Non-return valves are used to reduce back- pressure when pumping water through the drill string, or behind a rock bit. These NRV units have a minimum number of parts to give a long and trouble-free service life. The valve section is manufactured entirely from brass to resist corrosion and normally the only service required is occasional replacement of the O-ring seal and spring. Top and bottom adaptors are supplied to customer requirements in any combination listed below.
|Top Sub (Box)||Bottom Sub (Pin or Box)|
|2 3/8 API Reg||2 3/8 API Reg|
|23/8 API I.F. (HWY)||23/8 API I.F. (HWY)|
|2 7/8 API Reg (HY)||2 7/8 API Reg (HY)|
|3 1/2 API Reg||3 1/2 API Reg|
|4 1/2 API Reg||4 1/2 API Reg|