Wye Operations: Tactical and Strategic Problems

摘要

ATTEMPTING MODERN FIRE FLOWS of 160 to 185 gallons per minute (gpm) through a 13/4-m. hoseline when connected to a wye and a 21/2-in. trunk line presents troubling concerns. Even when the rules of equal leg lengths and matched nozzle pressure (NP) and flow are followed, problems can be significant. Negative issues can range from an uncontrollable nozzle to a substantial drop in flow from both of the 13/4-in. attack handlines. The hydraulic/mathematical examples at the end of this article demonstrate what occurs hydraulically and the negative impacts those insurmountable truths of physics will have on the fire stream's development of each handline leg of a wye operation. However, before we get to that point, let's have an honest discussion of the human factors of deploying a wye off a trunk line and reducing it into two smaller attack handlines. Not only hydraulic issues, which have been highlighted by the move to a nationally accepted 150-gpm minimum target flow rate for a small handline, but also human factors play a critical role.