Rising Stem Ball Valve 

 What is a rising stem ball valve? 

The rising stem ball valve is a type of ball valve with a long stem that rises above the body of the valve. A rising stem ball valve is used for on and off fluid flow applications. Rising stem ball valves are mostly all-metal and fireproof. Rising stem ball valves have wide range of temperatures of around -200^oC and 815^oC. Rising stem ball valves are designed such that movement of ball and seat does not create friction and the valve needs small torque to open and close. Rising stem ball valves are suitable for applications that need zero fluid leakage and which are subject to frequent operation. Rising stem ball valves are used in critical isolation of different applications. These valves are used in various applications such as water, acids, solvents, and natural gas among others. These valves use a tilt-and-turn principle which removes rubbing. Rubbing is the main cause of wear and valve failure in most ball valves. Rising stem ball valves do not have seal rubbing when opening and closing which makes last longer.

Figure: Risings stem ball valve.

Components of a rising stem ball valve 

There are various parts of a rising stem ball valve. Among the main parts include the following. 

Handwheel/actuator 

The handwheel is used in manual rising stem ball valves and it is where the valve operator applies torque to open/close the valve. When the orbit valve is automated it uses an actuator that provides torque to the ball to open/close the valve. 

Body/housing 

The body is also known as valve housing and it is the component of a rising stem ball valve used to provide cover to all internal parts of the valve. 

Bonnet 

Bonnet is a component that is placed on top of the valve body to provide cover to the internal parts of the valve. The bonnet is connected to the body using bolts and nuts. 

Stem 

A stem is the component of a rising stem ball valve that is used to connect the handwheel or actuator to the ball. The stem transmits torque from the actuator or handwheel to the ball so that it can open or close. 

Ball 

The ball is also known as the valve core. The ball has a hole at its center where fluid flows through. 

Seat 

This is a component placed between the ball and the body to prevent fluid leakage and support the ball. 

Figure: Components of a rising stem ball valve.

How does a rising stem ball valve work? 

The rising stem ball valve works by using a rotating motion as well as cam action to produce a perfect seal. The rising stem ball valve works by turning the handwheel several times for manual valves. To open the rising stem ball valve, the handwheel is rotated several turns. This makes the ball bore turn and become in line with the pipeline and then fluid starts flowing. To close the rising stem ball valve, the handwheel is rotated clockwise or the actuator rotates the stem for actuated ball valves. The rotation of the stem rotates the ball in the clockwise direction which makes the ball bore become perpendicular to the pipeline. In this case, the fluid cannot flow through the valve as it is blocked by the ball. The ball in a rising stem ball valve is held in a place away from the seat using the valve stem which helps to eliminate abrasion and makes the valve to use small torque to open/close relative to other ball valves. 

Types of rising stem ball valve 

Side entry rising stem ball valve 

Side entry rising stem ball valves are valves that have two or three pieces of the body. The pieces of a side entry rising stem ball valves are assembled from their sides using bolts and nuts. Each piece of a side entry rising stem ball valve is made using forging method. The forging method helps to eliminate defects associated with valves made through casting method. One of the main advantages of a side entry ball valve is that it is easy to assemble and that the internal components can be easily aligned. Also, side entry rising stem ball valves can be inspected, cleaned, and repaired. 

Figure: Side entry rising stem ball valve.

Top entry rising stem ball valve 

This is a rising stem ball valve that is assembled from the top side of the valve. In this rising stem ball valve, the valve operator can access the valve seats and ball easily from the top side during repair and maintenance without removing the valve from the pipeline. Top entry rising stem ball valves are made through casting method. This makes the valve undergo non-destructive tests to ensure it has no casting defect which can cause leakage when the valve is in use. The top entry ball valve has two pieces one at the bottom and another one at the top. The two pieces are held together using bolts and nuts which makes these valves easy to dismantle for repairs, cleaning, and inspection. 

Figure: Top entry rising stem ball valve.

Manual rising stem ball valve 

These are rising stem ball valves that are operated using a handwheel. As the name suggests, manual rising stem ball valves need the valve operator to be around every time the valve needs to be opened/closed. The valve operator applies torque on the handwheel to open/close the valve. When the handwheel of a rising stem ball valve is rotated in the anticlockwise direction it turns the valve on. When the manual rising stem ball valve handwheel is rotated in the clockwise direction it closes the valve. Closing and opening directions are indicated on the handwheel. One advantage of a manual rising stem ball valve is that it can also be automated if the user finds it necessary. Also, manual rising stem ball valves are cheaper compared to automatic counterparts. 

