SAFETY WARNING
IOM-013
Page 16 of 18
CP2 & CP5GM
Rev: D
Last updated: 4/14/2011
SAFETY ISSUE WARNING FOR LIQUID SAMPLE CYLINDERS
After drawing the sample into the cylinder, the inlet and pre-charge valves should be
closed. The sample line is then disconnected from the cylinder and the cylinder is
completely isolated from the process. Paperwork is processed and the cylinder is
prepared for transport. Prior to transporting the cylinder, it is a common and
recommended practice to plug or cap the valves on the cylinder. These valves may
terminate with a female NPT or a male NPT. The female valves are typically plugged,
while the male valves are typically capped.
In the case of liquid sampling and due to the potential extremes of thermal expansion of
many LPG products, caution should be taken to ensure that any residual liquid is drained,
blown, or absorbed from the accessible exterior dead volume of the valve body
(downstream of the seat) prior to plugging or capping the valve.
It is common to see temperature differentials of as much as 100° F (38° C) or more.
Liquid samples that are drawn at -40 to -50° F (-40 to -46° C) can be transported in
shipping cases that may see ambient temperatures as high as 100° F to 160° F (38° to 71°
C), and at times may exceed 160° F (71° C).
Operators should be familiar with the basic and general physical properties of the product
that they are sampling so that they can adequately estimate the expansion potential of the
sampled product within the cylinder and therefore have them allow ample outage for
expansion to occur. In a majority of cases, 80% fill and 20% pre-charge is acceptable,
but certain products may require a larger inert gas pre-charge ratio – i.e., 70%-30% or
60%-40%.
Burst discs are installed on these cylinders to protect them from structural failure. The
operator must be aware that flammable product will be released in the event of
overpressurization of the working pressure of the cylinder and therefore it is important
to allow for ample expansion within the cylinder prior to attainment of the rupture disc
activation.
If you have any questions, please contact Welker at 1-800-776-7267 in the USA or 1-
281-491-2331.
