The bonnet, which containing the moving parts, is attached to the body, usually with bolts, to permit maintenance. restriction is desired. Split wedge is self-adjusting and selfaligning to both seats sides. This happens, because the stem is threaded and mated with the bushing threads of a Yoke. In split-wedge gate valves (Fig. For a valve of the Rising Stem type, the stem will rise above the handwheel if the valve is opened. As such it is most susceptible to leakage. Seat ring construction provides seats which are either threaded into position or are pressed into position and seal welded to the valve body. This is particularly important where motors are used for opening and closing the valve. h�b```��&~�g`f`�s s�ve�\x��/y. Gate valves … Gate valves are general service valves primarily used for on/off, non-throttling service. �s�4#�0 Ut7J Gate Valves. Solid-wedge gate valves are considered the most economical. This type is preferred where the body seats might be distorted due to pipeline strain. The latter form of construction is recommended for higher temperature service. Almost all small, NPS 2 (DN 50) and smaller, gate valves are solid-wedge gate valves. | For rising-stem valves (gate and globe valves), the thrust needed to operate the valve … ), ( 3.1 MOV Functional Margin. Sometimes in high-temperature applications, the flow medium, such as water or steam, is trapped in the valve bonnet area when the valve is closed for system shutdown. Like the double-disc or parallel-seated gate valve, its disc seats against the downstream seat, depending on the flow direction. 2 G: Parallel-seat gate valve showing welded construction for high-temperature service with welded-in seat ring, Fig. A third type of gate valve, called conduit valve, is shown in Fig. In the open position, the wedge is completely out of the flow stream.

As the handwheel on the stem is rotated, the disk travels up or down the stem on the threads while the stem remains vertically stationary. Integral seats provide a seat of the same material of construction as the valve body while the pressed-in or threaded-in seats permit variation.

Pressure binding may not occur if the leakage past the upstream seat is 47 ;�7�����*��$vT$=u|"��"�2�{*{�G�`GCGD�x 8q� v ��B`� >3�iN�Jڝ�9%����b��`η��A�8i�T���� %%EOF endstream endobj 323 0 obj <>/Metadata 30 0 R/PageLayout/OneColumn/Pages 318 0 R/StructTreeRoot 41 0 R/Type/Catalog>> endobj 324 0 obj <>/ExtGState<>/Font<>/XObject<>>>/Rotate 0/StructParents 0/Type/Page>> endobj 325 0 obj <>stream 79 An evaluation of the operation of a motor-operated gate valve begins with two simple questions. A hollow wedge is a variation of solid wedge with the exception of a hole in the center. | The stem is threaded into the disk. There are four types of wedges: solid, hollow, split, and flexible wedge. It does not compensate for changes in seat alignment due to pipe end loads or thermal fluctuations.

), ( ), ( ), ( The typical applications of conduit valves include dirty river water with suspended solids or water with sludge or debris. © 2011 In the double-disc parallel-seat valves (Figs. Gate valves are bidirectional and therefore they can be used in two directions, Pressure loss through the valve is minimal, Gate valves are not suitable for regulate or throttle flow, They are sensitive to vibration in the open state. | The major advantage of this type is that the disc cannot be jammed into the body, an action that might make it difficult to open the valve. ), ( Stress Theory. PIPING GUIDE

The following are some of the disadvantages of gate valves that must be considered when selecting a gate valve for an application: Gate valves consist of three major components: Two basic types of gate valves are the manufactured-wedge type and the double-disc type, and there are several variations within each of these types. ), ( ), ( For a valve of the non Rising Stem type, there is no upward stem movement if the valve is opened. Ankit �hX��D�ф�D�z5��*�!$�{쨔S���5ph�C����sڻJɏlQ�?�׫�2[�A����ܶ����4�z��t�U?�����e�����SZguN'��[�����_M�&�E���缘�k�uD?��L0C��lVF:\�u��z~8S*�61�l�Gkf�b��n\,�\���j����:[*����oӳ�j1��=�7y=��BQu� 2�ѫ:[�^9[�ѴΗ_�]�)}�X׫ ��V"��ub������d5-��/�^Y�{Xl�z0�6pd�;pM�K�zDJ���{�x�p�G����z0&&�R"C-QJW����������:��0�+�]�[����'��;�Ʈn�9� E�X_ܣ-��f}�����R���&AQ*�� ��5���v�{g�1 T6�m��D���U��Qwa�d�bKR��0�K�8�� C�v2���:F�i�f�:[�db��5�@�Y�o�ڊ C: Non-rising stem gate valve for 250-psig steam service, Fig. ( The non-rising stem type (Fig. The valves that do not permit this trapped liquid or the condensate to reenter the piping either upstream or downstream may experience excessive pressures.

This valve shall be opened during start up. the operating threads are out of direct contact with the fluid or gas. Solid wedge is the most commonly used disk by its simplicity and strength. The stem, which connects the handwheel and disk with each other, is responsible for the proper positioning of the disk. 12 endstream endobj startxref D: Valve – Inside of the body is the valve.

C). 322 0 obj <> endobj A. ), ( ), ( A Gate valve can be used for a wide range of liquids and provides a tight seal when closed. 1. However, it is generally preferred because the position of the stem indicates at once whether the valve is open or closed. The design of the wastegate body and valve determine the … I: A hole on the upstream side of wedge to release built-up pressure in bonnet cavity. ), Fig. Flexible wedge is a one-piece disc with a cut around the perimeter to improve the ability to correct mistakes or changes in the angle between the seats. In service, these valves generally are either fully open or fully closed. B: Rising-stem solid-wedge gate valve for 250-psig steam service, Fig.

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