TB 7 - Fighting Fires with Large Spray Streams

Question 1

Advantages of Spray Streams:

Answer 1

1. Greater SURFACE AREA of cooling
2. More efficient use and less water damage due to more COMPLETE TRANSFER of HEAT
3. Smaller water droplets RAPIDLY convert into vapor (REDUCING surrounding 02)
4. SHIELDING personnel from RADIANT heat and can make an area MORE TENABLE where heat and smoke constitute a serious hindrance to firefighting.
5. Greater COVERAGE area due to wider angle of stream
6. More easily managed at higher PSI and delivering more GPM.
7. More effective on some flammable liquid and electrical fires

Question 2

Disadvantages of Spray Streams

Answer 2

1. Less reach due to “SKIN FRICTION” (water vs air)
2. “Skin friction” causes entrained AIR to be DIRECTED toward fire. (May or may not be desirable)
3. Some spray droplets MAY NOT be large enough to REACH heated area around fire due to WIND or drafts
4. Large fires demand good REACH and VOLUMES of water. Spray nozzles CANNOT DO BOTH simultaneously.
5. Creates more HOT STEAM which may make a confined area temporarily UNTENABLE

Question 3

Water expands into steam at a ratio of 1 to ______ with 1 gallon of water capable of producing about 227 cubic feet of vapor.

Answer 3

1700

Question 4

1 gallon of water absorbs _____ BTU in changing to steam

Answer 4

9330

Question 5

The PHYSICAL differences between spray streams and standard straight streams are:

Answer 5

-SIZE of water droplets

-SHAPE of stream

-Effective REACH

Question 6

Spray streams are of excellent value in killing the heat of a large body of flame if accompanied by?

Answer 6

sufficient VOLUME of discharge.

(VOLUME of water is generally MORE IMPORTANT than any excess in pressure over that necessary to produce a stream which will reach the seat of the fire.)