# Help...Calling all Engineers..!!

• 02-06-2010, 06:49 PM
RMAN
Help...Calling all Engineers..!!
does anyone have a easy way to determine how much available water is in a hydrant after calculating your static pressure and your residual pressure?

is there any study info or study questions that anyone can remember for a written engineers exam?? any websites with sample hydraulic questions? any help would be great. Thxs
• 02-06-2010, 07:39 PM
Firetacoma1
The way I've always heard it done was to note your static pressure. Then charge a line (say 1.75 for this discussion) and note your residual pressure. You have a drop. You can expect a similar drop for each line of the same size. So as long as you can maintain a residual pressure of 10 psi (my department SOG at least) you can keep adding lines of the same size.

Please someone correct me if I'm wrong!
• 02-08-2010, 01:12 AM
mikeyboy411
IFSTA Driver Operator.....
Check IFSTA Driver Operator/Pumper under the section that covers available water and hydrant operations (I don't recall the exact page # since my book is at work).

Hopefully, your Department uses the 10, 20, 30% (1st Degit Method) since it's easy enough to do in your head.

Here's how that method works:
Take the 1st digit (ex: 100 is 10) and multiply it by 1, 2, and 3. If the drop is between the number multiplied by 1 then you can add 3 like volume lines. If the number drop is above the number that comes from multipying by 1 and the number multiplyied by 2 then you can add 2 like volume lines; so on and so on.

If you're trying to determine your approximate static pressure while pumping then to do that how we do it is while pumping open another like-sized discharge that is capped or open the Tank-to-Pump Valve and note the drop. Once you note the drop add that to your current residual pressure and that will give you an approximate static pressure.

My only real issue with the Tank-to-Pump Valve is that if you open a 2 1/2" Valve like many Engines have then the flow will not be the same since there is less friction loss in the pipes of a 2 1/2" discharge.

I hope this helps.....
• 03-19-2010, 10:52 PM
ffmedcbk1
Available water per IFSTA Fire Stream Practices
% PSI Drop Available Lines of Similar Size
0 to10 % 3 X the amount being delivered
10 to 15% 2 X the amount being delivered
16 to 25% 1 X the amount being delivered
25 % or > None available for multiple lines
Table 3.12 page 118 Fire Stream Practices sixth edition 1980

This table can be used to figure out how many more hoselines that can be safely employed flowing the same amount as the first.
There must be knowledge however, of the initial static pressure without water flowing.

Examples:
1. At a fire, the engineer gets water from the fire hydrant. His initial pressure from the hydrant is 100 psi. He opens the discharge to the hose and begins to flow water. His pump intake gauge now reads 80 psi. There is a 20% drop in the pressure (80/100=8/10=80% percent remaining=20% drop) Using this and the above chart, we find that only one line more is available with out another water source.
Hydrant Pressure
Static:100
Residual: 80 Percentage drop: 20% drop
Available Lines: 1 hose of same flow amount as being delivered

2. At a fire, the engineer gets water from the fire hydrant. His initial pressure from the hydrant is 70 psi. He opens the discharge to the hose and begins to flow water. His pump intake gauge now reads 66 psi. There is a 6% drop in the pressure (66/70=94% percent remaining=6% drop) Using this and the above chart, we find that three line more is available with out another water source.

Hydrant Pressure Static: 70
Residual: 66
Percentage drop: 6% drop
Available Lines: 3 hoses of same flow amount as being delivered

hope it helps
• 03-20-2010, 01:33 AM
Each of our Engines carry a chart that list the hydrants, tested/expected static and residual pressures.

Most of the time the pressures will be very close to what the chart indicates.

But depending on the location, mainline size, whether the line is a dead end or looped, time of day in regard to heavy use or peak loads, and elevation can affect the actual pressures.

The chart is only to be used as a reference; the operator must adapt to the situation.
• 03-20-2010, 11:19 AM
ffmedcbk1
Quote:

Each of our Engines carry a chart that list the hydrants, tested/expected static and residual pressures.

Most of the time the pressures will be very close to what the chart indicates.

But depending on the location, mainline size, whether the line is a dead end or looped, time of day in regard to heavy use or peak loads, and elevation can affect the actual pressures.

