Valve is used for controlling the pressure and flow of the media that can be liquid, gas and even solid. It is very crucial for a piping system and can also be used for vapors and slurries.
What are various functions of Valves?
- Stopping and starting the flow of the media
- Adjusting the flow by lowering or enhancing the flow
- Managing the flow direction
- Mixing and diverting various fluids
- Acquiring suitable mixing of media having assorted temperatures & characteristics
- Is used as an emergency vent
What are categorization of Valves?
- Type of Actuation
- Type of construction
- Arrangement on the basis of type of automation
- Pressure rating
- Method of obturation
- Material of constructions of body and trim
What is general arrangement of Valves?
Body: Valve body is its main boundary / element since it holds all the other parts together.
Trim: Valve’s trim is suitable for parts disposed to media they carry. As a standard, it includes disc, seat, stem, and sleeves that are required to guide the stem.
Stem: It provide required movement to the disc, plug or the ball so that it is opened or closed. Valve stem also positions the obturator suitably.
Seat: It creates a seating surface for obturator, Disc, plug, ball or wedge. There can be more than one seats that create a seal with disc and stops the flow.
Disc: It permits, throttles, or stops the flow, on the basis of its position. In case of a ball valve or plug, the disc is not used to throttle however it is used for stopping or starting the flow.
Bonnet: It is the cover for the top opening in the body. It is 2nd most crucial boundary of a pressure valve.
What are GGC Valves?
GGC is abbreviation for a combination of Gate, Globe and Check Valves. It is commonly used in process industry.
Gate Valve: It is used for isolating the media flow. In other words, it stops or starts the flow. Construction gate valves are cost effective and simple to operate.
Globe Valve: Having less repairing cost, it is used for regulating the media flow. It is also used in conditions wherein a specific level of temperature or pressure needs to be sustained.
Check Valve: Its use is for checking the flow reversals and ensure unidirectional flow. It needs careful installation and placement.
What are High Pressure Valves?
These have pressure class rating above ANSI Class 300.
What is a Control Valve?
These regulate and control the media flow.
What is the difference between on-off valve and control valve?
On-off valves are used to start or stop the flow of media in a system. The media flow cannot be controlled in these types of valves.
In control valves, the flow of media is controlled and regulated by full or partial opening or closing of the valve.
Can I use Gate valve as a control valve?
No. The wedge/gate is designed to completely stop the flow and form a tight seal against pressure in either direction. Hence, gate valves are not suitable to regulate or throttle the flow.
Can I use Globe valve as a control valve?
Yes. Globe valves are used as on/off as well as control valve. These can shut off, open up or throttle the flow in a pipeline. For throttling, bit-by-bit alteration in the spacing amid the disk and the seat ring is used.
Can I use Swing Check valve as control valve?
No. It is a non-return type valve, which is self-operated. Hence, outside control is not needed for using it. In line with this, Swing Check Valves cannot be used as a control valve.
What is meant by upstream/downstream side of the valve?
Upstream side is incoming flow and downstream side is outgoing flow
What is the difference between unidirectional and bidirectional valve?
Unidirectional valve allows flow in one direction only.
Bidirectional valve allows flow in both directions.
Gate / Globe / Check valves are bidirectional or unidirectional?
Gate valve is bidirectional
Globe and Check valves are unidirectional.