I had an email exchange with the inventor of the multistage-stage back pressure regulator, Emerson’s Ruediger Niebel. Here’s the patent abstract:
Multi-stage fluid regulators are described. An example fluid regulator includes a regulator body having an inlet in fluid communication with a source of pressurized fluid. A first fluid valve is disposed within the regulator body and coupled to the inlet to regulate a pressure of the pressurized fluid at the inlet. A second fluid valve is disposed within the regulator body and coupled to the inlet and, via a passageway, to the first fluid valve. The second fluid valve is to cause a fluid pressure in the passageway to be regulated to a predetermined portion of the pressure of the pressurized fluid at the inlet.
Ruediger describes the use of two-stage pressure regulators in hydraulic applications, in a German-language LinkedIn post, Solve problems together! #Cavitation #TESCOM. Here’s the English translation.
He describes the cavitation phenomena (all quotes below from the English translation).
Cavitation can occur wherever there is a temporary narrowing of the cross-section with subsequent expansion. The flow speed increases at the narrow point. Like a water jet pump, the sudden increase in the area after the constriction results in a strong local pressure reduction.
The implosion of bubbles created by cavitation is what causes mechanical damage.
These [bubbles] implode with enormous force and high temperatures as soon as the pressure increases again, for example after a narrow point. Mechanical components are heavily stressed, even with hardened steel you can clearly see the cavitation craters.
Ruediger shares an interesting video showing the physics of cavitation created by submarine propellers.
The TESCOM 54-3500 Series Two-Stage Hydraulic Backpressure Regulator reduces the controlled inlet pressure in 2 steps. He explains:
The integrated second stage automatically adjusts the medium pressure to 50% of the inlet pressure, regardless of whether the fitting is spring-loaded, dome-controlled or equipped with a compressed air intensifier. The division of the differential pressure into two levels significantly reduces the occurrence of cavitation and erosion. A multitude of different materials for seals and valve seats allows an optimal selection depending on the medium.
See the array of back pressure regulators on Emerson.com to best fit your application. You can also connect and interact with pressure regulator experts in the Valves, Actuators & Regulators group in the Emerson Exchange 365 community.