The chart is only to be used as a reference; the operator must adapt to the situation.

we have 2000 hydrants in our district not including private hydrants. how many in yours?
• 03-20-2010, 02:32 PM
About 3200 hydrants covering our 375 sq mile 1st & 2nd due response area. We cover 2nd due for M/A for about 200 sq miles all directions since we have the only staffed stations. Many times our crews arrive about the same time as the First Due and we grab water as we go in.

I should have said Hydrant Charts. There are in Map Books by Section (Grid), but can also be pulled up on the Onboard-Laptop mapping system. While it is quicker, some details are lost when you need to review... hard copy gives them more data. Plus they can keep the book or page at their side... if it makes them feel better.:rolleyes:

We test all of the hydrants, ours and others, and share the data so everyone is on the same page. We have a full-time dedicated Hydrant crew that maintains, test and map. Each is tested about every 90 days or as needed if lines are modified or upgraded; about 12 to 15 each weekday.

It is alot easier if you have some idea of what you can expect.
• 03-21-2010, 08:38 PM
ffmedcbk1
Quote:

About 3200 hydrants covering our 375 sq mile 1st & 2nd due response area. We cover 2nd due for M/A for about 200 sq miles all directions since we have the only staffed stations. Many times our crews arrive about the same time as the First Due and we grab water as we go in.

I should have said Hydrant Charts. There are in Map Books by Section (Grid), but can also be pulled up on the Onboard-Laptop mapping system. While it is quicker, some details are lost when you need to review... hard copy gives them more data. Plus they can keep the book or page at their side... if it makes them feel better.:rolleyes:

We test all of the hydrants, ours and others, and share the data so everyone is on the same page. We have a full-time dedicated Hydrant crew that maintains, test and map. Each is tested about every 90 days or as needed if lines are modified or upgraded; about 12 to 15 each weekday.

It is alot easier if you have some idea of what you can expect.

that is amazing. how is your manning levels and how many calls. we are running 7 guys with 4400 calls a year..... not much time between training and runs to get all the hydrants tested and flowed as often as you guys.
• 03-22-2010, 08:05 AM
RFDACM02
Quote:

We have a full-time dedicated Hydrant crew that maintains, test and map. Each is tested about every 90 days or as needed if lines are modified or upgraded; about 12 to 15 each weekday.

Do you find that testing hydrants every 90 days actually reveals any significant inconsistencies? It would seem that this would be excessive. A dedicated hydrant testing crew? FT? Is this a water company based testing crew?
• 03-22-2010, 09:53 AM
voyager9
A quick question. How about for situations where the line is in service before the water supply is established? Depending on manpower and location we very easily could have the lines charged with tank water before the hydrant's hooked up and charged. Unless you have charts per-hydrant (we don't) or WAG'ing how would you figure static pressure? I know you can open another line and go from there.. just curious if it can be done before that. Also, in the example above you mention Tank-to-Pump. How does that cause a pressure drop? Or do you mean Tank-fill?
• 03-22-2010, 10:40 AM
ffmedcbk1
Quote:

Originally Posted by voyager9
A quick question. How about for situations where the line is in service before the water supply is established? Depending on manpower and location we very easily could have the lines charged with tank water before the hydrant's hooked up and charged. Unless you have charts per-hydrant (we don't) or WAG'ing how would you figure static pressure? I know you can open another line and go from there.. just curious if it can be done before that. Also, in the example above you mention Tank-to-Pump. How does that cause a pressure drop? Or do you mean Tank-fill?

that is a lacking feature of these calcs. you must know the static with nothing flowing. i do find that when the line is moved or repositioned they tend to shut it off for short times and you can get the static then.

with my company we drill and operate to get the hydrant charge relatively quick. this is done by the use of forward lays and the fact that the engineer breaks the ldh and connects to the side first prior to anything esle. at that point he calls for water (about 1 minute from brakes being set) hose is filled at about the same time as the attack team is at the entry point and calling for water. as they push through the door they are not flowing typically.

we find this arrangement with 4 or 5 man co's will get the hydrant man forward quicker to do ov duties or assist the eng co if by that time the truck co is arriving to do the ov duties.
• 03-23-2010, 03:53 AM