Application Note

ADVANTAGES OF USING

OPG550 for Real-Time Leak Detection
Air leaks on the tool are detected much faster, increasing throughput and quality while saving costsand energy.

INTRODUCTION
A critical step in the production of vacuum gauges is the calibration on the tool VEGA with a base pressure of 8.0x10-7 mbar.
Before, leaks were detected based on the total pressure profile during pump-down. Depending on the leak size, this took
about 10 minutes to 2 hours. Smaller leaks (rough estimatedsmaller than a hair leak) were often detected very late andthe calibration process had to be repeated. Especially for thetime-consuming calibration processes (> 4 h) that run overnight, an undetected leak means an enormous loss of time
and throughput.

ADVANTAGES AT A GLANCE• Fast air leak detection during pump down in< 1 minute• Higher throughput of about 160 units per week
• Parallel monitoring of total pressure and gas
composition in real-time• Intelligent algorithms: easy operation and simple
output of complex raw data
• Easy tool integration, automatic leak detection• Long sensor lifetimeNow, with the OPG550, leaks are reliably detected in less thana minute as the sensor provides the additional information on
the gas composition during pump-down in real time. In addition, leak detection is automatable and the user can be alerted
remotely. This saves work time and reduces errors.

EXPERIMENTAL
OPG550 was mounted on VEGA calibration tool to simultaneously measure total pressure and gas composition during
pump-down in real time. If the gas composition corresponding
to an air leak exceeds a predefined limit, the analog output
sends an alarm to the tool control.

RESULTS
The aim is the reliable detection of an air leak during pumpdown as fast as possible. For this purpose, the OPG550 monitors in real time and besides the total pressure the concentrations of the air components: nitrogen, oxygen and moisture. The
functional principle of the sensor is based on optical emission
spectroscopy (OES) of a DC plasma, which is generated in thesensor from the residual gas. In this plasma, moisture is split
into hydrogen (H) and hydroxide (OH) and these components arethen detected.
The moisture signal is used to distinguish leak detection during
pump-down from nitrogen purges during calibration. However,if the leak is too large, the moisture signal becomes too weak
and the oxygen signal is then taken into account. During thepump-down, a leak is detected based on the nitrogen partialpressure. Since different gases are taken into account and several conditions must be met to trigger an alarm, the leak detectionis less error-prone.

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OPG550 - VEGA calibration tool,
INFICON Balzers

OPG550 for Real-Time Leak Detection |    Application Note

In Figure 1 both, the total pressure and gas partial pressures for nitrogen, hydrogenand hydroxide (OH) are plotted as function of time. Data were taken during pumpdown on VEGA with different calibrated leaks attached.

(a)While for total pressure based leak detection only the hair leak is detected in the
short pump-down time of a few minutes, OPG550 can clearly detect even the smallest leak used (2x10-4 mbar l/s). The measured gas partial pressures of nitrogen, hydrogen and OH for the different leak sizes are compared in Table 1. In particular, itshows that the nitrogen partial pressure increases with increasing leak size.
In Figure 2 the OPG550 signals for the 1x10-3 mbar l/s leak and no-leak cases arecompared based on the measured time-dependent gas partial pressures and the gas
composition pie charts after 50s. There are clear differences between the two cases.
When there is a leak, the concentrations of nitrogen and oxygen are increased while
the amount of moisture (hydrogen and OH) is lower compared to the no-leak case.
This shows that already after less than 50s OPG550 detects a leak reliably.

Figure 1:
Total pressure (black) and gas
partial pressure for hydrogen(blue), nitrogen (green) and OH(orange) are plotted as functionof time for different leak sizes.
Data were taken with OPG550
during pump-down on VEGA
with the respective calibrated
leak attached.
Hydrogen

LEAK SIZE
in mbar l/s

NitrogenOH

total pressure

PARTIAL PRESSURE
HYDROGEN in mbar

PARTIAL PRESSURENITROGEN in mbar

PARTIAL PRESSURE
OH in mbar

No leak2 x 10-6<1 x 10-6

2 x 10-6

2 x 10-4

1.2 x 10-6

1 x 10-61.5 x 10-6

1 x 10-3<2 x 10-6

3 x 10-6

Hair leak<1 x 10

1.5 x 10-6(b)<2 x 10-6-5<1 x 10-6Table 1: Gas partial pressures measured with OPG550 during pump-down on
VEGA calibration tool are compared for different leak sizes.

CONCLUSION

Moreover, it offers the possibility to automate the leak detection. The large flexibility in available flanges and electronic connections together with the intelligent algorithms on the sensor make tool integration very simple. In comparison to totalpressure based leak detection or to oxygen sensors for example, several different gas
types are monitored in parallel and in real time. This enables that leaks are detected
faster and more reliable. For this application, other gas analyzers or leak detectors
have drawback of either size, prize or required time.

Do you know of similar applications? Then contact us!

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Figure 2:
Total pressure (black) and gas
partial pressure for hydrogen(blue), nitrogen (green) and OH(orange) measured with OPG550
during pump-down on VEGA
are plotted as function of time.
In addition, the gas composition
after 50s is shown as pie chart.
(a) Without leak(b) With 1 x 10-3 mbar l/s leakDue to our continuing program of product improvements, specifications are subject to change witout notice.

tiae20e1

OPG550 detects air leaks on VEGA calibration tool during pump-down in less than aminute reliably. Before, smaller leaks were often detected very late or even after thecalibration process, resulting in the loss of up to more than 4 hours. In these cases
OPG550 provides an enormous benefit and allows a time saving of about 4 hours ora higher throughput of 16 sensors per leak case. With about 10 time-consuming runs
per week with unrecognized leakage, this corresponds to a higher throughput of 160
units per week.