CNG Tube - Seamless & Welded Steel CNG Tubing Manufacturer China

Buyers sourcing a CNG tube for vehicle fuel systems or industrial gas storage need more than a low price. They need a supplier who understands pressure ratings, material grades, and the quality checks that keep a compressed natural gas line safe under real working conditions. This guide walks through how CNG tube is made, what standards it should meet, and what to check before you place an order with a Chinese manufacturer.
At Chewit, we manufacture both seamless and welded CNG tube alongside a wider range of seamless steel tube, stainless steel tube, and alloy steel tube products, so this article reflects the same specifications and processes used on our own production floor.

What is a CNG Tube?

A CNG tube is a precision steel tube designed to carry or store compressed natural gas at high pressure, typically between 200 and 250 bar. It is used in vehicle fuel delivery lines, CNG cylinder manifolds, refueling stations, and industrial gas distribution systems. Because the gas is stored under pressure, the tube must resist internal stress, fatigue from vibration, and in some cases corrosion from moisture in the gas stream.
Unlike ordinary structural tubing, a CNG tube is manufactured to tighter dimensional tolerances and is tested individually or in batches before it leaves the factory. Buyers comparing suppliers should always ask which standard the tube is produced to, since "CNG tube" on its own is a broad product category that covers several material and pressure classes.

CNG Tube Manufacturing Process – Seamless vs. Welded

 
There are two main ways to produce CNG tube, and the right choice depends on pressure requirements, budget, and application.

Seamless CNG Tube

Seamless tube is made from a solid steel billet that is pierced and drawn into a hollow section with no weld seam. This gives it a uniform wall thickness and consistent strength around the full circumference, which is why it is the preferred option for higher-pressure automotive and cylinder applications.

Welded CNG Tube

Welded tube is formed by rolling flat steel strip into a round shape and fusing the seam, usually followed by cold drawing to improve accuracy and surface finish. It costs less to produce and works well for lower-pressure or non-critical gas lines where the budget matters more than the highest safety margin.
Both processes can be followed by cold drawing, which is also used to produce our cold drawn steel tube line for hydraulic and automotive customers, giving buyers a tighter OD/ID tolerance and a smoother bore.

Material Grades We Use for CNG Tubing

Material selection affects strength, corrosion resistance, and cost. The most common grades used for CNG applications are:
  • Carbon steel (such as DIN2391/ST37.4, EN10305-4/E235, NFA 49-310/TU37b) – cost-effective for standard-pressure applications
If your project also requires alloy steel tube or stainless steel tube for connecting hydraulic or structural components, we produce these on the same production lines, which can simplify sourcing when you are ordering multiple tube types for one project.

CNG Tube Sizes, OD & Wall Thickness Range

We produce CNG tube across a wide dimensional range to fit both OEM fuel line design and aftermarket cylinder manifold requirements. Typical ranges are shown below; exact sizes are confirmed against your drawing or application.

Tube Type	OD Range	Wall Thickness	Length
Seamless CNG Tube	6,8,10mm or as per request.	0.6-1mm	Up to 6 m, coil available
Welded CNG Tube	6,8,10mm or as per request.	0.6-1mm	Up to 6 m
Custom / OEM Sizes	Per drawing	Per drawing	Per project requirement

Pressure Ratings & Safety Standards (DIN2391, EN10305-4, NFA 49-310)

Pressure rating is the single most important spec to confirm before ordering. CNG tube is generally produced to one or more of the following standards:

1. DIN 2391 – Seamless precision steel tubes; cold finished
2. EN 10305-4 – Steel tubes for precision applications — Technical delivery conditions — Part 4: Cold drawn seamless tubes for hydraulic and pneumatic power systems
3. NFA 49-310 – French standard for seamless precision steel tubes for hydraulic use

A responsible supplier will tell you which standard applies to a given batch and provide test reports on request. If a supplier cannot confirm the standard their tube meets, treat that as a warning sign, especially for a safety-related product like this.

Seamless CNG Tube – Features & Applications

 
Seamless CNG tube is generally chosen for:
  • High-pressure vehicle fuel delivery lines
  • CNG cylinder-to-manifold connections
  • Applications where fatigue resistance under vibration is critical
  • Projects requiring third-party pressure testing or certification
Its main advantage is consistency: because there is no weld seam, there is no localized weak point, which matters most in high-cycle, high-vibration environments like moving vehicles.

Welded CNG Tube – Features & Applications

Welded CNG tube is a practical choice for:
  • Lower-pressure gas distribution lines
  • Stationary or fixed installations with limited vibration
  • Budget-sensitive projects where seamless-grade performance is not required
  • Larger diameter runs where seamless production is less cost-efficient
When properly manufactured and tested, welded tube is a reliable option for a large share of CNG applications — it is simply matched to a different pressure and use case than seamless tube.

Surface Treatment Options: Bright Annealed, Galvanized, White / Black PVC Coated

Surface treatment affects corrosion resistance, appearance, and how the tube performs during bending or fitting installation.
Common options include:
• Bright annealing – heat treatment under controlled atmosphere for a clean, bright, oxide-free surface
• Galvanizing – zinc coating for extended corrosion protection
• with White / Black PVC coating – PVC outer layer providing additional anti-corrosion, scratch resistance and insulation
The correct surface treatment depends on the operating environment. Coastal or high-humidity regions generally call for galvanized or PVC coated options, while dry indoor installations can often use bright-annealed tube.

