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Thread: RPM's & GPM's

  1. #1
    Daron
    Firehouse.com Guest

    Question RPM's & GPM's

    I know there is a way to figure this but I can't seem to remember. How can I figure how many GPM's I am putting out of 1 or 2 2.5" discharges by RPM's. I can't quote the exact model # of our pumps but our truck company is using a Hale 1250 GPM 2 stage pump with a five speed manual transmission and our engine company is using a Hale 1250 GPM single stage pump with a 5 speed automatic Allison transmisson that pumps in 4th gear. I can't find any ratios on either pump. I realize friction loss is going to be a big factor depending oh what what size and how much hose we end up using but I need a starting point for GPM's to figure FL for relaying when I can't tell how many GPM's the receiving pumper is pumping.


  2. #2
    ADSN/WFLD
    Firehouse.com Guest

    Post

    The plate on your pump panel will tell you what your engine could do when it was new. As a rig get older the amount of water it can pump at a certain RPM decreases.

    A class "A" pumper will pump, from draft, 100% of capacity at 150 psi, 75% @ 200 psi, and 50% at 250 psi.

    Figuring flow from rpm is not reliable and not the preferred way of calculating flow. For more information on calculating fire streams I would recommend reading the IFSTA publication: Pumping Apparatus DRIVER/OPERATOR Handbook First Ed.

  3. #3
    Halligan84
    Firehouse.com Guest

    Post

    Too many variables for that to be a reliable method. When you are in a relay, knowlege of what the receiving pumper is putting out is irrelevant. The goal in a relay is to move all the water you are receiving, most places pump to hold a 20 psi residual and throttle up passing on all the water they can. Preplanning for relays involves determining your hose lays, common hydrant pressures, desired flows, etc and setting a maximum lay without relay pumper. For instance, given our hydrant pressure and hose size we set a limit of 800' before we go in relay to flow 1500 gpm.

  4. #4
    LHS*
    Firehouse.com Guest

    Post

    Using RPMS to set EPs for given flows is quite reliable. It is often used for pumpers equipped with a relief valve for initial attack off tank water. WHY?

    Say you arrive and pull an attack line. You throttle up to a pre-determined pressure say 150 psi and set the relief valve or have the relief valve pre-set at 150.

    The crew opens the nozzle and your EP will drop to say 120 psi. Why did it drop? The pump was not under load because yo were not flowing water it was a static pressure you were supplying. You now have an under supplied line.

    By simply posting a couple RPM's on a chart like this you won't have the drop.

    Deck Gun 1300 RPM EP 125 psi
    One 1 3/4" line 1500 RPM EP 200 psi
    Two 1 3/4" line 1700 RPM EP 200 psi
    One 2 1/2" line 1650 RPM EP 160 psi

    Another method is matching colored stripes on the discharge gauge and rpm gauge.

    As long as the relief valve is set, when the supply line comes you won't notice any difference. The engineer can get about other items without concern for drop in EP.

  5. #5
    ADSN/WFLD
    Firehouse.com Guest

    Post

    "The engineer can get about other items without concern for drop in EP."

    Isn't that his job to watch the pump panel?

    And what about your engine as it gets older, flowmeters aren't calibrated as often as they should be (and that's easy) I find it hard to believe that extensive testing is regularly done to ensure that the engine rpm still pumps what you want. I've also seen engine rpm's change due to dirty filters, small mechanical problems, or different grade fuel. Do you really want the safety and effectives of your crews to depend on all of those variables. If you drive more than one rig you also may run into some confusion. Find two rigs that came off of the line at the same time with all of the same specks and you will find the rpm / flows to be slightly different. Why subject your engineers to remembering different rpm's bases on what rig they are on. You can also have problems with the tack on the panel that will throw off what you are flowing. Tell me that you have never seen a rig with a broken tachometer.

    What about a longer stretch or something other than the routine? It sounds like the engineer now has to shift gears (figuratively) and figure out pdp the "old fashioned" way. Aren't you setting yourself up for failure?

    When I started at my part time department the FAE training consisted of; "kid just pump it at 150 and you'll be fine" because all of the preconnects were within 10 psi of 150. This led to many problems when a non routine stretch was ordered. Now almost everyone is an FAE and we don't have those problems.

  6. #6
    LHS*
    Firehouse.com Guest

    Post

    //Isn't that his job to watch the pump panel?

