Professional Engineeing Publication

Many important design provisions for chlorination building relate to the safe use of chlorine and the protection of those working with it. Chlorinator rooms should be at or above ground level and Container storage should be planned so that it is separate from chlorinators and accessories. It is logical to locate the chlorination room near the point of application to minimize the length of chlorine line for reducing the possibility of reliquefaction at the pressure gas manifold & chlorinator. Other general site considerations include a location which permits ease of access to facilitate container transport and handling, adequate drainage, and separation from other work areas.

1) Separation

Proper design standards require either a completely separate chlorination building or a room completely separate from the remainder of the building with access only through an outside door. There should be no apertures of any type from the chlorination room to other parts of a common building through which chlorine gas could enter other work areas.

2) Fire Hazard

The building should be designed and constructed to protect all elements of the chlorine system from fire hazard. If flammable materials are stored in the same building, a fire wall should separate the two areas. Fire-resistive construction is recommended. Water should be readily available for cooling containers/cylinders in case of fire.

3) Space Requirements

Modern chlorination equipment is available in modules so that the chlorinators and accessory equipment can be arranged in a skid mounting type. There should be about four feet between the front of a module and the nearest wall and about two feet on the sides and rear. There should be adequate room provided to allow ready access to all equipment for maintenance and repair. There should be sufficient clearance to allow safe handling of equipment containers.

4) Ventilation

Adequate forced air ventilation is required for all chlorine equipment rooms. An exception to this would be small chlorinator installation (less than 100 lb/day) located in separate buildings if the windows and doors can provide the proper cross-circulation. For a small building, windows in opposite walls, a door with a louver near the floor, and a rotating- type vent in the ceiling usually provide the necessary cross-ventilation.

Factors to be considered in the design of a ventilation system are: air turnover rate, exhaust system type and location, intake location and type, electrical controls, and temperature control. A forced air system should be capable of providing one complete air change in 2-5 minutes. Since chlorine gas is 2-1/2 times heavier than air, it is logical to provide air inlet openings for ventilation fans at or near floor level. (Room ventilation air should always enter at floor level and exit at ceiling or roof level, because vapor leaks will always followed by the air circulation path.)

For small installation it is common to employ an exterior exhaust fan with the intake duct extending to the chlorine room floor. A wall-type exhaust fan is an acceptable alternative. The exhaust system should be completely separate from any other ventilation system. For larger installations a blower-type fan is needed. The use of free-moving, gravity-operated louvers may be advantageous in colder climates for conserving room heat when the blowers are not in operation; however, venting systems should not have covers. The fan discharge should be located so as to not contaminate the air supply of any other room or nearby habitations. It is mandatory that the ventilation discharge be located at a high enough elevation to assure atmospheric dilution, e.g., at the roof of a single-story building.

Air inlets should be so located as to provide cross-ventilation. To prevent a fan from developing a vacuum in the room and thereby making it difficult to open the doors, louvers should be provided above the entrance door and opposite the fan suction. In some cases, it may be necessary to provide temperature control on the air supply so that the chlorination system is not adversely affected. A signal light indicating fan operation should be provided at each entrance when the fan can be controlled from more than one point.

5) Wind Socks

All installations should locate at lest one wind sock on the chlorine supply structure. This is very valuable in the event of a leak. The sock should be as high as possible.

6) Doors

Exit doors from the chlorination room should be equipped with emergency hardware and open outward. Some design guides recommend two means of exit from each room or building in which chlorine is stored, handled, or used; this would not appear to be essential in most cases.

7) Inspection Windows

A means should be provided which permits viewing of the chlorinator and other equipment in the chlorination room without entering the room. A clear-glass, gastight window which is installed in an exterior door or interior wall of the room is recommended. Door windows appear to be a logical provision even with a separate wall inspection window.

8) Heating

The chlorinator room should be provided with a means for heating and controlling room air temperature above 55^oF. A minimum room temperature of 60^oF has been recommended as a good practice. Ideally, the heating system should be able to reliably maintain a uniform moderate temperature throughout the chlorination room. Hot water heating is generally preferred because of safety considerations and the uniformity of temperature which this method of heating provides, without the extremes which might be experienced with failure of a steam heating system. Electric heating is suitable, and forced air heating would be appropriate if an independent system is provided for the chlorination room or building. Central hot air heating is not acceptable since gas could escape through the heating system.

Chlorine vapor leaving a container/cylinder will condense if the piping temperature is significantly lower than the temperature of container/cylinder. The design should provide a higher temperature in the chlorinator room than in container/cylinder room. This applies to systems using the gas phase from the containers/cylinders. Elimination of unnecessary windows may aid in maintaining uniform building temperatures. The minimum allowable temperature for the chlorine storage room area is about 50^oF. Below this temperature the flow of chlorine becomes sluggish and erratic, particularly for small installations, from 1 to 20 lb/day. Heat should never be applied directly to a chlorine container/cylinder. Steel will ignite spontaneously at about 483^oF in the presence of chlorine.

If the storage area for in-service containers/cylinders is properly designed, external chlorine pressure- reducing valves are not required. If the location of these containers/cylinders is remote, an external reducing valve should be installed as close as possible to the containers/cylinders. (When remote vacuum systems are used, external pressure reducing valves may be required to provide a two-step pressure reduction owing to ambient conditions.)

9) Drains

It is generally desirable to keep the plant floor drain system separate from that of chlorinator. Drainage from a chlorinator drain relief valve may contain chlorine. Consequently, hose, plastic pipe, or tile drains are recommended. The discharge should be delivered to a point beyond a water-sealed trap or disposed of separately where there is ample dilution.

Scale pits are generally designed with floor drains having a water-sealed trap. In actual practice most traps do not contain enough water to form a seal, and it would be preferable to provide a straight pipe drain outside to grade.

10) Vents

Chlorinators, external pressure-reducing valve, remote vacuum systems, and automatic switchover systems have vents to atmosphere. Since the advent of the 1988 Uniform Fire Code, (UFC) these vents cannot necessarily be allowed to discharge directly to the outside air as has been practiced since the use of vacuum operated chlorinators. This represents a span of 70 years without any damaging results because chlorine vapor emissions (as opposed to liquid spills) are diluted quickly by the ambient air. Dealing with these vents to comply with the UFC.

These vents lines must be piped in such a manner that moisture is not allowed to accumulate in the piping. This means that some will have to be equipped with a condensate trap if the piping cannot be arranged to allow the moisture to drain from the vent line. Those vents that are required to "Breathe" should be fitted with a wire screen at the discharge end to prevent the usual invasion of insets.

In all cases, manufacturers' instructions should be followed closely regarding piping requirements. It is acceptable to run the vent vertically (but no more than 25 feet) above the location of the unit that vents.

11) Electrical

Controls for fans and lights should operate automatically when the door is opened, and there should be provisions to active these manually from outside the room. Switches for fans and lights should be outside of the room at the entrance. A signal light indicating fan operation should be provided at each entrance when the fan can be controlled from more than one point.