CCS has developed pressure switches for non-hazardous industrial (604GV) and hazardous areas (646GVE) that are used to control both negative atmospheric vacuum pressures as well as positive gage pressures at the same time. In the chart below, you can see a comparison between the different pressure setting ranges of a standard gage (646GE1) or standard vacuum (646VE1) pressure switch and the 646GVE1 crossover switch.
Our standard 646GE measures only standard gage pressures from 0.4 to 16 psi. Our standard 646VE1 measures only negative atmospheric vacuum pressures from 0.4 to 28 inches of Mercury. The 646GVE1 cross-over switch has the ability to not only monitor gage pressures like the 646GE1, but can also measure vacuum pressures like the 646VE1 and can be set for either. You can see that the cross-over switch is typically used to prevent a vacuum situation from occurring, or allowing a slight vacuum but not a very high pressure vacuum situation.
A common application where using a crossover makes a lot of sense is to prevent pump cavitation damage. When using a pump, cavitation can occur when the Net Positive Suction Head is less than what is required, generally when a pipe becomes clogged and natural flow is interrupted. Loud wrenching noises will then occur as pipes and other vessels are strained. Flow is then stopped and the pump still wants to continue suction causing high vacuum pressures.
A CCS 646GVE1 cross-over switch can be set to trigger the pump to shut down when it senses that this high vacuum situation is about to occur and will prevent damage. And since this same switch can also monitor against standard gage overpressures in the vessel, it makes a powerful two-for-one combo.