ZDT series automatic recirculation valve
What is ZDT series automatic recirculation valve?
ZDT series automatic recirculation valve is a kind of pump protection device. It automatic protect centrifugal pump when pump body occur cavitation damage or unstable (especially conveying hot water at low load operation medium). Once pump flow is lower than the preseted flow, bypass can completely open to ensure the minimum required flow pump. Even running fully closed, namely running flow is zero, the minimum flow can also pass bypass for Automatic Recycle. Pressure reduced through the multistage bypass pressure reducing valve.
ZDT series has big bypass, and this valve is suitable for bypass with big flow, maximum pressure differential is 4MPa, specific choice is determined by factory.
Characteristics
- Simple structure, operation reliable and stabile, with few movement parts.
- Be easy for installation, can be installed vertically or horizontally on pump pressure outlet.
- Bypass flow is large, maximum flow is 60% of main flow, KV value can be adjusted.
- Maximum bypass operating pressure differential is 4MPa. Bypass non-return function is optional.
- Applicable medium including: water, oil, methanol and other liquid medium.
Working temperature is from -196℃ to +300 ℃.
Size and pressure range
- Valve body type: three-way casting valve
- Nominal diameter: DN25, 32, 40, 50, 65, 80, 100, 200, 250, 300, 350, 400
- Nominal pressure: PN 16, 25, 40, 64, Class 150, 300 L, etc.
- Connection type: flange FF, RF, RTJ, BW, SW etc .
Material temperature range
| Body material Sealing material |
WCB | LCB/LCC | CF8 | CF8M |
| NBR | -20～+100 | -30～+100 | -30～+100 | -30～+100 |
| FKM | -20～+200 | -40～+200 | -40～+200 | -40～+200 |
| PTFE | -20～+230 | -40～+230 | -80～+230 | -80～+230 |
| SS winding gasket | -20～+300 | -40～+300 | -196～+300 | -196～+300 |
Model selection
| ZD | T | Nominal pressure | Body material | Main diameter |
/Bypass diameter | Structure type |
| Auto recirculation pump protection valve | T type bypass assembly | PN16=PN16 CLSS150LB=CL150 |
C=WCB LC=LCB P=CF8 PL=CF3 R=CF8M RL=CF3M D=Customed |
DN25=25 NPS1″=1″ |
DN25=25 NPS1″=1″ |
V=vertically mounted H=Horizontally mounted Z=Bypass non-return D=With discharge mouth |
| Such as: T type automatic recirculation valve, pressure is PN40, body material is WCB, main diameter DN50, Bypass diameter DN 25, vertically mounted, Model: ZDT-PN40-C-50/25-V | ||||||
Working principle
According to the difference of inductive main flow, main valve disc check cone of automatic recirculation valve will automatically move to a certain position. At the same time the main valve disc drive bypass valve stem, transfer the movement of main valve disc to bypass, through control bypass valve disc position, change bypass throttling area, so as to control bypass flow. When main valve disc back into valve seat closed, all flow backflow through bypass. When mian valve disc to rise to top position, bypass is fully closed, all the flow of pump flow to process system. This valve set four functions in one body.
- Flow perception: automatic recirculation valve main valve disc can automatically perceive main flow of process system, thereby according to the flow to determine position of mian valve disc and bypass disc.
- Recirculation control: automatic recirculation valve can inhaled pump normal operation required minimum flow into storage device through bypass, so as to adjust pump H – Q characteristics, to realize recycling.
- Bypass multistage pressure reducing: bypass control system can reduced the backflow medium from high-pressure pump outlet to appropriate backflow to low-pressure storage device with low noise and small wear.
- Check: automatic recirculation valve also has check valve effect, preventing the liquid backflow to pump body. Bypass non-return function is optional.
- Special bypass size can be customized. The max flow rate of bypass is subject to the max Kv value.
