Valve Opening Time

The theoretical approach is based on the principle that liquids are incompressible, and as the pump impeller comes up to speed there will be a pressure at some speed that exceeds the cracking pressure of the valves. Therefore, the thing that needs to be quantified to determine the theoretical opening time of the valves is the acceleration rate of the pump impeller, which is a function of its moment of inertia.

In practice, the valves will open more-or-less as the pump starts. Why are the valves there, though (rhetorical question)? In practice, the one with the lower cracking pressure will take the greater part of the flow. They seem to be there simply as flow restrictors and the need for them to be either closed or not-closed is not apparent from the diagram in the original posting - unless they are non-return valves to prevent reverse flow, in which case why is the time-to-open of any relevance or use (rhetorical question)? If it's a heffing great pump, it will have heffing great fluid reservoirs at each end, so the response time will be slow; if it's a tiny pump then the response time will be fast. In either case, what is the relevance of the valve opening time?

Thank you sir, for your reply.

The need is at the end of two pipes with a valve, tanks are connected. i need to know at what time from 0 sec each tank is started getting water and how much time they take to become full (which is a function of operating point of pump). what exactly the water quantity after say t-sec in each tank. Will the valves open simultaneously if the two lines are having large unsymmetrics?

I believe that we have the beginnings of a Feynman Diagram here....

http://en.wikipedia.org/wiki/Feynman_diagram

If we allow the atomic nucleus to represent the pump, and the valves as electrons and positrons respectively, we can arrive at a simple, yet closed solution.

What is the included angle between the piping branches and what is the massflow rate of the pump ?

Thank you for the reply.

I can tell you the included angle between the pipes, which is 40 deg. But mass flow rate of the pump, i think can not be exactly specified, because during pump starting the flow rate rise from 0lpm to rated operating point lpm which depends on the system.

Could you explain your analogy between pump and atomic terms.

Yes, if you really need it. It is called INSTRUMENTATION and MEASUREMENT. Where did you get the brilliant idea, that the manufacturer may know anything about a valve on a theoretical basis?!?

What is the use of the presented diagramm? Aside an academic exercise, that is?

Uh, why wouldn't the valve(s) open when the control signal to the valve's actuator tells the actuator to drive open?

Oh, it does. But, to stick to the original question, please take a valve, any valve. Describe to us the time constants of its electrical components. Then, describe the behaviour of its mechanical components, in terms of rate of flow in specified condition in a milliseconds time base chart, starting with the applied electrical signal. I expect OP will receive this revelation with open arms vs. a math based derivation, that has no relations to anything resembling reality.

Then again, academia still manages to surprise me with their irrelevancies.