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Permalink Reply by Mike Schlags (Captain Busy) Retd on December 30, 2010 at 12:32pm

Hydraulics and Underwear

I don't know about anyone else, but my preference for remembering hydraulics was the companies name, HANES, as in the underwear / tee shirt folks...

H - hose diameter
A - appliances
N - nozzle type
E - elevation
S - standpipe

These are the basic factors that can affect friction loss and what is delivered out the nozzle...

CBz

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Permalink Reply by Ben Waller on December 30, 2010 at 1:37pm

The mechanical version of the old cartoon character "Pushmepullyou"?

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Permalink Reply by Ben Waller on December 30, 2010 at 1:42pm

The white hat in the second photo is mine.

There are good reasons for both photos. In the first, we were testing the accuracy of our 1.75 inch coefficients with both our apparatus-mounted flowmeters and hydraulic calculations. There were a second apparatus operator and a B/C verifying the numbers.

In the second photo, the officers were evaluating a new relief driver.

You guys didn't have adult supervision when you worked for "Santa North L.A."?

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Permalink Reply by Oldman on December 30, 2010 at 2:07pm

Ya mean we don't do that anymore?

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Permalink Reply by Jeff Cole on January 3, 2011 at 11:30am

It doesn't have to be so complicated. the probem begins with salesmen and those who are empowered to purchase not doing research. Many Officers and firefighters simply refuse to address this issue. Throttle up the rpm's until the nozzle team takes a ride was always good for a laugh, but just showed how a lack of education prevailed when it came to hydraulics. If you have to increase the pressures to get a decent flow, something is wrong with your equipment.

I know some firefighters who have more knowledge on their hobbies than they do with their jobs. Some can tell you the equations and factors of ballistics for hunting, for example, using various ammo rounds, calibre's, etc. Or the formula for improving horse power for their favorite NASCAR vehicle.

Few basics are as misunderstood as stand-pipe tactics. The use of smaller diameter hose with high friction loss, and adjustible nozzles that require 75-100psi to flow any appreciable amount of water is the all-too common set-up found on apparatus. But I am not looking to get into that subject here.

The bottom line is that you must know YOUR apparatus and equipment. Yes, some hose manufacturer's have high-end hose that actually allows for higher gpm's. Yet gpm's (which extinguish fire...not psi) are often over-looked. Your nozzles may be designed to actually look like mean water-throwing weapons. Painted blue, technical-looking, with "200-300 GPM" imprinted on them. But unless you flow-test EACH discharge, especially preconnects of various lenghts (due to piping configurations) along with each brand and type nozzle you are using, you really have no actual FACT as to what your flows are. It's all those hidden twists, turns, and defects that prove those mathmatical calculations wrong.

The best thing beyond flow-testing is standardizing your hose and nozzles. And NEVER assume your apparatus operators fully understand their jobs until they have been properly trained and then demonstate their ability. All too often the drivers you have had over the years have just done things their way, pulled the levers, throttled the engine, and water came out the nozzle. Over the years it's been handed off to another operator who passed the same, incorrect information to each new driver/operator, telling him/her not to worry about all that math stuff. Years ago it was 125-150gpm for 1.5" hose, and 225-250 gpm for 2.5" hose. Problem was those target flows came out of smooth-bore nozzle use. The introduction of combination nozzles never really addressed the issue, and often the end result was maybe 90 gpm due to low nozzle pressures.

Personally I would't be comfortable with less than 180gpm on an interior handline of 1.75".

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