Size
| Valve size | mm | 25 | 32 | 40 | 50 | 65 | 80 | 100 | 125 | 150 | 200 | 250 | 300 |
| in | 1 | 11/4 | 11/2 | 2 | 21/2 | 3 | 4 | 5 | 6 | 8 | 10 | 12 | |
| Max main flow | m3/h | 12 | 28 | 30 | 50 | 100 | 114 | 200 | 400 | 455 | 750 | 1250 | 1650 |
| Bypass size | mm | 15 | 20 | 20 | 25 | 40 | 40 | 50 | 80 | 80 | 100 | 100 | 150 |
| in | 1/2 | 3/4 | 3/4 | 1 | 11/2 | 11/2 | 2 | 3 | 3 | 4 | 4 | 6 | |
| Max bypass Kv | Cv | 2.3 | 4.6 | 4.6 | 6.9 | 18.5 | 18.5 | 34.7 | 69.3 | 69.3 | 116 | 116 | 170 |
Note: Valve mian ouelet size depends on the outlet size of pump.
Note
Other bypass size can be made according to client’s requirements, maximum bypass flow depends on maximum Kv value.
Installation
Automatic recirculation valve should be installed nearby the centrifugal pump need Protect as soon as possible, and be better to install the outlet of pump.
Distance between pump outlet and inlet should not exceed 1.5 meters, in order to preventing from liquid pulsing cause low-frequency water attack. Medium flows from top to bottom. Priority should be installed vertically, also can be installed horizontally.
Maintenance
Maintenance and installation according manual provided, inspect the pump weekly in routine, and at the same time inspect valve functions.
Main parts and out form dimension
| NO | Name | Material | NO | Name | Material | ||
| 1 | Body | WCB | CF8 | 11 | O ring | EPDM | EPDM |
| 2 | Recycle disc | 2Cr13 | 304 | 12 | Stud bolt | 45 | 0Cr18Ni9 |
| 3 | Recycle seat | 2Cr13 | 304 | 13 | Hex nut | 35 | 0Cr18Ni9 |
| 4 | Screw gland | 2Cr13 | 304 | 14 | Bonnet | WCB | CF8 |
| 5 | O ring | EPDM | EPDM | 15 | Guide block | 2Cr13 | 304 |
| 6 | Main disc | 2Cr13+STL | 304+STL | 16 | Bushing | 2Cr13 | 304 |
| 7 | O ring | EPDM | EPDM | 17 | Porous set | 2Cr13 | 304 |
| 8 | Gasket | 2Cr13 | 304 | 18 | End ring | 2Cr13 | 304 |
| 9 | Hexagon nut | 304 | 304 | 19 | Spring 2 | 60Si2Mn | 1Cr18Ni9Ti |
| 10 | Spring | 60Si2Mn | 1Cr18Ni9Ti | ||||
Dimension and weight
| Valve specification DNP DNR |
Size mm（in） | Bypass | Weight Kg | |||
| PN10/16/25 150lbs |
PN40/64 300lbs |
|||||
| S | H | L | （DNB） | |||
| 25（ 1″） | 115 | 102 | 267 | 15 | 12 | 18 |
| 32（ 11/4″） | 115 | 102 | 267 | 20 | 14 | 20 |
| 40（ 11/2″） | 115 | 102 | 267 | 20 | 14 | 20 |
| 50（ 2″） | 130 | 108 | 305 | 25 | 22 | 26 |
| 65（ 21/2″） | 165 | 127 | 381 | 40 | 46 | 51 |
| 80（ 3″） | 181 | 127 | 381 | 40 | 46 | 51 |
| 100（ 4″） | 209 | 159 | 495 | 50 | 105 | 118 |
| 125（ 5″） | 267 | 220 | 575 | 80 | 143 | 156 |
| 150（ 6″） | 267 | 220 | 575 | 80 | 220 | 240 |
| 200（ 8″） | 300 | 220 | 600 | 100 | 255 | 302 |
| 250（ 10″） | 356 | 305 | 780 | 100 | 400 | 455 |
| 300（ 12″） | 530 | 280 | 830 | 150 | 590 | 650 |
Since product innovation and technical innovation or some special requirements, various valve connecting size may change, please contact Datian Valve technical department to get the latest product information.