CT Dental Mech v2_1

Chức năng Van Tóm tắt thông tin Các bộ phận cơ bảnCó bốn loại cơ bản của các yếu tố kiểm soát dòng chảy làm việc trong thiết kế van. 1. Di chuyển một đĩa, hoặc cắm vào hoặc chống lại một lỗ (cho ví dụ, toàn cầu, kim loại van). Trượt một bề mặt phẳng, hình trụ, hình cầu qua lỗ (ví dụ, van cổng và cắm). Xoay một đĩa hoặc hình elip về một trục kéo dài qua đường kính của lỗ (ví dụ, một van bướm hoặc bóng). Di chuyển một vật liệu linh hoạt vào việc...
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CT Dental Mech v2_1Simpo PDF Merge and Split Unregistered Version - http://www.simpopdf.com V alves DOE-HDBK-1018/2-93 VALVE FUNCTIONS AND BASIC PARTS Sum m ary The following important information in this chapter is summarized below: Valve Functions and Basic Parts Summary There are four basic types of flow control elements employed in valve design. 1. Move a disc, or plug into or against an orifice (for example, globe or needle type valve). 2. Slide a flat, cylindrical, or spherical surface across an orifice (for example, gate and plug valves). 3. Rotate a disc or ellipse about a shaft extending across the diameter of an orifice (for example, a butterfly or ball valve). 4. Move a flexible material into the flow passage (for example, diaphragm and pinch valves). Valve stem leakage is usually controlled by properly compressing the packing around the valve stem. There are seven basic parts common to most valves. Rev. 0 ME-04 Page 7Simpo PDF Merge and Split Unregistered Version - http://www.simpopdf.comT YPES OF VALVES DOE-HDBK-1018/2-93 Valves T YPES OF VALVE S Due to the various environments, system fluids, and system conditions in which flow must be controlled, a large number of valve designs have been developed. A basic understanding of the differences between the various types of valves, and how these differences affect valve function, will help ensure the proper application of each valve type during design and the proper use of each valve type during operation. E O 1.4 Given a drawing of a valve, IDENTIFY each of the following types of valves: a. Globe g. Diaphragm b. Gate h. Pinch c. Plug i. Check d. B all j. Safety/relief e. Needle k. Reducing f. Butterfly EO 1.5 DESCRIBE the application of the following types of valves: a. Globe g. Diaphragm b. Gate h. Pinch c. Plug i. Check d. B all j. Safety/relief e. Needle k. Reducing f. ButterflyG ate V alvesA g ate valve is a linear motion valve used to start or stop fluid flow; however, it does notregulate or throttle flow. The name gate is derived from the appearance of the disk in the flowstream. Figure 4 illustrates a gate valve.The disk of a gate valve is completely removed from the flow stream when the valve is fullyopen. This characteristic offers virtually no resistance to flow when the valve is open. Hence,there is little pressure drop across an open gate valve.When the valve is fully closed, a disk-to-seal ring contact surface exists for 360°, and goodsealing is provided. With the proper mating of a disk to the seal ring, very little or no leakageoccurs across the disk when the gate valve is closed.ME-04 Rev. 0 Page 8Simpo PDF Merge and Split Unregistered Version - http://www.simpopdf.com V alves DOE-HDBK-1018/2-93 TYPES OF VALVES Figure 4 Gate Valve Rev. 0 ME-04 Page 9Simpo PDF Merge and Split Unregistered Version - http://www.simpopdf.comT YPES OF VALVES DOE-HDBK-1018/2-93 ValvesOn opening the gate valve, the flow path is enlarged in a highly nonlinear manner with respectto percent of opening. This means that flow rate does not change evenly with stem travel.Also, a partially open gate disk tends to vibrate from the fluid flow. Most of the flow changeoccurs near shutoff with a relatively high fluid velocity causing disk and seat wear and eventualleakage if used to regulate flow. For these reasons, gate valves are not used to regulate orthrottle flow.A gate valve can be used for a wide variety of fluids and provides a tight seal when closed. Themajor disadvantages to the use of a gate valve are: It is not suitable for throttling applications. It is prone to vibration in the partially open state. It is more subject to seat and disk wear than a globe valve. Repairs, such as lapping and grinding, are generally more difficult to accomplish.G ate V alve D isk D e s ignGate valves are available with a variety of disks. Classification of gate valves is usually madeby the type disk used: solid wedge, flexible wedge, split wedge, or parallel disk.Solid wedges, flexible wedges, and split wedges are used in valves having inclined seats. Paralleldisks are used in valves having parallel seats.Regardless of the style of wedge or disk used, the disk is usually replaceable. In ser ...