Deep Bed Fiberglass Filter Systems

DOE-STD-1066-99

The spray nozzles for horizontal beds or drawers should be oriented above each bed or

drawer and be of such design to distribute water evenly across the top of each bed or drawer

at a minimum density of 0.25 gallons per minute per square foot.

The spray nozzles for vertical beds should be oriented at the top of the bed and be of such

design to distribute water evenly across the top of the bed at the rate of 3.2 gallons per

minute per cubic foot of charcoal bed.

A supervised fixed temperature detection system should be provided and connected to an

annunciator in the control room. The detectors should be located on the down stream side

of the charcoal bed for automatic operation of the spray systems.

The spray system should be equipped with a local alarm and connected to an annunciator

in the control room.

The air flow should terminate (fan shut off) upon water activation.

For the pressure vessel type charcoal filter, where a shut-off by-pass arrangement is

employed around each tank, an automatic water spray system is not required. We [the

insurance carrier] recommend a hose connection be available on the side of the tank to allow

the introduction of water.

Deep Bed Fiberglass Filter Systems

One method investigated to extinguish fiberglass filter fires was water spray systems. Early designs

of deep bed fiberglass filters did not address filter media replacement, and over a period of years, the

fiberglass filters plugged to the extent that the systems could not meet ventilation airflow requirements.

Water sprays and steam were applied to the filters for cleaning the plugged filters, but with little

success. It is generally accepted that water applied to this type of filter media in the event of fire could

extinguish the fire. However, accumulation of radioactive material present in the filter media would

still be released to the environment when the water is applied.

Since the goal of ventilation systems is to continue to perform their safety functions effectively under

all conditions by confining radioactive or other potentially dangerous materials and the efficiency of

deep bed fiberglass filter systems is generally not adequate, these type of filters must be accompanied

by additional downstream filters such as a HEPA.

Deep Bed Sand Filter Systems

For the most part, sand filters are fire resistant, chemically inert, and require no special fire protection

systems. Sand filters are usually accompanied by HEPA filters. When a sand filter is used in series

with HEPA filters it should be upstream of the HEPA. In this position, the sand filter can protect the

HEPA filters that provide the final containment barrier.

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