Density Meter LPGDi (DM250.3) Owner’s Manual
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11.2. Sampling and density meter purging
There are two methods for sampling and density meter purging:
a) Sampling from tank to sampling cylinder and following density meter
purging from cylinder;
b) Sampling from tank to density meter directly through connector.
Standard sampling cylinders with volume 0.25-1 L are recommended (pic.6.).
Minimum volume of sample is 0.25 L for density meter purging. Ensure LPG
sampling according to standard practice by ASTM D1265 method!
11.2.1. Connect LPG source (tank or sampling cylinder) to inlet valve of density
meter by the aid of flexible gas hose. Density meter should be levelled up
horizontally the source to be higher than outlet valve. Ensure all valves to
be closed!
Pic. 6. Standard sampling cylinder
11.2.2. Purge the transfer line by opening the valves. Check for leaks. If a leak is
detected at any time during the sampling operation, discard the sample.
Repair or replace the leaky unit (hose, valve or device) before obtaining
another sample.
11.2.3. Open density meter inlet valve.
11.2.4. Turn the outlet hose on the open territories or away from people and
equipment. Carefully open outlet valve and bleed air-gas mixture till white
colour liquid phase is leaking. When liquid phase appears, close initially
outlet valve and then inlet valve.
Initial purging accompanies with LPG boiling that is a result of temperature and
pressure difference. It could cause insufficient measuring chamber purging and
absolute error increase. It necessary to purge over the density meter if boiling was
detected (wait app. 1 minute after boiling shutdown).
11.2.5. Repeatedly open inlet valve. Open outlet valve and bleed air-gas mixture
carefully till white colour liquid phase looks like liquid jet is leaking. When
liquid phase appears, quickly close initially outlet valve and then inlet
valve.
11.2.6. Bleed excess liquid phase by careful opening/closing outlet valve till gas
phase appears.
11.2.7. Keep purged density meter for 5-10 minutes for temperature balance.
