Orbit Valve

What is an orbit valve?

Orbit valve is a type of ball valve. Orbit valve employs a tilt and turn mechanism that eliminates seal rubbing. Seal rubbing is the main cause of failure in valves such as ball valve, gate valve and plug valve. These valves have strong seals mostly made of metal to enhance their ability to work in challenging and aggressive conditions. Orbit valves are suitable for use in meter isolation, flow lines, bypass and block, dryer switching, emergency shutdown, product segregation, discharge, and suction isolation among others. Orbit valves is are used in several industries such as gas, oil, petrochemical, and other industries.

Figure: Orbit valve

Working of orbit valve 

Orbit valves are designed with switch and tilt operation to help eliminate seal rubbing which is the main cause of wear in ball valves. When in a closed position, the orbit valve core becomes automatically stuck against the seat. When in this position, the valve enhances positive shut-off. When the valve starts opening, the core is tilted far from its seat allowing line flow to pass uniformly around the core face. This helps to get rid of localized high-velocity fluid flow which creates uneven wear on a seat in conventional ball valves, plug, and gate valves. Next, the core rotates to complete an open position. Without seal rubbing through each shutting and opening helps to enhance low torque, simple valve operation as well as a long run and reliable valve performance. When closing an orbit valve, turning the handwheel starts lowering the stem. There are precision grooves in the stem that act against fixed guide pins making the core and stem rotate. When you continue turning the handwheel the stem and core rotate to make 90^o turn without the core contacting the seat. The final rotation of the wheel mechanically wedges the stem down. This helps to press the core rigidly against the seat and closing fluid flow.

Figure: Working of an orbit ball valve

Types of orbit valve 

Manual orbit valves 

Manual orbit valves are valves that use a manual actuator to control fluid flow. As the name suggests, these valves do not need power from outside to operate them but rather use a handwheel mechanism to enhance flow control. This valve’s mechanism has a series of gear that enhance output torque relative to the input torque applied by the valve operator. Manual orbit valves have the advantage of being inexpensive, reliable and do not need an external power source like electricity or pneumatics. These valves are self-contained and because they use the same handwheel to open/close it is easy for the operator to spot the cause of technical problem or error. However, manual orbit valves cannot be automated and as such, they need to be manually controlled all the time. This would mean that an operator must be available to control and see the smooth operation of the valve. 

Figure: Manual orbit valve with a handwheel for applying torque

Pneumatic orbit valves 

Pneumatic orbit valves are valves that use pressurized air to operate the orbit valve. These valves work by using the force of air which is applied to a diaphragm or piston attached to the stem of the valve. Unlike manual orbit valves, pneumatic orbit valves can be automated fully or semi-automated. The pneumatic orbit valves are the most common of orbit valve types due to their simple design and reliability. The advantages of pneumatic orbit valves are low costs, low risks to fire, easy operation, simple and reliable design. However, these valves perform poorly at low speeds. 

Figure: Pneumatic orbit valve

Electric orbit valves 

Electric orbit valves are valves that use electricity to operate. These valves use electric motors to convert electrical energy to mechanical energy suitable for operating (opening/closing) the valve. Electric orbit valves are versatile since they can open/close automatically, semi-automatically, or manually. In electric orbit valves, the motor can operate in both directions. This helps to drive valve stem using gears. The advantages of electric orbit valves are they do not need fluid or pressurized air and can produce very high torque for heavy-duty applications. However, these valves are very expensive relative to manual and pneumatic orbit valves. Also, electric orbit valves are hazardous to fire and susceptible to power loss

Figure: Electric orbit valve

Hydraulic orbit valves 

Hydraulic orbit valves are valves that use fluid under pressure to control fluid flow. The hydraulic fluid used in these valves is either oil or water. The pressure in the fluid causes a piston to move which then controls fluid flow. Hydraulic orbit valves can be automated or semi-automated. The hydraulic orbit valves are known to be more powerful compared to pneumatic orbit valves of the same size. These valves can achieve precise fluid control and they have little energy loss because of the fluid incompressibility. However, hydraulic orbit valves need an external hydraulic pump to enhance fluid flow. Also, these valves can leak the hydraulic fluid which can easily cause fire. 

