What are the installation steps of stainless steel welded ventilation pipes in subway?

Here's a set of installation steps of stainless steel welded ventilation pipes in subway that can be directly constructed on site, which are simple, practical and follow the process:

Standard installation steps of stainless steel welded ventilation pipeline in subway

First, the construction preparation

Familiar with drawings, air duct number, elevation, direction, fire zone and seismic requirements.

Inspection materials:

Certificate and warranty of stainless steel plate (304/316L)

Welding wire (ER308/ER316L)

Gasket (nonflammable/nonflammable), stainless steel bolt

Tool preparation:

Argon arc welding machine, angle grinder, tape measure, level gauge, hanging wire hammer, airtight test equipment.

Site cleaning, pay-off, positioning, elevation review.

Second, the hanger installation (hanger first, then pipe)

Drill holes and install expansion bolts/chemical anchors according to the drawings.

Install anti-seismic supports and hangers (mandatory requirement for subway).

Spacing between supports and hangers:

Rectangular duct ≤400mm → spacing ≤ 4 m.

> ＞400mm → spacing ≤3m

Rubber/PE spacer must be added between stainless steel air duct and carbon steel support to prevent electrochemical corrosion.

Leveling and straightening to ensure that the air duct is straight after installation.

3. Prefabrication and welding of air duct ground

Cut the board and fold the square according to the size.

* * TIG welding is adopted, and the weld seam is fully welded continuously.

Welding requirements:

One-sided welding and double-sided forming

The inner wall weld is polished smoothly.

Passivation treatment by pickling after welding

After prefabrication, the port is sealed and protected to prevent dust and scratches.

Four, duct hoisting and docking

Lifting by sections, lifting smoothly, avoiding collision and deformation.

After the air duct is in place, temporarily fix it first, and then adjust the level and verticality.

Flange butt joint:

The two flanges are parallel and centered.

The gasket is centered, without distortion and staggered joints.

Tighten stainless steel bolts diagonally and evenly.

Keep the pipe sections straight without obvious bending and twisting.

Five, through the structure parts processing

Crossing the wall and floor: steel casing is set, and the gap is sealed with incombustible materials.

Crossing the fire zone:

Install fire damper

Fire-proof wrapping/sealing of air duct

Connect with equipment (fan, muffler, static pressure box):

Adopt soft joint to prevent vibration transmission.

Six, system leak test (key process)

Do air leakage test/air tightness test in sections.

Test pressure: generally 0.5kPa.

Check the welds, flanges and joints with soapy water, and it is qualified if there are no bubbles.

Subway ventilation requires extremely low air leakage rate, so it must be accepted section by section.

Seven, weld and surface treatment

Visual inspection of all welds: no air holes, cracks, undercut and slag inclusion.

The solder joints and scratches shall be passivated.

Clean up the sundries, welding slag and oil stains in the pipe, and purge them with compressed air.

Eight, heat preservation and protection (if any)

Sticking thermal insulation cotton (non-combustible grade A).

The insulation layer is staggered and dense, and is covered with aluminum foil or stainless steel protective layer.

The positions of supports and hangers shall be treated as anti-cold bridges.

IX. System Adjustment and Acceptance

Check:

Elevation, slope, levelness and verticality

The supports and hangers are firm and anti-seismic.

Fire damper, flexible joint and tuyere are installed correctly.

Joint debugging: air volume, wind pressure and noise test.

Submission of information:

Material certificate

Welding record

Air tightness test record

Acceptance record of concealed works

Minimalist process formula

Pay-off → bracket installation → prefabricated welding → lifting and docking → plugging through structure → air tightness test → surface treatment → heat preservation → commissioning and acceptance.