The direct probing of leaks to atmosphere technique is used to detect leaks in objects, which have been back-filled and pressurized with a tracer gas.

1. MD-490S
Vacuum Instruments Corporation, LLC
April 2017

2. Helium sniffing
• Sensitivity 5 x 10-6 cc/ sec using mass spectrometer - Pressurize part
with helium and place sniffer probe at suspected leak points.

3. • Advantages
• Lowest cost of mass spec method. Sensitivity of 5 x 10-6
cc/sec in production applications
• Uses helium as tracer gas which is nonhazardous to
environment and personnel
• Ability to pinpoint leaks. Accurately quantifies leaks.
• Disadvantages
• Operator dependent
• Adequate ventilation is needed to remove residual helium.

4. Test Object Charged
with Helium
MD-490S Helium
Sniffer
•Object to be tested contains
helium gas
•Sniffer probe is connected to
the leak detector through a
flexible hose
•When the sniffer probe
approaches a leak, the
escaping helium enters the
vacuum system by the way of
the sniffer probe and is
detected by the mass
spectrometer tube

5. Comments on Leak Location
The direct probing of leaks to atm technique is used to detect
leaks in objects, which have been back-filled and pressurized
with helium tracer gas
•The operator holds the sniffer probe perpendicular
to the test object.
•In operation, as the probe tip is drawn over the
exterior of the test object, it samples the
atmosphere adjacent to the test object surface.
•Helium escaping from a leak, will be drawn into the
probe tip and pass into the leak detector through
the connecting tubing where it becomes visually
evident on the leak rate meter.

6. •When probing products for general leakage
location, always start leak probing from the lowest
point on the product and proceed systematically
to the highest point. This will prevent an unusual
reading if a large leak is present at the lowest
point and rises up.
•Probe at a rate of (1) one inch per second.
•Example, suppose the leakage area is a welded
seam running around a vertical pipe. Holding the
probe perpendicular to the surface of the pipe and
moving slowly around the pipe weld will
effectively locate the leakage point. When a
leakage point is discovered, the area of leakage
will be indicated by the largest rise in the leak rate
meter.

7. MD-490S Sniffer Features Include
•Fastest sniffer response time in the
industry
•Auto zero with background
suppression
•Fully interactive system diagnostics
•Built-in 10-5 cc/sec gas leak traceable
to the NIST
•Probe Blockage Detection
•Specifically designed for industrial
conditions

8. MD-490S Sniffer Unique Features Include
• Automatic background and
compensation for any negative
leak rate displays
• Automatic calibration sequence
with operator procedural
prompting

9. MD-490S Sniffer Unique Features Include
• Patent pending vibrating probe
handle with background suppression
button on probe handle
• Probe provides tactile vibration
feedback when the leak rate exceeds
the reject set point
• Ideally suited for noisy environments
where audio alarms cannot be heard

10. • Sensitivity = Smallest detectable helium leak rate 2.5 x 10-7
Atm-cc/sec helium
• Response Time = Approximately 0.5 seconds
• Leak Rate Range = 10-3 to 10-7 Atm-cc/sec direct reading of
helium leak rate
• Pumps = Oil-Free, built-in dry diaphragm fore-pump, and 33-
liter/second air-cooled molecular drag pump
• Start-up Time = Less than 3 minutes, one button automatic
operation
• Power Requirements = 115 volts/60 Hz, 6 amp (other voltages
available on request)
• As history has demonstrated by the operation of the MD-290S
and MD-390S, VIC’s sniffing machines are industry proven to
withstand the harshest environments
MD-490S Specifications