Actuated rising stem ball valve 

This is a rising stem ball valve that is operated using an actuator. The work of the actuator is to provide the torque required to open or close the rising stem ball valve. The actuator provides rotary motion to the ball valve causing its opening/closing operation. Actuated rising stem ball valves can be fully automated or semi-automated. One advantage of an actuated ball valve is that it can work without a valve operator. Rising stem ball valves with actuators are suitable where the torque required to open the valve is very high. However, actuated rising stem ball valves are expensive unlike their manual counterparts. The actuators that can be used in rising stem ball valves are hydraulic, pneumatic, and electric actuators. 

Features of a rising stem ball valve 

Rising stem ball valves are anti-abrasion

The ball surface is hardened which helps to meet seal performance even in severe media. 

Mechanical wedge force 

Rising stem ball valves have a cam bevel at the lower end of the valve stem meant to provide wedge force for keeping the seat and ball tight. 

Dual stem guides 

Rising stem ball valves are designed with stem guide grooves to slide along a rigid guide pin to control the lifting of the stem and rotate smoothly. 

Self-cleaning 

Rising stem ball valves are such that when the ball deviates from the seat, the fluid flows 360^o degrees along the sealing surface which helps to rinse impurities. 

No wear in rising stem ball valve

The design of a rising stem is such that the ball rotates away from the seat. This helps to eliminate friction between the ball and seat common in other ball valves. 

Small operating torque 

The rising stem ball valve employs a design that makes the sealing surface free from friction which reduces the torque needed to open and close the valve. 

Applications of rising stem ball valves 

• Used in natural gas applications 
• They are used in steel mill plants to control furnace gas.
• Pulp and paper industries.
• Petroleum industries.
• Steam power plants 
• Chemical industries to open/close flow of required compounds.

Advantages of rising steam ball valves 

• Do not experience wear between the seat and the ball which makes them abrasion-free. 
• Require low torque to open/close relative to other ball valves because they do not have rubbing between the ball and seat. 
• Self-cleaning which reduces the chances of particles build up. 
• Can be opened for inspection, repair, and maintenance. 
• Have optimum fluid flow because their openings enhance the high coefficient of flow. This helps to enhance pumping efficiency and reduce erosion problems. 
• These valves are durable because they can be repaired for reuse every time they break down. 
• Versatile because they can be used in different industries for different applications. 
• These valves can be manual or operated using an actuator as per customer preferences. 
• Easy to open or close. 

Disadvantages of rising stem ball valves 

• More expensive relative to other ball valves of the same functions. 
• Heavy relative to other ball valves. 
• These valves must be installed vertically. 

Troubleshooting rising stem ball valves 

Leakage through valve connections 

• Worn out gasket. Replace the gasket. 
• Loose bolts and nuts. Tighten the bolts and nuts. 
• Excess fluid pressure. Ensure the valve pressure rating matches the fluid pressure. 

Rising stem ball valve experiencing leakage through the seat

• Damaged seat. Replace the seat. 

Leakage through the ball

• Damaged ball. Replace the ball. 
• Debris in the ball bore. Clean and or replace the ball. 

The rising stem ball valve is hard to rotate 

• Broken stem. Replace the stem. 
• Ball blockage. Remove sediments blocking the valve.
• High application pressure. Ensure fluid pressure does not exceed valve pressure rating. 

Noisy operation or water hammer

• High fluid velocity or wrong valve sizing. Verify that the valve used is suitable for that fluid flow. 

Summary 

A rising stem ball valve is a type of ball valve. The rising stem has a long stem rising above the valve body. The valve is an on/off ball valve. This valve can be used in a wide range of temperatures ranging between -200 ^oC and 815 ^oC. Rising stem ball valve manufacturers design the valve such that the ball and seat do not rub each other making them free from abrasion wear. As such, they need low torque to open or close relative to other ball valves. They are made of strong metallic materials to help them mechanically strong and resistant to high temperatures. Valve types include manual rising stem ball valves, actuated rising stem ball valves, top entry rising stem ball valves, and side entry rising stem ball valves. Rising stem ball valves are used in different applications such as petroleum, natural gas, chemical industries, paper, and pulp industries, and steam power generation industries among others. Advantages of rising stem ball valves include self-cleaning, quick to open/close, versatile, durable, low torque operation, they can be cleaned, inspected, and repaired while in the field, abrasion-free and very strong. However, rising stem ball valves are expensive and they can only be installed in a vertical position. Nevertheless, the advantages and special features of rising stem ball valves outweigh the few disadvantages by great margin.