Gas Flow Meters Installed Below the Process Line

This section applies to noncondensing gas flow meters where the physical layout of plant piping, structures, or equipment requires that the flow meter be mounted below the line. In these installations, condensate accumulators must be installed.

The objective of this orientation is to ensure that all condensed liquid will drain out of the impulse leads and into the condensate accumulators. The condensate will have to be periodically manually drained or pressured out of the accumulators.

• For horizontal meter runs, use the flange taps located above the center line of the pipe.
• Locate condensate accumulators below the flow meter, in an area accessible for periodic draining of the condensate.
• Mount the flow meter and install the three- (or five-) valve manifold so that the flow meter and manifold are self-draining to the condensate accumulators.
• Route the tubing leads between the flow meter and the root valves so that they slope continuously downward toward the condensate accumulators and are, therefore, self-draining. Ensure that there are no pockets where condensing vapors can get trapped.
• Route the accumulator lines to an environmentally acceptable drain system or sump. (Frequently accumulators are under pressure and the drain system is not. When such condensate is emptied into a low pressure system it can vaporize. The vapor must be vented into a closed system. This is especially a concern if the condensate contains dissolved toxic gases, e.g., H2S.)

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