Stone valves were already use in the ancient Roman Empire and Islamic period to stop or divert water flow for human use. In spite of this, valves, as we know them today, have their origins in the first industrial revolution, when steam-powered machines. As modern engineering equipment, valves have contributed to the development of the industrial world since the XX century. No modern society could function without valves to assist in manufacturing. we are the leading valve manufacturer and supplier.
Hydraulic systems are compos of three main components: Pumps that extract pressure, Pipes that transport fluids, and Valves that control fluid flow. These major components are the foundation for all other components.
What is the best way to define valves?
In the piping system, mechanical devices use to control fluid flow. A valve is a component of piping that operates on fluids by opening and closing, partially throttling, or diverting them. CEN (European Committee for Standardization) EN -736-2 defines a valve as any component which opens and closes, partially throttles, or diverts fluids.
1.1.- Common components of valves
Regardless of the valve style, there are common components that follow a similar function. Below is a typical valve style (globe valve):
- In direct contact with the fluid is a plug, also called a disc.
- A stem, also called a spindle, is an element that fixes and drives the plug.
- Seats are metal surfaces that seal plugs to them.
- The stem packing protects the fluid from atmospheric evaporation by wrapping it around the stem
- A sealing ring is an optional component in some valves that ensures a tight seal between the plug and the seat as long as the temperature permits.
- Pressure is retaine the body and bonnet shell, which cover the inner valve components.
- Ends are the pipe connecting parts, they commonly weld, thread, or flanged. In addition, there are wafers and lugs for installation between external counter flanges.
- The union bolts connect the pressure retaining parts. Atmospheric tightness is ensure sealing gaskets.
The operator is the device that operates the valve.
Aira Euro Automation is the leading valve manufacturer in India. We offer various industrial valves like ball valves butterfly valves, control valves, plug valves, pressure reducing valves, and many more.
2.- Types of valves
Valves can be classified into the following main categories based on their purpose:
- When require, isolation is design to stop the full flow rate across the pipe.
- The non-return valve prevents the flow from returning to the pressurized side.
- Throttling: Reduces flow by partially closing the valve, deviating or mixing it manually, remotely, or automatically.
- Designed to protect personnel and equipment from overpressure hazards.
3.- Isolation Valves
Due to their function within the flow control system, these valves are also known as stop valves, block valves, and shutoff valves. Bas on the stem movement, this valve style can also divide into two categories:
Linear isolating valves feature a vertical movement of the stem and closing element; downward for closing and upward for opening. These are multiturn operate and feature gradual and slow operations. Steam and vapors are compressible fluids that may be adversely affected by fluid phenomena caused by a quick closing action.
Rotating the valve stem will open or close the valve. Non-compressible fluids such as water and other low-pressure media are usually suitable for these valves since they are quick-operating. In the case of a slower operation, a hand lever or worm gear is used.
3.1 – Linear Isolation Valves
In terms of linear isolating valves, the most common types are globe valves (including variants such as bellows sealed types), gate valves (such as knife gate, slab gate, penstocks, etc.), and diaphragm valves.
3.2 – Rotary Isolation Valves
The most common types of rotary isolating valves are butterfly valves, ball valves, and plug valves.
3.3 – Isolation Valves Styles according to the operation mode
The common classification of isolating valve styles is based on how they operate:
Because manually operated valves are manned by plant operators, they should be placed within reach and should not require frequent operation cycles.
Self-operating valves are operated by the same line flow exerting the thrust on the closing element, depending on a set parameter (temperature, flow rate, pressure…).
In addition to air (pneumatic), electricity (electric), and liquid (hydraulic) powered valves, auxiliary powered valves are typically used on repetitive processes, non-easily accessible points, and where good process accuracy is required. We know today’s industry is 4.0 as a result of valves like these.
4.- Non-Return Valves
A non-return valve prevents the flow from returning to the pressurized side of the system. They are unidirectional valves, where the disc opens flow-wise and closes counter-clockwise. (Always follow the instructions in our Operating Manuals when installing).
Depending on the construction design, there are a variety of Non-return valve styles:
- Check valves with a swing action.
