Val-Matic Stories – Overcoming the problem of air in a pipeline
10:00 - Explaining the Problem
My phone rang; it was my old engineering partner Jim. He was in trouble as he had just started up the backwash pumps at the East Lake plant and boiled the sand in the number three water filter even though the venture showed a good controlled flow rate.
I got him to explain the system layout to me. There were four vertical turbine backwash pumps feeding a 14” line that had a century and modulating butterfly valve for backwashing the sand filters in sequence.
11:00 - Problem Worse Than First Thought
Jim declared that he had checked for air in the line and that the problem was much deeper, I couldn’t leave the problem so I decided to jump into my car and head towards the problem.
12:00 - Pump Discharge Air Valve Missing?
When I arrived I checked the application and found that the four pumps had a 12 feet lift out of the clearwell and pumped the backwash water through 8” Tilted-Disc Check Valves into a header equipped with Val-Matic Model 202C Combination Air Valves. The combination Air Valve will not only release air rapidly during initial filling of the head, but will also relieve accumulated air during operation. That all looked fine, however, the pump discharge air valves were missing from the plans, so I wondered what Jim installed?
13:00 - Establishing the Problem
The pump discharge air valves must rapidly expel that gulp of air that is delivered by the pump during every start. If the wrong size air valve is used for pump discharge, air can easily be sent downstream to the filters. So I got Jim on the phone and asked him for the model number of the pump discharge air valves?
Jim stated that he’d installed some 2” valves. I pointed out that not all 2” valves are alike. Jim said the valve was a 2” Val-Matic Model 32 or 38, something like that.
I then explained to Jim that a 2” inlet does not imply a 2” orifice. Air Release Valves need a large inlet to allow the water to easily flow in and out of the valve to activate the float but the outlet orifice is small so that air can be relieved at high pressures. You need a Well Service Air/ Vacuum Valve with full size orifice in pump discharge service. I concluded my lecture to Jim with a reminder that air valves are clearly defined in the American Water Works Association (AWWA) Standard C512 and that he should read it.
14:00 - Resolving the Problem
Having pointed out Jim’s error he decided to install some Val-Matic 102WST Well Service Air Valves which are specifically designed for vertical turbine pumps. The 2” outlet allowed the air to be rapidly expelled during pump starts before the check valve opened. Full vacuum flow was provided after pump shut down through the Dual-Ported Throttling Device, which has an independent inlet orifice.
See the diagram below to get a better understanding of the Val-Matic Well Service Air Valve.
Well Service Air Valve
It is understood that this is a common problem is something that can cause major problems in your application. Have you come across this problem before? How did you overcome it?
Feel free to leave your comments below, or alternatively, get in touch with one of our experts in our solution centre?
Val-Matic Valve and Manufacturing Corporation
Val-Matic Valve & Manufacturing Corp. is a leading designer, manufacturer and marketer of check valves, quarter turn shut-off valves, air valves and foot valves for water/wastewater, industrial and building markets.
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