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The below is from Prof Terry Thomas at Warwick University. I received it a long while ago and thought I had posted it to the site but cannot see it here so please read on:

Dear Binaya

Your enquiry has been passed to me, but in the form of a web page with no obvious 'send' button on it. I will try to add to Steve's answer but my experience of interactive web pages is heavily negative (they work only for particular combinations of software) so my reply may not travel. You seem to be getting reasonable performance (efficiency of about 60%) when delivering 5 litres/min to 20m, yet you get no delivery to 26m. The absolute max delivery head (in m) for a steel pipe system is about 140 x max drive-water velocity (in m/s). At mean flow of 0.5 L/s in a 2" pipe your max velocity as the impulse valve shuts would be between 0.2 and 0.35 m/s; 0.2 m/s is only just enough to deliver to 26m and as Steve has said, minor defects could make it insufficient (defects such as slow delivery valve reclosure, flexibility in pump body or drive pipe or impulse valve, leaky impulse valve etc) - I don't know which ram pump design you have or whether your drive pipe slope is small). If your drive pipe is plastic, the max delivery head falls to about 40 x max water velocity. Can you adjust the impulse valve to increase the drive flow? (I am assuming your cycle time is not longer than 1.5 seconds), or have you hit the limit on available drive water? Your drive pipe diameter is rather large for this low drive flow.

good luck

Terry (t.h.thomas@warwick.ac.uk)

The below is from Prof Terry Thomas at Warwick University. I received it a long while ago and thought I had posted it to the site but cannot see it here so please read on:

Dear Binaya

Your enquiry has been passed to me, but in the form of a web page with no obvious 'send' button on it. I will try to add to Steve's answer but my experience of interactive web pages is heavily negative (they work only for particular combinations of software) so my reply may not travel. You seem to be getting reasonable performance (efficiency of about 60%) when delivering 5 litres/min to 20m, yet you get no delivery to 26m. The absolute max delivery head (in m) for a steel pipe system is about 140 x max drive-water velocity (in m/s). At mean flow of 0.5 L/s in a 2" pipe your max velocity as the impulse valve shuts would be between 0.2 and 0.35 m/s; 0.2 m/s is only just enough to deliver to 26m and as Steve has said, minor defects could make it insufficient (defects such as slow delivery valve reclosure, flexibility in pump body or drive pipe or impulse valve, leaky impulse valve etc) - I don't know which ram pump design you have or whether your drive pipe slope is small). If your drive pipe is plastic, the max delivery head falls to about 40 x max water velocity. Can you adjust the impulse valve to increase the drive flow? (I am assuming your cycle time is not longer than 1.5 seconds), or have you hit the limit on available drive water? Your drive pipe diameter is rather large for this low drive flow.

good luck

Terry (t.h.thomas@warwick.ac.uk)

The below is from Prof Terry Thomas at Warwick University. I received it a long while ago and thought I had posted it to the site but cannot see it here so please read on:

Dear Binaya

Your enquiry has been passed to me, but in the form of a web page with no obvious 'send' button on it. I will try to add to Steve's answer but my experience of interactive web pages is heavily negative (they work only for particular combinations of software) so my reply may not travel. .....

You seem to be getting reasonable performance (efficiency of about 60%) when delivering 5 litres/min to 20m, yet you get no delivery to 26m. The absolute max delivery head (in m) for a steel pipe system is about 140 x max drive-water velocity (in m/s). At mean flow of 0.5 L/s in a 2" pipe your max velocity as the impulse valve shuts would be between 0.2 and 0.35 m/s; 0.2 m/s is only just enough to deliver to 26m and as Steve has said, minor defects could make it insufficient (defects such as slow delivery valve reclosure, flexibility in pump body or drive pipe or impulse valve, leaky impulse valve etc) - I don't know which ram pump design you have or whether your drive pipe slope is small). If your drive pipe is plastic, the max delivery head falls to about 40 x max water velocity. Can you adjust the impulse valve to increase the drive flow? (I am assuming your cycle time is not longer than 1.5 seconds), or have you hit the limit on available drive water? Your drive pipe diameter is rather large for this low drive flow.

good luck

Terry