Overview & Product Identification

Industrial CNG applications demand uncompromising structural integrity under repeated high-pressure gas filling cycles. Our seamless CNG gas cylinders are hot-formed from high-purity alloy steel billets (typically 34CrMo4) utilizing precision piercing and hot-spinning technology.

Built for heavy-duty commercial vehicles and gas cascade storage, these cylinders eliminate longitudinal or circumferential welds, ensuring uniform stress distribution and predictable fatigue life under operating pressures of 200 bar to 250 bar.

Technical Specifications & Selection Matrix

Selecting the correct cylinder requires balancing payload capacity, vehicle space constraints, and working pressure ratings. Refer to the standard manufacturing configurations below for engineering evaluation.

Model Reference	Water Capacity (L)	Working Pressure (bar)	Test Pressure (bar)	Outer Diameter (mm)	Length Range (mm)	Nominal Weight (kg)	Material Grade
CC-320-50	50L	200 bar	300 bar	320 mm	950 - 1050	48 - 52 kg	34CrMo4
CC-356-80	80L	200 bar	300 bar	356 mm	1100 - 1250	72 - 78 kg	34CrMo4
CC-406-140	140L	200 bar	300 bar	406 mm	1450 - 1650	115 - 124 kg	34CrMo4
CC-406-180	180L	250 bar	375 bar	406 mm	1800 - 1950	145 - 158 kg	34CrMo4

Core Manufacturing & Quality Control Process

Structural reliability originates from controlled metallurgy and precise hot-forming execution. Our production facility operates under strict traceability protocols from raw material intake to final hydrostatic validation.

Steel Billet Inspection: Incoming 34CrMo4 continuous casting billets undergo ultrasonic testing (UT) to detect internal inclusions, segregation, or micro-cracks before thermal processing.

Hot Piercing & Drawing: Billets are induction-heated to 1150°C - 1200°C and pierced on a hydraulic push-bench to form a thick-walled hollow cup, followed by mandrel redraw operations to achieve uniform wall thickness distribution.

Hot Spinning (Neck Formation): Computer-controlled hydraulic spinning machines shape the open ends of the cylinder, maintaining symmetrical wall thickness at the shoulders and neck without material fold defects.

Quenching & Tempering Heat Treatment: Cylinders pass through a continuous walking-beam furnace, followed by rapid water quenching and high-temperature tempering to achieve the target martensitic-bainitic micro-structure, balancing tensile strength and impact toughness.

Non-Destructive & Destructive Testing:
100% Ultrasonic Examination (UT) and Magnetic Particle Inspection (MPI) for surface and subsurface flaws.
Batch destructive testing includes flattening tests, tensile tests, Charpy V-notch impact tests (-50°C low-temperature operation), and burst pressure verification.

Hydrostatic Pressure Testing: Every individual cylinder is pressurized to 1.5 times the working pressure (e.g., 300 bar or 375 bar) for a minimum dwell time of 30 seconds to verify elastic deformation limits.

Application Suitability

Commercial Transit & Fleet Vehicles: Integrated into roof-mounted or side-rail rack systems for municipal buses, long-haul freight trucks, and waste collection vehicles.

Gas Transport Cascades (Virtual Pipelines): Grouped in multi-cylinder skids or trailers for bulk transport of CNG from mother stations to industrial daughter stations.

Industrial Gas Storage Stations: Stationary buffer storage banks deployed at refueling stations to manage fast-fill dispensing pressure surges.

Compliance, Certifications & Mill Traceability

Procurement teams require verifiable regulatory documentation to secure local import clearances and vehicle homologation. Every shipment includes comprehensive documentation packages.

Certifications: ISO 11439, ECE R110, DOT-SP (available upon project review), and ISO 9809-1 manufacturing compliance.

Traceability Documentation: Mill Test Certificates (MTC) adhering to EN 10204 3.1, detailing chemical composition heat analysis, mechanical property test results, and individual serial number punch records.

External Surface Treatment: Shot-blasted to Sa 2.5 cleanliness standard, coated with a corrosion-resistant epoxy-zinc rich primer, and finished with a UV-stable polyurethane topcoat (standard color: RAL 9010 white or custom fleet branding).

Frequently Asked Questions

Q: What is the standard design life (service life) of Type I seamless steel CNG cylinders?

A: Type I seamless steel CNG cylinders are engineered for a standard operating life of 15 to 20 years, subject to mandatory periodic re-inspection intervals mandated by local transport authorities (e.g., every 3 to 5 years per ISO 19078 or DOT guidelines).

Q: Can you provide custom outer diameters and lengths for specific vehicle frame layouts?

A: Yes. While standard diameters (320mm, 356mm, 406mm) leverage existing tooling and reduce unit cost, custom lengths and specific water capacities can be engineered depending on batch volume minimums and structural FEA (Finite Element Analysis) validation.

Q: What is the minimum order quantity (MOQ) for custom-stamped or painted cylinders?

A: Standard production runs typically require an MOQ equivalent to one 20-foot container load (approx. 40 to 80 units depending on cylinder size) to optimize thermal treatment furnace loads and logistics efficiency.

Q: How do you prevent internal corrosion from moisture in compressed natural gas?

A: While CNG must meet dry gas filtration standards (low dew point) at filling stations, our cylinders undergo internal bore cleaning and inspection to eliminate scale. Optional internal corrosion-resistant passivation layers are available for specific regional gas compositions.

Request a Technical Quotation / RFQ Submission

To evaluate pricing, shipping schedules, and certification requirements for your upcoming project, please prepare the following parameters for our engineering team:

Required Water Capacity (L) or Physical Space Constraints (Max OD & Max Length).

Operating Pressure (200 bar / 250 bar).

Target Regulatory Standard (ISO 11439, ECE R110, or DOT).

Estimated Annual Volume and Delivery Port (Incoterms 2020: FOB/CIF).

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