Top entry ball valves are valves in which the ball is mounted at the top end. They are similar to a ball valve with a body and cover, except that the internal part uses a ball. They consist of a single unit. Top entry ball valves are usually made of cast metal. Since they are made from casting, some additional non-destructive testing is required to ensure there are no defects in the casting process. Top entry ball valves are often used in applications where limited disassembly is required for in-line maintenance of internal components. It is also very common to use high pressure ball valve inlets that require constant maintenance, such as: B. HIPPS Valves (High Integrity Pressure Protection System), etc. The advantage of the top entry ball valve is its design that allows limited thread interaction so that the possible leakage path can also be minimized.
What is a top entry ball valve?
Ball valves are widely used in oil and gas pipelines and machinery in the petroleum, refinery, petrochemical, chemical, metallurgical, electrical, nuclear, food and paper industries.
Due to the special environmental and operating conditions of the process, a conventional ball valve is not sufficient and the system requires high performance. The top access structure eliminates the need to remove the ball valve from the line during maintenance or seat replacement. Therefore, checking and maintaining the ball valve is easy.
Typically, the top entry configuration changes the position of the seat using a wedge or threaded seat on the outside. However, the external wedge improves the external leakage point and reduces the sealing efficiency, while the thread seat of large-diameter valves is quickly destroyed and the service life is reduced. Considering the above conditions, a consistent upper inlet structure is designed such that the valve seat consists of a V-shaped outer circle designed to be inclined toward the contact portion of the control rod. This reduces stress on the control rod and poppet valve mating surface to maximize service life. Furthermore, the V-shaped outer circle geometry allows the valve seat to be separated from the valve body when removing the valve seat.
How does a ball valve with top entry function work?
Ball valves have a ball supported by a pin at the bottom. When the hole faces the line, the valve is in the open position, allowing fluid to enter. The shaft starts moving downwards and rotates 90° due to the channels built into it, causing the ball to rotate in the same direction. So some of the grooves are machined and the shaft can't just go down.
In this case, the shaft guides the ball to the lower pivot and to the seat thanks to the inclined surface. The ball only hits the seat in this position and there is no pressure during the rest of the movement.
Top entry ball valves come in two main configurations:
Total hole: The size of the cap is the same as the thread. In this case the valve is ideal for pigging.
Reduced diameter: The casing height is smaller than the pipe size.
Types of ball valves with top inlet connection.
Tap-mount ball valve with top access
The top trunnion mounted ball valve is specifically designed and constructed for low operating torque and quick maintenance. Rugged, one-piece body allows easy access to shaft and ball for field repairs. Top mount trunnion ball valves are available in a variety of configurations with flanged or welded ends in various sizes. Standard features of top trunnion mounted ball valve include double block and bleed, fireproof design, emergency sealant injection and ISO mounting pad, which also depend on the manufacturer. An extended stem/cover for underground operation is also a standard alternative to the top trunnion mounted ball valve.
Floating ball valves with top access
Top entry floating ball valves are primarily used for fluid control in steam, boiling and other general industrial system applications. Top entry floating ball valve is a valve with a ball that floats in the valve body, floats to the downstream side, and presses firmly against the seat under medium pressure to ensure sealing reliability. It has simple structure and good sealing ability, but the seat material needs to adapt because the sealing pressure is supported by the seat ring.
What are the advantages and characteristics of a top entry ball valve?
TOP ENTRY BALL VALVE is mainly used in industrial pipelines and systems, and has top entry and line maintenance function. It has many advantages such as low fluid resistance, simple design, compact volume, light weight, reliable salting, easy repair and control, easy opening and closing, and flexible starting and closing.
The main difference from the standard ball valve is that it can be fixed to the pipeline even without disassembly. The rear seat configuration is customized to the seat and the rear of the seat support is angled to prevent contaminants from affecting the rear seat.
A one-piece body is used to ensure sufficient strength and rigidity at the body's highest rated operating pressure. The valve's internal components are specially designed and selected to ensure stability under all operating conditions. Sufficient rim wall thickness and adaptation to high-strength connecting bolts are convenient for valve maintenance and the ability to withstand pipe pressure.
Top Entry Ball Valve vs. Top Entry Ball Valve ball valve with side entry.
These ball valve concepts refer to the manner in which the valve ball and its internal components can be accessed, either from the side of the valve or from the top of the valve (top inlet).
The top entry design is used when repeated in-line maintenance operations on the valve are required. This is because top entry ball valves provide increasingly faster access to the ball and valve assembly than side entry valves, which require more repair time and space for the same operations.
The two types of ball valves can be distinguished as follows:
Top access ball valves are generally manufactured with a cast steel body, while side access ball valves are made from (robust) sheet steel.
Top entry ball valves are monolithic in construction (made in a single piece), while side entry valves consist of two or three assemblies.
Due to their castings, ball valves with top entry function require more non-destructive testing than ball valves with side entry function. Side entry valves are easier to install and assemble than top entry valves, which are time-consuming and require a lot of craftsmanship to function properly.
Top entry ball valves are typically more expensive than side entry valves and have longer lead times due to the casting processes used to produce the body.
