The reducing valve structural classification
Reducing valve according to structural form can be divided into diaphragm type, spring-diaphragm type, piston type, lever type and bellows type; according to seat number could be devided into single-seat type and double-seat type; according to disc different positions can be divided into positive effect type and negative effect type.
| No. | name | working principles |
| 1 | direct-acting diaphragm reducing valve | outlet pressure increases, diaphragm moves upward, the valve opening decreases, flow rate increases, pressure drop increases, back pressure reduces, the outlet pressure drop decreases. diaphragm moves downward, valve opening increases, flow rate decreases, pressure drop reduces, back pressure increases. the outlet pressure after valve is always maintained by the constant pressure of setting regulating screw. |
| 2 | direct-acting bellows reducing valve | outlet pressure increases, bellows moves upward, the valve opening decreases, flow rate increases, pressure drop increases, back pressure reduces, the outlet pressure drop decreases. Bellows moves downward, valve opening increases, flow rate decreases, pressure drop reduces, back pressure increases. the outlet pressure after valve is always maintained by the constant pressure of setting regulating screw. |
| 3 | pilot piston reducing valve | twisting regulative screws, open pilot disc, medium enters into the top of piston from the inlet side, due to piston area is larger than main disc area, promoting the piston moves down, makes main valve opened, by back pressure balanced regulating spring pressure to change pilot opening degree, thereby changing pressure above the piston, controlling main disc opening, makes the back pressure maintain a constant value. |
| 4 | pilot diaphragm reducing valve | the working principle is the same with aboved. diaphragm upper cavity pressure is controlled by bypass regulating valve |
| 5 | pilot diaphragm reducing valve | When the adjustable spring is in a free state, main valve and pilot valve are closed. Handwheel clockwise, pilot valve diaphragm downward to push the pilot valve, the medium flows to the top of main diaphragm through the pilot valve, thereby promoting main valve, makes main valve opened, media flows outlet, and enter into the below pilot diaphragm, outlet pressure up to the balance with spring force. Such as the outlet pressure increases, pilot diaphragm moves up, pilot valve opening degree decreases. At the same time the medium flow rate decreases below main diaphragm, pressure drops, oulet pressure reduces to a new balance, and vice versa |
| 6 | Modular reducing valve | reducing valve is composed by main valve, pilot valve, globe valve. When adjustable spring is in a free state, main valve and pilot valve closed. Twisting adjustable screw, media push pilot valve, while entering into main valve rubber diaphragm chamber 1 and keep balance with adjustable spring pressure, entering into main valve rubber diaphragm chamber 2, makes rubber diaphragm upwards, main valve opens, media flow to the outlet (At this point globe valve is opened to maintain a certain pressure of chamber 2). Outlet medium then feeds back to the rubber diaphragm upper chamber 3 and pilot below chamber 4 when the outlet pressure increases, the pilot diaphragm upward, pilot opening reduces to chamber 1 medium pressure drops, while chamber 2 pressure drops, main valve rubber diaphragm moves down, main valve opening decreases, outlet pressure drops to reach a new balance; and vice versa |
| 7 | lever reducing valve | the reducing valve through lever heavy hammer balancing pressure. The acting principle: When the lever is in a free state, the double-seat disc and valve seat are in closed state. Under the inlet pressure effect, push the disc upward, the outlet end forms pressure, through the balance of lever heavy hammer, adjusting important convey to the desired outlet pressure. When the outlet pressure exceeds given pressure, due to media pressure force on the upper seat is larger than on the below seat, forming a certain pressure, makes disc moving down, reducing throttling area, outlet pressure has declined to reach a new balance; and vice versa |
| 8 | pilot bellows reducing valve | Structural principles are the same with the pilot piston reducing valve |
