Project: Baton Rouge Wastewater Pump Station SCADA System – October 4th

By Control Engineering Staff October 5, 2005

October 4, 2005

Some of the items on last week’s meeting agenda with the city of Baton Rouge indicated they did not believe the plans and specifications adequately addressed their maintenance personnel’s needs at the individual pump stations. This
issue centered on wiring documentation for the complete pump station and elimination of excess relays from earlier installations. There was disagreement between our and the primary consultant’s interpretation of the specifications regarding the obligation of the contractor to document the complete station’s connections, including new and existing wiring.

It was the city’s belief that the plan documents did not adequately describe what currently existed at most stations. Preparation of plans and specs was contracted to an electrical sub-consultant who was not present at that meeting. We agreed to visit a typical station and trace wires to see what was installed, and compare this to the plans.

So, this week we inspected a typical pump station employing three variable frequency and two fixed speed pumps. An integrated control panel with micro-controller and bubbler systems originally regulated the station. When telemetry was first added 10 years ago, a second control panel was installed with a combination RTU/controller. The original micro-controller in the bubbler panel was removed and replaced with an HMI connected back to the RTU/controller. All interposing relays and inter-wiring from the original micro-controller remained.

We located copies of the manufacturer’s original drawings for the bubbler panel, micro-controller, RTU/controller, and variable speed drives, using these to trace thru actual field wiring.

Missing from the plans is detail on how devices are physically wired at present. Also, the need to do demo work to eliminate the multitude of relays is not noted. Our tracing showed almost all the 50+ relays installed could be eliminated and that more than half of those existing are no longer used. Differences between the actual RTU I/O count and that indicated in the
plans could result in the contractor asking for additional compensation. We offered to create a set of revised drawings for the inspected station for use as a template that the electrical sub-consultant could use to revise the others.