1 rising stem gate valve: valve stem nut on the valve cover or support, when you open and close the gate by rotary valve stem stem nut to achieve lift. This structure is good for lubrication of the valve stem, opening and closing significantly, so it is widely used.
2 Inside screw nonrising stem type gate valve: valve stem nut on the valve body, and direct contact with the media. When opening and closing the gate, rotate the valve stem to achieve. The advantages of this structure are: height of the gate valves always remains the same, so small installation space, suitable for large-diameter or gate valve for installation where space is limited. This kind of structure to be fitted with opening and closing indicator to indicate the degree of opening and closing. The disadvantage of this structure are: stem thread failed to lubricate, and simply accept the erosion of media and easily damaged.
The main difference:
1. dark Rod method blue gate of upgrade screw rod is only rotating and no Shang and Xia mobile, exposed of just a root rod, its nut is fixed in gate Board Shang, through screw rod of rotating to upgrade gate Board, no visible of door frame; Ming Rod method blue gate of upgrade screw rod is exposed of, nut close handwheel and is fixed of (not rotating also not axis to mobile), through rotating screw rod to upgrade gate Board, screw rod and gate Board only relative of rotating movement and no relative of axis to displacement, appearance for has door shaped bracket.
2 non-rising stem valves see screw, and screw is able to see the screw.
3. the valve of dark pole switch steering wheel and stem is connected with relatively fixed, it is through the valve stem in a fixed point to drive the valve lift and lower lock to complete opening and closing. Rising stem valve through the valve stem screw drive with the steering wheel to raise or lower the disc.