Design Considerations


This analysis is intended to bring out the efficiency of the various primary water supplies and fire protection delivery systems. The four sources of water supply in the order of the frequency with which they are found are waterworks, gravity tank, pressure tank and automatic fire sprinkler pump. A glance at a fire protection system shows that the automatic fire sprinkler pump was comparatively seldom found, while the waterworks was the source of supply in a little over one half of the fire protection systems.


A further study of any fire prevention system will show the relative water pressures found in these fire protection systems. The decidedly higher average for fire sprinkler pressure tanks should be noted and kept in mind when some of the other sprinkler head data is considered. A complete fire sprinkler system also shows the average number of sprinkler heads operating for each fire sprinkler system, and here we find a much better value for the pressure tank than for, the others, while the automatic pump is decidedly the poorest of the four. This fact seems to emphasize the necessity of giving a system depending on an automatic sprinkler system pump a more liberal water supply than is customary for others less efficient sprinkler fire protection systems.

An automatic fire sprinkler system is intended to furnish direct comparison of the different sources of water supply with respect to a fire protection system’s efficiency in the control of fires and prevention of property loss. There seems to be two important points brought out in respect to the control of fires:

(1) The automatic fire sprinkler system with a pressure tank has a decidedly higher percentage of extinguished fires and the lowest value for unsatisfactory fires;

(2) The automatic fire sprinkler system that uses a pump has had by far the largest percentage of unsatisfactory fires. There are several conditions which bring about unsatisfactory results from automatic fire sprinklers in case of fire, among which the proper maintenance of the fire protection system is probably the most important. This sprinkler pipe and sprinkler heads would seem, therefore, to indicate the greater probability of a supply from an automatic fire sprinkler pump being out of order. The reasons for the superior showing of the fire sprinkler system that uses the pressure tank are probably due to several factors, one of which may be the higher average pressure.

The lower half of the fire prevention system brings out practically the same points, when we consider the four sources of water supply, in reference to the amount of fire loss or damage. A little more than half of the fire protection and automatic sprinkler fire protection systems that use pressure tanks fires have resulted in no claim for fire loss, while the probability of a large fire loss with this kind of water supply is only seventy-five percent as great as for the average of all water supplies. The probability for a large loss with an automatic sprinkler system using a pump is over twice as great as with a pressure tank and fully one and one-half times as great as the average for all sources of the entire water supply.

Many new sprinkler heads offer a means for comparing the pressure and number of automatic fire sprinkler’s opening for different fire protection systems as well as for fires extinguished, held in check, no claim, small fire loss, etc., for the same system. The first noticeable fact is that in every case the average water pressure of any fire sprinkler system is the lowest value for unsatisfactory or large loss fires. However, the pressure for such fires is not decidedly less, nor does it present such a difference, as exists between the average pressures of the various fire protection systems.


The comparatively low pressure of the fire sprinkler system that uses a gravity tank is emphasized. This low average water pressure for the gravity tank fire system presumably must have been somewhat of a drawback to such a system but not as great as one might imagine, as is evidenced by the comparative results shown in the fire sprinkler head’s failure. The average number of automatic fire sprinkler heads shows some interesting features. Note the tremendous increase of fire sprinkler heads opening under large loss fires and the generally higher value throughout for the automatic sprinkler system pump.


#firesafety #firesprinklers

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