In our last post, we discussed ozone generator protection in general. In this post we will cover protecting the ozone generator from back flow of water. When ozone is being injected into a pressurized water line, it is possible under certain conditions for the water to back flow into the generator causing sever damage to the system.
In order to prevent this catastrophic failure, back flow prevention systems must be used. Given the potential damage possible, multiple protection devices are employed. The simplest is a check valve. While check valves are simple and inexpensive, they are not particularly reliable. Check valves are almost always used, but not as the sole method of protection. A new type of check valve using the hydrophobic properties of flouropolymers are being tested as a solid state check valve, but these devices have seen limited use to date.
Typically, ozone is introduced into pressurized lines by means of a venturi injector. The venturi creates a vacuum that draws the ozone gas into the liquid. If this vacuum is lost, it is possible that water could back flow. So, one protection method employed is a vacuum switch. When vacuum is lost a signal can be sent to a solenoid valve to close before water has a chance to flow towards the ozone generator. Alternatively, a pressure switch could be used if it is set below the pressure of the generator.
A third level of protection employed is a liquid trap. This device has a float that opens when water back flows into it. The float opens a line to drain to divert the back flowing water to the drain instead of the ozone generator. It is important to make sure that the materials in the liquid trap are compatible with ozone exposure.
A fourth level of protection is a sensor that detects liquid somewhere in the gas line between the venturi and the ozone generator. One such device employs ultra sonics. It has a forked sensor that can detect a difference between air and a liquid in the gap of the fork. This signal can be used to shut the solenoid valve protecting the ozone generator.
A well designed ozone water treatment system with ozone feed into a pressurized line should have at least two and probably three of these devices in place to protect the ozone generator. Spartan Environmental Technologies employs a three way protection system in its SPARTOX ozone water treatment system.
