KNF associates are frequently asked, “How do I select the best pump for my application, given a specific set of requirements”? While it is worth noting that no two design engineers’ specifications are alike, there are pump selection guidelines which are both useful and consistent across many diverse applications. The following article, authored by KNF Business Development Manager, Dave Vanderbeck, provides 11 such tips for selecting an electric air/gas pump.
“The fundamental design criteria for selecting an electrically operated diaphragm pump to handle air or gases has been well-covered around essential issues such as flow rates, inlet and outlet loads, chemical compatibility, voltage, and ambient and media temperature. But other equally important parameters are often overlooked. Here’s a rundown of the most important:
1. External Leakage. This involves media escaping from inside the pump or outside air leaking in and diluting the sample. Depending on the application, a simple bubble-tight construction may be acceptable with various improvements, including use of a secondary safety diaphragm to provide leak tightness of <0.000006 mBar l/sec. The first step is to define the level of leakage that the system can tolerate and then accommodate from there.
2. Reverse Flow Leakage. The valves inside a pump typically are not designed to be absolutely tight when the pump is off. If absolute tightness becomes necessary, a pump modification, check valve or other option should be discussed with the pump designer’s technical contact.
3. Through Leakage. The internal geometry of a pump is such that flow from inlet to outlet occurs with minimum loss. Ideally, the loss is only the force necessary to open the valves. In the “off” position this leads to the possibility of a siphoning effect through the pump. A simple pressure control valve, check valve with suitable cracking pressure, or other modifications to the pump and/or system should be considered as counter-measures.”