    Oh. I thought it might be nice if he contributed to the fire fighting effort. You know, placed a clamp, connected the supply line, released the clamp, opened the intake valve (which may not be on the pump panel), pulled any remaining hose from the hose bed, ran around front or back to insure he was in fact charging the line pulled not the wrong one, unhooker the hose from a fire extinguisher or ax, helped extend the attack line for the crew donning SCBA, started the generator, positioned flood lights, pulled cord lights, located equipment, was able to leave the panel and see when the crew wanted the line charged, removed kinks, put a blower at the front door, helped someone with an air pack, maybe threw a ladder, operated a deck gun, etc. My mistake. Do you actually have hand cuffs on the pump panel? We trust our engineers to do the right thing

    ////Isn't that his job to watch the pump panel?

    Is something broken? Do you have a relief valve and /or governor? They can’t hold the pressure? Your ¾ mile diesel engine crap out on you a lot? Gee, what is he looking at the panel for? If a vehicle system fails all kinds of alarms go off. If he left the tank suction line open..and for some reason the supply line died, the situation would take care of itself wouldn’t it? IFD an attack line burst the crew would know as fast as he would, how could he possibly effect the situation? What is he doing there at the panel?

    Three guys on a rig and the pump operator stays at the panel. Who relieves he hydrant man to turn the hydrant on and come help fight fire? You have an extra guy to make and break lines? That leaves just to officer to fight the fire? “Isn't that his job to watch the pump panel?” Not in the real world, dam boy!

    //And what about your engine as it gets older, flow meters aren't calibrated as often as they should be (and that's easy).

    Someone say anything about flow meters? You know the transmission might not have any fluid in it and that might effect pump pressure too. Or maybe someone didn’t put the 6 inch suction cap on that could eff3ect the ability to pump.

    // I find it hard to believe that extensive testing is regularly done to ensure that the engine rpm still pumps what you want.

    Probably not, because the variation of the 10 engines on our FD have less than 50 rpm difference on their actual pump test records. Of course they range from a 1950 to a 2001. MAYBE, it isn’t a problem, at all?

    OK, let’s say you are right. Oh gosh I’m off by 30 rpm. Beats being off by 30 to 60 psi. Most FD’s are not wearing their pump motors out. The engine in almost all cases is way larger than what is needed to run the pump. Gee the pump motor is designed for the worse case at draft, at maximum capacity, 10 foot lift, 20 feet of hose and a strainer, through a single suction, that requires an extra 1/3 horsepower, compared to going off tank water or a pressurized source or lifting from a drop tank at 4 feet of lift and one length of suction hose and almost never coming anywhere near pump capacity. So gee, if we lose 1/3 of our horse power, were screwed. Why is it every single Las Vegas engine turned in passed it’s pump test within 50 rpm of the pump plates? Paul’s old rig was pushing 200,000 miles? Why did the ones with even higher miles pass? Maybe it isn’t an issue. Where is your data?

    // I've also seen engine rpm's change due to dirty filters, small mechanical problems, or different grade fuel.

    Yeah you gain what 200 to 400 horsepower with a better rocket fuel or something? Throttle up, set the relief valve, throttle up a bit more to hold the pressure. Itdoes not matter what the rig is running like, you either hit the pressure or you don’t?

    Dang, So my panel say 2300 gpm at 150 psi 1550 rpm, 2100 gpm at 200 psi at 1675 rpm and 2000 gpm at 250 psi at 1750 rpm. IS it really going to make that much difference? Dam it Boy! The discharge gauges have a 2% margin for error, in other words 24 psi, the hose could have 100 psi, the relief valve has a 60 psi swing. What if you go from 2000 feet elevation to 11,000 feet on the same day, what if the truck gets hit by a car, what it what it, what if. I guess it is impossible to do anything.

    I’ll stand by the rpm/psi post, it works almost all of the time.

    //// I've also seen engine rpm's change due to dirty filters,

    Well next time buy the filter the manufacturer of the fire truck suggested.

    /// Do you really want the safety and effectives of your crews to depend on all of those variables.

    Gee, can you believe we are relying on a human being?

    // If you drive more than one rig you also may run into some confusion.

    Yeah maybe you should just drive one rig at a time. Or maybe you can’t read the chart that day on the pump panel, or or or or or…

    //Find two rigs that came off of the line at the same time with all of the same specks and you will find the rpm / flows to be slightly different.

    Dang, you mean each rig might need a chart? That might take 50 years to make.

    // Why subject your engineers to remembering different rpm's bases on what rig they are on.

    Why? Because you can make a chart for each rig and be right 99% of the time.

    // Why subject your engineers to remembering different rpm's bases on what rig they are on.

    Dam it Boy, who suggested that? I said make a chart for the rig, not one chart that ad to work with the brush truck in Seattle and the crash truck in Philly and the tanker in Key West, dam it boy think!

