There are many types of valves with a wide range of applications in pipelines. Sometimes they serve as primary equipment, playing a controlling role, while other times they act as auxiliary equipment. Improper use can lead to issues like leakage, which can affect production or even cause accidents. Therefore, understanding and correctly using valves is crucial.

Valves used in heating systems come in various types, including gate valves, globe valves, ball valves, butterfly valves, check valves, safety valves, regulating balance valves, and self-operated balance valves. Below, we will introduce each of them.

Working principle: The sealing surface of the gate and the seat is highly smooth, flat, and consistent, forming a very tight seal. The gate controls the flow of the medium by lifting or pressing down on the valve stem. It functions to shut off the flow in the pipeline.

Advantages: Low fluid resistance; the sealing surface is not eroded when fully open; can be used for bidirectional flow without directionality; sturdy and durable; suitable for both small and large valves.

Disadvantages: Large height; long opening and closing time, heavy, difficult to repair, manual operation of large-diameter gate valves requires significant effort. Gate valves are classified into rising stem and non-rising stem types based on the type of valve stem; parallel and wedge types based on the gate structure; and single gate and double gate types. In heating engineering, commonly used types include rising stem wedge single gate gate valves and non-rising stem wedge single gate gate valves, with the former installed on the primary side of the thermal station and the latter on the secondary side. They generally serve two purposes: as the main equipment to control the flow and as auxiliary equipment for maintenance. When installing gate valves, avoid placing the handwheel below the horizontal line (inverted), as this can cause the medium to remain in the valve cover for extended periods, leading to corrosion of the valve stem. Gate valves were once the mainstay of valves in heating engineering. Now, with the widespread adoption of butterfly valves, gate valves have been replaced by butterfly valves.

Globe Valve

Working principle: Similar to the gate valve, the closing member (valve disc) moves along the centerline of the seat. It shuts off the flow in the pipeline and can roughly adjust the flow rate.

Advantages: Easy to manufacture, convenient to maintain, sturdy and durable.

Disadvantages: Only allows unidirectional flow of medium, directional during installation. High flow resistance, poor sealing. Classified based on structure into straight-through, right-angle, straight-flow, and balance types. Flanged straight-through and internal thread straight-through types are commonly used in engineering. Globe valves are directional and should not be installed upside down.

In daily life, direct-through and small-diameter globe valves were commonly used in the past, but they have gradually been replaced by ball valves.

Ball valves

Ball valves, compared to gate valves and globe valves, are a new type of valve that is gradually being widely adopted. Its working principle is as follows: the valve core is a spherical body with a through hole, controlled by the valve stem to rotate 90°, allowing the valve to open or close. It functions to shut off the flow in the pipeline.

Advantages: In addition to the advantages of gate valves and globe valves, ball valves are also compact, have excellent sealing (zero leakage), and are easy to operate. They are currently widely used in sectors such as petrochemicals, power generation, nuclear energy, aerospace, and aviation.

Disadvantages: Difficult to maintain.

Ball valves come in two forms: floating ball and fixed ball. In heating engineering, at critical locations such as important branches and connections to thermal stations with DN250 and below, the valve body is integral and welded, resulting in fewer failure points. Due to its sealing performance and operational reliability, ball valves have long been favored by users. Ball valves have no directional restrictions and can be installed at any angle. When horizontally installed, the valve must be open to avoid electric sparks during welding and damage to the ball surface; when installed on vertical pipelines, if welding on the upper interface, the valve must be open, and if welding on the lower interface, the valve must be closed to prevent internal damage from high heat.

Butterfly valves

Working principle: The valve disc is a circular disc, which rotates through the valve stem, allowing the valve disc to rotate 90° within the valve seat range to open or close the valve. It functions to shut off the flow in the pipeline and can also regulate flow.

Advantages: Simple structure, lightweight, easy to operate, good sealing.

Disadvantages: When fully open, the valve disc (sealing ring) is subjected to erosion from the medium. In heating engineering, butterfly valves used include triple eccentric metal-sealed butterfly valves and rubber-sealed butterfly valves.