Trunnion metal sealing ball valve
Overview
The ball of the ball valve is trunnion and does not move when pressed. Trunnion ball and ball valves all have floating valve seats. After being subjected to medium pressure, the valve seat moves, causing the sealing ring to press tightly on the ball to ensure sealing. Bearings are usually installed on the upper and lower shafts of the ball, with small operating torque, and are suitable for high-pressure and large-diameter valves.
In order to reduce the operating torque of the ball valve and increase the availability of the seal, oil-sealed ball valves have appeared in recent years. Special lubricating oil is injected between the sealing surfaces to form an oil film, which enhances the sealing and reduces the operating torque, more suitable for high-pressure and large-diameter ball valves.
Principle of structure
The electric ball valve has a simple structure and is composed of a few parts. It has the advantages of small size, light weight, small installation size, small driving torque, easy and agile operation, and can be quickly opened and closed by simply rotating 90°. It has good flow regulation effect and closed sealing characteristics; in the application range of large and medium diameter, medium and low pressure, electric ball valve is one of the leading valves. It is mainly used to cut off, distribute and change the flow direction of the medium in the pipeline. When the electric ball valve is fully open, the medium flows through the ball core port without any resistance, so the pressure drop generated through the valve is very small, so it has good flow control characteristics.
Structure of electric ball valve
There are many types of electric ball valves. They are generally divided into two categories according to their structural forms, namely O-type structure and V-type structure. The ball openings of the two are different and their applications are also different. The O-type is generally suitable for shut-off use and occasional adjustment. , while the V-type is more suitable for adjustment (larger adjustable ratio).
The structure of O-type ball valve
The O-type ball valve has a ball with a middle through hole installed inside the valve body. The ball has a through hole with a diameter equal to the diameter of the pipe. When fully open, it is a non-blocking valve with large flow capacity and no directionality of fluid entering the valve. The ball can rotate in the sealing seat, and there is an annular elastomer on both sides in the direction of the pipeline to achieve sealing. By rotating the ball 90°, the direction of the through hole can be changed, thereby realizing the opening and closing of the ball valve.
The function of ball valve
The opening and closing part of the ball valve is a round sphere with a hole. The ball core is used to rotate 0-90° back and forth around the axis of the valve stem to open or close the valve. Ball valves have many functions. They are generally used for switching, cutting off or regulating media in pipelines. Among them, the three-way ball valve can flexibly cut off, distribute and change the flow direction of the medium. The sealing surface of the ball valve is usually in a closed state with the spherical surface, so it is not easily eroded by the medium. It is easy to operate, has a simple and compact structure, and can be used in working conditions with water, natural gas, acid, solvents, etc.
The use of ball valve
Ball valves can generally be divided into three categories according to their structural forms: floating ball valves, trunnion ball valves, and elastic ball valves. According to different sealing properties, they are divided into metal-sealed ball valves and soft-seal ball valves. The soft-seal ball valve has better sealing performance and can achieve zero leakage. It is generally used in normal temperature and pressure pipelines with corrosive media, while metal-seal ball valves are not only It can be used at normal temperatures and pressures, as well as in low-temperature, low-pressure and high-temperature and high-pressure pipelines.
Installation
Make sure that pipes and valves have been cleaned before operation.
The actuator operation of the valve drives the valve stem to rotate based on the size of the input signal: when it rotates 1/4 turn (900) in the forward direction, the valve is closed. When rotated 1/4 turn (900) in the opposite direction, the valve opens.
When the actuator direction indicator arrow is parallel to the pipeline, the valve is open; when the arrow is perpendicular to the pipeline, the valve is closed.
Maintenance
Having a longer service life and maintenance-free time will depend on several factors: normal operating conditions, maintaining a harmonious temperature/pressure ratio, and reasonable corrosion data
Note: When the ball valve is closed, the fluid pressure in the valve body still exists.
Before servicing, remove line pressure and leave valve in open position
Before servicing, disconnect the power or air supply
1. Packing lock
If the packing culvert is slightly leaking, the valve stem nut must be tightened.
Note: Do not lock, usually 1/4 ring to 1 ring, the leakage will stop.
2. Replace the valve seat and seals
Disassembly
Leave the valve in the half-open position to flush any hazardous materials that may be inside and outside the valve. Close the ball valve, remove the bolts and nuts from the flanges on both sides, and completely remove the valve from the pipe. Disassemble the driving device in sequence - actuator, connecting bracket, anti-loosening washer, stem nut, butterfly shrapnel, glamor, wear-resistant sheet, and stem packing. Remove the body cover connecting bolts and nuts, separate the valve cover from the valve body, and remove the valve cover gasket. Make sure the valve ball is in the "off" position, which will make it easier to remove it from the valve body, and then remove the valve seat. Gently push the valve stem downward through the middle hole of the valve body until it is completely removed, and then remove the O-ring and packing ring.
NOTE: Use caution to avoid scratching the stem surface and the valve's packing seal.
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