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#47 Technical Specification of CNG Cascade

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Technical Specification of Cascade:

  1. Each CNG cascade shall have a storage capacity of a minimum 2000 liters water capacity at 15 degrees Celcius. The number of cylinders in the cascade shall be divided into independent banks of the low, medium, and high-pressure banks for differential storage pressure as required by 3 lines sequential dispensing system of the electronic CNG dispensers. The vendor shall optimize the number of cylinders in each bank for maximizing the recovery from the cascade storage.
    All cylinders are to be painted white with signal red on the cylinder neck portion as per directions of Chief Controller of Explosives (CCOE), Govt. of India, and assembled into a freestanding, galvanized steel welded frame. In the case of a painted frame, the paint shall be chosen, primed, and applied to have a service life of 10 years. The exterior surface is required to be corrosion-free for ten years and to have fade-free life without oxidation of paint surface for five years in an environment of bright sunlight with intense UV content. Cascade frame shall have provision for lifting by crane from the top of the frame with the full weight of cylinders filled with compressed natural gas (at 255 bar pressure) and shall have tie-down clamps at the top and bottom. The bottom and top of the frame shall be reinforced to prevent any twisting or stress to cylinder connection during lifting by crane. Cascade frame shall be provided with an inbuilt canopy to protect the cylinders from rain and sun. All cylinders shall be mounted inside the frame horizontally. Proper guards shall be provided in the cascade frame, for protecting the cylinder valves and other fittings against any damage.
  2. Cascade storage capacity – The water storage capacity of each cascade shall be 2000 liters at 15 degrees Celcius with no negative tolerance.
  3. The overall dimension of cascade & weight with gas shall not exceed as given under Height: 1.45 Mtr. , Width: 1.9 Mtr. , Length : 2.7 Mtr. & Weight: approx. 4.0 tons.
  4. Inbuilt canopy shall be provided with the cascade for protection from sun and rain. The canopy shall be in line with the approved drawing of CCOE and shall be designed to take care of the wind load, thrust, vibration, etc. The canopy shall be designed in such a fashion that it covers the complete cascade system. The material for inbuilt canopy shall be GI of minimum 16-gauge thickness. The canopy shall be designed to provide adequate ventilation/dispersion of gas in the event of any leakage. Due to space constraints, we may install the stationary cascade on the top of the canopy of the compressor. Vender shall consider the same during designing.
  5. The frame structure shall not allow lateral and rotational movement of cylinders during regular road transport under any circumstances. The vendor shall take into account rough patches or bump on roads.
  6. The frame structure of each cascade shall be capable of withstanding impact up to 4-G (four times gravity) from any direction without any distortion.
  7. All items used in the frame shall be weather-proof.
  8. Each cascade shall be provided with an identification plate of stainless steel material and of adequate size. The identification plate shall carry the name and logo of the entity, including cascade serial no., name of the manufacturer, year of supply, cylinder serial nos. last hydro test date, maximum working pressure, a total water capacity of the cascade, next hydro test due date, and entity serial no. (to be left blank) The matter on the identification plate shall be of suitable size and shall be engraved.
  9. Each bank shall have one 4” liquid filled pressure gauge (0 – 400 kg/cm2g) connected in the piping with a 3-way isolating valve. Thus each cascade shall have three pressure gauges. Pressure gauges shall be securely mounted and casing shall be of Stainless Steel material. The pressure gauge shall have shutter proof glass.
  10. Construction, licensing & inspection, markings, fitment, handling, storage, and all other relevant aspects of cylinders and fittings shall be governed under ‘The Gas Cylinder Rules, 2004’ and shall be approved by Chief Controller of Explosives (CCOE), Government of India. In case any factor, parameter or requirement given in the tender or offered by the vendor is changed or modified by CCOE or any other Indian Statutory Authority before delivery of cascades to the site(s), same shall be carried out without any extra price implication to the entity and to the satisfaction of CCOE or statutory authority, as the case may be.
  11. A minimum gap of 30 mm between cylinder to cylinder shall be provided and maintained.
  12. Each cylinder shall be equipped with a high flow shut-off valve and safety relief device consisting of a fusible burst disc assembly. The cylinder valve shall conform to requirements of IS: 3224 or as per the design approved by Chief Controller of Explosives (CCOE), Govt. of India. The burst disc shall rupture on excess pressure as well as excess temperature either individually or combined, as per internationally accepted code of practices. The orifice of the cylinder valve shall be designed for high flow to permit the combined flow of 100 kg/min from each bank at a pressure of 250 bar.
  13. The burst disc discharge shall be manifolded to a common header for safe venting. All tubing & fittings used for vent manifolding shall be SS316.
  14. All cylinder valve fittings and pipe fittings shall be rated for the full range of temperatures and pressures and the valve/fittings shall show stamp or otherwise permanent mark on the body to indicate the service ratings.
  15. Inlet connection (for filling) to cascade and outlet connection (for discharge) from cascade: Full bore ball valves for isolation shall be provided on each inlet /outlet connection along with separate bleed valve. End terminations for connection to dispenser tubing shall be minimum ¾” OD tube fitting.
  16. Piping/Tubing: The cascade cylinders shall be manifolded in 3-bank configuration and all inter-connection tubing (including tubing between the main header to individual cylinders) of minimum 3/4″ O.D. will be sized according to requirements of code ANSI B31.3, looped for contraction, expansion and stress relief. The sizing of connecting tubing between each outlet and its associated cylinders shall be such that the total incoming flow areas shall not be less than an outgoing area. Piping/tubing shall be suitably clamped. Materials used for the piping shall be stainless steel 316 – high quality fully annealed seamless conforming to ASTM A269 with maximum hardness Rb80 or less and suitable for bending and flaring. O.D tolerance shall not exceed +/-0.005”.
  17. Fitting: All fittings including valves shall be of material SS316 conforming to ASTM A269. Cascade isolating valves shall be full flow ball valves.
  18. Vendor to design the flow rate of the whole cascade in such a way that gas speeds are kept low. The tube, fittings, and valves shall be designed for high flow to permit the combined flow of 100 kg/min from each bank at a pressure of 250 bar.