How CNG Tubes Are Tested for Quality (NDT, Hydrostatic, Eddy Current)

 
Because CNG tube carries pressurized gas, testing is not optional. Standard quality checks include:
  • Eddy Current Testing (ECT) – detects surface defects on the inner and outer wall
  • Hydrostatic pressure testing – confirms the tube holds pressure without leaking or deforming
  • Dimensional inspection – verifies OD, wall thickness, and straightness against tolerance
  • Chemical composition analysis – confirms the material matches the specified grade
  • Visual and surface inspection – checks for scratches, pitting, or seam defects
Ask your supplier which of these tests are performed as standard versus which are available on request, and whether test reports are issued per batch or per production lot.

Applications of CNG Tube in Automotive & Gas Systems

CNG tube is used across several industries beyond passenger vehicles:
  • Automotive CNG fuel systems for passenger cars, taxis, and light commercial vehicles
  • Heavy-duty trucks and buses running on natural gas
  • CNG refueling station piping and dispenser connections
  • Industrial gas storage and distribution manifolds
  • CNG tube skid transport systems for regional gas delivery
Many of these systems also use related components such as hydraulic pipe/tube for auxiliary lines and connections, which we supply from the same facility.

Why Choose Chewit as Your CNG Tube Manufacturer

We manufacture CNG tube alongside our broader steel tube, aluminum, and forging product lines, which gives buyers a few practical advantages:
  • Direct factory production with in-house cold drawing and heat treatment
  • Material traceability from raw billet to finished tube
  • Flexible order quantities for both trial orders and long-term supply contracts
  • Export documentation and packaging suited for sea and air freight
  • Technical communication in English for engineering and procurement teams
We do not claim to be the largest or the cheapest supplier in the market. What we offer is consistent quality, clear communication, and a factory that can support both one-time projects and long-term OEM partnerships.

CNG Tube vs. LPG Tube – Key Differences

 
Buyers new to gas fuel systems sometimes assume CNG and LPG tubing are interchangeable. They are not, and the difference matters for safety and compliance.

Factor	CNG Tube	LPG Tube
Gas Type	Compressed natural gas (methane-based)	Liquefied petroleum gas (propane/butane)
Typical Pressure	~200–250 bar	~2–25 bar
Common Standard	ISO 11439, ASTM A519	EN 1440, national LPG codes
Wall Thickness	Generally thicker, high-pressure rated	Generally thinner, lower pressure

Custom CNG Tube Sizes & OEM Support

Most CNG tube orders are project-specific rather than off-the-shelf. We support custom requirements including:
  • Non-standard OD, wall thickness, or cut length
  • Custom surface treatment or coating
  • Drawing-based production for OEM fuel system components
  • Small trial batches before committing to full production volume
  • Private labeling and export packaging to buyer specification
If you already work with aluminum telescopic pole or aluminum tube products from us for other projects, we can often combine steel and aluminum orders into a single shipment to reduce freight cost.

Certifications & Export Compliance for CNG Tubing

Before finalizing an order, confirm the following with any supplier:
  • Which product standard (ISO, ASTM, GB, or ECE) the tube is certified to
  • Whether mill test certificates (MTC) are provided with each shipment
  • Export packaging suitable for your destination market and shipping method
  • Lead time for both sample orders and full production runs
  • Payment terms and minimum order quantity for first-time buyers
We provide relevant certification and test documentation for our CNG tube on request, matched to the standard your project requires.

FAQs About CNG Tube

What is the standard pressure rating for CNG tube?

Most automotive CNG tube is rated for working pressures around 200 to 250 bar, though the exact rating depends on the material grade and the standard the tube is manufactured to, such as ISO 11439.

What is the minimum order quantity (MOQ) for CNG tube?

MOQ depends on the size, material, and surface treatment requested. We can discuss trial order quantities for buyers who want to test quality before committing to a full container order.

Can you produce CNG tube to a custom size or drawing?

Yes. We regularly produce CNG tube to buyer-supplied drawings, including custom OD, wall thickness, and length, for both OEM and aftermarket applications.

Do you provide test reports and certificates with each order?

Yes, we provide mill test certificates and relevant inspection reports matched to the standard applicable to your order, such as ASTM A519 or GB/T 3639.

What is the typical lead time for a CNG tube order?

Lead time depends on order size, material availability, and surface treatment. Sample or trial orders generally ship faster than full production runs; we confirm exact timing once we have your specification.

Do you ship CNG tube internationally?

Yes. We export to North America, Europe, the Middle East, Asia-Pacific, South America, and Africa, with export packaging suited to sea and air freight.

Conclusion

Choosing the right CNG tube supplier comes down to three things: confirming the correct material and pressure standard for your application, understanding what quality testing is actually performed, and working with a factory that communicates clearly about specifications and lead times. Whether you need seamless CNG tube for a high-pressure automotive fuel line or welded tube for a stationary installation, getting these details right at the sourcing stage will save time and reduce risk later.
If you are currently evaluating suppliers or preparing a project specification, Contact Chewit for a quotation, technical data sheet, or sample discussion. Our team can review your drawing or application and recommend the right CNG tube specification for your market.