Recirculation of Fluids in a Pumping System

Cavitation is more common in centrifugal pumps.

However, reduction of vapor pressure is certainly possible with a PD pump.

Wiki says:

"Hydrodynamic cavitation describes the process of vaporisation, bubble generation and bubble implosion which occurs in a flowing liquid as a result of a decrease and subsequent increase in pressure. Cavitation will only occur if the pressure declines to some point below the saturated vapor pressure of the liquid and subsequent recovery above the vapor pressure. If the recovery pressure is not above the vapor pressure then flashing is said to have occurred. In pipe systems, cavitation typically occurs either as the result of an increase in the kinetic energy (through an area constriction) or an increase in the pipe elevation."

Depending on the type of PD pump in use, I'd say the damage could range from minimal to catastrophic.

I'd never allow this condition to exist and you won't have a problem.

It depends. Consider the possibility during the HazOp Study.

What is the fluid: water, hydraulic fluid, etc.?

What is the pump flow rate and operating pressure?

Does your system have a reservoir?

What is the diameter of the output, suction, drain lines?

If you want answers to your question, you need to bottle the egg

Looks like you will be wagging your tail in soup.

It will definitely warm up.

Is there anyting more in the system than a pump that feeds from outlet to inlet.

Why would there be a checkvalve on the outlet?

I reckon thats a hypothetical question?!

Domestic central heating circulating systems do not need a check valve. Cavitation is a rarity, and usually caused by something going on in the system such as an air-lock.

OP didn't say it is a heating system, I used that as an example. But I can't see why there would ba a NRV in any recirculation system, maybe special cases where it's needed, but I can't think of one offhand.

2*100% centrifugal pumps arranged in a parallel piping scheme as duty/standby would need non-return valves downstream of each pump. Centrifugal pumps are the most common circulator in pumped domestic central heating systems. The original poster is talking about positive displacement pumps, for which no non-return valve would be required were it a single pump installation; if the rotor of an installed standby pump were unrestrained, the actions of a parallel duty pump would tend to drive the standby pump backwards. The original poster still needs to consider the possibility of cavitation during the HazOp Study, on the assumption that this is some industrial installation that would merit using the protocol. Here, as elsewhere, details of the original poster's installation are too scant at this time to merit an absolute answer. <unsubscribes>

OK pumps in parallel clearly need NRVs. I should have thought of that, I've installed enough of them.