We are an Iranian major contractor in petrochemical oil and gas industries, Our company established
in 1969 in Tehran Iran, first we begin with manufacturing Steam traps and gradually
we focus on other products like Check valves, Ball valve, Butterfly valve and etc.
We have honor to representative of some big and famous companies in Asia and Europe
like Politeknik, Valftek, some Chinese companies.
This Company prepare all type of valves for NIOC (national Iranian oil company),
NIGC (national Iranian gas company), and Petrochemical major company in Iran.
Kar Avaran Bokhar company aim for future to have big business in world marketing.
And it is a honor for us to have a business with your company.
Articles
Ball valve
5/25/2009 10:49:12 AM
There are four general body styles of ball valves: single body, split body, top entry, and welded.
There are four general types of ball valves: full port, standard port, reduced port, and v port.
A full port ball valve has an over sized ball so that the hole in the ball is the same size as the pipeline resulting in lower friction loss. Flow is unrestricted, but the valve is larger.
In reduced port ball valves, flow through the valve is one pipe size smaller than the valve's pipe size resulting in restricted flow.
A v port ball valve has either a 'v' shaped ball or a 'v' shaped seat. This allows the orifice to be opened and closed in a more controlled manner with a closer to linear flow characteristic. When the valve is in the closed position and opening is commenced the small end of the 'v' is opened first allowing stable flow control during this stage. This type of design requires a generally more robust construction due to higher velocities of the fluids, which would quickly damage a standard valve.
A trunnion ball valve has a mechanical means of anchoring the ball at the top and the bottom, this design is usually applied on larger and higher pressure valves (say, 4" and above 600 psi and above).
Manually operated ball valves can be closed quickly and thus there is a danger of water hammer. Some ball valves are equipped with an actuator that may be pneumatically or motor (electric) operated. These valves can be used either for on/off or flow control. A pneumatic flow control valve is also equipped with a positioner which transforms the control signal into actuator position and valve opening accordingly.
Source:
http://en.wikipedia.org/wiki/Ball_valve
Types of check valves
8/3/2008 10:17:47 AM
A ball check valve is a check valve in which the disc, the movable part to block the flow, is a spherical ball. In some (but not all) ball check valves, the ball is spring-loaded to help keep it shut. For those designs without a spring, reverse flow is required to move the ball toward the seat and create a seal. The interior surface of the main seats of ball check valves are more or less conically-tapered to guide the ball into the seat and form a positive seal when stopping reverse flow.
Ball check valves are often very small, simple, and cheap. They are commonly used in liquid or gel minipump dispenser spigots, spray devices, some rubber bulbs for pumping air, etc., manual air pumps and some other pumps, and refillable dispensing syringes. Although the balls are most often made of metal, they can be made of other materials, or in some specialized cases out of artificial ruby. High pressure HPLC pumps and similar applications commonly use small inlet and outlet ball check valves with balls made of artificial ruby and seats made of artificial sapphire, both for hardness and chemical resistance. After prolonged use, such check valves can eventually wear out or the seat can develop a crack, requiring replacement. Therefore, such valves are made to be replaceable, sometimes placed in a small plastic body tightly-fitted inside a metal fitting which can withstand high pressure and which is screwed into the pump head.
There are similar check valves where the disc is not a ball, but some other shape, such as a poppet energized by a spring. Ball check valves should not be confused with ball valves, which is a different type of valve in which a ball acts as a controllable rotor to stop or direct flow.
A diaphragm check valve uses a flexing rubber diaphragm positioned to create a normally-closed valve. Pressure on the upstream side must be greater than the pressure on the downstream side by a certain amount, known as the pressure differential, for the check valve to open allowing flow. Once positive pressure stops, the diaphragm automatically flexes back to its original closed position.
A swing check valve is a butterfly-style check valve in which the disc, the movable part to block the flow, swings on a hinge or trunnion, either onto the seat to block reverse flow or off the seat to allow forward flow. The seat opening cross-section may be perpendicular to the centerline between the two ports or at an angle. Although swing check valves can come in various sizes, large check valves are often swing check valves.
This Siamese clappered inlet allows one or two inputs into a deluge gun.A clapper valve is a type of check valve used in firefighting, and has a hinged gate (often with a spring urging it shut) that will only remain open in the outflowing direction.
A stop-check valve is a check valve with override control to stop flow regardless of flow direction or pressure. When the valve is open, it acts as a check valve, but the valve can be deliberately shut to stop flow.
A lift-check valve is a check valve in which the disc, sometimes called a lift, can be lifted up off its seat by higher pressure of inlet or upstream fluid to allow flow to the outlet or downstream side. A guide keeps motion of the disc on a vertical line, so the valve can later reseat properly. When the pressure is no longer higher, gravity or higher downstream pressure will cause the disc to lower onto its seat, shutting the valve to stop reverse flow.
A double check valve is often used as a backflow prevention device to keep potentially contaminated water from siphoning back into municipal water supply lines.
There are also double ball check valves in which there are two ball/seat combinations sequentially in the same body to ensure positive leak-tight shutoff when blocking reverse flow; and piston check valves, wafer check valves, and ball-and-cone check valves.
Source:
http://en.wikipedia.org/wiki/Check_valve
check valve
8/3/2008 10:13:09 AM
A check valve, clack valve, non-return valve or one-way valve is a mechanical device, a valve, which normally allows fluid (liquid or gas) to flow through it in only one direction. Check valves are two-port valves, meaning they have two openings in the body, one for fluid to enter and the other for fluid to leave. There are various types of check valves used in a wide variety of applications. Check valves are often part of common household items. Although they are available in a wide range of sizes and costs, many check valves are very small, simple, and/or cheap. Check valves work automatically and most are not controlled by a person or any external control; accordingly, most do not have any valve handle or stem. The bodies (external shells) of most check valves are made of plastic or metal.
An important concept in check valves is the cracking pressure which is the minimum upstream pressure at which the valve will operate. Typically the check valve is designed for and can therefore be specified for a specific cracking pressure.
Heart valves are essentially inlet and outlet check valves for the heart ventricles, since the ventricles act as a pump
Source:
http://en.wikipedia.org/wiki/Check_valve
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