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| Standards Design and manufacture:Cast steel globe valve to BS 1873 and ASME B 16.34; Forged steel globe valve to API 602. Inspection and test: API598. End flange dimension: ASME B 16.5 BW end dimension: ASME B 16.25 Socket-weld dimension: ASME B 16.11 Face to face and end to end: ASME B 16.10 Pressure-temperature ratings: ASME B 16.34 Gasket of cover flange Stainless steel + flexible graphite wounded gasket is used for Class 150 and Class 300 globe valve. Stainless steel + flexible graphite wounded gasket is used for Class 600, and ring joint gasket is also optional for Class 600. Ring joint gasket can be used for Class 900 globe valve. Pressurized seal design is used for Class 1500-2500 globe valve. Packing seal Molded flexible graphite is used for packing material. PTFE or combined packing material can also used if it's requested by the customer. The internal surface of the stuffing box, of which area is contacted with the packing, is of excellent finish(Ra3.2 um). The stem surface, contacting with the packing, should be rolled and pressed after being precisely machined, so as to reach to the high finish and compactness (Ra0.8um) and ensure the reliable tightness of the stem area. Body and bonnet connection The body and bonnet of Classs 150-900 globe valves are usually connected with studs and nuts. The body and bonnet of Class 1500-2500 gate valves are usually of pressurized seal design. Actuation Hand wheel, impact hand wheel & gear box is usually used for globe valve's actuation. Chain wheel and electricactuator can be also used for actuation if being requested. The featrues of globe valve Bolted bonnet: outside screw and yoke; rising stems; metallic sealing surfaces. Belleville spring loaded packing impact system If being requested by customer, the belleville spring loaded packing impacting system can be adoptefor enhancing the durability and reliability of the packing seal. Back seating design All our globe valves have the back seating deign. In most cases, the carbon steel gate valve is fitted with a separate back seat. For stainless steel gate valve, the back seat is machined directly in the bonnet or is machined after welding. When the gate valve is at fully open position, the sealing of the back seat can be very reliable. However, as per the requirement of API600, it is not advisable to add or change packing by the mean of back seating when the valve is ressure containing. Seat For carbon steel globe valve, the seat is usually forged steel. The sealing surface of the seat is spray welded with hard alloy specified by the customer. Separate thread seat is used for NPS<=10" gate valve, and welded on seat can be also optional if being requested. Welded on seat is used for NPS>=12" carbon steel gate valves. For stainless steel gate valve, integral seat is usually adopted, or to weld hard alloy directly integrally. Threaded or welded on seat is also optional for stainless steel gate valve is required by the customer. Stem design The stem is of integral forged design. Stem nut Usually, the material of stem nut is ASTM A439 D2. It's also can be made of copper ally if required. For large size gate valve, rolling bearing is fitted at the two sides of the stem nut in order to minimize the open and close torgue of the gate valve. |
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