This code is intended to provide safety requirements for design in construction of Acetylene pipe lines having working pressure rating above 2.5 kg/cm²g and less than 26 kg/cm²g and filling and discharge manifolds for Acetylene service as well as Acetylene Compressors & High-Pressure Driers.
This code applies to plants and premises which are engaged or in use in the compression of Acetylene, charging of Acetylene cylinders or discharging of acetylene cylinders through a stationary manifold system.
• An existing plant or a premise which is not in strict compliance with the provisions of this code may be continued in use when such use does not constitute a distinct hazard to life or adjoining property. But in case of any renovation or changes necessary, this standard should henceforth be followed.
• This standard does not apply to plants which only compresses Acetylene for chemical operation and or which only produces compressed Acetylene less than 1.55 kg/cm²g. This also does not apply to the general use of acetylene directly from one cylinder for welding. cutting, heating and heat treatment operation.
For the purpose of this standard the following definition shall apply:
• ACETYLENE COMPRESSION: Includes Compression, high pressure drying, cylinder filling, and transmission of gas through pipe line above 1.55 kg/cm2g pressure either in single stage or multiple stages. The compression would include and mean increasing the pressure by any means.
• AUTHORITY HAVING JURISDICTION: Means Chief Controller of explosives, Nagpur or his authorized Representative
• SHALL: Indicates a mandatory requirement.
• SHOULD Indicates a recommendation or that which is advised but not absolutely necessary.
• UNPIERCED WALL: A wall which may have pipes or conduits passing through it or windows, glazed with safety glass and wired glass set in it, but such openings must be sealed to prevent the flow of air between adjacent rooms.
• MANIFOLD: Manifolding of cylinders is for the purpose of centralizing the gas filling or supply to provide a continuous supply or filling of gas where cylinder individually is not sufficient.
• STATIONARY MANIFOLD: These are essentially of a wall or floor supported provided with fittings for connecting of cylinders by means of leads (pig tails). In case of discharge manifold one or more permanently mounted regulators serve to reduce and regulate the pressure of the gas from the cylinders to the point of consumption.
• PORTABLE MANIFOLDS – There are basically two types:
A. In this gas passes from connected cylinders through individual leads to a single common lead to blocks. From there through a single pressure reducing station in case of discharge manifold to the consumption point.
B. The cylinders are connected through coupler tees attached to a shut off valve of each cylinder. Gas from or to each cylinder passes through the coupler tee and joins the main stream flowing through a common line.
• LEADS OR PIG TAILS Flexible device made of metallic reinforced rubber, Teflon or steel suitable to connect the manifold pipe to the cylinder through proper connections.
• FLASH BACK ARRESTOR/FLAME ARRESTOR As defined in IS-11006-84. of device to arrest the propagation of flame or flash.
LOCATION OF OR ARRANGEMENT OF CONSTRUCTION AND UTILITIES
• Location and building shall confirm to the Ministry of Industry Government of India, Notification No. 625 dated 7th August,1983.
• The Building housing acetylene compressor, filling manifold or discharge manifold unless it is part of the Acetylene manufacturing and charging plant shall be located at least 15 meters from Public Right of way and from line of adjoining property or building that may be built upon. Boundary wall Or Barbed wire fencing must be laid around the building at minimum distance of 9 meters to avoid any authorised entry of any person with clear sign boards indicating hazardous area and no smoking in the premises. Conspicuous signs reading “NO TRESPASSING – NO SMOKING OR OPEN FLAMES” or equivalent should be displayed.
• The building walls should be constructed of non-combustible or limited combustible materials and have a fire resistance rating of at least 1 hour.
• ‘The Compressor’s station or Filling Manifold or Discharge manifolds should be housed where it has basement floor above it.
• The roof of the building should be made of light material or be provided with explosion venting area of not less than 0.06 square meter per cubic meter of room volume.
• The building/room housing shall be well ventilated both at floor level and roof level. The ventilation provided should be such that flow of ventilation is not less than 3.3 cubic meter per minute per sq. meter of ceiling area. The ventilators should be covered with 2 layers of 11 mesh per linear centimetre stainless steel or any non-corroding material wire mesh and brass mesh if used, shall have more than 65% copper content.
• In case any heating is required, it shall be by steam or hot water
• Boiler, heaters and other heating equipment employing flames or capable of creating sparks shall be located in a separate building situated minimum 15 meters away.
• Electrical equipment and wiring in rooms housing compressing, filling and discharge of acetylene shall have flame proof fittings don forming to IS-2148 and suitable for gas group class IIA and IIB. All the equipment shall be electrically grounded i.e. earthed properly.
• The Acetylene or acetone fire is not normally extinguished with hose water or portable extinguishers when it is large in nature, therefore, the best way to avoid any fire is to ensure leak free pipe lines and use of good quality valves. However, for fire protection the following precautions must be taken:
1. For waste disposal the receptacles should be self-closing metal (non-sparking type).
2. The area shall be equipped with 40 NB hose station equipment unless continuous water spraying or circulating system is provided for the compressor, filling and discharge manifold or alternatively automatic sprinkler system be provided by means of fusible plugs so that the water coverage is not less than 2.2 litres/second per square meter of floor area.
