Restriction orifices and Critical orifices

Autek restriction orifice is used to create a calculated pressure drop within a gas, vapor or liquid flow over the plate. A critical flow device is designed with the assumption that some fluids will reach sonic velocity trough the bore of the restriction. It is more predictable to achieve sonic velocity trough the bore for a thick plate than a standard restriction orifice. Critical orifices are therefore typical thicker than a restriction orifice.