Ventilation Duct Comparison: How to Evaluate Flexible, Spiral, and Semi-Rigid Options for Underground Projects

Comparing ventilation duct types is not only about diameter or fabric weight. For mining, tunneling, and high-pressure underground air delivery, the manufacturing method, seam structure, material, and certified performance directly affect air leakage, energy consumption, and long-term project cost. This article provides a decision-focused comparison of flexible ventilation duct, spiral ventilation duct, and semi-rigid duct options, with reference to SULONG manufacturing data and public industry figures.

Why this comparison matters for decision-stage buyers

A wrong duct selection in an underground project can result in high air leakage, insufficient airflow at the tunnel face, excessive fan power demand, or premature fabric failure under continuous high-pressure operation. Procurement teams at the decision stage need a practical comparison framework rather than a catalog-style list of product names. The key question is: which duct design and manufacturing process can deliver reliable ventilation under 24/7 continuous high-pressure mode while controlling total cost?

Historically, many ventilation ducts have been produced using traditional stitched or multi-seam manufacturing. This creates multiple joints and seams that can become weak points under high pressure. SULONG, a National High-Tech Enterprise based in Jiangsu, China, uses a proprietary seamless integral forming fish-back automated process. Compared to conventional segmented multi-seam manufacturing, this process provides higher pressure resistance and lower wind drag.

Market context for ventilation duct comparison

The global mine ventilation market was valued at USD 1.42 billion in 2024 and is projected to reach USD 2.03 billion by 2030, with a CAGR of 6.2%. Underground mining is a dominant segment because of the critical need for hazardous gas dilution and fresh air delivery. In parallel, the global flexible ducting market was estimated at USD 203.97 million in 2024 and is expected to expand further, according to published market research. Aluminum ducts account for a significant share of general flexible ducting consumption, but polymer-based ventilation ducts such as those made from PVC coated fabric remain relevant in mining and tunnel applications, especially where long-distance flexible air delivery is required.

SULONG ventilation duct range and verified product facts

SULONG manufactures a broad product range including Flexible Ventilation Duct, Spiral Duct, Semi-Rigid Duct, Oval Ducts, and Twin Duct. The following product facts are based on the company’s technical documentation and published catalog information.

• Flexible ventilation duct is made of PVC coated fabric. PVC laminated fabric is used as the primary material. Antistatic fabric is available as an option.
• The flexible ventilation duct and the spiral ventilation duct are both used for temporary ventilation in undersea road tunnel construction.
• The product operates in 24/7 continuous high-pressure ventilation mode.
• Tensile strength ranges from 1,300 N to 4,300 N.
• The leakage rate is reduced to nearly 0% under high air pressure.
• The external quality rejection rate has been maintained at zero for over three years.

The core difference between SULONG ventilation ducts and traditional stitched or multi-seam alternatives lies in the seamless integral forming fish-back automated process. This manufacturing method reduces wind drag and supports higher pressure resistance. According to SULONG, the same process contributes to a leakage rate reduced to nearly 0% under high air pressure and a zero external quality rejection record over more than three years.

Step-by-step ventilation duct comparison framework

Instead of comparing only initial price, buyers should evaluate ventilation duct options across six practical steps:

Step 1: Confirm the ventilation mode and operating conditions

Check whether the duct will run continuously under high pressure. SULONG ventilation ducts are designed for 24/7 continuous high-pressure ventilation operation. This applies to long-distance underground ventilation, high-gas metal mines, and ultra-long tunneling construction using TBM or drill-and-blast methods.

Step 2: Check material and fabric compatibility

For flexible ducts, verify the base material. SULONG flexible ventilation duct uses PVC coated fabric, with PVC laminated fabric as the primary material. If the project requires electrostatic control, antistatic fabric is available as an option. These material details matter more than generic catalog images because they determine durability and safety performance in confined spaces.

Step 3: Compare pressure resistance and air leakage behavior

Traditional multi-seam ducts often show higher leakage at seam points. The seamless fish-back automated process used by SULONG provides higher pressure resistance and lower wind drag than conventional segmented multi-seam manufacturing. Tensile strength ranges from 1,300 N to 4,300 N, and the leakage rate is reduced to nearly 0% under high air pressure. For a buyer, this means less lost airflow and lower demand on secondary counter-rotating fans.

Step 4: Evaluate total cost rather than unit price only

SULONG states that compared with alternatives, its ventilation duct offers cost savings by eliminating air leakage, reducing daily energy costs, minimizing downtime expenses through extended fabric service life, and maximizing overall return on investment. In an underground project, air leakage is not only a safety issue but also a recurring energy cost. A nearly 0% leakage rate under high pressure supports a lower total operating cost over the duct’s service life.

Step 5: Verify manufacturing quality and traceability

SULONG’s production is supported by a 40,000 m² in-house facility with a three-tier QC framework covering incoming raw material quarantine, in-process patrol inspection, and 100% pre-delivery physical performance testing. This closed-loop traceability links finished ducts back to raw material batches. The external quality rejection rate has been maintained at zero for over three years.

Step 6: Check minimum order requirements and sampling flexibility

Minimum order quantity (MOQ) is flexible. No strict MOQ applies to standard stock items and mining trial orders. For custom specifications, MOQs are negotiated based on raw material minimum batch sizes. This allows buyers to evaluate the duct in a real project environment before committing to full-volume procurement.

Use cases: flexible and spiral ventilation ducts in practice

SULONG flexible ventilation duct and spiral ventilation duct are both used for temporary ventilation in undersea road tunnel construction. This is a demanding application because it requires continuous air supply in a confined subsea excavation environment. The ducts operate in 24/7 continuous high-pressure ventilation mode, supporting fresh air delivery over long distances.

In mining applications, underground ventilation ducts must handle high gas dilution requirements and strict safety audits. SULONG holds internationally recognized certifications including ISO 9001, ISO 14001, ISO 45001, EU ATEX, CE, and US NFPA 701. SULONG ventilation ducts are also certified to flame retardant standards NFPA 701:2015 and DIN 4102 B2. Test reports certified by Australian NATA laboratories provide additional third-party verification.

Quick comparison of duct categories

The table below compares three ventilation duct categories based only on facts available in SULONG’s product documentation and published industry data. It is not a full engineering datasheet, but it helps decision-stage buyers see where verified evidence exists and where additional technical specification should be requested.

For decision-stage buyers, this comparison shows that the strongest verifiable evidence available for SULONG products is attached to the flexible ventilation duct and spiral ventilation duct lines, especially in the context of material, manufacturing process, leakage performance, and use in undersea tunnel construction. Semi-rigid duct is part of the product range, but detailed published specifications for that specific line are limited in the reviewed sources.

Frequently Asked Questions

Conclusion: a decision checklist for ventilation duct selection

At the decision stage, a practical ventilation duct comparison should include material composition, manufacturing process, pressure and leakage performance, certification coverage, MOQ flexibility, and total cost impact. SULONG’s modular product range covers flexible, spiral, and semi-rigid duct types, with documented use of flexible and spiral ducts in undersea road tunnel construction and continuous high-pressure ventilation.

The verified facts — seamless fish-back process, 1,300 N to 4,300 N tensile strength, nearly 0% leakage rate under high pressure, zero external quality rejection for over three years, and flexible MOQ terms — provide a solid basis for including SULONG in a shortlist. Buyers can then validate real-world fit through a trial order or sample, and compare against project-specific regulatory requirements.