There are mainly the following types of valves commonly used in sugar factories.
1. Globe valve (ball valve, ball valve)
Because the shut-off valve can accurately adjust the flow rate and cut off the channel tightly, it is the main opening and closing device on the sugar liquid and steam pipelines, and can also be used on the pipelines of various materials such as water and gas in sugar factories.
However, when it is used in a medium with a lot of suspended matter (such as one-carbon full juice), it is easy to cause precipitation to accumulate between the valve disc and the valve seat, making the closing loose, and causing the contact surface to wear and leak. In this case, a stop valve with a rubber diaphragm can be used. The simpler method is to fix a rubber pad on the valve disc. When the valve is closed, the rubber pad is in contact with the valve seat, and the rubber pad can be replaced during maintenance. Globe valves can generally use this method.
At present, the nominal diameter of the globe valve does not exceed DN200.
The installation principle of the globe valve is that the fluid flows through the valve disc from bottom to top, so that the resistance is minimal at this time, and the opening is labor-saving. When it is closed, the stuffing box and the valve stem are usually in contact with different media.
Features of globe valve:
(1) The structure is complex and the price is more expensive;
(2) Reliable operation and not very laborious;
(3) It is easy to adjust the flow or cut off the channel;
(4) The resistance of fluid flow is relatively large;
(5) Slow opening and closing, no water hammer.
2. Gate valve (gate valve, gate valve)
Gate valves in sugar mills are widely used in larger diameter water, compressed air, vacuum, sugar liquid, and other pipelines, as well as lower pressure steam pipes; small diameter material pipelines are also commonly used, but not used for sediments. (Such as full juice filling, etc.) on the pipeline; use a gate valve on the pipeline with a diameter of more than 250 mm.
The characteristics of the gate valve are:
(1) complex structure, large size, high price;
(2) minimum hydraulic resistance;
(3) slow opening without water hammer;
(4) easy to adjust the flow rate;
(5) closing surface wear Faster, more difficult to grind.
3. Plug valve (cock valve)
The cock in the sugar factory is often used for sampling, venting, inspection, etc., and is rarely used to adjust the flow rate.
At present, the nominal diameter of the cock is 15 to 80 mm, and the nominal pressure is 10 kg/cm2.
The characteristics of the plug valve are:
(1) Simple structure;
(2) Open and close quickly;
(3) The resistance is very small;
(4) Rotation is laborious;
(5) Grinding costs and labor.
Where the plug valve is not suitable：
(1) The flow must be accurately adjusted (because the channel opens and closes quickly and unevenly);
(2) Steam or high-temperature liquid (because of thermal expansion and jamming of the pressing surface);
(3) Liquid with higher pressure (due to the water hammer phenomenon that can occur during rapid opening and closing).
4. Check valve (check valve)
In sugar factories, check valves are often used on the output pipeline of the pump, the drain pipeline of the drain, and other pipelines that do not allow the medium to flow in the opposite direction.
A check valve is a valve that automatically opens and closes according to the pressure difference of the medium before and after the valve. It prevents the liquid from flowing in the reverse direction and only flows in a certain direction. For example, pressing this valve on the pump outlet pipe can prevent the pump from stopping suddenly. , The return of materials causes spillage and other accidents.
5. Safety valve
It is a valve that automatically opens and closes according to the working pressure. When the working pressure exceeds the specified value, it automatically opens the valve disc and discharges the excess medium. When the pressure is restored, the valve disc automatically closes. Its structure is similar to an angle stop valve, but without an adjusting handwheel.
The lever hammer type is a commonly used one. Sugar mills are often used in steam drums and steam chambers.
In addition to the above-mentioned commonly used valves, the currently standardized valves for sugar factory equipment include:
(1) The bottom valve of the box is suitable for storage boxes of various materials for discharge or sewage discharge. There are three kinds of DN=40, 80, 100 (Q/TJ32-75).
(2) Seedbox discharge valve, suitable for seedbox control materials, used in normal pressure or under vacuum. There are three kinds of DN=150, 200, 250 (Q/TJ33-75).
(3) The massecuite gate of the crystallizer is used for the outlet of the crystallizer under normal pressure control. There are two specifications (length×width of the discharge port): 180×200 and 200×250 (Q/TJ34-75).
(4) Two-way valve, suitable for operation under the conditions of juice pressure Pg≤6kg/cm2 and temperature≤150℃, often used in juice heater. There are four types of DN=80, 100, 125, 150 (Q/TJ36-75).
(5) Juice steam three-way valve, used for manual valves operated under Pg≤2.5kg/cm2 or under vacuum conditions. There are DN=200, 250, 300, 350, 400, 500, 600, 700 and many other specifications (Q/TJ37-75).
(6) Juice steam valve, which is suitable for manual juice steam valve operated under vacuum conditions. It can be equipped with a sprocket for remote control. There are six specifications of DN=300, 350, 400, 500, 600, 700 (Q/TJ38-75).