Skip to main content



A valve is a device that regulates the flow of a fluid (gases, liquids, fluidized solids, or slurries) by opening, closing, or partially obstructing various passageways. Valves are technically pipe fittings, but are usually discussed as a separate category. In an open valve, fluid flows in a direction from higher pressure to lower pressure.
Valves are used in a variety of contexts, including industrial, military, commercial, residential, and transport. There are many types of valves such as gate valve, glove valve, angle valve, automatic stop valve, cheek valve, back pressure valve, butterfly valve, diaphragm valve etc.
Valve materials:
Ø  For larger size cast iron or cast steel or forged steel is used.
Ø  For valves seats, discs and spindles brass is used.
1.      Gate valve, Glove valve, Angle valve, Automatic stop valve etc are called normally stop valve because they are used to stop the flow of fluids.
2.      Reducing valve: The function of reducing valve is to change pressure in a steam line.
3.      Check valve: Check valve permits the flow in one direction.
4.      Back pressure valve: It is used in connection with the exhaust piping of the engine to permit underused in pressure.

See full size image
                            See full size image                                          
Hydraulic flow control valve                 Cheek valve                               Gate valve
                                     Figure: Various flow control valves
Butterfly valve:
            A butterfly valve is a valve which can be used for isolating or regulating flow. The closing mechanism takes the form of a disk. Operation is similar to that of a ball valve, which allows for quick shut off. Butterfly valves are generally favored because they are lower in cost to other valve designs as well as being lighter in weight, meaning less support is required. The disc is positioned in the center of the pipe, passing through the disc is a rod connected to an actuator on the outside of the valve. Rotating the actuator turns the disc either parallel or perpendicular to the flow. Unlike a ball valve, the disc is always present within the flow therefore a pressure drop is always induced in the flow, regardless of valve position.
  1. Resilient butterfly valve: It has a flexible rubber seat. Working pressure 232 psi
  2. High performance butterfly valve: It is usually double eccentric in design. Working pressure up to 725 psi.
  3. Tricentric butterfly valve: It is usually with metal seat in design. Working pressure up to 1450 psi.
                         Figure: Butterfly valve                   Figure: Diaphragm valve

Diaphragm valve:
Diaphragm valve consists of a valve body with two or more ports, a diaphragm, and a "saddle" or seat upon which the diaphragm closes the valve. The valve is constructed from either plastic or steel.
There are two main categories of diaphragm valves: one type seals over a "weir" (saddle) and the other (sometimes called a "straight-way" valve) seals over a seat. The main difference is that a saddle-type valve has its two ports in line with each other on the opposite sides of the valve, whereas the seat-type has the in/out ports located at a 90 degree angle from one another. The saddle type is the most common in process applications and the seat-type is more commonly used as a tank bottom valve but exists also as a process valve
Diaphragm valves can be manual or automated. Their application is generally as shut-off valves in process systems within the food and beverage, pharmaceutical and biotech industries.
 Body materials of diaphragm valve:
Ø  Brass
Ø  Steel (cast iron, ductile iron, carbon steel, stainless steel etc)
Ø  Plastic (PVC-U or PVC-C )

Diaphragm materials:

Ø  Natural rubber

Ø  Silicon rubber

Ø  Nitrile

Ø  Plastics


Advantages and disadvantages:

Types of valve



Glove valve

Better flow closed, properly flow control.

Head loss is more.

Gate valve

Laminar flow

Time required is more for closing the valve

Butterfly valve

Quick flow control, laminar flow and easy operation

Limitation of temperature

Diaphragm valve

No need of gland

Limitation of temperature and pressure




Popular posts from this blog

“Equalizer connection is needed in lap winding armature but not in wave winding “ why ?

The equivalent circuit of a four point – pole dynamo with a simplex winding. The voltage induced in each path is assumed to both to be same and should be if the reluctance of each magnetic path is the same, so that the lines of flux cut by each inductor of each path are the same. However wear of the bearings or deflection of the armature shaft may cause the armature to be closer to some poles and farther from others, thus changing the length of the air gap, and therefore the reluctance of the magnetic circuits of the poles is not identical. This factors cause the voltage in the materials making up the magnetic circuit. These factors cause the voltage in each parallel path differ, and the unequal voltages in turn cause flow of a circulatingcurrent through the windings and brushes , undue heating of the armature and waste the power. To reduce the circulating current, points on the winding which should be at the same potentials are brought to the same potentials by connecting them with …



What are the advantages and disadvantages of hydraulic brakes?

Differentiate among progressive die, compound die and combination die.

Progressive die: The dies which performed two or more operations at different stages every time the ram descends is known as Progressive die.
The principle advantage of Progressive die is in the number of operations that can be achieved with one handling of the stock strip. The main disadvantage is that work pieces may become “dished” as they pushed through the die as they generally have very little support.

Compound die: A compound die differs from a progressive die in that it performs two or more cutting operations during one stroke of the press at one station only.

Compound dies are slower in operation than progressive dies but they have advantages for certain jobs, especially where tolerance are close (1)the cutting operation, by the action of the knockout plate ,ensures flatness of the blank.2 Large parts can be blanked in a smaller press if compound dies rather than progressive dies areused.
Combination dies:A die in which a cutting operation is combined with a noncutting operation …

Why a dc generator fails to build up voltage?



Boiler: A steam boiler is usually a closed vessel made of steel. Its function is to transfer the heat produced by the combustion of fuel to water and ultimately to generate steam.
Types of boiler:
           1. Fire tube or smoke tube boiler            2. Water tube boiler

                                          Figure: Boiler
Fire tube boiler: In fire tube steam boilers, the flames and hot gases, produced by the combustion of fuel pass through the tubes which are surrounded by water. Fire tube boilers are generally used for relatively small steam capacities and low to medium steam pressure. As a guideline fire tube boilers are completive for steam rates up to 12000kg/h and pressures up to 18 kg/cm².Fire tube boilers are available for operation with oil, gas or solid fuel.

                                   Figure: Vrious parts of boiler
Example: Cochran boiler, Locomotive boiler, Scotch marine boiler, Velcon boiler, simple vertical boiler.

Thermal Power Plant

what is the difference between long shunt and short shunt dc generator?

Therbligs and Basic 17 motion name of therblig

What are the factors that control the speed of a dc motor? Describe Ward-Leonard system to control the speed of a dc motor