TANK GAUGING AND SAMPLING THROUGH UNPERFORATED STILL PIPES (STAND PIPES)

Petroleum and Petrochemical Bulletin
The risks and problems associated with the use of un-perforated still pipes for gauging and sampling
are well known within the industry. The use of this apparatus can result in significant measurement
errors and/or samples that subsequently prove to be unrepresentative.
For many years, the use of un-perforated still pipes has not been recommended for custody transfer
measurements due to the possibility of serious errors.
The most recent revision to API MPMS Chapter 3.1A now specifically prohibits the use of unperforated
or un-slotted still pipes for tank gauging. API MPMS Chapter 3.1A, Section 8.2.4 (h) states,
“Tank gauging shall not be carried out from un-perforated or un-slotted still pipes (which are referred
to as “guide poles” or “stand pipes”), since the liquid level measured inside the un-perforated or unslotted
still pipes is usually not the same the liquid level outside the still pipe. Tank gauging shall only
be taken from still pipes that have perforations or slots that allow free flow of liquid into and out the still
pipe. In certain locations, still pipes without slots are used to comply with local air pollution regulations.
These “solid” still pipes can lead to serious liquid height measurement, temperature determination,
and sampling errors.”
Where IFIA members are requested to take measurements or samples from un-perforated still pipes
they should advise their principals immediately and seek instruction. Such measurements and
samples shall not be used for custody transfer or other purposes without the approval of all concerned
parties. Appropriate qualifying statements should be used on any documents or reports where such
measurements or samples are involved.