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General Characteristics of Gas Cylinders:
It is advisable to obtain gaseous substances from the central pipelines (e.g. natural gas, compressed air). However, many gases are not available via such a system, which means obtaining them from cylinders in the work place. Such cylinders contain either a compressed gas under high pressure (e.g. nitrogen, oxygen, hydrogen, argon), or a gas compacted to a liquid (e.g. ammonia, butane, propane, freon, laughing gas). Data concerning the cylinder contents can be derived from the colour of the cylinder or from any labels or imprints it may carry. In case of doubt, the imprinted information is decisive. A gas cylinder contains a large amount of a substance under high pressure; furthermore, the substance concerned may be toxic and/or combustible. This means that it is risky to use gas cylinders. Therefore, there are three types of safety measures in this respect:
- The lowest possible number of cylinders should be kept in the work place, and each cylinder should be as small as possible.
- The frequency with which cylinders are moved or transported should be kept as low as possible.
- The user should acquaint himself or herself with the rules applying to the use of cylinders in the work place.
Being forced to leave cylinders behind will pose a problem, especially if fire breaks out: heating may cause the pressure in a cylinder to rise to such a level that an explosion occurs.
Cylinders are supplied in various sizes; e.g. man-sized cylinders with a volume of approximately 40 litres are very common. However, from a viewpoint of safety, cylinders should preferably be as small as possible; what are known as "lecture bottles" are available with a volume of approximately 1 litre. However, too small a cylinder (a rare thing) would result in excessive transport of cylinders (supply and removal).
Cylinders are supplied in various sizes; e.g. man-sized cylinders with a volume of approximately 50 litres are very common. However, from a viewpoint of safety, cylinders should preferably be as small as possible; what are known as "lecture bottles" are available with a volume of approximately 1 litre. However, too small a cylinder (a rare thing) would result in excessive transport of cylinders (supply and removal).
The pressure in a cylinder is usually many times higher than the desired working pressure (200 bar or even 300 bar is very common). Special equipment is thus used to tap gas from cylinders. Depending on the type of cylinder, such equipment consists of either a regulating disc (also called "pressure regulator", see figure), or a precision control valve (this is used especially for smaller systems, such as lecture bottles).
In a precision control valve, there is direct pressure of the cylinder contents on the valve (needle valve). The pressure-resistance of such valves is limited; precision control valves are thus used only for systems with a rather low cylinder pressure.In a pressure regulator (by far the most common system in the Process Engineering Department), the cylinder pressure is first reduced using a valve fitted with a spring, the pressure of which can be adjusted with a set screw. Next, gas is tapped from the compartment containing gas at a reduced (working) pressure via a needle valve. If the pressure in this compartment becomes too high, a safety valve opens and gas escapes.
There are special regulating discs (depending on design, choice of material, and pressure-resistance) for most types of gas and cylinders. Thus, an oxygen cylinder should be equipped with a regulating disc for oxygen. In order to prevent incorrect valve-cylinder combinations, every cylinder (and the accompanying valve) has a characteristic screw thread (lead, turning to the left or to the right, inside or outside).
Table 1: Some common gas cylinders with colour code and type of connection
(R/L: right or left thread; U/I: outward or inward thread; number: pitch); B:flammable; T: toxic; C: corrosive.
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| Gas |
Type |
Colour |
Connection |
| Oxygen |
Pure |
Blue |
R12 |
| Nitrogen |
Pure |
Green |
RU3 |
| Carbon Dioxide |
Pure |
Grey |
RU1 |
| Helium |
Pure |
Brown |
RU3 |
| Ethylene |
Pure |
Purple |
LU1 |
Table 1 gives a few specific examples.
Design of the Cylinders:
The raw materials (manganese steel, chrome-moly steel) are selected carefully considering the operating conditions.
Chemical and mechanical properties are decided accordingly.
In addition, all cylinders for domestic market are also approved by Chief Controller of Explosives, Government of India.
Prototype Approval
The prototype cylinders are subjected to the following tests, as per appli
ble standard in addition to the in-process testings to verify the design and hence ensuring complete safety of the cylinders.
Approval of design calculations and certification by relevant inspecting authorities.
Raw material verification i.e. verification of chemical and mechanical properties .
Verification of minimum designed thickness · Pressure cyclic testing.
Hydraulic burst testing.
Acceptance Tests
- TENSILE TEST
- BEND TEST
- IMPACT TEST
- ULTRASONIC TEST
In addition to the above tests, the cylinders are subjected to continuous in-process inspections at various stages of production, viz
- Inspection of internal and external surfaces before final closing in operation
- Measurement of finished thickness
- Circularity of the cylindrical shell - verticality
- Verification of specified internal and External finish
- Hardness test
- Hydro stretch test
- Air leakage test
- Verification of critical dimensions
- Verification of threading details
- Verification of marking details
VALVES, we can supply::::
SLAM SHUT-OFF VALVE
NEEDLE VALVE
LINE VALVES
HIGH PRESSURE GAS CYLINDER VALVES
ADAPTORS & REGULATORS, we can supply::::
DOMESTIC REGULATORS
ADJUSTABLE PRESSURE REGULATORS (LOW FLOWRATE)
ADJUSTABLE PRESSURE REGULATORS (HIGH FLOWRATE)
ADJUSTABLE PRESSURE REGULATORS (HIGH PRESSURE & HIGH FLOW RATE)
SERVICE REGULATORS
PRESET PRESSURE REGULATORS
PRESET PRESSURE REGULATORS (FIXED INLET PRESSURE)
PRESET PRESSURE REGULATORS (VARIABLE INLET PRESSURE)
SPECIAL PURPOSE PRESSURE REGULATORS
ADAPTORS
FLAME ARRESTORS
PLEASE NOTE: ONLY AVAILABLE PRODUCTS WOULD BE MADE AVAILABLE TO SALE.
© 2008
ALPHA OVERSEAS
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ALPHA OVERSEAS
REGISTERED OFFICE:
B-52, RAMA ROAD INDUSTRIAL AREA, NAJAFGARH ROAD, NEW DELHI-110015 INDIA
Tel: (91-11) 65380335 Fax:
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42728100
Mobile: (91-11) 9899216655
E-mail: alphaoverseas@gmail.com
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