Dear Sir
Thank you for your interest. Although a bypass around the side of the valve does basically the same thing, it has several flaws. We started building CSV’s that way more than 20 years ago.
The first problem was evident. The external bypass was very noisy. With high differential pressure it sounded like a jet engine.
The second problem was water hammer or surge from the main valve when it closed fully or popped open from the fully closed position. When using valve speed controls, a diaphragm type valve will always speed up dramatically as the valve gets closer and closer to closing, and the differential pressure increases. You really cannot slow down the last ¼” of closing enough to prevent surge, without really slowing down the upper stroke of the valve, making the valve work much too slowly. Controlling the valve speed to prevent opening or closing too quickly causes surges and pump cycling when the valve cannot keep up with sudden flow changes in the distribution system.
The third problem was the bypass getting clogged with debris. Since the main purpose of the bypass is to properly cool the pump/motor, a clogged bypass is devastating.
The fourth problem took a little time to show its face. The velocity through the small bypass can exceed 200 feet per second. This causes minerals to precipitate out of solution and grow to clog the bypass, the same as holes in a showerhead become clogged.
For many years other valve companies have tried external bypasses. They never really caught on because of all the problems listed above.
The non-closing seat of the CSV solved all those problems.
The internal bypass is completely quite.
Water hammer or surge is eliminated, as the CSV can never fully close or have to pop open from a closed position.
The non-closing CSV can be made to operate many times faster than fully closing valves without causing hammer or surge. Making the valve able to keep up with any sudden changes in flow. Not only do we not use any speed controls but instead supercharge the pilot system to make the CSV open and close as fast as possible.
Also the “two half moon” type bypass that come together to make a hole when the valve closes, will split in two each time the valve opens, flushing through any debris that maybe trying to clog the bypass. Since the CSV maintains a set downstream pressure, a clogged bypass would lower the downstream pressure, causing the two half moons to split apart, automatically flushing any debris.
The internal bypass of the CSV that splits apart also eliminates clogging from minerals precipitating out of solution during high velocity.
After experiencing all the problems of an external bypass, the solution was found to be the internal, self-flushing bypass design that we use today. While theoretically a bypass is a bypass and should work the same, the non-closing bypass design of the CSV solved all the problems we encountered with an external bypass. When placed side by side there is no comparison. The CSV bypass design is greatly superior to an external bypass.
Please let me know if you have more questions.
Thanks
Cary Austin
