Basic Knowledge of Sanitary-grade Directional Control Valves

Sanitary-grade directional control valves are directional control valves with more than two flow paths and more than two ports. They are valves used to control the communication, shut-off, and reversal of hydraulic fluid flow, as well as pressure relief and sequential action control. They are directional control valves that rely on the relative movement of the valve core and the valve body. There are two types: rotary valve type and spool valve type. They are classified by the number of working positions the valve core stays in within the valve body (two-position, three-position, etc.); and by the number of oil passages connected to the valve body (two-way, three-way, four-way, and six-way, etc.). The methods of operating the valve core include manual, mechanical, electric, hydraulic, and electro-hydraulic types.

Directional control valves, also known as reversing valves, are a type of valve with multi-directional adjustable channels that can change the direction of fluid flow as needed. They can be divided into manual directional control valves, electromagnetic directional control valves, and electro-hydraulic directional control valves.

During operation, the external drive mechanism rotates the drive shaft, which drives the rocker arm, activating the valve plate. This causes the working fluid to flow from the left inlet to the lower outlet of the valve at one time, and then from the right inlet to the lower outlet at another time, achieving the purpose of periodically changing the flow direction.

This type of reversing valve is widely used in petroleum and chemical production, and is commonly used in synthetic ammonia gas production systems. In addition, directional control valves can also be made in a valve disc structure, which is mostly used in applications with smaller flow rates. During operation, the direction of the working fluid flow is changed simply by rotating the handwheel through the valve disc.

Sanitary-grade directional control valves mainly consist of a valve body, sealing components, cam, valve stem, handle, and valve cover (Figure 1). The valve is driven by the handle, which rotates the valve stem and cam. The cam has the function of positioning, driving, and locking the opening and closing of the sealing components. When the handle is rotated counterclockwise, the two sets of sealing components close the two lower channels under the action of the cam, and the two upper channels are connected to the inlet of the pipeline system. Conversely, the two upper channels are closed, and the two lower channels are connected to the inlet of the pipeline system, achieving non-stop flow reversal.