Flexible Wedge Gate Valve

Standard and Scope:

Size: NPS 1/2"～56" DN15～DN1400                           
Pressure Rating: Class 150～2500 PN2.5~PN160               
Connection: Flaged,Butt weld,Socket weld(RF, BW, RTJ,SW and so on)
Material: Carbon steel,Stainless steel, Alloy, Duplex (CS, SS, ALLOY and so on)
Design and Manufacture: API 600(Cast steel gate valve), ISO10434, BS1414, ASME B16.34, API603(cast stainless steel); DIN3352, BS EN1984
Test and Inspection: API600, API598, API6D; ISO 5208, BS6755, DIN3230, BS EN12569
Pressure-temperature ratings:ASME B16.34.
Face-to-Face: ASME B16.10, BS EN558, DIN 3202
End Connection: ASME B16. 5（for NPS≤24）; ASME B16.47 series B、API 605 or ASME    B16.47 series A、MSS SP-44（for NPS＞24）; BS EN1092-1, DIN2543,DIN2544, DIN2545, DIN2546   
BW End connection: ASME B16.25

Design feature:

Design of Disc, solid wedge or flexible wedge
Gate Valves with NPS ≥ 2 are usually of flexible wedge gate for better seal performance and cost reason;
Gate valves with NPS < 2 are of solid wedge gate, Gate Valve with high pressure and big size can also be solid wedge if required.

Stem(shaft) type, Rising or Non-rising, integral forged steel, quenched and tempered with surface nitriding Treament
Gate valves are characterized as having either a rising (outside screw and yoke) or a non-rising stem. Rising stems provide a visual indication of valve position but require bigger installation space. Non-rising stems gate valve are used where vertical space is limited or underground.                                        

The stem is integral forged design, welding fabricated is not allowed. Stem and disc is connected in “T” type, The strength of the connecting area is higher than that of the T threaded part of the stem. Min diameter of shaft should be as per relevant standard to keep enough strength
The shaft is quenched and tempered, and its surface is treated by nitriding treatment, thus it has good corrosion resistant and friction resistant.

Shaft Nut
Usually, the shaft nut is made of copper alloy or ASTM A439 D2. For large sized gate valves (NPS 10 for Class 150, NPS 8 for Class 300, NPS 6 for Class 600, NPS 5 for Class 900), a roller bearing is fitted underside of the stem nut in order to minimize the opening and closing torque of the gate valve.

Body and Bonnet Connection, studs and nuts or pressure seal
The body and bonnet of Class150～Class900 wedge gate valves are usually connected with studs and nuts. And the body and bonnet of Class1500～Class2500 gate valves are usually of pressure seal design. But if required, pressure seal can be also available for class600 or class900.

Gasket of Cover Flange
Usually Carbon steel or stainless steel + flexible graphite combined gasket is used for Class150 gate valve; Stainless steel + flexiblegraphite wounded gasket is used for Class 300 gate valve; Stainless steel + flexible graphite wounded gasket is used for Class600 gate valve, and ring joint gasket is also optional forClass600 gate valve; Ring Joint gasket is used for Class 900 gate valve; Pressurized seal design is used for Class1500 ～Class500 gate valve.

Seat
For carbon steel gate valve, the seat is usually forged steel.The sealing surface of the seat is spray welded with hard alloy specified by the customer. Renewable threaded seat is used for NPS ≤ 10 gate valves, and welded on seat can be also optional if being requested by the customer. Welded on seat is used for NPS ≤10 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 if being requestedby the customer.

Back Seat
All Sangong Gate valves have a back seating design. In most cases, the carbon steel gate valve is fitted with a renewable back seat while 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 is very reliable. However, as per API 600, the packing shall not be added or changed by the mean of back seating when the valve is Pressure containing.

Packing Seal
Molded flexible graphite is used for packing material. PTFE or combined packing material can be also used if required. The internal surface of the stuffing box, of which area is contacted with the packing, is of excellent finish (Ra3.2μm). The shaft surface, contacting with the packing, should be rolled and pressed after being precisely machined, so as to reach to the high finish and compactness (Ra0.8μm) and ensure the reliable tightness of the stem area.

Operation
Hand wheel or gearbox are usually applied, if required, chain wheel, impact wheel is also available. Top flange dimension as per ISO 5211, electric, pneumatic is also available if required.

Other Special Gate Valve

Besides the normal wedge gate valves, Sangong also offer Extension Stem Gate Valve, Cryogenic Gate Valve, Jacketed Gate Valve, and Bellow Sealed Gate Valve for many kinds of application.

The above information is for reference only, Sangong keeps right to amend without notice.