German Knoll valves Knoll models Knoll prices

Knoll valves, also known as globe valves, are forced-seal valves. Therefore, when the valve is closed, pressure must be applied to the disc to force the sealing surfaces to prevent leakage. When the medium enters the valve from below the disc, the resistance that the operating force must overcome is the friction between the valve stem and the packing plus the thrust generated by the medium pressure. The force required to close the valve is greater than the force required to open it, so the valve stem diameter must be large; otherwise, the valve stem may bend. According to the connection method, they are divided into three types: flange connection, threaded connection, and welded connection. Since the advent of self-sealing valves, the medium flow direction of globe valves has changed to enter the valve cavity from above the disc. In this case, under the action of medium pressure, the force to close the valve is small, while the force to open the valve is large, and the valve stem diameter can be correspondingly reduced. At the same time, under the action of the medium, this type of valve is also tighter. China's valve "Three Modernizations" once stipulated that the flow direction of globe valves must always be from top to bottom. When a globe valve is opened, the opening height of the disc is 25% to 30% of the nominal diameter, at which point the flow rate has reached its maximum, indicating that the valve has reached the fully open position. Therefore, the fully open position of a globe valve should be determined by the travel of the disc.

Knoll valve working principle and characteristics

Valves play an important role in cutting off and throttling the medium in the pipeline where they are located. As an extremely important type of shut-off valve, the globe valve achieves sealing by applying torque to the valve stem, which axially applies pressure to the disc, causing the disc sealing surface to fit tightly against the seat sealing surface, preventing the medium from leaking through the gap between the sealing surfaces. The sealing pair of a globe valve consists of the disc sealing surface and the seat sealing surface. The valve stem drives the disc to move vertically along the centerline of the seat. During the opening and closing process of a globe valve, the opening height is small, making it easy to regulate flow. It is also convenient to manufacture and maintain, and has a wide pressure application range.

Knoll valve specification precautions

Acceptance follows HG 20202-2000 "Code for Construction and Acceptance of Degreasing Engineering Projects". Before assembly, each component is wiped with clean precision filter paper. Choosing dead corners of the components, if the filter paper does not change color, it is considered qualified. 1) The valve model should indicate the required national standard number. If it is an enterprise standard, relevant explanations of the model should be provided. 2) Valve working pressure: it is required to be ≥ the working pressure of the pipeline. Without affecting the price, the working pressure the valve can withstand should be greater than the actual working pressure of the pipeline. 3) Valve manufacturing standards: the national standard number relied upon should be specified. If it is an enterprise standard, enterprise documents should be attached to the procurement contract.

Knoll valve classification

1) Straight-through globe valve 2) Y-pattern globe valve: In Y-pattern or Y-pattern globe valves, the flow channel of the valve body forms an oblique line with the main flow channel. This results in less disruption of the flow state compared to conventional globe valves, and thus the pressure loss through the valve is correspondingly smaller. 3) Angle globe valve: In angle globe valves, the fluid only needs to change direction once, so the pressure drop through this valve is smaller than that of conventional structure globe valves. American standard bellows globe valve ZDAJ41W type stainless steel valve body American standard bellows globe valve ZDAJ41W type stainless steel valve body 4) Plunger globe valve: This form of globe valve is a variant of the conventional globe valve. In this valve, the disc and seat are usually designed based on the plunger principle. The disc is polished into a plunger and connected to the valve stem. Sealing is achieved by two elastic sealing rings sleeved on the plunger. The two elastic sealing rings are separated by a collar, and the sealing rings around the plunger are pressed firmly by the load applied to the bonnet via the bonnet nuts. The elastic sealing rings can be replaced and can be made from various materials. This valve is mainly used for "open" or "close" functions, but with specially shaped plungers or special collars, it can also be used for flow regulation.

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