How deep should a sampling tube be inserted into a pipe?
In the industry, it was and still is common practice for the tip of the rod to be inserted up to the second third of the pipe.
It's true that the end of the probe must be far enough from the wall to keep the membrane in the gas flow and to avoid it coming into contact with any liquids present along the wall.
However, it is also essential to limit the length of pipe inside the pipeline to avoid any failure due to vibratory phenomena.
GPA 2166 specifies that probes must never be inserted more than 25 cm from the ground (10 inches).
SOCLEMA and A+ Corporation strongly recommend inserting them no further than 3-5″ (about 10 cm ). This is unnecessary, and the further the rod is inserted into the pipe, the more subject it will be to vibration.
Tests were carried out by the Gas Research Institute in the USA to determine the impact of insertion length on gas density and energy value. Samples were taken at various points in the pipeline. The tests revealed no significant difference in sample density or energy value.
