Drop-in Type Check Valve : It is an internal preventer. When blowout happens, the kelly rodwill be removed immediately and throw the back pressure valve assembly into the water hole and then pump downward to the required place. Thus , the blowout can be prevented.

Type	Stop Ring I.D. (mm)	Joint			Check Valve Assembly		Working Pressure (Mpa)	Connection
		O. D (mm)	I.D (mm)	Length (mm)	O.D (mm)	I.D (mm)
FT89	30	89	35	335	33	8	35     70	NC26
FT105	33	105	38	350	36	10	35     70	NC31
FT121	50	121	56	395	54	18	35     70	NC38
FT159	54	159	60	435	58	23	35     70	NC50
FT168	64	168	70	435	68	33	35     70	NC50
FT178	64	178	70	515	68	33	35     70	5-1/2FH
FT203	64	203	70	620	68	33	35     70	6-5/8REG