is preferred where space is limited and where the fluid passing through the valve will not corrode or erode the threads or leave deposits on the threads. | This is particularly important where motors are used for opening and closing the valve. Solid-wedge gate valves are considered the most economical. %%EOF A hollow wedge is a variation of solid wedge with the exception of a hole in the center. A Yoke is an integral part from a Rising Stem valve and is mounted to the Bonnet. 37 Stems are usually forged, and connected to the disk by threaded or other techniques. It is common practice to use cast iron or ductile iron solid-wedge gate valves in cold or ambient water lines.
Solid-wedge gate valves are generally used in moderate to lower pressure-temperature applications. However, it is generally preferred because the position of the stem indicates at once whether the valve is open or closed. ( Gate valves … Gate valves. In service, these valves generally are either fully open or fully closed. Pressure binding may not occur if the leakage past the upstream seat is These valves are used in pipelines where pigs are run through the piping to perform cleaning of builtup deposits or debris. 25 322 0 obj <> endobj Atom This valve shall be opened during start up. 338 0 obj <>/Filter/FlateDecode/ID[<60D703B227C74E4AAA5C34E8F1E6FBBD><1188EC1EC15E95468AA88842E2D6A12B>]/Index[322 26]/Info 321 0 R/Length 80/Prev 81216/Root 323 0 R/Size 348/Type/XRef/W[1 2 1]>>stream | This type is preferred where the body seats might be distorted due to pipeline strain. (1) Given a certain differential pressure across the disc, how much thrust (downward force) will be needed to lower the disc to close the valve? Stress Theory. 3.0 THEORY OF MOV DESIGN BASIS OPERATION . As such it is most susceptible to leakage. I: A hole on the upstream side of wedge to release built-up pressure in bonnet cavity. 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. �s�4#�0 Ut7J A. ), ( The hollow wedge travels along the stem when the threaded stem is rotated, thus opening or closing the valve port. h�bbd``b`z$[AD(�`�$�W�$ It does not compensate for changes in seat alignment due to pipe end loads or thermal fluctuations. 35 Sitemap, About Us E,F and G). Gate valves are general service valves primarily used for on/off, non-throttling service. | ), (
The non-rising stem type (Fig. Also, the non-rising stem valve is preferred for buried service. 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. This leaves an opening for flow through the valve at the same inside diameter as the pipesystem in which the valve is installed. 1.0 THEORY OF OPERATION GATE VALVES | Gate valves are designed to close off or open up the flow in a pipeline. Almost all small, NPS 2 (DN 50) and smaller, gate valves are solid-wedge gate valves. h�b```��&~�g`f`�s s�ve�\x��/y. ), ( Split-wedge or flexible-wedge type gate valves are expected to perform better than solid-wedge gate valves when thermal binding is a concern. In the main Menu "Valves" you will find links to detailed (large) drawings of both stem types. ToS ), ( A third type of gate valve, called conduit valve, is shown in Fig. 19 C).
For a valve of the Rising Stem type, the stem will rise above the handwheel if the valve is opened. the two-piece wedge disc is seated between matching tapered seats in the body. 34 %PDF-1.6 %���� ), ( For rising-stem valves (gate and globe valves), the thrust needed to operate the valve … 4 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.
restriction is desired. C: Non-rising stem gate valve for 250-psig steam service, Fig. To prevent leakage, in the area of the seal, a fine surface finish of the stem is necessary. Write For Us, Gate valves are primarily designed to serve as. 3.1 MOV Functional Margin. The solid wedge is a single-piece solid construction. ( ), Gate Valve Types, Construction, Applications and Advantages, Post Comments �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 2 Gate valves are available with different disks or wedges. In the open position, the wedge is completely out of the flow stream.
the discs are forced against the valve seats by a wedging mechanism as the stem is tightened. 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 The design of the wastegate body and valve determine the … There are four types of wedges: solid, hollow, split, and flexible wedge. 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. Non-rising stem valves are sometimes provided with an indicator for this purpose.
The valve trim consists of the stem, the gate, the disc or wedge and the seat rings. Except for NPS 2 (DN 50) and smaller, solid-wedge discs are generally not recommended for use in applications having temperatures in excess of 250 deg F (121 deg C).
6 D). In split-wedge gate valves (Fig. The disk of a Gate valve is completely removed when the valve is fully open; the disk is fully drawn up into the valve Bonnet. - Designed by Like the double-disc or parallel-seated gate valve, its disc seats against the downstream seat, depending on the flow direction. 12 following options offer solutions to this problem: ● Drill a small hole on the upstream side of the disc. Allowable Stress for Piping Materials … 85
The latter form of construction is recommended for higher temperature service. Gate valves are primarily designed to start or stop flow, and when a straight-line flow of fluid and minimum flow restriction are needed. 1. Solid wedge is the most commonly used disk by its simplicity and strength. ), 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. The stem is threaded into the disk.
133 This wedge type consists of two-piece construction which seats between the tapered seats in the valve body. Gate valves consists of three main parts: body, bonnet, and trim. A Unique blog for Oil and Gas Professionals covering topics related to Piping and Process.
This type of wedge is suitable for the treatment of non-condensing gases and liquids at normal temperatures, particularly corrosive liquids. ), ( D: Valve – Inside of the body is the valve.
G: Parallel-seat gate valve showing welded construction for high-temperature service with welded-in seat ring, Fig. Gate valves are primarily designed to start or stop flow, and when a straight-line flow of fluid and minimum flow restriction are needed. 79 ), ( h��V�o�0�W��=t��D�*+[��V Z'U}� �hI���ߝ��x��p�s_�����B$�!� ,����h\�Z� Cast steel wedged gate valve for oil and gas industry, Microbiologically Induced Corrosion (MIC), Differences between Castings and Forgings, Differences between Cast Iron and Cast Steel, Fireproofing for Petrochemical facilities, Standards defined on this website (19 pages), Dimensions Across Flats and Heights of Hex Nuts, Introduction to air-cooled heat exchangers, Image presentation Hot tapping and Line stopping, North Transgas and North European Gas Pipeline (10 Pages). H: Pressure binding caused by built-up pressure in bonnet cavity, Fig. 3