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BAM 1020-9800 Manual Rev W.docx
Page 34
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The reason for the 1.0 L/min leak flow allowance is due to the test conditions. With
the inlet closed, the vacuum in the system is many times greater than during normal
sampling. If the leak flow during this test is less than 1.0 L/min, there should not be a
significant leak during normal operation.
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The leak flow value may take a minute or two to stabilize if an inlet tube longer than 8
feet is used.
Advanced Leak Checks: If a leak is found which persists after the nozzle and vane are
cleaned, then the source of the leak can be further isolated using a rubber shim, such as part
7440 supplied in the optional BX-308 tool kit. The filter tape can be removed and the shim
inserted with the hole centered under the nozzle to eliminate the effects of leakage through
the filter tape during the leak check. The shim can also be turned around and the solid side
positioned under the nozzle in order to isolate leaks downstream of the vane.
Troubleshooting Section 7.5 contains additional tips for resolving leaks in the flow system.
7440 Leak Isolation Shim
5.6 Nozzle and Vane Cleaning Procedure
The nozzle and tape support vane (located under the nozzle) must be inspected regularly
and cleaned as needed in order to prevent leaks at the interface between these parts and the
filter tape. We recommended that the nozzle and vane be inspected monthly for tape build
up. Some sites may require a more frequent inspection and cleaning interval. BAM 1020
monitors operated in hot, humid environments may require more frequent nozzle and vane
cleaning. When the nozzle and vanes are not regularly cleaned filter tape debris may build
up. This can lead to pin holes being punched through the filter tape which can in turn cause
flow leaks and erroneous beta ray measurement. Use the following steps to clean the nozzle
and vane parts:
1. Latch up the tape pinch rollers, and raise the nozzle in the TEST > PUMP menu. Slide
the filter tape out of the slot in the beta block nozzle area. It is not necessary to
completely remove the filter tape from the BAM 1020.
2. With the nozzle up, use a small flashlight to inspect the vane. Any debris will usually
be visible. Clean the vane surface with a cotton-tipped applicator and deionized water
or isopropyl alcohol. Hardened deposits may have to be carefully scraped off with the
wooden end of the applicator. Take care not to damage the vane!
3. Lower the nozzle in the TEST > PUMP menu. Lift the nozzle with your finger and insert
another wet cotton applicator between the nozzle and the vane. Let the nozzle press