See full version: Petroleum Equipment Institute
A valve installed in an aboveground tank system to prevent liquid from accidentally flowing out of the tank. An anti siphon valve is often needed where the liquid level in the tank is higher than the elevation of the dispenser or any of the product piping.
An alternate anti-siphon scheme operates not as a flow preventing valve, but rather as a siphon breaker. On systems where the piping connections come out of the top of an AST it consists of a small normally open solendoi valve which is installed in the highest point in the pipe run. It is de-energized (open) when the pump is not running. Loss of prime back into the tank is prevented by installing a check valve in the suction riser pipe coming up out of the tank. When the pump is turned on, the solenoid is energized, and it closes. Normal pump suction draws fuel up out of the tank, and down to the pump. When the pump is shut off the solenoid (siphon breaker) opens again. If there is a leak, or a valve in the pump or downstream of the pump is accidentally left open, or of a pump seal fails, fuel will flow out of the system, but with the siphon breaker introducing air into the piping as fuael flows out, only the amount of fuel held in the pipe will spill out. None will be drawin out of the tank by siphon, because the siphon breaker has introduced air into the suction line and broken the continuaou siphon effect. [links]
The force of gravity causesfuel in the tank constantly to try to flow through the pipe connecting it to the dispensing pump at the marina below. Some positive shut off device needs to be present in the piping to prevent this from happening, except during those periods when the operator specifically desires that product flow through the pipe.
Between the injection point on the exhaust elbow and the heat exchanger. here
If there’s a vent tube heading to the vent overboard, be sure to check whether it is clogged, as clogging (by bugs and other stuff) might produce a similar effect to when the valve remains closed – that is, the siphon flow is not stopped when it should. here
Also, you need to clean them at least once per year to ensure there is no clogging. That way, you will keep them working properly.
In contrast, as the water flows, the valve ought to stay closed, so the water doesn’t come out of the air hole.
When the spring is as shown in the illustration, the inertial force is already gone, and the pump (piston) is in its discharge cycle. The diaphragm pump function increases the pressure inside the piping, which overpowers the spring and opens the valve to discharge liquid. here
An anti-siphon check valve also prevents the overfeeding that may occur due to inertial resistance. Basically, an anti-siphon check valve accomplishes this by holding the exit of the pipe with a force greater than the inertial resistance. It typically uses a spring to hold down the exit with a specific pressure. The valve opens only when a force exceeding that pressure is applied. here
An anti-siphon check valve has the following three functions.
One of its functions is to prevent siphoning, which is where its name comes from.
Siphoning is a phenomenon that occurs when the tip of the pump's discharge-side pipe is placed lower than the liquid surface in the suction-side tank and the liquid keeps flowing after the pump stops.
Let's think about an application as shown in the example above. If the pressure inside the tank is high, without a check valve, gas or liquid will blow out the moment the hose is removed, creating a dangerous situation. That’s why a check valve needs to be in place to ensure safety. This check valve mechanism is particularly useful during maintenance.
The pump (piston) is already in its suction cycle, so the force applied to the valve is only the inertial force.
Pa (pascal) is a symbol for a unit of measurement for pressure and indicates how many newtons (N) of force is applied per square meter. Pa is a small unit to be used as pressure for pumps, and hence is bound to have large digits. Therefore, MPa (megapascal), which is one million Pa, is commonly used. here
Let's think about an application as shown in the example above. If the pressure inside the tank is high, without a check valve, gas or liquid will blow out the moment the hose is removed, creating a dangerous situation. That’s why a check valve needs to be in place to ensure safety. This check valve mechanism is particularly useful during maintenance.
An anti-siphon check valve also prevents the overfeeding that may occur due to inertial resistance. Basically, an anti-siphon check valve accomplishes this by holding the exit of the pipe with a force greater than the inertial resistance. It typically uses a spring to hold down the exit with a specific pressure. The valve opens only when a force exceeding that pressure is applied. here
One of its functions is to prevent siphoning, which is where its name comes from.
Siphoning is a phenomenon that occurs when the tip of the pump's discharge-side pipe is placed lower than the liquid surface in the suction-side tank and the liquid keeps flowing after the pump stops.
When the spring is as shown in the illustration, the inertial force is already gone, and the pump (piston) is in its discharge cycle. The diaphragm pump function increases the pressure inside the piping, which overpowers the spring and opens the valve to discharge liquid. here