Let's think about what kind of problems can occur when bubbles enter into the pump head of a diaphragm pump.

Suppose that air bubbles entered the pump head when the diaphragm is at the top dead center, i.e. the innermost position, as shown in Fig. 1.

When the diaphragm moves out, negative pressure develops inside the pump head, and the bubbles expand. (Fig. 2)
At almost the same time, liquid is sucked in to cancel out the negative pressure, and the pressure and the air bubbles return to their original size.
Here, if there were no bubbles, liquid is barely compressed; when the diaphragm moves forward, the liquid immediately pushes the check valve up and is discharged out of the pump.

However, when air bubbles are inside the pump head, the following occurs due to the property of gas that when gas is compressed, its volume decreases.

As the diaphragm moves forward, bubbles are compressed. Based on Boyle's law ("4-1. Air Chamber"), this indicates an increase in the pressure of the air bubbles. (Incidentally, the liquid around the bubbles also has the same pressure as the bubbles.) Here, if the pressure inside the pump head is greater than the force holding down the ball check valve at the discharge side, the liquid and bubbles push the check valve up and flow out of the pump. (Fig. 3)

However, when it is the other way around, i.e. if force (1) is greater than force (2), the consequences are quite different.

When a condition as illustrated in Fig. 4 occurs, the check valve acts like a cap or seal, and the bubbles inside the pump head only contract and expand along with the motion of the diaphragm. As a result, the bubbles and liquid inside are not discharged.
This is called a gas lock.

Gas locks are also discussed in the Topic "What is Gas Lock?" A video on TACMINA's anti-gas lock pump, designed specifically for the sodium hypochlorite process, is also available for your viewing ("Actual video of automatic air release mechanissm").

TACMINA's DCLPW Series, dedicated to sodium hypochlorite injection, offers a perfect solution to injection problems with its double block mechanism that prevents gas locks.
More...