3. The fire hose and water spray. actuation valves shall be located so that they can be operated from out-door or at an exit.
• Each plant shall have detailed emergency procedure and shall conduct periodic fire drill. A flame-proof alarm shall be provided for summoning and cautioning people in emergency
• Under one roof more than 80 cylinders should not be connected to a manifold. In case more than these cylinders have to be connected under one roof, manifold should be so separated by a concrete wall 2.5 meters high and not less than 200 mm thick so that in an area isolated by the concrete walls not more than 80 cylinders connected to manifolds are kept.
ACETYLENE COMPRESSORS AND HIGH-PRESSURE DRIER
• The inlet and outlet piping of each compressor shall be provided with readily accessible shut off valves that can be closed in an emergency.
• Drain lines from high pressure above 1.55 kg/cm²g of oil separation condensate traps and drains shall be led to a ‘separator’ fitted with a safety valve set at 1.5 kg/cm2g outlet of which should be connected to inlet of compressor Suction or piped out to vent the gas at a height of 5 meters and away from the building. The condensate, liquid etc. shall be piped outside the building away from any source of ignition and combustible material should be drained to effluent water drains.
• The compressor shall be fitted with pressure relief valve (safety valve) of full size on suction and discharge of each stage.
• the compressor shall be provided at suction and discharge with pressure switch or a similar fail-safe device capable of shutting down the compressor if the compressor suction pressure falls below a pressure of not less than 25 centimetre of water column above atmospheric pressure or if the discharge pressure Cross the set pressure which in no case can exceed 28 kg/cm²g. No shut off valve or by-pass valve for the pressure switch shall be installed.
The flow of Acetylene through the interconnecting piping shall be designed for the velocities of not more than specified below:
|Pressure||Up to 6 kg/cm2g||From 6 -11 Kg/cm2g||From 11-21 Kg/cm2g||From 21-26 Kg/cm2g|
|Linear speed meters per second||10||5||3||2.5|
• Compressor shall be constructed so that the acetylene is cooled during and after each stage of compression. When water is used, the flow of water from cooling jacket and inter-coolers shall be visible to the operator.
• Where the compressor is water cooled valve. On water inlet line should be provided for regulating water flow.
• Transmission belt when used in compressor should be antistatic type.
• The piston speed should not be more than 0.7 meter/second.
• The Temperature of Acetylene at the discharge valve of any stage should not exceed 140°C.
• The compressor should have a connection so that the whole of it can be rinsed/purged with nitrogen and or water.
• The Compressor should be Pneumatically tested at its operating pressure by holding pressure in the system for 24 without any visible leak. The fall in pressure should not be more than 0.2% per hour of the initial pressure.
• The Compressor shall be provided with remote emergency switching off device.
• Suction, discharge and each stage pressure and temperature measuring devices should be provided.
• Where oil lubrication is provided oil pressure gauge to show oil lubricated pressure should be provided.
• In case of lubricated compressor having on oil pump a suction filter should be provided. Use of porous metallic or ceramic filter elements is recommended.
• If Nitrogen fail safe device is connected directly to the Acetylene Compressor it should have non-return valve and automatic devices to provide flow of Nitrogen in the compressor in case of emergency.
• The compressor shall be provided with a local as well as remote emergency switching off device.
• A Fore cooler with condensate trap shall be provided in the Suction of the compressor.
• The High-Pressure Drier should have down-stream pressure regulator to regulate the back pressure at 14 to 17 kg/cm²g.
• The design of the High-Pressure drier should be such that the velocity of Acetylene should increase by 0.20 to 0.25 meters/second.
• Before and after the High-Pressure Drier filters should be provided.
• Where Calcium Chloride used as a drying medium the drier should have arrangements to blow it off with Nitrogen or Acetylene to remove air wherever fresh charge or long stoppage of use.
• The drying agent like Calcium Chloride should be filled in baskets made of solid sheet having perforation of 5 mm dia in triangular pitch for case of removable and recharging.
• The specification here covers high pressure piping above 2.5 kg/cm2g piping for use after 1st stage of the Acetylene Compressor up to filling manifold and discharge manifolds.
• Piping and fittings shall be steel, wrought iron, malleable iron or copper alloy having less than 65% copper or unalloyed free silver or mercury.
• All piping and equipment shall be electrically continuous and bounded to any grounding electrode as defined in any international or national electrical codes.
• Pipe size more than 25 mm nominal bore should be avoided as far as possible, but in no case pipe size more than 40 mm nominal bore be used. Where for higher flow larger diameter is necessary multiple pipes of 25 nominal bore is recommended.
• The working pressure of Acetylene pipeline shall not be more than 26 kg/cm2 absolute.
