Helium Spray Method

Method selection

When the helium spray method is the right choice

Workflow

Typical helium spray test workflow

1. 1

   Connect and evacuate the workpiece

   Seal the workpiece to the leak detector or test fixture, then evacuate it to a pressure range where the detector can operate with stable sensitivity.

2. 2

   Stabilize the background

   Allow the leak detector reading to settle, confirm the system is not saturated by residual helium, and verify that fixture seals are not dominating the signal.

3. 3

   Spray suspected areas systematically

   Apply helium from a spray gun to weld seams, joints, connectors, and sealing faces in a controlled order instead of flooding the whole part at once.

4. 4

   Watch the response and mark peaks

   A real leak produces a delayed but repeatable rise in the helium signal. The maximum response helps localize the leak zone.

5. 5

   Repair, clean down, and retest

   After the first leak is found and repaired, repeat the inspection to find smaller leaks that may have been masked by the original large leak.

Operating principle

What happens inside the detector

Sensitivity

Spray method versus sniffer method

• Use spray testing when the workpiece can be evacuated and leak localization accuracy is important.
• Use sniffer testing when the workpiece must be pressurized or cannot be placed under vacuum.
• Use a vacuum chamber or integral method when the goal is a total leak-rate result rather than locating the exact leak point.

Result stability

Factors that affect the helium signal

• Helium flow rate and spray duration: too little helium can miss a small leak; too much can saturate the area and make localization slower.
• Distance and angle of the spray gun: keep the application controlled and repeatable around each suspected point.
• Workpiece volume and connection length: large internal volumes and long vacuum lines delay the detector response.
• Background helium: poor ventilation or repeated heavy spraying can raise the room background and reduce confidence.
• Fixture and adapter integrity: a leak at the test connection can look like a product defect unless it is checked separately.
• Operator scan sequence: a consistent route makes the result easier to interpret and repeat after repair.

Precautions

Operational precautions from field practice

• Confirm that the workpiece can withstand negative pressure before evacuation, especially thin-wall parts, tanks, and assemblies with flexible sections.
• Find and repair large leaks first. A large leak can mask smaller leaks and flood the detector response.
• When two suspected leak points are close together, cover one point and use the finest spray nozzle on the other point to separate the signals.
• If the leak detector changes slowly after spraying one point and the reading is inconsistent, suspect a larger nearby leak or a delayed response path.
• After any leak is found, repeat the test several times after repair to confirm that the signal is gone and no secondary leaks remain.
• Keep the test area well ventilated, but do not direct airflow across the helium spray path in a way that pushes helium away from the suspect point.
• Avoid contaminating the test environment with excessive helium. High background makes subsequent small-leak detection slower and less reliable.
• For large cavities or long pipelines, use a known reference leak or controlled helium introduction at the far end to estimate detector response time before judging each spray point.
• Follow a defined sequence, typically top to bottom and near to far, so the operator does not chase residual helium from a previous location.
• During rough search, use a broader spray pattern to cover area quickly; after the leak zone is found, switch to a smaller nozzle to locate the exact point.

Applications

Where customers use this method

Wayeal support

How Wayeal helps turn the method into a usable process