Back-pressure valves are necessary to prevent motor when drill string running and also to prevent showings of oil, gas and water from the well through the drilling string when drilling oil and gas wells. Back-pressure valves are mounted above positive displacement motor. Main advantages of back-pressure valves designed by NGT company in comparison with those of other manufacturers are listed below:

1. Back-pressure valve design doesn't have hard alloy units at all which simplifies it, ensures its reliability, and, consequently, ensures considerable valve operation life.

2. Back-pressure valve design doesn't have rubber sealing elements which allows applying back-pressure valves in any, even high-temperature, wells and also enhances its reliability and simplicity of its repairs.

3. Protective coverage of valve spring and its piston allows the valve working in any corrosive environment during longer period of time in comparison with the valves of other manufacturers.

Due to the abovementioned design features, the overhaul period of our back-pressure valves is around 250 working hours.
 

Specifications	Designations
	KО-76	KО-95 KО-106	KО-120	KО-165	KО-178	KО-195	KО-210	KО-240
Outer diameter, mm	76	106	120	165	178	195	210	240
Total length, mm	226	329	382	484	497	497	497	547
Case length, mm	190	240	280	370	370	370	370	420
Connecting thread, top (box)	З-66	З-86	З-102	З-133	З-147	З-147	З-152	З-171
Connecting thread, bottom (pin)	З-66	З-86	З-102	З-133	З-147	З-147	З-152	З-171
Valve closing pressure, kg/cm2	0,3	0,3	0,3	0,4	0,4	0,3	0,3	0,3
Mud flow rate, l/s, not more than	5	13	20	40	40	55	60	70
Weight, kg	6	13	18	47	52	66	78	116

Sand content in the mud shouldn't be more than 1%. Mud density shouldn't be more than 2 g/cm³. Valve proof-test pressure while underfeeding is 350 bar.