Piping Design Considerations

1,000 mL/min.--it is clear that this indicates that 1,000 mL of liquid is flowing each minute. However, the devil is in the details.
In an extreme example, both a continuous flow of running tap water (centrifugal pump) and an intermittent flow with which the full liquid volume flows in a mere second of the one minute can be expressed as having a flow rate of 1,000 mL/min.
While such extreme cases are rare, a similar condition occurs with the use of a diaphragm pump due to the pulsation that it causes.

Diaphragm pumps discharge liquid in smaller portions 20 to 150 times a minute depending on the pump. Naturally, the discharge volume per interval is greater than the average discharge volume of a continuous flow (in this case, 1,000 mL/min.).
This means that instantaneous flow is greater as shown in (2) of Fig. 1, and thus it appears as if the pump capacity is larger.

So, specifically just how much larger is the flow rate?

In other words, a diaphragm pump that produces a flow rate of 1,000 mL/min. has a peak flow rate that is equal to a centrifugal pump that gives a flow rate of about 3,140 mL/min.
For this reason, when using a diaphragm pump with a flow rate of 1,000 mL/min., 3,140 mL/min. must be used in the calculation of pressure loss.

In general, the diameter of pipes connected to a diaphragm pump should be greater (thicker) than those for a centrifugal pump for the above reason.

A solenoid-driven metered pump produces greater pulsation than a motored metered pump. It discharges liquid at very small intervals of 1/10 to 1/100 of a second. This is because the solenoid is a kind of electromagnet, which instantaneously discharges electricity (magnetic attraction).

Therefore, inertial resistance at larger instantaneous flow rates is very high.
For this reason, joints and hoses used with a solenoid-driven metered pump are larger than those used with a motored metered pump with the same capacity per minute.

TACMINA's Smoothflow Pump is a diaphragm pump with no pulsation, which relieves it from the impact of inertial resistance. It can be used with smaller, longer, and more affordable pipes.
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