Waukesha Air Blow Check Valve with FNPT Connection
In a previous post we have discussed sanitary check valves, their design and applications. There is a one type of sanitary check valve we did not cover, the air blow sanitary check valve. The sanitary air blow check consists of a sanitary clamp two piece body with an orifice on the product side. A rubber spring loaded stem seats in the orifice. The connection on the other end is normally either a female NPT or hose barb. This end is designed to attach to an airline. This valve can be purchased as a standalone valve or as part of a sanitary ball check valve/air blow check assembly. The assembly is made up of a standard sanitary ball check valve with a disk type air check valve clamped to the wye branch.
When do you use a sanitary air blow check valve? Primarily for product line evacuation. Many sanitary process line applications have a check valve mounted downstream of pumps to prevent any backflow when the pump is shut off. If an air blow check is mounted to the branch of the valve, the valve can also be used to push residual products downstream at the end of a process run. It can also be used as an entry point for an air/nitrogen blow down of lines post cleaning cycles, eliminating the need for an additional tee and valve in a process line.
The other application we see all the time for air blow checks is in PIG operations. If you want to completely evacuate your lines and recover any residual product, you normally have to PIG the lines. This is especially true with thick, viscous products like chocolate. Pigging a line entails forcing an elastomer projectile through the process line which forces residual product out the other end. A variation of the sanitary ball type air blow check valve is often used as the PIG loading/launching point. This entails using a sanitary lateral wye, where the branch has a fairly long tangent (longer than the length of the PIG you are using). An air blow check
Air Blow Stems are Available in Either EPDM or FKM
valve is clamped to the end of the wye. The line is then evacuated by removing the air blow check for the wye and inserting the PIG. The valve is then clamped back onto the wye. When air pressure is applied to the air check, the PIG is forced down the line, evacuating all of the product. A second check valve or shutoff valve is required upstream of the wye to allow the line to pressurize and the protocol to work. You also need a PIG capture device on the other end of the line that automatically relieves the gas pressure in a safe manner, in addition to stopping the pig. We will discuss the entire pigging process in more detail in a future post.
Sanitary air check valves are available to fit 1” through 4” sanitary clamp lines. They come standard in 316 stainless steel. Valve stems are available in both EPDM and FKM (Viton). It’s a handy little device that can be used in a lot of applications. Contact us if you have any questions on this or any other sanitary process applications. We don’t mind. It’s what we do.