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Hi all

I did some training in hydraulics with my crew yesterday. We placed an inline pressure gauge at various positions along hose lines of various configurations and flow rates. Our hydraulics training manual provides fireground friction loss figures. They basically state a figure, given as a pressure (kPa for us) for each length of hose at the various diametres. For example it states that a 45mm (1 3/4") will loose 150kPa per 25 metre length. We all know that this is dependant on flow, and these figures are based on our common nozzle flow of 475 l/m (125GPM). Our practical tests showed friction loss was much less. We were loosing just under 100kPa (13 psi I think) per length. When I played with the formula I discovered that the friction factor (co-efficient) was set at a figure (0.006 for our metric calculations). This has been the figure for many years, since we were using rubber lined canvas hose. Now that we use synthetic hose, I'm thinking that the interior surface may be more smooth, and the co-efficient of friction may be less. I can't find anyone who knows how these co-efficients are arrived at. Are they based on tests using gauges and made the subject of the equation? Or are there special science type people who work it out another way? I played with the formula and changed the co-efficient to suit our results, and it worked in every scenario. I know this may seem fairly insignificant, but if we are to emphasise the importance of hydraulic knowledge and provide information to our firefighters, I think we need to reflect reality and be accurate. The figures published in our manual have always been the subject of disbelief, based on practical experience. Can anyone provide me with any information on this?

Regards

Mike Dombroski
New Zealand

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Mike,
This is why every new piece of Apparatus should have the plumbing and hose checked on arrival. You got lower friction loss than you expected. I have seen much higher than expected. Get in touch with Kirk Allen and he'll tell you about the Phoenix Fire Engine that had something like 130 psi of FL from the pump to the discharge. It's all case dependent, be a sceptic and check everything.
Larry
/Mike,

You did what you needed to do. The in line pressure gauge will tell you what you are actually achieving with your specific set up. Hose technology is like anything else, it improves over time. The manufactures learn how to reduce friction loss in the hose. Now that you know exactly what your apparatus and hose combination provide you can have the engineer provide the correct pressure for your application.
I also agree with Larry. We had an engine that had a hard time passing pump test. It could only do it with a couple outlets, not any given one. That relates back to how the truck was plumbed at the factory. The in line pressure/flow gauges will tell you what exactly your truck is capable of.

Walt
Mike: The imperical formula developed in the 1880's called the Hazen-Williams formulae for pipe puts the pipe diameter raised to the 4.87 power in the bottom of the equation. Try taking your friction loss number and multiplying it by your nominal hose diameter raised to the 5th power. We will use a typical US hose size of 5" with a Fl of 6 psi/100 at 1,000 gpm. 5^5=3125 so the number becomes 6 * 3125 = 18,750. Lets assume that new hose diameter expands by 1/4" under pressure so 5.25 raised to the 5th power is 3988 and the friction loss drops from 6 psi per hundred to 4.7 psi per hundred ft. Newer hose weaves, particularly single jacket or urethane covered can easily grow by 1/2 inch in diameter.
"We placed an inline pressure gauge at various positions along hose lines of various configurations and flow rates."

Did you compare static pressure on that gauge with the panel gauge to make sure it was reading accurate? Did you use a calibrated flow meter to establish the flow rate for the test? If not, the reduced FL number may be becuase your not flowing the flow you think.

Are you testing off the side discharge? If so, realize those numbers are going to be quite different in most cases because of the difference in plumbing from crosslays, preconnets, etc.

The best research I have been able to confirm is that the co-efficiants were based on testing with in line gauges at each connection and measuring the actual pressure drop in each section of hose based on a measured flow. The reason for doing this was it established a known set of numbers for a specific peice of hose. That element has been lost in todays marketing and education system. We flow test and FL test each section of hose once each year. When I see a climb in FL from year to year then I know I have something going on inside that section of hose.

Different hose will have different numbers. I have seen first hand one brand hose that could flow 80gpm more than another. The best we could tell was the high FL hose had a much rougher liner than the other. Bothed measured 1.80" ID.

"I know this may seem fairly insignificant, but if we are to emphasise the importance of hydraulic knowledge and provide information to our firefighters, I think we need to reflect reality and be accurate."

God Bless You! It is NOT insignificant! Our lives are on the line! I have begged Fire Schools, Universities, Big city departments etc for years to change what they are teaching becasue all they are doing is teaching a guy how to pass a test.

I prove weekly that the information in the text book more often than not is wrong. I cant tell you how many times people come up with numbers and then want to put it in an SOP only to find out the numbers are not going to work on each engine, let alone each pre-connect.

We need to teach a FLOW based hydraulics that is established using calibrated flow meters. Flow Meters that YOU can calibrate in the field, not one that some manufacture tells you is good to go for a year.

Test everything in the manner which you are going to use it. I know pulling a crosslay or preconnect gets the guys upset because they have to put it back but those numbers are what you need.