• Where pipe material as specified in 7.5 above is used the pipe wall thickness should be:
A. Where the ends of the pipe, bends elbow, reducer, enlarger, joints, openings are strengthened by a length at least twice the inside diameter of pipe and to a thickness twice the pipe thickness, the thickness shall be 0.16 X inside diameter. The strengthening may be accompanied by welding the reinforcement or by screwing or by bolting.
B. Where no reinforcement is used the thickness of the pipe should be 0.30 x inside diameter.
• The length of pipe (straight portion) should be such, that it is less than or exceeds the ‘Critical Distance’.
• The radius of curvature of pipe should not be less than 5 x inside diameter.
• The reinforcement of the pipes as recommend need not be provided if proper flash back arrestor fitted with non-return valves are provided at each such point. However, reinforcement at the end of the pipe shall be necessary flash back arrestor does not serve any purpose at the ends.
PRESSURE GAUGES/TEMPERATURE GAUGES AND SAFETY VALVES
• Pressure gauge used in the system should be safety type described in relevant IS standard with blow disc.
• Before every pressure gauge throttle should be installed limiting the flow less than 10 litres/minute at normal conditions.
• Pressure Gauge range should be such that at the normal working pressure the indicator is situated at the middle of the dial.
• Temperature Gauges for measurement of temperature should have a minimum graduation of 2°C.
• The maximum working pressure and temperature should be marked in red on the dial of the gauges.
• Safety valve should be full flow type capable of venting maximum flow for which the pipe line is intended at 10% over pressure. The valve should be fitted with test lever to be able to open and check the operation of the safety valve manually.
• The vent of the safety valves or any other vent should be discharged outside the building at a height of 5 meters and one meter away from any part of the building or combustible material and or source of ignition or openings. The end should be constructed so that it cannot be obstructed by rain, snow, ice or birds rather should be hooded or bend covered with wire mesh.
• No isolation valve shall be provided on the safety valve inlet.
ACETYLENE CYLINDER CHARGING AND DISCHARGING MANIFOLDS
• Each cylinder charging or discharging Manifold shall be provided with a shut off valve, vent valve and a safety valve. The vent valve may be connected to the low-pressure system or vented to atmosphere.
• A non-return valve with flame arrestor shall be installed in the pipe line at each cylinder charging or discharging manifold or in each cylinder charging, discharging lead pig tail.
• Each outlet or inlet from the manifold should be provided with shut off valve.
• The cylinder charging or discharging leads (pig tails) shall be so arranged that excessive stress in the cylinder leads are prevented.
• The cylinder charging or discharging leads shall be arranged so that they are either 200 to 300 mm above or lower than the cylinder valves.
• Each cylinder charging or discharging limb shall be provided with 3 flame arrestors with non-return valve in series.
• The length and size of manifold pipe shall be based on one cubic meter of Acetylene flow per hour per connected cylinder and spacing between 2 connections, should be minimum such that it is one quarter times the maximum diameter of Acetylene cylinder that will be connected to the manifold.
• All leads (pig tails) should have a bursting pressure of 600 kg/cm²g and have a test pressure of 210 kg/cm²g.
• The electrical resistance where the leads are joined to the manifold should not be more than 10 Kohms.
• The protect the manifold from flame or over heating due to any reason it is advisable to either arrange for continuous water spray or provide the pipe line of the manifold placed in ‘C’ channel filled with sand or circulating water.
• Where rubber hose pipes are used they should be reinforced with metallic fibre and should be compatible with Acetylene and Acetone. The metallic braiding of the hoses should be used for earthing.
VALVES AND FITTINGS
• All fittings should be seamless socket welded or butt welded. Wherever, butt welded is used arrangements to clean the inside of weld should be made or ‘Y’ filler or backing strips used.
• For connecting pressure gauges, transmitter etc. threaded joints can be used but the threads should be tapered gas threads as per relevant IS Standard.
• The valves should be of a class suitable for working pressure of 210 kg/cm2 at ambient condition.
• The flanges used, if any, should be suitable for a working pressure of 210 kg/cm2 and should be slip-on type having male female faces.
• The bolts and Nuts used should be high tension bolts and nuts.
• Gasket material used should be compressed, graphited asbestos or S-Buttons and or Neoprene Rubber.
• Packing material should be graphite impregnated Asbestos or Teflon.
Pipe line or manifold should be supported as follows:
|Nominal Diameter of pipe size in mm||10||15||20||25||30||40|
• Unions, Flanges, Threaded joints should be avoided as far as possible and the pipe sections should be socket welded.
• Bends formed with a maximum 5 x Inside diameter are recommended in place of bends or elbows.
• Elbows, Bends, Tees, should be preferably forged carbon steel socket weld type suitable for working pressure of 280 kg/cm2.
The system should be Hydraulically tested as per the individual section test pressures specified hereinabove. But where the system is to be treated one unit having possibilities of pressure intermixing, the whole system has to be hydraulically tested at 300 kg/cm2g for a minimum period of 2 hours without any pressure drop or damage to any part. Rubber hoses or any part which can stand such high pressure but can get permanently deformed may be isolated and pressure released after holding pressure for 2 minutes.