Certification
|
Leak rate
of 0.005 gph as vapor with PD = 100% and PFA = 0%. |
Leak Threshold
|
A tank system
should not be declared tight when the change in helium
concentration in the interstitial space over time
exceeds the method's preset threshold. |
Applicability
|
Method tests
under pressure the primary containment of secondarily
contained tanks, piping and other components. The
primary and secondary components of the system under
test must be dry, containing no liquid. |
Tank Capacity
|
Not limited
by capacity.
|
Test Period |
Minimum 10
minutes for piping and 20 minutes for tanks. Test
period varies in accordance with iota® software
and test procedures, and is a function of several
factors, including interstitial volume, flow rate,
diffusion rate, and the concentration of helium in
the component being tested. |
Waiting Time
|
No waiting
period is required between adding helium to the primary
containment and starting the test. |
Dosage |
Helium dosage varies depending on the component being tested. In all cases, 100% industrial helium is used as prescribed in the manufacturer's test procedures.
|
Sampling Points |
Sampling is
performed by circulating air through the interstitial
space between the primary and secondary walls of the
component(s) being tested and measuring the He levels
in the circulated air. |
Groundwater |
Groundwater
level is not determined and does not impact the test.
Flow meter is used to verify that the interstitial
space is dry and has sufficient air movement. |
Detector |
Helium is
measured by the helium detector, which supplies data
to the iota® system for analysis and pass/fail
determination. Third-party evaluation was conducted
using the Varian models PHD-04 and 979 detectors,
but evaluator indicates that any helium detector meeting
at least the following performance standards can be
used: |
|
Minimum Detectable
Concentration
Smallest Detectable Leak
Response Time
Background Suppression |
2 ppm
5 x 10-6 atm-cc/sec
< 2 seconds
Automatic |
Calibration |
Helium detector
performs an auto calibration on start up and must
be checked monthly and, if necessary, calibrated in
accordance with manufacturer's instructions. |
Comments
|
This method
is intended primarily for use on new installations
before product has been added to the system.
The interstitial volume of the components being tested
must be entered manually, or the iota® software
can calculate volume based on piping type/length or
sump dimensions entered by the tester.
Third-party evaluation included tests to show that
the method can find leaks on a variety of UST system
components, including double-wall piping, double-wall
USTs, and primary components contained within tanktop/under
dispenser sumps.
This method is only able to test double-walled tanks
that have 2 interstitial access ports on opposite
ends of the tank and have a dry primary and interstitial
space.
The method was evaluated on a 32 foot long tank with
access ports spaced 28 feet apart.
The method cannot be used to satisfy the requirement for ELD testing of existing UST systems that are located within 1000 feet of a drinking water well. |