How to do an air leakage test?

Here is a simple, safe, step-by-step method to perform an air leakage test (commonly used for sheet metal tanks, ducts, and low-pressure vessels).

Air Leakage Test – Step-by-Step

1. Preparation

Ensure all welding, bolting, and fittings are complete

Clean weld seams and joints (remove dust, oil, paint)

Close and seal all openings:

Manholes

Nozzles

Drains

Install:

Regulated air supply

Calibrated pressure gauge

Relief valve (recommended)

2. Test Pressure

⚠ Important: Use low pressure only

Typical test pressure:

2–5 kPa (0.3–0.7 psi) for atmospheric / sheet metal tanks

Never exceed design pressure

Pressurize slowly to avoid damage.

3. Pressurization

Open air valve slowly

Increase pressure in small steps

Stabilize at test pressure for 5–10 minutes

Isolate air supply

4. Leak Detection (Soap Bubble Method)

Mix soap and water or use commercial leak detection fluid

Apply solution to:

Weld seams

Joints

Nozzle connections

Bolted flanges

Observe closely:

Continuous bubbles = leak

Foaming or growing bubbles indicate air escape

5. Repair and Retest

Mark leak locations

Release pressure completely

Repair leaks (reweld, reseal, tighten bolts)

Repeat test until no bubbles appear

6. Acceptance Criteria

✔ No visible bubbles at test pressure

✔ Pressure remains stable during inspection

7. Depressurization

Release air slowly

Remove test equipment

Reopen sealed nozzles

Safety Rules (Critical)

Never stand in line with manholes or weak panels

Keep personnel clear during pressurization

Use calibrated gauges

Do not hammer or weld while pressurized

Stop test immediately if deformation occurs

Optional Alternative Methods

Pressure decay test – Monitor pressure drop over time

Vacuum box test – For local weld seam testing

Helium test – For very high leak-tightness requirements

Simple Checklist

✔ Sealed all openings

✔ Pressure gauge installed

✔ Test pressure confirmed

✔ Soap solution applied

✔ Leaks repaired and retested

If you want, I can:

Write a formal test procedure (SOP)

Create a test report format

Recommend exact test pressure for your tank thickness and size

Just tell me what equipment or tank you are testing.   

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