泡沫消防系统外文翻译(编辑修改稿)

泡沫消防系统外文翻译(编辑修改稿)内容摘要：

not possible to produce a foam which has all the desired properties, the experienced firefighter will utilize his foammaking appliances to the best effect according to the cirumstances. For example, varying the amount of foam pound introduced into the water stream will affect the expansion ratio, shear atress, and drainage rate, and formulations of foam pounds can be selected to give low (6 to 7 ), intermediate (8 to 12 ) or high expansion (12 to 16) foams. There are three main ytpes of foam extinguishment systems. The fixed system consists of storage tanks of the foam concentrate, foam pumps and proportioning system, as well as pipelines to various equipment or structures, and foam discharge devices. It is a centralized foam solution system, that will produce foam only at specified locatoins. The fixed systems have been used where large storage tanks are in use such as large marine terminals or bulk storage plants. The advantages of a fixed system are the following. (1)It is fast to operate. (2)It requires low manpower. (3)It makes efficient use of foam. The disadvantages include the following: (1)low flexibility (2)no mutual aid backup (3)high maintenance costs and high initial capital investment The semifixed system is the same as the fixed system with respect to foam discharge devices except that there is no central foam solution production and storage. Instead, mobile foamproportioning trucks or trailer mounted units are used to produce the foam solution. A backup truck is usually used for resupplying the units with foam concentrate. The advantages of this system are as follows: (1)flexibility to cover the entire plant (2)mutual aid possible (3)low maintenance costs (4)low capital investment The disadvantages of this system are as follows: (1)a time delay to operate of 5 to 15 minutes (2)manpower requirements are in the 24 man range Portable systems may be a bination of mobile and hand transportable equipment. The foam discharge devices may be foam towers, monitor nozzles or foam nozzles. This ststem is especially suited for spill fires. Some of the advantages of this system are: (1)flexibility (2)mutual aid (3)low maintenance costs The main disadvantages are: (1)high manpower requirements (2)not effective for large cone tanks. B. Foam Making Devices Both the fixed and semifixed methods use the same foam making devices, usually at the base of the tank. One system consists of a pipeline called a foam lateral, st。