Q. Air chamber vs. surge tank in pressurized pipelines?

Air chambers and surge tanks are generally installed in water main to ease the stress on the system when valves or pumps suddenly start up and shut down. A surge tank is a chamber which contains fluid that is in direct contact with atmosphere. For positive surge, tank can store excess water so preventing the water pipes from expansion and water from compression. In case of down surge, surge tank can supply fluid to prevent formation of vapour column separation. Though if the relief of surge pressure is substantial, height of surge tank has to be large and sometimes it's not cost-effective to build such a large tank. Quite the opposite, an air chamber can be adopted in this case since air chamber is an enclosed chamber with pressurized gases inside. Pressure head of the gas inside the air chamber may combat the hydraulic transient. Volume of liquid inside the air chamber must be adequate to avoid the pressure in pipelines falling to vapour pressure. Air volume must be sufficient to produce cushioning effect to positive surge pressures. Basically air chambers can typically be designed to be more compactthan surge tanks. Air chamber has the disadvantages that regular maintenance has to be carried out to check volume of air and proper design of pressure level of gas has to be conducted.