Restriction Orifices
To limit a flow or regulate a pressure
The function of a restriction orifice is to limit a flow rate or to reduce a pressure in a pipe. It is calibrated according to the technical specifications of the installation so as to reach the desired pressure or flow rate; according to the values to be achieved, either simple restriction orifices (single-hole or multi-hole) or multi-stage restriction orifices can be proposed.
It advantageously replaces a simple valve: simpler, more economical, more robust and maintenance free.
The operation of a restriction orifice is represented below:
The fluid pressure decreases when going through the restriction. It reaches its minimum value shortly after the orifice (Pmin) and then increases to a stable pressure (P2). The permanent pressure loss Δω (P1 - P2) generated by the turbulences makes it possible to reduce the pressure in a pipe and / or to limit a flow.
Our expertise covers all aspects of the study of restrictions. We take into account the essential operating conditions as well as specific parameters such as noise level, cavitation and critical flow (sonic conditions).
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Cavitation in a liquid corresponds to the formation of gas bubbles due to a too low local pressure (lower than the vaporization pressure), which can happen when the pressure drops passing through the orifice. The implosion of these gas bubbles generates significant noise levels and can damage the metal elements. This is why we size the restriction orifices avoiding this phenomenon of cavitation. If the pressure remains below the vaporization pressure downstream of the restriction, the fluid remains in gaseous form. This is the phenomenon of flashing.
In the vicinity of the restriction, the fluid is accelerated until it reaches its maximum speed at the restriction. If the sonic velocity is reached (choked flow for a gas) or if cavitation is too important (choking cavitation for a liquid), the flow passing through this orifice does not increase even if the downstream pressure continues to fall. Thus, we optimize the calculation of our restriction orifices while staying below the critical flow limit or choked flow.
The thickness of the plates is calculated as a function of the generated differential pressure and the internal diameter of the piping to prevent deformation of the plate during operation.
This graph indicates the minimum thickness to be respected for a 316L stainless steel plate at 20 ° C according to B31.3.
