... flow through chamber. The valve stem is driven by diaphragm up and down, and driven force comes from the differential pressure taken ... , safe, reliable, easy, convenient to install and adjust and offers a long service life.Specifications: 1) Pressure rating: PN10. PN16. PN25 ... /Class1502) Size range: DN20mm-DN800mm (3/4" ¨C 32")3) Test and inspection: GB/T 13927, API598