- Check valves with tilting swings.
- Check valves with dual plates.
- Check spring-loaded valves.
- Check valves with ball bearings.
- A flexible lip check valve.
- Check valves of the piston type.
5.- Throttling / Regulating Valves
Control valves, also known as throttling valves, are used to modify the flow rate in a system. External inputs (electrical or pneumatic, for example) are the most common. In a flow control system, control valves are used for frequent and accurate flow control operations. In addition to externally operated throttling valves, manual globe valves with profiled plugs are also considered to be throttling valves. Self-operating valves, however, should be considered ON/OFF valves since the stem and plug do not perform intermediate functions.
What is the process? The parameter to control is set into the PID (electronic controller), and the actual parameter sens at the system transfer to the PID interprets the values and sends an electronic signal to the valve actuator or electro-pneumatic positioner, which in turn instructs the valve to open or close. A change in valve state will cause a change in the processing system where a downstream sensor will emit new sensing parameters to the PID for new actions.
It is possible to design control valves in straight-through patterns as well as in three ways for flow deviation or mixing. In mixing valves, two different fluids mix at the valve inlet ports to form a single fluid at the valve outlet ports. Diverting valves work by diverting a single fluid at the valve inlet port to the other two valve outlet ports. Below is an illustration of the plug configuration based on the valve style.
6.- Safety and Pressure Relief Valves
Pressure relief valves prevent overpressure in pressurized vessels by self-acting. To blow the fluid off the system better, these valves typically design with a 90-degree angle. As spring-load valves, the spring is set at a certain rate above the system pressure, above which the valve lift will blow off, releasing excess fluid until the pressure in the system is restore.
In closed pressurized vessels, safety valves are crucial when the pressure of non-compressible fluids rises, causing the vessel to burst, and causing harm to people and property.
7.- GLOSSARY OF TERMS AND DEFINITIONS
Main linear isolation valves; definitions:
A globe valve consists of:
Weir-body valves with a closing disc that seats onto a precisely machined seat ring to ensure tightness. These valves are unidirectional, with the flow inlet underneath the disc, which closes the valve. Packing rings surround the valve stem to ensure atmospheric sealing.
Sealed globe valves list below:
Metallic bellows around the stem ensure atmospheric tightness by the non-wearing out soft packing, which is based on the same concept design as globe valves.
Globe valves that balance:
The valves are throttling globe valves with upstream and downstream gauges for adjusting the right valve flow.
Valves with gates:
These valves feature a wedge sliding through two parallel discs to ensure closure. The valves have high capacities and are bidirectional, but they suit for throttling.
Knife Gate Valves:
Gate valves with edgy ends to cut through viscous fluids are a variant of gate valves. They are unidirectional designe to installed flanges in either wafer or lug form.
The diaphragm of these valves is flexible and deformable, which is actually a compressor that connects to the bonnet assembly. A bidirectional valve is open with the diaphragm concave and closed with the diaphragm convex. Typically, there are two styles. Depending on the fluid and application, weirs and straight-outs can select.
Main Rotary Isolation Valves; Definitions:
Valve with a circular disc, which turns the stem, allowing the flow to pass when the stem is parallel and blocking it when it is perpendicular. Depending on how the disc is turning, the flow can pass or block. In essence, these are bidirectional valves. As the stem and two-disc sides represent a butterfly and its wings, the term “Butterfly” comes from a popular comparison.
There are three types of butterfly valves: concentric, eccentric, and triple offset. The product manuals available on this website contain detailed information about the working principle and limits of use and application.
Inlet and outlet valves with a perforate ball as a closing element, which is to turn the stem, leaving the free passage through the ball and blocking the flow. An instant visual indication is provided by the handle position. When the handle aligns with the valve ports, it indicates open, and when it is turning at an angle, it indicates close.
Floating ball valves are the most common type, the stem exerts the ball’s movement with the upper part, while trunnion valves have the ball guided by the upper and lower parts. In large units, this is the most common design.
With plug valves, a perforate plug uses the closing element, which in turns the stem, leaving a free passage through it when the plug aligns with the pipeline. Plugs can lubricate or sleeve.