Posts in fire stuff

Yet another pump operations/water flow post, sorry folks! If only it weren't so darn interesting...

This is another "Zeph convinces themself that the book is right" post, this time on a statement about laminar versus turbulent flow in hoses:

The pressures in hose are typically high enough to cause turbulent flow.

If you're interested in a demonstration of this, buckle in and come along! If not, might I suggest different reading material?

Yet another post on pump operations, sorry y'all. This one, like a previous post, is me coming to terms with a statement about water flow in a textbook. This time around, I'm looking at how to estimate additional hydrant capacity if you're already flowing some amount of water from your hydrant.

Big picture, I'll do some calculations based on Bernoulli's equation to show how much additional water flow a hydrant can provide, then I'll briefly compare that to two of the three methods discussed in Sykes and Sturtevant's 1999 Fire Apparatus Operator: Pumper textbook.

Well, guess who's still making sense of water flow through hose and pumps these days? (Yep, you got it. It's me.)

Today I finally figured out a point of confusion I'd had for weeks around the relationship between pressure and volume of flow out of a nozzle. Turns out the answer has to do with a new-to-me way of viewing pressure that offers some additional tools for reasoning about how water flow works.

Head pressure is the pressure created by a difference in height between where water is coming from and a discharge. It's important for things like how much pressure you'll get from a hydrant or how much pressure you lose if you're pumping up a steep driveway. If you read a textbook, it'll say something like

To convert head in feet to head pressure in psi, divide the number of feet by 2.304.

This is me proving to myself that that works. (Spoiler alert: it does.)

I've been slowly learning how to operate the pumps on Mt. Erie's apparatus. A lot of that is hands-on stuff – flip this switch and then pull this lever to accomplish goal xyz. Those details are really important, but for my specific brain, I benefit from understanding the underlying theory too, so I've been reading up a bit and trying to build intuition around some of the fundamentals.

In doing so, I learned something that blew my mind: there is a physical limit to how high up you can possibly suck water, no matter how good your pump is. This is my attempt to explain that in a way that actually builds intuition rather than just memorizing "oh, we can only suction 10 vertical meters in the best case".