These tests were performed by Lyndon Cousins. Below is Lyndon’s explanation of his tests from the Firenotes mailing list.
Subject: [FN] Kinks
From: Lyndon Cousins
Date: 09/10/15 11:58 PM
To: Firenotes Mailing List
This is a project I’ve been trying to complete for some time, and I finally got it done: http://youtu.be/YBReQ_uuF4o
It’s obvious that kinks reduce the flow in hose lines, but I was curious just how much. I’d read an article about some tests that some FFs did with automatic nozzles, low pressure automatic nozzles, and solid bore nozzles, and the findings they got. Which prompted me to try a test with the leader line that we most commonly use.
I’ve attached the whole chart (see YYC Handline Kink Tests 44mm.xlsx) with all the test results to this as well. In the video, I focused on the results with 950 pump discharge pressure, but we also did the same tests with 620 PDP, which you’ll see on the chart. I think it makes a pretty clear argument for stretching your dry lines clean and setting up properly before charging. And then once you charge the line, ensure that it’s kink free before committing to fire attack. It takes some practice, but is very worth it.
Estimate the hose required, stretch it dry to the threshold, flake it out cleanly, charge it, flow it to ensure a good stream (if you don’t practice with the proper flow rates regularly, you won’t know what it feels like to know if it’s right when you need it.) and then advance it into the fire area. It takes a disciplined team to do it efficiently, especially when there are lots of corners and obstacles, or conditions are difficult. Practice.
Here’s another link to a video that shows just how little water hammer makes it back to the truck when you shock the line to push the kinks out: (Scroll down, it’s the only video on the page.)