This series of butterfly check valve with small resistance and slow closing adopts swash plate large eccentric design and double eccentric structure. At the same time, it is equipped with a graded buffer cylinder, which can realize two-stage closing, that is, fast closing 85% - 90% (not subject to cylinder damping), and then slowly closing 10% - 15% (subject to cylinder yangni). The slow closing time can be adjusted to achieve the best effect of eliminating water hammer. It is installed at the outlet of the pump to prevent destructive water hammer when the pump is stopped. Therefore, the valve can be widely used in municipal, power plant, metallurgy, petrochemical and other industries of water supply and drainage system.

It adopts swash plate large eccentricity design and double eccentric structure, which has good dynamic performance of opening and closing, low opening pressure (≤ 0.08mpa), small flow resistance, small vibration, no need of heavy hammer and obvious energy saving effect.
The slow closing device has the advantages of novel design, compact and reasonable structure, reliable performance, fast and slow closing time. The slow closing time of slow closing section is adjustable from 1 to 60 seconds, which can be applied to different working conditions and reduce the impact of water hammer.
The valve shaft is of inertia type, safe and reliable. The back end of the valve body adopts the axial adjustable mechanism of the valve disc, with good sealing effect and adjustable zero leakage.
The bearing of valve shaft adopts self lubrication bearing, with small friction resistance and no need of oil injection.
The valve disc and valve shaft are connected by pull-out pin structure, which is closely combined without gap, and the shaft disc connection is more firm.

There are soft and hard sealing structure for users to choose according to different working conditions.

Nominal diameter		250～2000
Nominal pressurePN（MPa）		0.6	1.0	1.6
Test pressure	seal up	0.66	1.1	1.76
	housing	0.9	1.5	2.4
Applicable media		Sewage, clean water, mud, oil, etc
Standard materials	valve body	Ductile iron
	Disc	Ductile iron
	valve seat	Stainless steel, aluminum alloy
		stainless steel
	seal ring	Engineering plastics, rubber, stainless steel, copper alloy

Flange connection standard	accord withGB/T17241.6-2008 （IS07005.2）
Structural length standard	GB12221-2005 14series （IS05752）Size specification
Test standard	GB/T26480-2011 （API STD.598）implement

This type of check valve is mainly composed of valve body, disc, rotating shaft, rocker arm, buffer hydraulic cylinder, etc. The valve is driven by the inlet pressure to open the valve disc to make the medium pass through. The valve disc drives the rocker arm through the rotating shaft to pull the piston rod in the buffer cylinder to the open position. When the medium stops flowing (e.g. the pump stops suddenly), the valve disc will close automatically due to the self weight of the valve disc and the effect of medium backflow. Due to the action of buffer device, the valve disc closing is divided into two stages.

The first stage: from the full open position to 85% - 90% of the stroke is the fast closing section. In this stage, the valve disc drives the rocker arm to move clockwise at the same time, and the cylinder piston rod is pressed back into the cylinder block. At this stage, the damping device has little effect and the valve disc closing speed is very high. The second stage: from 85% to 90% of the stroke to the full closing is the slow closing section. In this stage, the damping device plays a very important role. In order to obtain the appropriate closing speed, the damping value of the oil system can be adjusted by adjusting the opening of the one-way throttle valve, so as to eliminate the destructive water hammer and protect the pump, valve and pipeline system

Serial number	name	texture of material	Serial number	name	texture of material
1	valve body	QT450-10	6	rocker arm
2	Disc	QT450-10	7	Buffer cylinder	Assembly
3	Shaft	2Cr13	8	Withdrawal pin	1Cr17Ni2
4	Bearing	ZCuAl10Fe3	9	Disc seal ring	polypropylene
5	Cylinder bracket	Q235-A	10	valve seat	0Cr19Ni9

DN	A			C			b			f	L	E	F	H	J	K	M	T1	T2	T3	N-φ1	N-φ2
	PN6	PN10	PN16	PN6	PN10	PN16	PN6	PN10	PN16													PN6	PN10	PN16
250	375	395	405	335	350	355	22	22	22	3	250	260	355	270	250	250	30	418	297	115		12-φ19	12-φ23	12-φ28
300		445	460		400	410		24.5	24.5	4	270	247	356	280	250	270	52	428	304	134			12-φ23	12-φ28
350		505	520		460	470		24.5	26.5	4	290	313	385	300	300	290	73	473	342	144			16-φ23	16-Φ28
400		565	580		515	525		24.5	28	4	310	343	470	350	400	310	94	387	404	157			16-φ28	20-φ31
450		615	640		565	585		25.5	30	4	330	377	512	350	400	330	109	552	408	161			20-φ28	20-φ31
500		670	715		620	650		26.5	31.5	4	350	417	568	400	500	150	139	699	566	223	4-φ21		20-φ28	20-φ34
600		780	840		725	770		30	36	5	390	477	640	450	600	150	181	819	671	251	4-φ23		20-Φ31	20-Φ37
700		895	810		840	840		32.5	39.5	5	430	542	705	500	700	150	241	930	782	293	4-Φ23		24-φ31	24-Φ37
800		1015	910		950	950		35	43	5	470	610	854	550	780	180	246	1067	875	278	4-Φ26		24-Φ34	24-Φ40
900		1115	1025		1050	1050		37.5	46.5	5	510	642	879	600	900	200	302	1087	906	363	4-Φ26		28-φ34	28-Φ40
1000	1175	1230	1125	1120	1160	1170	40	40	50	5	550	760	1016	650	1000	220	345	1318	1106	349	4-φ27	28-φ31	28-φ37	28-φ43
1200	1405	1455	1255	1340	1380		45	45		5	630	902	1158	800	1200	230	504	1365	1213	579	4-φ27	32-Φ34	32-Φ40
1400	1630	1675		1560	1590		46	46		5	710	1076	1447	930	1400	230	514	1604	1372	588	4-φ33	36-Φ37	36-Φ43
1600	1830	1915		1760	1820		49	49		5	790	1220	1568	1020	1600	230	624	1739	1496	686	4-φ33	40-Φ37	40-Φ49
1800	2045	2115		1970	2020		52	52		5	870	1338	1668	1150	1800	240	695	2028	1726	753	4-Φ40	44-Φ40	44-Φ49
2000	2265	2325		2180	2230		55	55		5	950	1438	1768	1280	2000	310	830	2028	1774	928	4-Φ40	48-Φ43	48-Φ49