Gate valves are characterized as having either a rising or a non-rising stem. Rising stems provide a visual indication of valve position because the stem is attached to the gate such that the gate and stem rise and lower together as the valve is operated. Non-rising stem valves may have a pointer threaded onto the upper end of the stem to indicate valve position, since the gate travels up or down the stem on the threads without raising or lowering the stem. Non-rising stems are used underground or where vertical space is limited.
1. Full port
2. Outside screw and yoke
3. Bolted bonnet
4. Flexible wedge, fully guided integrated seats
5. Rising stem and non-rising hand-wheel
6. Tongue and groove between body and bonnet
1. Gate valves API 600
2. Steel valves ANSI B16.34
3. Face to face ANSI B16.10
4. End flanges ANSI B16.5
5. Butt weld ends ANSI B16.25
6. Inspection and test API 598
The construction of steel gate valves of MSA corresponds to API 600 and BS 1414. Gate valves are yoke, flange or welded with unnarrow flow rate and with flexible or fixed wedge. Bodies, covers and yokes are cast. Wedges could be forged or cast. All wedges are guided. Sealing seats are bolted or welded into the body. Overlays in seats depends on Trim. Valves have rising non-rotative spindle and bolted joint of body-cover. Standard spindle threads are ACME2G-LH.
Operation with a handwheel. On the basis of mutual agreement, the gate valves can be operated by angle transmission, electric actuator or pneumatic actuator. For easier control the gate valve with larger diameters are equipped with bearings. Sealing material is pressed rings from expanded graphite and graphite plaited rings. The properties of gate valve packing meet the requirements of the directive Clean Air Act, Amendment from 1990. The gate valves can be also equipped with: drainage, venting, relief from inter-space and bypasses, on the special customer´s request.
The dimensions of standard design are stated in the table below.
The gate valves are supplied in different material variants.
The yoke gate valve can be assembled in any position into the pipeline.
The gate valves are subjected to pressure tests according to the standard API 598: on strength and tightness, tightness of backseat, closure tightness by low pressure, closure tightness by high pressure (on request).