Three designs of Gate Valve Stem
Three different bonnet/stem design configurations are used in the gate valve construction: the lower threaded rising stem, the non-rising stem and the upper threaded bracket.
The lower threaded lift bonnet/stem design is the most commonly used design for today's bronze valves. Because the stem threads are exposed to the process medium, potential corrosion damage can cause valve stems and gates to fail. The lower threaded lift design is not suitable for critical industrial applications.
The non-lifting stem type is a special type of vertical space used above the handwheel for restricted use.
This is because the non-lifting stem valve cannot rise when the valve is open. Today, most non-lifting stem valves are made of iron or bronze. Space-tight applications (such as underground operations) use steel non-lifting stem gate valves.
Industrially, the valve stem/bonnet design with threaded brackets is often used. Especially in corrosive environments, because the threads are far from the contaminated area of the medium, they are far from potential corrosion. This structure is also different from other designs in which the hand wheel is connected to the bushing at the top of the valve bracket, rather than directly to the valve stem itself, so the hand wheel does not rise as it opens.
There are also knife and slide valves in the gate valve family. Knife gate valves without bonnets are especially suitable for use in mud environments such as paper mills. The knife gate valve is very thin and only slightly wider than its closure (valve). Due to the unique geometry and thin cross section of the knife gate valve, it is limited to low pressure applications.
In appearance, the slide valve is not a member of the gate valve family, but based on the design of the slide valve, it has the characteristics of a gate valve. The slide valve is limited to very low pressures and in many cases is limited to simple indenters, mainly used in waste water and flushing systems.
The lower threaded lift bonnet/stem design is the most commonly used design for today's bronze valves. Because the stem threads are exposed to the process medium, potential corrosion damage can cause valve stems and gates to fail. The lower threaded lift design is not suitable for critical industrial applications.
The non-lifting stem type is a special type of vertical space used above the handwheel for restricted use.
This is because the non-lifting stem valve cannot rise when the valve is open. Today, most non-lifting stem valves are made of iron or bronze. Space-tight applications (such as underground operations) use steel non-lifting stem gate valves.
Industrially, the valve stem/bonnet design with threaded brackets is often used. Especially in corrosive environments, because the threads are far from the contaminated area of the medium, they are far from potential corrosion. This structure is also different from other designs in which the hand wheel is connected to the bushing at the top of the valve bracket, rather than directly to the valve stem itself, so the hand wheel does not rise as it opens.
There are also knife and slide valves in the gate valve family. Knife gate valves without bonnets are especially suitable for use in mud environments such as paper mills. The knife gate valve is very thin and only slightly wider than its closure (valve). Due to the unique geometry and thin cross section of the knife gate valve, it is limited to low pressure applications.
In appearance, the slide valve is not a member of the gate valve family, but based on the design of the slide valve, it has the characteristics of a gate valve. The slide valve is limited to very low pressures and in many cases is limited to simple indenters, mainly used in waste water and flushing systems.
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