139. The operator of an aluminum smelter must install, on each potline gas scrubber, a continuous gas measuring and recording system that enables the operation of the scrubber to be verified at any time.
The system, (1) in the case of a wet scrubber,
(a) must continuously measure and record gas pressure loss through the scrubber using a differential pressure gauge accurate to within 0.5 kPa;
(b) must continuously measure and record the flow and scrubbing liquid pressure, measured at the delivery pipe inlet using a pressure gauge accurate to within 10% of rated pressure in that delivery pipe; and
(c) must continuously measure and record scrubbing liquid pH using a device accurate to within 20%; and
(2) in the case of a dry scrubber, must have a continuous leak and malfunction detection and recording device.
In addition, every scrubber of emissions from an anode baking furnace must have a continuous leak and malfunction detection and recording device.
Subparagraph 2 of the second paragraph applies to dry scrubbers of an existing aluminum smelter as of 30 June 2012.