Features of orbit valves 

Orbit valves are free from rubbing between the sealing surfaces

These valves employ tilt-turn operation which eliminates abrasion of seal which is the main cause of wear on seats in most ball valves, plug valves, and gate valves. 

Injectable packing 

During in-service maintenance, material for the stem packing can be injected via the packing fitting to give whole control on fugitive emission. 

Single-seat design 

Orbit valve manufacturers design this valve with a stationary, single-seat in both directions. This helps to reduce the chances of trapped pressure between the valve seals. 

Long service life 

Manufacturing of orbit valves has helped to eliminate troublesome valves as these valves employ designs that enhance performance advantages that result in reduced plant outage and ownership costs. 

Orbit valves enhance the optimum flow 

Reduced port or full port openings in orbit valves give a high coefficient of flow. This improves pumping efficiency and reduces erosion problems. 

Top-entry design 

Orbit valves employ top entry design which helps during repair, in-line inspection, and after depressurizing it simplifies maintenance operations. 

Orbit valves employ dual stem guides 

These valves are made of hard stem slots and strong guide pins to control the turn and lift action of the valve stem.

Self-cleaning

When the core is tilted away from the seat before rotation it immediately causes circular flow around the core face. Fluid flow flushes away any foreign particles from the seat without high-speed, localized erosive flow. 

It needs low torque to operate 

Orbit valve manufacturers design these valves to work without seal rubbing which makes them turn easily using low torque. 

Orbit valves are resistant to wear

Orbit valves are made with a hardcore face of polished material that helps them to work in harsh conditions without loss of seal integrity. 

Components of orbit valve 

Orbit valve has several components as shown in the figure below. Some of these components are discussed below.

Valve body

Valve body is the outer casing on an orbit valve. It is used to house internal components of the orbit valve. The valve body needs to be strong to withstand the high pressures associated with the flowing fluid. Such materials used to make the valve body are stainless steel, brass, and carbon steel.

 Bonnet 

This is the component of an orbit valve used to cover the valve body. This part is connected to the valve body using nuts and bolts or by use of screws. When installing an orbit valve, internal components are put in the valve body and next the bonnet is connected to the body. 

Stem 

The stem is a strong component made of metallic materials like steel. It is used to connect the external control mechanism to the internal mechanism of the valve. In short, the stem connects the orbit valve to the actuator. 

Packing 

Packing is a seal kept around the stem to prevent the fluid from escaping.

Actuator 

The actuator in an orbit valve is the source of power to open/close the valve. The actuator can be manual, pneumatic, electrical, or hydraulic. 

Anti-fire gasket

This is a gasket used to protect the valve against fire especially when the valve is used to work on flammable products such as petroleum. The gaskets are made of anti-fire materials like graphite. 

Bearings

Bearings are used to support the shaft of the orbit valve against loads while enhancing low operating torque as well as reducing wear. Bearings are made of strong materials such as stainless steel so that they can withstand the internal weight of the components and internal pressure. 

Figure: Components of orbit valve

What should you consider when selecting/purchasing an orbit valve? 

Pressure rating 

Orbit valves manufacturers make the valves with different strength to handle different levels of pressure. So, when selecting an orbit valve first know how much pressure the valve will be exposed to. This can be determined based on what pressure the media will have. If the fluid pressure strength is higher than the strength of the valve, the orbit valve will be damaged or injure the valve operator. 

Temperature range

Orbit valves can work in a wide range of pressures. However, orbit valve manufacturers design the valves with a specific operating temperature range. Before purchasing the orbit valve it is very important to know the minimum and maximum temperatures that the media will have. High temperatures can damage the valve. Very low temperatures can cause freezing in the valve. 

Source of power for the orbit valve 

The opening and closing of an orbit valve need some power to provide a turning effect for closing or opening the valve. The power source determines the actuator to be used. So select the orbit valve based on the available power that is manual (hand-operated), electrical, pneumatic, or hydraulic actuator. 

