Cover Story

Mass flowmeter chlorine gas measurement
at historic water treatment plant

Photos courtesy Endress+Hauser Canada Ltd.

The R.C. Harris Filtration Plant is an historic landmark on Toronto's lakefront. Constructed in the late 1930s, this architectural masterpiece has been declared a National Historic Civil Engineering Site.

Inside the massive and silent marble halls, a lot of high-tech instrumentation is quietly at work ensuring safe drinking water for the citizens of Toronto. The R.C. Harris plant can provide for up to 950 megalitres per day and supplies 45% of the city's water.

Some three years ago, a team was established at R.C. Harris to explore new technologies available to the industry. One of the goals they wanted to achieve was an accurate and instantaneous measurement of chlorine gas in the post-chlorination stage. Post-chlorination, one of several stages at which chlorine is added to destroy harmful pathogens, immediately follows filtration. An instantaneous measurement of gas flow provides an additional input to the logic of the chemical loop control and adds the possibility of remote feed rate monitoring within SCADA. This provides a valuable and instant diagnostic tool to fine-tune and troubleshoot the system.

Endress+Hauser Technical Representative, Gord Dalley, suggested that a Promass 63 F Coriolis mass flowmeter with stainless steel tubes might provide such a measurement and, after reviewing alternative designs and specifications, the project team decided to put a Promass 63 on trial. As a result of that trial, a meter was purchased and has been running since 1998. It has been taken out of service once during that time for inspection and absolutely no corrosion or deterioration was evident.

The unit measures volume flow in kg/hr which can be totalized. It is presently connected to a controller with a local display in the main hall, but future plans include a link to future SCADA system upgrades.

R.C. Harris has purchased a second meter for sulphur dioxide measurement and another installation on chlorine gas has been made at the Toronto Island Filtration Plant.

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