The purpose of the restriction orifice can be:
- To reduce the flow rate
- To create a pressure drop
- To decrease temperature
The restriction orifice plates are some times placed downstream of a turbine meter to guard against over-spin. A restriction orifice is denoted by “RO” or “FO”.
When specifying a restriction orifice, plate thickness “E” should be large enough to keep the plate from deflection. As a rule, the maximum pressure drop across a single orifice for a gas is 50%. For greater drops, multistage orifices may be used.
- 304/304L or 316/316L Stainless Steel; ASTM A240 (the most common)
- Stainless Steel 316Ti; DIN 1.4571()
- Hastelloy® C-276; ASTM B575
- Cupronickle 30%
- Aluminum bronze
- Monel 400
- Haynes Stellite 25
- Yellow Brass