What is a Force Main System?
In the various blogs the I write, I've mentioned that Pipeline Pigging is the preferred method to clean Force Main Systems, but I skipped the part where I explain just what a Force Main Systems actually is. I checked the EPA website to make sure my explanation of this topic was fairly on-point. Force Main Piping Systems transport wastewater away from a pump or pneumatic ejector, under pressure, toward a discharge point. The power equipment is located at a lift station and provides the energy to move the wastewater through the piping system. A Force Main System includes Pipes, Valves, Pressure Surge Controls and, usually Force Main Cleaning Apertures. Force Main Systems are constructed with a variety of materials and in various diameters of pipe. Wastewater content is the main determining factor for piping material and the required flow rate is the key to choosing the diameter and wall thickness. Corrosion resistance will be among the variables considered, as will operating pressure and trench conditions. Some facilities aerate the wastewater and chlorinate it at the lift station. This helps control odor and limits corrosion. Pressure surge control devices mitigate system damage, especially during system startup and shut-down. These are often automatic cone or ball valves. Force Main System cleaning is often accomplished using Inline Pipe Pigging. (Sometimes called Poly Pigging because the Pig is a Poly Urethane device) Pig insertion facilities (launchers) are often included in the lift station and a retrieval station is placed at the discharge point. Longer Force Main Systems may include multiple launch and retrieval points throughout their course, allowing easier access for cleaning. When might a Force Main System be needed? Besides a Force Main System, a piping system engineer may consider a gravity driven system. If the processing center is at a lower elevation than the source, this generally works fine, but if you reverse it, you need a Force Main System to combat gravity and lift the wastewater. Force mains can also be used to reduce costs because they can generally be constructed in shallower trenches and use smaller diameter pipes. Force Main System reliability duty life are similar to that of gravity lines. Pipeline reliability may be reduced by excessive pressure surges, corrosion, or lack of proper maintenance. Pipeline Pigging for cleaning and inspection should play a significant role in that routine maintenance schedule.
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