Environmental conditions 

This is the case where the valve can be exposed to conditions that can affect its working such as hot/cold temperatures and corrosive media. A hot environment can damage the valve or cause fire if it is working on flammable products like petroleum. Very low temperatures can cause freezing. Corrosive material can damage external components of the valve-like screws, nuts, and bolts weakening the valve body. 

Weight and support 

It is important to consider the orbit valve weight and its support. Some valves are very heavy and this could put a lot of pressure on other plumping components and finally destroy them. 

Size of the valve 

Knowing the size of the valve is important as it will help to purchase an orbit valve that will easily fit in the other plumping components. This will also ensure that the orbit valve is not hitting other components of the piping system or it will not make it necessary to alter the piping system. 

Applications of orbit valves 

• Used in the control of petroleum products as they employ fire-resistant gaskets. 
• These valves are used in chemical industries. 
• Clean water supply. 
• Oil and gas production. 
• Work in viscous fluids. 
• Pharmaceutical industries. 
• Mole sieve dryers. 

Advantages of orbit valves 

• Free from seat rubbing. 
• These valves employ a simple design which makes their repair easy. 
• Free from leakages which reduces wastage and environmental pollution. 
• Resistant to corrosion. 
• Hot or heat transfer fluids. 
• Emergency shutdown. 
• These valves employ a top-entry design which enhances access to in-line inspection for repairs. 
• Resistant to abrasion. 
• Operated using different actuators according to customers’ preferences. 
• Self-cleaning. 
• These valves have a wide range of operating temperatures from -104°C to 427°C.

Disadvantages of orbit valves 

• Expensive relative to other valves. 
• Critical applications that need operations to be done as per the manufacturer’s instructions to avoid causing fatal damage to the environment for example those used in the petroleum industry. 

Troubleshooting orbit valves 

Structural breakage 

• Handle broken. This could be due to frozen movements or external impact. Identify and correct the source of the problem. 
• Stem broken. It could be due to external impact or frozen movements. Check frozen movement solution criteria and the cause of the impact failure. 
• The end connection is broken. It could be due to misalignment or due to external impact. Ensure system alignment is perfect. 

Body is broken

• System misalignment. Ensure the system is properly aligned. 
• Excess internal pressure. Ensure internal pressure is as recommended by the orbit valve manufacturer.
• Chemical attack. Ensure the chemical working on the orbit valve is compatible with the valve’s internal materials to avoid attack on the valve. 

Difficult in closing or opening the valve 

• Internal obstruction; particle or sediment buildup. Remove the orbit valve to check for debris, solids, or solvent cement deposits. Clean these materials and reinstall the valve again. 

Internal leakage 

• Thermal damage. This can distort the orbit valve. Check the orbit valve operating range of temperatures as well as external heat sources produced from system design. 

Orbit valve not shutting-off

• Wrong direction of rotation. Check the direction of shutting the valve according to the manufacturer’s instructions. 
• Automation has a fault. For automated orbit valves, it could be due to faulty actuator. If it is a semi-automatic valve, use a manual system to shut off the valve. Otherwise, call a technical expert to work on the actuator. 

Summary 

Orbit valves are valves that employ a tilt and turn open/closing mechanism. These valves are very advantageous compared to other valves because they use a mechanism that eliminates seal rubbing which is the prominent cause of failure in valves such as gate valves, plug valves, and ball valves. Orbit valve manufacturers design the valves with strong materials that make them resistant to abrasive and corrosive materials.

These valves can be classified based on the actuator types used that is manual orbit valves, pneumatic orbit valves, hydraulic orbit valves, and electric orbit valves. Orbit valve manufacturers employ common design principles on-orbit valves which makes these valves have the same working principle and features. Features of orbit valves are single-seat design, zero rubbing between seat surfaces, self-cleaning, top entry design, and low torque operation because there is zero rubbing, wear, and abrasion resistance. Such features give orbit valves advantages over other conventional valves such as ball valves, gate valves, and plug valves.

These valves are used in different industries such as oil and gas, petroleum, chemical, water supply among others. However, despite these valves having super features and advantages, they are costly to manufacture and purchase.