Valve is a device that regulates, directs or controls the flow of a fluid (gas, liquid, fluidized solids) to open, close, or close a portion of the flow path.
Valve (valve) in everyday life, the most obvious is a water pipe, as the tap water. Other familiar examples include gas control valve on the stove, a small valve that is installed in the bathroom and much more. Valves play an important role in industrial applications ranging from drinking water transport as well as to control the ignition in the rocket engine.
Valve can be operated manually, either by the handle, lever pedal and others. Besides being able to manually operated valve can also be operated automatically by using the principle of flow changes in pressure, temperature etc. Perubahan2 can affect the diaphragm, a spring or a piston which in turn activates the valve automatically.
Kind of Valve that is often used is as follows:
- GATE VALVE
Gate valve is a type of valve that is used to open the flow by raising its gate closing a round or rectangular.
Gate Valve is a kind of valve that is most often used in the piping system. Whose function is to open and close the flow.
Gate valve is not to adjust the pace of a small fluid flow by opening a half or a quarter of its position, so the position of the valve gate should really open (fully open) or completely closed (fully closed). If the gate half open position, there will be turbulence in the flow and turbulence will cause:
a) There will be erosion of the corners of the gate. fluid flow rate turbulence that can erode the corners of the gate which can cause erosion and ultimately valve can not work perfectly.
b) There is a change in the position of closing the gate holder. Gate closing will occur pengayunan against mounting position (seat), so that over time it will change the position of the seat (seat) so that when the valve closes the gate closing will not be in the right position, so that it can lead to passing.
There are 3 types of gate valve:
1. Rising Stem Gate Valve
if operated handwheel stem rise and also climbed
 |
1. Body 2. Bonnet 3. Seat(s) 4. Disk 5. Stem 6. Back seat 7. Packing
8. Gland 9. Gland follower 10. Yoke 11. Stem nut 12. Handwheel |
2. Non Rising Stem Gate Valve;
if operated handwheel fixed and stem is also fixed.
3. Outside Screw & Yoke Gate Valve;
if operated handwheel remains but its stem rise.
Rising Stem & Non Rising Stem is used for the pressure is not too high, and is not suitable for vibration. Outside Screw & Yoke Gate Valve is very suitable for high pressure. Usually OS & Y are widely used in oil field, high field, high temperature. Because the OS & Y stem up or down can be used as a marker. For example, if a high stem that indicates the position of the valve being fully open. Basically the body and bonnet at the gate is made of the same material.
The advantage of using Gate Valve:
Low pressure drop when fully open Very tight and quite nice full closing time free of contamination As a full closure gate, so there is no pressure anymore. Suitable when will perform service / repair on the pipeline
Disadvantages of using Gate Valve:
Not suitable in use for half open, because it will cause turbulence that can lead to erosion and change the position of the gate on the stand To open and close the valve in the longer term and require torque / high torque; For the size 10 "and above are not suitable for steam.
- BALL VALVE
Ball Valve is a valve or a valve to control the flow of a round disc-shaped (like a ball / hemisphere). The ball has a hole, which is in the middle so that when the hole is a straight line or in line with both ends of Valve / Valve, the flow will occur.
But when the valve is closed, the position of the holes are perpendicular to the end of the valve, the flow will be blocked or covered.
Ball valve is widely used because of ease of repair and ability to withstand pressure and high temperature. Depending on what material they are made, Ball Valve can withstand pressures up to 10,000 psi and temperatures of about 200 degrees Celsius.
Ball Valve is used widely in industrial applications because they are very versatile, able to withstand pressures up to 1000 barr and temperatures up to 482 ° F (250 ° C). Its size usually ranges from 0.2 to 11.81 inches (0.5 cm to 30 cm).
Ball Valve can be made of metal, plastic or ceramic materials. The ball is often coated with chrome to make it more durable.
There are 2 types of Ball Valve, namely:
a.full bore ball valve
Full bore ball valve is a ball-type ball valve with a bore diameter equal to the diameter of the pipe. Type full bore ball valves are typically used to blow down, piggable line, production manifolds, pipeline etc.
b. Reduced bore ball valves
Reduced bore ball valves are the type of ball valve which ball is not the size of the hole diameter to the size of the pipe.
The minimum diameter of a ball valve which is one size reduced lower than the actual size of the pipe diameter. For example, the size of the pipe diameter of 4 inches and the diameter of the ball valve is 3 inches.
-Check Valve
Check valve is a device used to make the fluid flow only flows in one direction only, or to avoid reversed flow / back flow. Applications valve of this type can be found in the outlet / discharge of a centrifugal pump.
When the fluid flow rate in accordance with the direction, the flow rate will make the plug or disk opens. If there is pressure coming from the opposite direction, the plug or the disc will close.
The types of check valve:
a. Swing Check Valve
This type check valve consists of a disk the size of the pipe is used, and is designed to hang on the shaft (hinge pin) at the top. In case of forward flow or flow foward, then the disc will be pushed by the pressure so open and fluid can flow towards the outlet channel.