    // You can also have problems with the tack on the panel that will throw off what you are flowing.

    Then get Seven tachs, if you are having that much trouble, Maybe 8!

    // Tell me that you have never seen a rig with a broken tachometer.

    Golly, all rigs have two! Maybe you shouldn’t be in the fire service because you are having a hard time thinking on your feet. Here, I’ll help. Right under the chart type:

    If the tachometer is out again, if the oil filter clogs, if, if, if, if,

    Simply throttle up to 150 psi (or the psi indicated on the chart), set the relief at 150 then take one complete extra turn on the throttle, that will hold the pressure.

    //What about a longer stretch or something other than the routine?

    That wold follow the line below the chart above, it is an “if”.

    //It sounds like the engineer now has to shift gears (figuratively) and figure out pdp the "old fashioned" way.

    No go to the last line of the chart do what it says under “if” and then read the
    handy chart you posted on the panel that looks like this or similar:

    Pump Chart
    MAGNOLIA, TEXAS

    Nozzles GPM NP FL 50' 100' 150' 200' 300' 400' 500' 600'

    25 100 9 105 (109) 114 118 127 136 145 154
    1” Lines 3/8” 30 50 14 107 114 121 128 142 156 170 184
    3/8” 40 50 24 112 124 136 148 172 196 220 244


    30 100 1 101 101 102 102 103 104 105 106
    1 3/4" Lines 95 100 14 107 114 121 128 142 156 170 184
    125 100 24 112 124 136 148 172 196 220 244
    150 100 35 118 135 153 170 205 240 --- ---
    200 100 62 131 162 193 224 --- --- --- ---
    1/2” 50 50 4 52 54 56 58 62 66 70 74
    7/8” 160 50 40 70 90 110 130 170 210 250 ---
    15/16” 185 50 53 126 153 179 206 --- --- --- ---


    125 100 3 102 130 104 106 109 112 115 118
    150 100 5 103 105 108 110 115 120 125 130
    200 100 8 104 108 112 116 124 132 140 148
    2 1/2” Lines 250 100 13 107 113 120 126 133 146 159 172
    1/2” 65 50 1 51 51 52 52 54 55 56 57
    1” 210 50 9 55 59 64 68 78 87 96 105
    1 1/8” 265 50 14 57 64 71 78 92 106 120 134
    Cellar Tip 250 100 13 107 113 120 126 133 146 159 172


    DECK GUNS 500-1250 100 -- --------- 125 psi --------------------


    500 100 2 101 102 103 104 106 108 110 112
    PORTABLE GUN 5” 750 100 5 103 105 108 110 115 120 125 130
    1000 100 8 104 108 112 116 124 132 140 148
    1250 100 13 107 113 120 126 139 152 165 178
    1 3/8” 500 80 2 81 82 83 84 86 88 90 92
    1 1/2” 600 80 3 82 83 85 86 89 92 95 98
    1 3/4” 800 80 5 83 85 88 90 95 100 105 110
    2” 1060 80 9 85 89 94 98 107 116 125 134


    Apartment lay
    150’ 1 ¾” 300 152 6 155 158 161 164 170 176 182 188
    200’ 1 ¾” 300 170 6 173 176 179 182 188 194 200 206


    TOWER LADDER 1000 100 -- -------- (190 psi) -------------------
    1500 100 -- --------- 225 psi --------------------
    5" Inlet 1000 180 8 185 185 185 185 185 185 185 185


    FIRE: Charge one 5". Pump 150 psi.
    Make sure the post indicator valve is open.
    SPRINKLERS
    NO FIRE: Connect but do not charge line. If gong
    sounds or if wall drain flows tell I.C. you
    have a water flow indication, charge line.


    Hookup lines and a float and put it under 2 feet of
    water, Throttle up to 175 psi, Make sure there aren't
    any kinks in the line, Open the pet **** drain on the
    Turbo Draft suction valve, Charge the 3 inch line, Close the air
    drain, SLowly open the side suction, Fill your water
    tank, Slowly charge your hose lines watch, the 5 inch
    line when it gets soft stop opening the lines, throttle
    up or limit the flow, Use two turbo drafts for more water.


    5 inch RELAYS(pump 185 psi) GPM
    200' 300' 400' 500' 600' 700' 800' 900' 1000' 1100' 1200’
    3000 2940 2545 2270 2070 1915 1790 1685 1600 1525 1455

    1300' 1400' 1500' 1600' 1700' 1800' 2000' 2500' 3000' 3500' 4000'
    1400 1345 1300 1260 1220 1185 1120 1000 910 840 785


    5 inch HYDRANT SUPPLY(36 psi) GPM
    100' 200' 300' 400' 500' 600' 700' 800' 900' 1000' 1100'
    2375 1670 1360 1175 1045 950 880 820 775 730 695

    1200' 1300' 1400' 1500' 1600' 1700' 1800' 2000' 2500' 3000' 3500'
    665 640 615 595 575 555 540 525 510 455 380

    odds are the fire will go out.

