What is the principle of the helium leak test?

A leak is detected through the helium leak test by charging helium gas to the tested work and passing the leaked gas through the mass analyzer tube to detect helium only. Helium is used for the gas to be charged in the tested work. For concentration, helium gas of 100% as well as dilute gas can be used.

Why is helium used in mass spectrometry?

Helium is used as a tracer because it penetrates small leaks rapidly. Helium also has the properties of being non-toxic, chemically inert and present in the atmosphere only in minute quantities (5 ppm). Typically a helium leak detector will be used to measure leaks in the range of 10−5 to 10−12 Pa·m3·s−1.

How do you calculate helium leak rate?

To calculate the partial pressure of helium in ambient helium we simply multiply the air pressure in mbar times the concentration of helium in ambient air. (5ppm or 5 *10-4%) Assuming ambient pressure at 1000 mbar, the partial pressure for helium is then calculated to be 5 * 10-3 mbar.

What are some common methods for helium leak testing a vacuum system?

As with almost every facet of vacuum systems, there is no single method which fulfils every situation and every criterion. This is certainly the case with leak detection, with four main methods being employed: the bubble test; pressure decay test; pressure rise test; and helium sniffer mode/helium vacuum mode tests.

What is a helium sniffer?

Helium sniffing is a leak finding method in which Helium is used as a trace gas in the test object. The instrument can then detect a presence of Helium which has leaked out to the external Environment.

How do you use a helium sniffer?

Typical Helium Sniffing Leak Test Procedure

1. Seal any ports or openings on the test part, leaving a single port for filling / charging with helium.
2. Evacuate the internal volume of the part (if possible)
3. Fill / charge the internal volume with helium.
4. Scan the test part checking for leakage.

Why do we use helium as carrier gas in gas chromatography?

Many gas chromatography (GC) labs use helium as a carrier gas because it is faster than nitrogen and safer than hydrogen.

How is leak measured?

There are three commonly used fundamental techniques for leak measurement: a pressure change within a known volume, a direct measurement of flow, or measurements of changes in concentration. Absolute measurement. A transducer or gauge is used to measure pressure change within the device being tested.

What is the purpose of leak testing?

Leak testing is a procedure that inspectors use to determine whether an object or system is functioning within a specific leak limit. Leaks occur when there is a defect—a hole, crack, or some other kind of flaw—in an object, allowing whatever the liquid or gas it is holding to flow out.

What is a sniffer leak detector?

Generally, sniffer leak detection is used to locate leaks in parts or systems so that they can be identified and repaired. The part or system is first pressurized with the tracer gas. The operator then systematically scans suspect leak locations with the sniffer probe in order to identify a possible leak.

WHy helium is often used instead of argon as the carrier gas in GLC when TCD is used as the detector *?

Typically, helium is used because of its large difference in thermal conductivity compared to most compounds. However, nitrogen, hydrogen, and argon can be used as well.

WHy is helium and hydrogen better than nitrogen as mobile phase in gas chromatography?

Hydrogen and helium are the preferred mobile phases in GSC giving higher efficiency of separation because of their higher thermal conductivity.

Which is a detector in mass spectrometry?

The detector used for most routine experiments is the electron multiplier. Another type of detector is photographic plates coated with a silver bromide emulsion, it is sensitive to energetic ions. A photographic plate can give a higher resolution than an electrical detector.

How do you calculate leakage?

To calculate the permitted leakage for a test with water the following steps shall be performed in sequence:

1. Step 1 – Check for flow restriction.
2. Step 2 – Calculate rated capacity Q [m³/h] in accordance with EN 60534-2-1.
3. Step 3 – Multiply the rated capacity Q by the leakage factor in accordance with EN 60534-4.

What are the different methods of leak detection?

The most commonly used leak test methods are underwater bubble test, bubble soap paint, pressure and vacuum decay, and tracer gas detectors (halogen, helium and hydrogen).

How can helium leak detection help the life sciences industry?

Use of helium leak detection in the life sciences industry ranges from leak testing of process or production equipment, much in the way they were first used in the 1940s, to testing of sealed packages or hermetically sealed devices such as pacemakers.

Why does a small helium leak produce a small signal?

In one case, there is a large leak, so only a small amount of helium at low pressure is left. This low helium pressure/concentration is producing a small signal for a large leak. In the other situation the helium pressure and concentration are higher and consequently it can produce the same signal for a small leak. (See curve to the right)

How to calculate the helium concentration of a helium leak?

1 * 10-2 mbar * (5 * 10-4)% helium concentration = 5 * 10-8mbar.l/s. (Please be advised this value is never the value of the leak that is being measured!)

How is the ambient reading on the calibrated helium detector measured?

The ambient reading on the calibratedhelium leak detector may be measured as: 1 * 10-2 mbar * (5 * 10-4)% helium concentration = 5 * 10-8mbar.l/s. (Please be advised this value is never the value of the leak that is being measured!)