Whereas in case of reverse flow or reverse flow, fluid pressure will push the disc shut so that no fluid flows. The higher the pressure the more tightly behind the disk mounted on the stand.
b. Lift Check Valve
Use for fluid steam, gas, or liquid that has a high flow. in a configuration similar to a globe valve only on the globe valve disk rotation or valve can be manipulated while the lift check valve is not (because of a globe valve is a type of rotary valve and control valve).
Inlet and outlet ports are separated by a cone-shaped plug which is located on a holder, generally made of metal. When going foward flow, the plug will be pushed by the pressure of the liquid so separated from its seat and the fluid will flow into the outlet channel.
Whereas in case of reverse flow, fluid pressure it will put a plug on the stand, the greater the pressure the more tightly also the position of the plug on the stand, so that the fluid can not flow.
material from the plug holder is a metal, it is considered a very slight degree of leakage of the check valve. Generally lift check valve is used for the application of fluid leakage of gas due to a small level. The use of this lift-type check valve in the industry is to prevent a backflow of condensate into the steam trap which can cause corrosion in steam turbines.
The advantage of using the lift check valve is located on the simplicity of design and requires little maintenance.
The disadvantage is the installation of a check valve type of lift is only suitable for horizontal pipes with large diameters.
c. Back water check valve
Back water valve, widely used in underground drainage systems that prevent backflow of drain during floods. Currently sewer flooding will be full and high pressure so as to allow the occurrence of backflow, using a back water valve, this can be overcome with good.
d. Swing Type Water Check Valve.
In the use of swing check valve and check valve lift is limited only to pipe size (diameter DN80 or more). so as the solution is to use a wafer check valve. By using wafer ceck valve can be used tubing sizes converging on one side so that it can be applied on a smaller pipe size.
e. Disc Check Valve
This type consists of a valve body, spring, spring retainer and disc. The principle works is when there foward flow, then the disk will be driven by fluid pressure and push the spring so that there is a gap that causes the fluid flow from the inlet to the outlet.
On the contrary in case of reverse flow, fluid pressure will push the disk thereby closing the fluid flow the pressure difference required to open and close the valve of this kind and this is determined by the type of spring used. In addition to the standard spring, there were also some spring options are available:
= No spring - Used where a small difference in pressure in the valve.
= Nimonic spring - Used in high temperature applications.
= Heavy duty spring - This increases the required opening pressure.
When installed in line boiler feed water, can be used to prevent steam boilers of flooding when they unpressurised.
f. Split Disc Check Valve
check valve of this type is composed of a disk that the center is a shaft that allows the disc to move as if split in two when driven from the correct direction (foward flow) and closed tightly when pressed from the wrong direction (reverse flow).
- Safety Valve
Safety valve mechanism is a type of valve that automatically releases the substance of the boiler, pressure vessel, or a system, when the pressure or temperature exceeds a predetermined limit. Safety valve was first used in the boiler during the industrial revolution.
How it works Pressure Safety Valve:
Savety pressure valve has three main parts: the inlet, outlet and spring set. A pressurized fluid inlet is at PSV. PSV closed position during the fluid pressure is smaller than the spring pressure on the spring sets.
Conversely, if the fluid pressure is higher than the pressure of the spring set springset will move up and open the valve that will dispose of pressure through the outlet to a maximum fluid pressure equal to the pressure spring sets.
- Butterfly Valve
Butterfly Valve is a valve that can be used to isolate or regulate the flow. Closing mechanism takes the form of a disk. system operation is similar to a ball valve, which allows quick to close.
Butterfly Valve is generally preferred because the price is cheaper compared to other valve types. valvenya design lighter in weight than other types of valve to another.
Maintenance costs normally are lower because the minimal number of moving parts. A butterfly valve, illustrated in Figure below, is the movement of a rotating valve used to stop, regulate, and start fluid flow. Butterfly Valve is easy and quick to operate because of 90o rotation is driven by handwheel by moving the disk from fully closed to fully open position.
Butterfly Valve is suitable for handling large flow of liquid or gas at relatively low pressure and for handling slurries or liquids with large amounts of suspended solids.
- Globe Valve
Globe Valve is a kind Valve used to regulate the flow rate of fluid in the pipe.
The basic principle of operation of Globe Valve is a movement perpendicular to the disk of the stand. This ensures that the ring-shaped space between the disc and seat ring gradually close as Valve is closed.
There are three main types of designs Globe Valve body shape, namely: Z-body, Y-body and body Angle-:
= Z-Body design is the most common type that is often used, with the Z-shaped diaphragm disc tray horizontal position and movement of stem disk perpendicular to the axis of the pipe or the disc tray. The form is symmetrical facilitate the manufacture, installation and repair.
= Y-Body design is an alternative to high pressure drop. The position of the disc holder and the stem (stem) with a 45˚ angle from the direction of the fluid flow. This type is particularly suitable for high pressure.
= Angle-Body design is a basic modification of Z-Valve. This type is used to transfer the flow from vertical to horizontal.
Various forms Disc / plug of the Globe Valve:
a. Type Plug Disk
b. Regulating the type of disk
c. Type flat disk
d. Type soft seat disc
e. Type of disk guide
The advantage of using Globe valve are: The ability to close well. throttling capabilities (set flow rate) Pretty good.
The main weakness is the use of Globe Valve: The pressure drop is higher than the Gate Valve Valve large size requires considerable power or larger actuators to operate
