Pressure transducers have sensitive electronics, membranes and vent tubes. They can fail in a number of different ways. The FOGRod is basically 10 pieces of wire, held in place by CPVC – no moving parts, no electronics and no sensitive components. Even if one wire or metal contact “fails” (and this is obviously much less likely than sensitive electronics failing) then a higher level contact/wire will ensure the pumps start (or alarm functions).
Running pumps dry costs lots of money. The FOGRod always stops the pumps because once the wastewater level drops below the bottom of the FOGRod there is no way for current to flow through the fresh air to the receding water level. It’s the laws of physics. Any failure mechanism will stop the pumps.
This wastewater level sensor works using conductivity. Fresh air is an insulator and water is a conductor. The FOGRod has 10 metal contacts down its length, each one internally connected to a core of 10-core cable. The control panel unit (called the LIT) puts 5v on each wire and looks for current flow to ground. When a metal contact is under water then current flows, and when it is above the water no current flows. So the water acts like a lightswitch and the LIT can determine the level in the wetwell.
Cleaning the FOGRod
The FOGRod hangs by its cable, from a mounting bracket that you install just under the lid. When it needs cleaning just pull it up through the wiper that is an integral part of the bracket.
Works in Grease – grease is an insulator so doesn’t this stop the FOGRod working? It’s surprising to everyone the first time they see this technology working in wastewater. The reason conductivity rods work in grease is it is almost always “broken up” as it adheres to the rod – especially if you install the FOGRod in its ideal position near the inflow, in the more turbulent part of the wetwell. Eventually grease does start to cause measurement problems, but the LIT gives you an alarm when this happens, and it keeps operating as close as possible to the intended start and stop points for a long time afterwards.
Control – The LIT has a stepped analog output which increases by 1mA for each point on the FOGRod – this can be used for level control as a direct replacement for a pressure transducer. The LIT also has 10 level relays – they are like 10 floats, so to replace floats just pick the relays you want to use and wire them into the same terminals that the floats were wired into – with no change to your existing control panel wiring.
If you are using the level relays for control, you can use the analog output with SCADA/telemetry for remote level monitoring.
LIT installed in control panel, level relays used for control (top), analog connected to SCADA (bottom left) and FOGRod cable (bottom center)
We offer a FREE trial to any city, town, county or parish. Call us today: 406 545 3023.
Read more about how the FOGRod works, or see how easy it is to install.