1.Rising stem gate valve:
when the stem nut is on the bonnet or bracket and the gate is opened and closed, the stem can be lifted and lowered by rotating the stem nut.
This kind of structure is advantageous to the lubrication of the valve rod, and the opening and closing degree is obvious, so it is widely used.
The advantages of rising stem gate valve are:
◆ the fluid resistance is small, and the sealing surface is scoured and eroded by medium is small.
◆ opening and closing are labor-saving.
◆ the flow direction of medium is not limited, does not disturb the flow and does not reduce the pressure.
◆ simple shape, short structure length, good manufacturing technology and wide application range.
The disadvantages of rising stem gate valve are:
◆ it is easy to cause erosion and abrasion between sealing surfaces, so it is difficult to maintain.
◆ the overall dimension is large, opening requires a certain space, and the opening and closing time is long.
2. Non-rising stem gate valve:
the stem nut is in the valve body and directly contacts with the medium. When opening and closing the ram, it is realized by rotating the valve rod.
The advantage of this structure is that the height of the gate valve is always the same, so the installation space is small, which is suitable for the gate valve with large diameter or limited installation space. The structure shall be equipped with an opening and closing indicator to indicate the opening and closing degree.
The disadvantage of this structure is that the stem thread is not only unable to be lubricated, but also directly eroded by the medium and easy to be damaged.
◆ the structure is complex.