Flow meter on the intake side. Tank to Pump Closed, Tank Fill Closed, Recirculation line closed:
Put a pressure gauge in the preconnect at the hose inlet. Place another one at the Nozzle inlet. Charge the line and see if the panel gauges and the inline gauges are reading the same. If they are, flow water to a smooth bore of a known size (15/16ths @50psi = 185gpm) and pito the stream (NFPA14 explains how) and make sure the flow meter is in fact reading what it is suppose to for the pressure on the smooth bore.

Once thats done, test away! If your pumping 150psi and your hose inlet gauge shows 100, then you have already lost 50 psi in the plumbing before it even gets to the hose.

We build pump charts specific to the equipment on each engine. Flow based numbers not Pressure based. Sure, we pump a given pressure but we have to focus on the flow, not the pressure.

If using an automatic governor I prefer to use it in RPM mode instead of Pressure mode. There tends to be far less idling down when the hose is kinked in RPM mode than in pressure mode. I have seen governors idle the endine down for a hose kink that only makes the flow problem worse. If I had it my way I would have manual throttles on every engine!

Its exciting to see more folks realizing the book numbers are not accurate. I urge everyone to start asking two questions when people make a claim or a text book states something:

Says Who? and With What Proof?
Thanks William

Our friction loss formula is different because we use the metric system, so I can't quite follow all of what you're saying. I will break it down though, and do the conversions.

Thanks again
Mike D

William Hoehn said:
Mike: The imperical formula developed in the 1880's called the Hazen-Williams formulae for pipe puts the pipe diameter raised to the 4.87 power in the bottom of the equation. Try taking your friction loss number and multiplying it by your nominal hose diameter raised to the 5th power. We will use a typical US hose size of 5" with a Fl of 6 psi/100 at 1,000 gpm. 5^5=3125 so the number becomes 6 * 3125 = 18,750. Lets assume that new hose diameter expands by 1/4" under pressure so 5.25 raised to the 5th power is 3988 and the friction loss drops from 6 psi per hundred to 4.7 psi per hundred ft. Newer hose weaves, particularly single jacket or urethane covered can easily grow by 1/2 inch in diameter.
Hi Kirk

Thanks for your input. I'm glad that there's people out there who have the same belief about the importance of flow, as opposed to an over emphasis on pressure. As we all know, fire releases an amount of heat at a given rate, and it is an amount of water at a given rate that will absorb enough of it to make it stop. We are more vulnerable to a lack of understanding over here (from what I can gather) because we use a British based system of hose lines which doesn't include preconnects. Therefore it is possible, and does happen, that some will select a larger diameter hose, but still have a low flowing nozzle (operating at the same pressure), and they will actually believe they are putting more water on the water. I also see pump operators using the standard friction loss figures to provide pressure to hose lines of various flows, at both ends of the scale. They take hose diameter and the length of the line into consideration, add the standard figure (which is based on 125 gpm) but ignore the flow, even though it has the greatest influence on friction loss. It is not taken into consideration because it is not well taught and understod.

In our tests we didn't have a flow meter (I can't get hold of one yet). The inline pressure gauge read the same as the outlet gauge with no flow. Our outlet gauges are at the coupling on the pump, so are on the discharge side of the pump plumbing. I assumed the flow based on nozzle size and pressure at the nozzle. I tried several different nozzles as well as select o flow adjustables and the friction loss was fairly constant assuming the flows were what they should be. I just think that modern hose has produced a smoother interior surface from when the old co-efficient of friction was established into our formula. I'm currently talking to a hose supplier to try and get some facts around this. They may also be able to loan me an inline flow meter so I can do some more accurate testing.

Thanks again for your input.
Regards
Mike D

Kirk Allen said:
"We placed an inline pressure gauge at various positions along hose lines of various configurations and flow rates."

Did you compare static pressure on that gauge with the panel gauge to make sure it was reading accurate? Did you use a calibrated flow meter to establish the flow rate for the test? If not, the reduced FL number may be becuase your not flowing the flow you think.

Are you testing off the side discharge? If so, realize those numbers are going to be quite different in most cases because of the difference in plumbing from crosslays, preconnets, etc.

The best research I have been able to confirm is that the co-efficiants were based on testing with in line gauges at each connection and measuring the actual pressure drop in each section of hose based on a measured flow. The reason for doing this was it established a known set of numbers for a specific peice of hose. That element has been lost in todays marketing and education system. We flow test and FL test each section of hose once each year. When I see a climb in FL from year to year then I know I have something going on inside that section of hose.

Different hose will have different numbers. I have seen first hand one brand hose that could flow 80gpm more than another. The best we could tell was the high FL hose had a much rougher liner than the other. Bothed measured 1.80" ID.

"I know this may seem fairly insignificant, but if we are to emphasise the importance of hydraulic knowledge and provide information to our firefighters, I think we need to reflect reality and be accurate."

God Bless You! It is NOT insignificant! Our lives are on the line! I have begged Fire Schools, Universities, Big city departments etc for years to change what they are teaching becasue all they are doing is teaching a guy how to pass a test.

