- Steam or water in the process pipe should be sampled isokinetically. This can be achieved
using an
EPRI Isokinetic Sampling Nozzle.
- For steam sampling, the isolation valves on the EPRI Nozzle and the sample tubing
between the isolation valves and the primary sample cooler should have approximately the
same bore as the EPRI Nozzle.
This will maintain a constant flow velocity and minimize
the amount of deposition between the Nozzle and primary
cooler by eliminating dramatic
pressure changes.
- The sample velocity in all tubing after the primary cooler
should be in the turbulent flow
range (Re > 4,000, 4 to 6 ft/sec for liquid water) so that the amount of deposition
in the
sample tubing is minimized. Also, the pressure drop throughout the entire sampling system
must
be low enough to ensure that there is enough pressure after the secondary sample
cooler to provide adequate flow to the
online instruments and grab sample tap.
- Sample tubing should be as short as possible, sloping downward along the entire length.
For steam sampling, the tube section between the Sampling Nozzle and the primary sample
cooler should be less than 20
ft long.