Chlorination / Dechlorination Shelters
Purpose of Dechlorination / Chlorination Shelters
A subset of our Water and Wastewater Shelters, Openchannelflow’s Chlorination / Dechlorination Shelters are to house chemical treatment systems, and their corrosive effects away from other parts of your plant. By housing the systems in purpose-built shelters, operators are kept safe and the equipment secure!
Gaseous chlorine is heavier than air. This means that in the event of a leak, the chlorine will sink to the floor of the shelter and then fill the shelter from the floor up. To protect operators, it is important to keep this in mind when locating fans, shutters, and other equipment in gaseous chlorine shelters.
The traditional approach to operator safety is to locate an EXHAUST fan LOW in the shelter, towards the floor, with a switch on the outside of the shelter so that the operator can exhaust the shelter before entering. The fan is located as far away from the shelter’s door as is practical so that the operator is not exposed to the exhausted air. The INTAKE shutter is typically mounted HIGH in the chlorine shelter, on a wall OPPOSITE the wall the fan is mounted on. This allows fresh air to be drawn across the room and the chlorinated air is exhausted.
Unfortunately, this means that the LOW mounted EXHAUST fan is exposed to the corrosive effects of chlorine gas - limiting the life of the fan.
A better approach is to use a CORROSION RESISTANT fan in lieu of a standard construction exhaust fan. This will extend the life of the fan and improve operator safety - but only to a point.
Better yet, the chlorine shelter’s fan can be mounted HIGH and in a SUPPLY (blowing in) configuration. Here the fan is kept out of the heavier chlorine gas if there is a leak, increasing long term reliability. The shutter is mounted in an EXHAUST configuration and away from the shelter’s door.
For the ultimate in reliability and operator safety, this SUPPLY fan layout should be coupled with a corrosion resistant fan.
Note that shutter motors are not recommended in fan HIGH, shutter LOW configurations as the shutter motor could corrode and stop the shutter from opening when the fan is activated.
The corrosive nature of chlorine gas is of great importance when selecting HVAC, electrical, and door hardware for chlorine shelters.
By its very nature, chlorine gas has little effect on fiberglass - making fiberglass shelters the natural starting point to house gaseous chlorine.
As we have seen above, supply fan should be of a corrosive resistant construction. Likewise, shutters should have fiberglass and/or stainless steel construction.
For heaters, as they are usually mounted lower in the shelter, towards the floor, they should be easily field replaceable. Milk-house style heaters on shelves are best here. Should the heater fail, it can be easily unplugged and replace, eliminating the need for an electrician to wire a new heater as would be the case with an on-wall, line powered heater. Heat lamps are also a low cost solution to maintain the temperature in smaller chlorination / dechlorination shelters.
Load centers should be rated at a minimum of NEMA 3R and the housing should be non-metallic. Ideally, the load center housing should be NEMA 4 or 4X where practical. This may require that the load center be housed in a surrounding, rated enclosure.
Interior light fixtures should similarly be gas tight and corrosion resistant, with LED fixtures being preferable as there is no need for the regular changing of bulbs as there are with incandescent or fluorescent bulbs.
Door hardware should always be stainless steel. Hinges should ideally be SURFACE mounted on the OUTSIDE of the chlorination / dechlorination shelter - keeping the hinges away from the gaseous chlorine.
Interior access hardware should be of a PUSH / PANIC BAR style and of stainless steel construction to allow the operator to exit the shelter as quickly as possible in the event of a leak. Outside, it is common to see a key locked or padlocked, lever style latch.
Two/three-point hardware should NOT be used in gaseous chlorine applications as even with an anti-entrapment configuration, the operator will not be able to exit the shelter as quickly as they can with a push / panic bar.
The door should have a stainless steel overhead hydraulic closer on the inside to ensure the door closes in the event of a leak. Like other stainless steel elements exposed to the environment inside the chlorination / dechlorination shelter, the door closer should be 316 stainless steel.
Operator safety can be enhanced by the inclusion of observation window set in the door. U.V. resistant polycarbonate with a push-in-place gasket is a common for door windows.
At smaller treatment facilities, it is not uncommon to see a single shelter used to house both electronics / controls and chlorine gas cylinders. In those applications, the chlorination / dechlorination shelter is usually partitioned into two gas tight compartment. With the chlorine cylinders / feed equipment in one compartment and the controls / electronics in the other compartment.
