Apparatus pumps and pump panels are getting a lot of attention lately. Some suggest that the recent shift in apparatus design to more multifunctional units means the pump module must be reduced in size to accommodate the extra equipment these multipurpose vehicles now carry. March’s Fire Industry Today countered that high-gallon-per-minute (gpm) pumps and additional compartment space are both required and very possible in today’s apparatus. This doesn’t mean, however, that our suppliers aren’t working toward reducing pump size. Customers are calling for it, and at last month’s Fire Department Instructors Conference, various pump manufacturers debuted recent evolutions of existing products as well as new ones to address this demand.
This month the pump discussion turns to single- vs. two-stage pumps. The debate over which to spec out on an apparatus reminds me a lot of the smooth bore vs. combination fog nozzle debate. Proponents on both sides will argue over the advantages of each, and often neither side changes positions. Dominic Colletti breaks it down into very simple terms: The pressure range in which you are likely to operate should determine which type of pump you spec.
My company runs two engines, both equipped with 2,000-gpm two-stage pumps. When I was an engineering officer, on the list of things I always went over when training new operators was a background on the pump. There was one thing I was always stuck on the drivers remembering. It’s one thing to remember that our trucks have two-stage pumps on them, but I wanted to ensure they knew when to operate in pressure and in volume. It’s one thing to know we have two-stage pumps. It’s another knowing how to use them properly. Pressure’s pretty easy-nine out of ten fires we’ll respond to won’t require us to be in volume. Get on scene, change the transfer valve from volume to pressure (to exercise the transfer valve), and away we go. It’s the large flows we need to worry about. And, we don’t always start out with the larger flows.
Besides large-diameter hose (LDH) drills, I don’t remember changing from pressure to volume once. I recall one LDH drill as a new pump operator where my truck was in the middle of a relay. The target flow was 1,000 gpm. I don’t remember why we did this, but in the middle of the evolution, we decided to run a portable deck gun off of my truck. When I charged the line going to the deck gun and brought it to the pressure I wanted, the truck started “screaming.” I soon remembered I was still in pressure. I reduced the rpm a bit, changed the transfer valve to the volume setting, and the truck settled down. Simply opening the discharge to the portable monitor increased my flow to more than 1,000 gpm.
The debates regarding the maintenance requirements of the two pump types, how simple one is vs. the other, or whether or not it even matters what departments spec notwithstanding, the type of pump you have on your engine doesn’t matter if you don’t know how to use it. Maintenance requirements? Not knowing how to use the pump is going to cause more problems than whether or not you have one or two impellers. Still testing your own hose? No pump is designed to operate for prolonged periods of time at high rpm without flowing any water. The pump won’t care how many impellers it has as it overheats.
Take a look at Firefighting Field Notes this month for more on single- and two-stage pumps. Also, check the “Talking Trucks and Equipment” radio show archives at www.fireapparatus.com for my interview with Dominic Colletti where we tackle the various ways pump design is impacting today’s apparatus design.
May Points to Ponder
Bill Adams’s Apparatus Purchasing installment this month covers center of gravity (CG) and how National Fire Protection Association (NFPA) 1901, Standard for Automotive Fire Apparatus, defines it. He goes on to explain how CG affects rollover stability and the certification that comes with a newly built apparatus. Adams asks, “How many people have taken delivery of a new rig contracted to be NFPA 1901-compliant and actually received certification of its rollover stability?”
My hunch is that many purchasing committees have one or two members who actually know such a certification arrived with the new apparatus. But, many things change between delivery and an in-service time of a few years, with equipment being a major factor. We all add items to our trucks over time. The question is, would your apparatus as equipped today still meet the guidelines it met to receive rollover stability certification at delivery? If you don’t know, figure it out now and take corrective action if necessary.
As always, you can reach me at email@example.com.