    // Aren't you setting yourself up for failure?

    Gee, pull an attack line, throttle up a bit more than what is indicated on the pressure gauge and set a relief valve, versus knowing for sure every time an attack line is opened the pressure will drop because you are ignoring the difference in static pressure and a pump under load residual pressures. NAH, I think if yo are not doing something to address the drop you are failing every single time to do yor job properly.

    //When I started at my part time department the FAE training consisted of; "kid just pump it at 150 and you'll be fine" because all of the preconnects were within 10 psi of 150. This led to many problems when a non routine stretch was ordered. Now almost everyone is an FAE and we don't have those problems.

    So is someone suggesting always pump the exact same discharge pressure the way YOU were taught. We are all not that stupid. Just because you place was that dumb give the rest of us the shadow of the doubt. Different pressures for different lines, verified by the psi gauge, a preset relief and an RPM gauge is pretty frickin certain I think. Non-routine, maybe you ought to train a bit more. Did anyone suggest using this method on anything but a preconnect?

    I bet you don't have a clue how to pump a 14,000 gpm monitor, figure friction loss for 7 and a quarter inch hose, pump 4 inch foam lines to trasfer concentrate...but then
    again, that wasn't the topic of this post.

    So stay on track, preconnects, tank water, rpm gauge, it works fine.



  7. #7
    Halligan84
    Firehouse.com Guest

    Post

    "Using RPMS to set EPs for given flows is quite reliable. It is often used for pumpers equipped with a relief valve for initial attack off tank water. WHY?"

    Larry, given that scenario, I agree. When you know have a given flow and taking tank suction, it is easy to determine how many RPMS will be necessary to get the correct NP. I answered based on his point about relay, figuring that he had varying incoming pressures and an unknown flow at the fire.

  8. #8
    ADSN/WFLD
    Firehouse.com Guest

    Post

    Nice off topic response. BOY!

    Almost that entire response was focused around using a pump chart with PSI, not rpm's. I have no problem using a pump chart or cheat sheet. As a matter of fact our engineers carry small cheat sheets, the rig has another one and the hose record that is on the rig has several references to routine operating pressures.

    As for my part time department's reference it was meant as an example of what problems you can run into when you use shortcuts only and don't give your chauffeur all of the tools he needs.

    Most of our leadouts use a reverse lay so we don't have the luxury of doing everything on the fireground. We need to stay relatively close to the rig. When we use preconnects our engineers do several tasks, KEEPING AN EYE ON THE PANEL.

    BTW we currently meet NFPA 1701 staffing levels so often it is not necessary for the engineer to do other things.

    Our response to a structure is:
    3 engines
    2 ladders
    1 Heavy rescue
    2 Medic units
    At least 1 chief and a safety officer.

    All full time, at their respective stations.

  9. #9
    Junior Member
    Join Date
    Jun 2001
    Location
    Tennessee
    Posts
    13

    Default

    IN MY OPINION IT WOULD BE VERY DIFFICULT TO DETERMINE THE GPM BEING DISCHARGED IF YOU WERE THE RELAY ENGINE. THE BEST METHOD WOULD BE TO USE THE RULE OF THUMB METHOD FOR RELAY PUMPING. I WILL EXPLAIN IT TO YOU!


    2.5 OR 3"

    SHORT LAY (500' OR LESS) EP= 100PSI
    LONG LAY (500 FT. TO 1000' ) EP= 150PSI

    4" OR 5" LDH

    SHORT LAY (500 FT. OR LESS) EP= 50PSI
    LONG LAY (500 FT. TO 1000 FT.) EP= 100PSI

    IF THE INTAKE ENGINE NEEDS MORE WATER THEN THE RELAY INCREASES PRESSURE BY 20PSI UNTIL THE DESIRED FLOW IS MAINTAINED. THE INTAKE ENGINE MUST MAINTAINE 50PSI ON THE COMPOUND GAUGE.

  10. #10
    Member
    Join Date
    Nov 2000
    Location
    Glasgow, KY.
    Posts
    61

    Default

    One thing everyone doesn't seem to account for is if you are pulling your water from a hydrant your rpm thinking is out the window because if you are on a good plug you may have to use your truck as a gate to keep the pressure off of the lines.

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