Cylinder Specification:

  1. Design code: As per Gas Cylinder Rules, 2004 and IS 7285-1988 and prior approval of Chief Controller of Explosives (CCOE), Government of India.
  2. Water storage capacity – Minimum 75 liters per cylinder
  3. Working pressure – 255 kg/cm2g
  4. Neck threads – Screwed 1” dia standard. The valve shall be attached to the cylinder neck by screwing only. The cylinders shall be fitted with appropriate valves conforming to the requirement of IS-3224 or as per the design approved by CCOE, Govt. of India.
  5. Collar thread – Dia 80 X 11 T.P.I
  6. Material – Seamless chrome-moly alloy steel.
  7. Painting of cylinders – Cylinders shall be painted as per Gas Cylinder Rules/ IS code as follows: White color on the cylinder body, Signal red on cylinder neck portion & The cascade frame shall be painted yellow. The first coat shall be applied with epoxy primer to achieve DFT of 25 microns. This will be followed by the second and third coat of epoxy paint and the DFT per coat shall be 25 microns. The paint shall be chosen, primed, and applied to have a service life of 10 years. The exterior surface is required to be corrosion-free for ten years and to have fade-free life without oxidation of paint surface for five years in an environment of bright sunlight with intense UV content.
  8. Cylinder Test Certificates – Vendor to obtain CCOE approval/license to fill and store CNG in cylinders manufactured by submitting original production certificates for each cylinder. All cylinders shall be subjected to hydraulic stretch tests at a minimum pressure of 422 bar or to pressure as determined and approved by CCOE and as required under rules 39 to 42 of Gas Cylinder Rules, 2004 (India). Test certificates shall also be submitted to the Chief Controller of Explosives for physical properties and chemical analysis of the steel used in the manufacture of cylinders (batch-wise) along with mill test certificates. All certificates shall be submitted to CCOE in original duly signed by approved inspecting authority.
  9. Inspection and testing: Vendor shall carryout all standard shop tests/inspection for cylinder manufacture as per vendor’s recommended and CCOE approval QA/QC procedure. A copy of the tests/inspection procedure shall be provided to the entity. Each cascade assembly with all tubing, fittings, valves shall be pressure tested with air at the required pressure to ensure no leakage prior to dispatch, and the same will witnessed by the entity or its authorized representatives. Cascade assembly shall be purged with N2 prior to dispatch.
  10. Field Performance Test: Once cascades have been received and connected to our sites, the vendor shall depute his representative to demonstrate satisfactory operability of the system within specified parameters for a period of two (2) days after commissioning. There will not be any backflow between any bank with all valves open during actual operation. If any leakage, backflow, or any other malfunction is observed or noticed on any cascade during the test period, the vendor shall do the necessary repairs and repeat the test afresh and without any extra cost to the entity.

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