Gate Valves are Isolation Valves with generally two seats and a gate moving up and down by use of a stem operated either by Wheel, Gear or Actuator. Gate Valves is always bi-directional.
Gate Valves looks similar to a Globe Valves from the outside due to the fact that they often are producers from the same body and it could be a challenge to recognize a Gate Valve from a Globe Valves. However the Globe Valves should be easy recognized since it always has an arrow on the body which is grinded off on a Gate Valves. This arrow also defines the flow direction of the Globe Valves.
Gate Valves are mainly used for isolation
Well head valves are always Gate Valves
Gate Valves could be damaged if it is operated during production or when there is a differential pressure over the Gate Valves.
- Gate Valves could have fixed or floting seats- expanding or parallel gate
- Trough conduit or normale wedge Gate Valves – reversed or normal operated
- In general there are a lot of different models and options of the Gate Valves. This might cause some confusion when Gate Valves of different types and brands are installed on the same location.
Globe Valves are available in a lot of different options, and it can be a challenge to recognize Globe Valves from a Gate Valves from the outside design only. As mentioned under Gate Valves description there should be an arrow on the Globe Valves body. This arrow is grinded off on Gate Valves body. This arrow also defines the flow direction of the Globe Valves.
- Globe Valves is designed to be operated with differential pressure over the valve and while there is process flow in the line, and it might be used as a control valve.
- Control Globe Valve
- Chock Globe valve
- Flow reducer Globe Valve
Ball Valves are the most common Valve within the Oil & Gas business.
The main function of a Ball Valve is sealing of the flow. A Ball Valve should not be used for throttling (semi open / closed position). This will cause damage the ball due to erosion on the ball it selves.
- Ball Valves are probably the type of Valve with the highest failure rate of all Valves. Some Ball Valves might be destroyed after only one single operation, while others might last for many years, it’s all dependent on how the Ball Valve is treated, and the amount and quality of maintenance carried out.
- A Ball Valve body could be assembled from typical two or three main parts sealed and bolted together, or alternatively welded together to increase the safety of the Ball Valve, especially used in the pipeline industry. There are a lot of different ball valve designs; however the basic principle is the same for all of them.
The Ball Valve consists of a highly polished ball place within the body of the valve. The ball is either floating or trunnion mounted. A floating ball has only one support from the top of the ball, and it is free to move against the downstream seat while the pressure is rising.
The higher pressure the tighter valve is the basic principle of a Ball Valve with floating ball. A new Floating Ball Valve will seal off both on the upstream and downstream seat.
On a trunnion Ball Valve the ball has support on both top and bottom, and the ball will not move under pressure. A trunnion Ball Valve has springs pushing the seats against the ball both up and downstream
High Performance Butterfly Valve (HPBV) designs use the pressure in the pipeline to increase the interference between the Seat and the Disc edge to prevent backflow in any direction.
HPBV valves are especially designed for use in high pressure pipelines (ASME 150# to 1.500#), suitable for tougher service and are prone to less wear.
Supplied as Soft- or Metal-seated, any type of materials and may be used in Throttling Service.
The most common method to be installed in a piping-system:
- Double Flanged Type.
- Wafer Type w/4 unthreaded Guiding Lugs/Grooves
- Lug Type w/Threaded/Unthreaded Lugs
HPBV types are manufactured as Double- or Triple Eccentric construction per API609 Cat. B
Other butterfly designs are resilient (Rubber, PTFE etc.) Concentric valves. (API 609 Cat. A)
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Non-return Check Valve or one-way Check Valve is a mechanical device, a valve, which normally allows fluid (liquid or gas) to flow through it in one direction only.
- The main mission of a Check Valve is to avoid back pressure in the process (avoid that the flow is switching direction)
- A Check Valve can also be used for isolation purpose.
- There will normally be regulations telling how many and in which location Check Valves are to be installed in the process.
- As for most valves there are a lot of different designs of Check Valves. The basic design is a Duo Check Valve with two discs mounted on an hinge pin in the center of the Check Valve. The Check Valve has a standby closed position with springs pushing the discs towards the seats. These valves are designed for installation on a horizontal line where the hinge pin is placed in a vertical position.
- To reduce space and weight these Check Valves are often delivered as wafer valves.
Other types of Check Valves:
- Swinging Check Valve
- Tilting Disc Check Valve
- Piston Check Valve
- Non slam Check Valve
- Needle Check Valve
- Nozzle Check Valve
Plug Valve is the oldest known kind of valve. It is a commend assumption that the plug in the plug valve is taper (conic) . The fact is that there is a huge verity of the inside construction of a plug valve.
- The plug valve is a 90 deg (quarter turn) operated valve.
- The main purpose of a plug valve is isolation, and it will than either be fully open or fully closed
- The secondary function of the valve is regulation which is achived by tapering the valve bore. This will reduce the aperture of the plug.
Range of application:
• Oil production
• Water injection
• Mud systems.
• Shut down valve on production
• Water injection and test manifold
• Between valve tree and separator.
• Change-over valve between filters.
• Meetering stations
- Cylindrical without seats (integrated sets in the valve body)
- Full bore “through conduit”
- Venturi with reduced bore
- As a rule plug valves are expected to be maintenance free, however for some valves maintenance is highly required to secure operation and avoid damage.