Basics｜Precision pumping technology 2-4. Pulsation: Anti-Siphon Check Valve
An anti-siphon check valve has the following three functions.
Function 1: Holding and Stopping Water From Flowing Out
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.
You may have experienced an experiment like the above in elementary school science. The same phenomenon occurs in a diaphragm pump.
It is easy to fill the hose with water using a diaphragm pump--you merely have to turn on the switch. The liquid will keep flowing even after turning off the switch.
As shown in the diagram to the right, if the liquid surface is higher than the tip of the discharge-side pipe, liquid will keep flowing out due to siphoning, even when the piping is as illustrated by the dotted line.
Function 2: Preventing Overfeeding Caused by Inertial Resistance
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.
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.
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.
The actual structure is as shown below.
Function 3: Check Valve Action
The anti-siphon check valve also functions as a normal check valve.
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.
TACMINA's Smoothflow Pump is a diaphragm pump with no pulsation, which relieves it from the impact of inertial resistance. Be completely free from the problem of overfeeding.
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