I prove weekly that the information in the text book more often than not is wrong. I cant tell you how many times people come up with numbers and then want to put it in an SOP only to find out the numbers are not going to work on each engine, let alone each pre-connect.

We need to teach a FLOW based hydraulics that is established using calibrated flow meters. Flow Meters that YOU can calibrate in the field, not one that some manufacture tells you is good to go for a year.

Test everything in the manner which you are going to use it. I know pulling a crosslay or preconnect gets the guys upset because they have to put it back but those numbers are what you need.

Flow meter on the intake side. Tank to Pump Closed, Tank Fill Closed, Recirculation line closed:
Put a pressure gauge in the preconnect at the hose inlet. Place another one at the Nozzle inlet. Charge the line and see if the panel gauges and the inline gauges are reading the same. If they are, flow water to a smooth bore of a known size (15/16ths @50psi = 185gpm) and pito the stream (NFPA14 explains how) and make sure the flow meter is in fact reading what it is suppose to for the pressure on the smooth bore.

Once thats done, test away! If your pumping 150psi and your hose inlet gauge shows 100, then you have already lost 50 psi in the plumbing before it even gets to the hose.

We build pump charts specific to the equipment on each engine. Flow based numbers not Pressure based. Sure, we pump a given pressure but we have to focus on the flow, not the pressure.

If using an automatic governor I prefer to use it in RPM mode instead of Pressure mode. There tends to be far less idling down when the hose is kinked in RPM mode than in pressure mode. I have seen governors idle the endine down for a hose kink that only makes the flow problem worse. If I had it my way I would have manual throttles on every engine!

Its exciting to see more folks realizing the book numbers are not accurate. I urge everyone to start asking two questions when people make a claim or a text book states something:

Says Who? and With What Proof?
"Our outlet gauges are at the coupling on the pump, so are on the discharge side of the pump plumbing"

I suspect the pressure sensors were installed just downstream of the discharge valve which only tells you the pressure at that point. Its the plumbing from the sensor location to the actual hose connection that is not being accounted for and unless your engine specification outlined where to put the sensor I suspect you will find its not anywhere near the hose connection, accept for the side discharges, which has them right after the valve which is right behind the panel.

"I'm currently talking to a hose supplier to try and get some facts around this. "

I have to say I get a chuckle out of that comment and I have to say, Good Luck and please let me know what they tell you!.

Chief Halton and I several years ago did a right up in Firehouse on this topic and after contacting 13 hose manufactures there was only ONE that had any fact based measured numbers and those numbers were the very ones I provided for them as they ALL had no clue! They just kept pointing to NFPA formulas. It was a sad thing to see and unfortunatly its pretty much the same with the exception of a couple manufactures.
Thanks Kirk

I'll keep that in mind about the hose guys. I got an email yesterday telling me that the're looking into it (bit like a mirror).

We have Hale QPAC mid mounted pumps. The outlets are on the side and the pressure sensor is about 2-3inches from the hose coupling. I'm assuming this would give an accurate presure reading from the specific outlet. The only thing in the way between the gauge sensor and the hose is the coupling. Interestly enough, the main presure gauge, which is straight from the discharge before the seperation into the 4 outlets, reads the same as the outlets(when fully open and flowing). I take that as meaning that the plumbing betwen the discharge of the pump and the outlet coupling is very efficient, with no losses evident. This would make sense, as the pump casing is right behind the outlets, and pipe work does not appear to be restricting in any way.

Following this discussion, I've decided to follow this up more vigorously. I've contacted our national fire engineering department, but still waiting to hear back. I'm going to try and get hold of an inline flow gauge and get some more accurate data.

Cheers for the help.

Mike D

Kirk Allen said:
"Our outlet gauges are at the coupling on the pump, so are on the discharge side of the pump plumbing"

I suspect the pressure sensors were installed just downstream of the discharge valve which only tells you the pressure at that point. Its the plumbing from the sensor location to the actual hose connection that is not being accounted for and unless your engine specification outlined where to put the sensor I suspect you will find its not anywhere near the hose connection, accept for the side discharges, which has them right after the valve which is right behind the panel.

"I'm currently talking to a hose supplier to try and get some facts around this. "

I have to say I get a chuckle out of that comment and I have to say, Good Luck and please let me know what they tell you!.

Chief Halton and I several years ago did a right up in Firehouse on this topic and after contacting 13 hose manufactures there was only ONE that had any fact based measured numbers and those numbers were the very ones I provided for them as they ALL had no clue! They just kept pointing to NFPA formulas. It was a sad thing to see and unfortunatly its pretty much the same with the exception of a couple manufactures.
as
The reason your main pump gauge is reading about the same is your not flowing much water at all. Assuming you have a 1000gpm pump your going to have to pop that 200gpm mark or better before you start to see the difference in master pump pressure and discharge pressures. Little water, little FL.

John K. Murphy said:
as

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