What exactly is the difference between a globe valve and a gate valve?

Valve is a fluid delivery system in the control components, with a cut-off, regulation, infusion, to prevent backflow, pressure regulation, shunt or overflow pressure relief and other functions. Valves for fluid control systems, from the simplest globe valve to the extremely complex self-control system used in a variety of valves, its varieties and specifications are quite numerous.

Globe valves, gate valves, butterfly valves, check valves and ball valves, etc. These valves are now indispensable control components in a variety of piping systems. Each kind of valve whether in appearance, structure and even functional use are different. But the shut-off valve and gate valve in appearance have some similarities, at the same time have in the pipeline to do the function of the cut-off, so there will be a lot of contact with the valve not many friends will be confused with the two. In fact, if you look closely, globe valves and gate valves are quite different.

1. Structure

Installation space is limited in the case of selection to be noted. Gate valve can rely on media pressure tight and sealing surface tightly closed, so as to achieve the effect of non-leakage. When opening and closing the spool and seat sealing surface is always in contact with each other and friction, so the sealing surface is easy to wear, the gate valve is close to closing, the pipeline before and after the pressure difference is very large, so that the sealing surface wear is more serious.

2. working principle

Globe valve in the opening and closing, is the rising stem type, that is to say, turn the handwheel, the handwheel will follow the valve stem with the rotation and lifting movement. The gate valve is to rotate the handwheel, so that the valve stem to do lifting movement, the position of the handwheel itself is unchanged. The flow rate is different, the gate valve requires full open or full closed, while the globe valve does not need. Globe valves have provisions for inlet and outlet direction; gate valves do not have import and export direction requirements.

In addition, the gate valve only fully open or fully closed two states, the gate opening and closing stroke is very large, opening and closing time is long. Globe valve valve plate movement stroke is much smaller, and the valve plate of the globe valve can be stopped at a certain place in the movement, to do flow regulation. The gate valve can only be used to do cut-off, no other function.

Gate valve structure will be more complex than the globe valve, from the appearance, the same diameter, gate valve is higher than the globe valve, globe valve is longer than the gate valve. In addition, the gate valve also has an open stem and concealed stem. Globe valve does not.

3. Performance differences

Globe valve can be used as both cut-off, can be used to do flow regulation. Globe valve fluid resistance is relatively large, opening and closing more effort, but because the valve plate from the sealing surface of the short distance, so the opening and closing stroke is short.

Gate valve can only be fully open and fully closed, it is fully open, the valve channel in the medium flow resistance is almost 0, so the gate valve opening and closing will be very energy-saving, but the distance from the sealing surface of the gate is far, opening and closing time is long.

4. Installation and flow direction

Gate valve flow in both directions have the same effect, the installation of no import and export direction requirements, the media can flow in both directions. Globe valve needs to be installed in strict accordance with the direction of the valve body arrow marking, about the globe valve import and export direction there is an express provision, China's valve ‘three to’ the provisions of the flow of globe valves are used in all directions from top to bottom.

Globe valve is low into the high, from the outside there is a clear pipeline is not in a phase of the horizontal line. Gate valve flow in a horizontal line. The stroke of the gate valve is larger than that of the globe valve.

From the point of view of flow resistance in the full open gate valve flow resistance is small, load stop valve flow resistance is large. Ordinary gate valve flow resistance coefficient of about 0.08 ~ 0.12, opening and closing force is small, the medium can flow in both directions. Ordinary globe valve flow resistance is 3-5 times the gate valve (public number: pump housekeeper). When opening and closing need to be forced to close in order to achieve sealing, the spool of the globe valve is completely closed before contacting the sealing surface, so the sealing surface of the wear and tear is very small, due to the flow of the main force of the globe valve need to add the actuator should pay attention to the torque control mechanism adjustment.

Globe valve in the installation of two ways, one is the medium can be from the spool of the lower part of the entry, the advantage is that when the valve is closed when the packing is not under pressure, you can extend the service life of the packing, and can be in the valve before the pipeline under pressure, the replacement of the packing work; the disadvantage is that the valve's driving torque is larger, is the upper part of the flow into the 1 time or so, the valve stem by the axial force of the large stem is prone to bending. So this way is generally only applicable to small diameter globe valve (DN50 below), DN200 above the globe valve are selected from above the medium into the way. (Electric globe valve is generally used in the way that the medium enters from above.) Medium from above into the shortcomings of the way just the opposite of the way below.

5. sealing

Globe valve sealing surface is a small trapezoidal side of the valve heart (depending on the shape of the valve heart), once the valve heart off, equivalent to the valve is closed (if the differential pressure is large, of course, not tight, but the stop effect is not bad), gate valve is by the valve heart to seal the side of the gate, the sealing effect is not as good as the globe valve, the valve heart off will not be equivalent to the valve as the valve is closed.