1 Application scope
1.0.1 The restriction orifice shall be set in the pipeline to limit the flow of fluid or reduce the pressure of fluid. The restriction orifice shall be used in the following aspects:
1.0.1.1 The process materials need to be depressurized, with low precision requirements.
1.0.1.2 If a great pressure drop is required on the upstream and downstream of the valve in the pipe, in order to reduce the fluid erosion on the valve, an orifice may be connected in series at the upstream of the valve on the premise that no gas phase will be generated after throttling through the orifice.
1.0.1.3 Places where low and continuous flow of fluid is required, such as flushing pipes of pumps, bypass pipes of hot standby pumps (low flow protection pipes), analysis and sampling pipes, etc.
1.0.1.4 Places where pressure relief is required to reduce noise or wear, such as venting systems.
1.0.2 Unless otherwise specified in this standard, the pressures are absolute pressures.
2 Classification and selection points
2.0.1 Classification
According to the number of holes on the restriction orifice, it can be divided into single-hole orifice and multi-hole orifice; according to the number of plates, it can be divided into single-plate orifice and multi-plate orifice.
2.0.2 Selection points
2.0.2.1 Gas and steam
In order to avoid choking flow in pipelines using restriction orifices, the restriction orifice outlet pressure (P2) shall not be less than 55% of the restriction orifice inlet pressure (P1), i.e. P2 ≥ 0.55 P1. Therefore, if P2 < 0.55 P1, single-plate orifice shall not be used, and multi-plate orifice shall be selected, and the number of plates shall ensure that the outlet pressure of each plate is greater than 55% of its inlet pressure.
1 Application scope
2 Classification and selection points
3 Calculation methods
4 Calculation examples
5 Calculation table and summary list of restriction orifice
6 Attached figures and tables
