1% of its volume at standard atmospheric pressure. It is stored and distributed in hard containers, at a normal pressure of 200–220 bar (20–22 MPa), usually in cylindrical or spherical shapes to maintain equal pressure on the walls of the containers.
In response to high fuel prices and environmental concerns, compressed natural gas is starting to be used in light-duty passenger vehicles and pickup trucks, medium-duty delivery trucks, and in transit and school buses. Read the rest of this entry »
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Posted by nlplpg
May 7, 2008
Because Natural Gas is a ’simple’ yet high octane fuel it produces far fewer emissions than other fuels and combusts efficiently. The efficiency and emissions of the engine vary depending on the combustion and injection methods used.
Stoichiometric
Stoichiometric combustion is when the chemically exact amount of fuel is added to the air so that when the combustion is completed the chemical formula for the fuel is completed:
CH4 + 2O2 = CO2 + 2 H20 i.e. methane + 2 oxygen = carbon dioxide + 2 water
This offers exceptionally clean combustion and exhaust gases. The downside is that the power output of the engine may be lower and its fuel consumption slightly higher when compared with a diesel engine. Due to the reduced efficiency of low sulfur diesels, this is becoming less of an issue.
Lean Burn
The lean burn system employs an air/gas mixture that has more air than the stoichiometric ratio in the combustion cylinder. Looked at the other way, it requires less fuel in the cylinder. This can result in lower fuel consumption compared to stoichiometric combustion with the power output usually maintained by turbocharging. Read the rest of this entry »
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Posted by nlplpg
May 7, 2008
Natural gas can be used in all classes of vehicles - motorcycles, cars, vans, trucks, buses, lift trucks, locomotives, even ships and ferries. Natural gas can be used either by converting an existing gasoline or diesel engine, or by using a purpose built natural gas engine.
Benefits of natural gas vehicles include:
- Reduced particulate and NOx (Nitrogen Oxides) emissions
- Reduced greenhouse gas emissions
- Widespread availability of natural gas
- Lower cost
- Can be derived from renewable sources (biogas)
- Technically proven
- Available now
- Can be used in all vehicle classes
- Minimal processing or refining requirements
- Safer than most liquid fuels
- Can be refueled at home or workplace
- Noise reductions of as much as 50%
- Reduced engine wear
- and more…
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Posted by nlplpg
May 7, 2008
Gas cylinders — Refillable welded aluminium-alloy cylinders — Design, construction and testing
Abstract
ISO 20703:2006 specifies minimum requirements for the material, design, construction and workmanship, manufacturing processes and tests at manufacture of refillable, transportable, welded aluminium-alloy gas cylinders of water capacities from 0,5 l up to and including 150 l, and of a test pressure not greater than 60 bar (6 MPa) for compressed, liquefied and dissolved gases.
It includes requirements for spherical receptacles and cylinders made from seamless bodies with welded non-pressure-bearing attachments such as shrouds and foot-rings. Read More
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Posted by nlplpg
May 7, 2008
Gas cylinders — Refillable welded steel cylinders — Part 1: Test pressure 60 bar and below
Abstract
ISO 4706-1:2008 specifies the minimum requirements concerning material selection, design, construction and workmanship, procedure and test at manufacture of refillable welded-steel gas cylinders of a test pressure not greater than 60 bar, and of water capacities from 0,5 l up to and including 500 l exposed to extreme worldwide temperatures (-50 °C to +65 °C) used for compressed, liquefied or dissolved gases.
Transportable large cylinders of water capacity above 150 l and up to 500 l may be manufactured and certified to ISO 4706 provided handling facilities are provided.
ISO 4706 is primarily intended to be used for industrial gases other than Liquefied Petroleum Gas (LPG), but may also be applied for LPG. For specific LPG applications see ISO 22991. Read More
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Posted by nlplpg
