Pumping in RPM Mode with pressure governor

[esmith990sfd]

I need some literature on pumping in RPM mode with a pressure governor. We had a discussion on pumping in RPM mode and it was brought up anytime you flow large GPM's pump in RPM mode. RPM mode is not volume. It is a single stage pump. My understanding is you use RPM mode in drafting operations, if you are relaying water, or if the pressure gauge is not working properlly.

[ChiefDog]

I need some literature on pumping in RPM mode with a pressure governor. We had a discussion on pumping in RPM mode and it was brought up anytime you flow large GPM's pump in RPM mode. RPM mode is not volume. It is a single stage pump. My understanding is you use RPM mode in drafting operations, if you are relaying water, or if the pressure gauge is not working properlly.

Single Stage pump means you are not changing from pressure to volume like a two stage.

Drafting is how they test a pump at the factory so whom ever told you RPM is not volume is mistaken. I would suggest going to Hale or Waterous website and looking at their documentation or the manufacturer of the pressure governor.

[firepundit]

When in RPM mode is the same as pumping an older unit with a manual throttle except that under a load it will try to maintain a constant engine speed. If the pump is equipped with a relief valve you are in business. If not, you will have to be on your toes when running multiple lines.

[kuh shise]

esmith: ChiefDog picked up on the problem. You need to look at pump diagrams for both a single and two stage pumps. Gasoline and older Detroit motors with relatively narrow torque ranges need a way to reach higher RPM at low pressures (150) and a way to keep the engine rpms lower at high pressures
(250). When large, high torque Diesel engines were developed, it was no longer necessary to have 2 stage pumps to supply both high pressure and high volume. In fact with high torque motors, and proper transfer case ratios, the 150 psi point will be able to supply more volume than is listed on the pump test plate, and still meet the 1/2 gpm point at 250 psi.

[kuh shise]

esmith: Please look at the following article posted by (competitor) Fire Apparatus Magazine. http://www.fireapparatusmagazine.com...niversity.html

Short article doesa a good job of describing single vs 2 stage pumps with diagrams.

Kuh

[ElmGrove]

We use RPM mode anytime we are drafting especially out of a portatank. Air is often introduced into the tanks when they are being refilled. Problem is with the new computer controlled engines and pressure controllers even a wiff of air introduced into the pump causes the controller to throttle down the engine when in pressure mode. Whomever came up with the specs should be drawn and quartered, our pressure controllers idle down the engine down in 5 seconds.

[johnsb]

esmith: ChiefDog picked up on the problem. You need to look at pump diagrams for both a single and two stage pumps. Gasoline and older Detroit motors with relatively narrow torque ranges need a way to reach higher RPM at low pressures (150) and a way to keep the engine rpms lower at high pressures
(250). When large, high torque Diesel engines were developed, it was no longer necessary to have 2 stage pumps to supply both high pressure and high volume. In fact with high torque motors, and proper transfer case ratios, the 150 psi point will be able to supply more volume than is listed on the pump test plate, and still meet the 1/2 gpm point at 250 psi.

We just got some engines with 2-stage pumps so that the engines could run at lower rpm's (in pressure mode) for suppling hand lines, since that's mostly what we are doing. When relaying or supplying multiple lines for master streams we can switch to volume mode. Less wear on the engine and pump over the life of the engine, and better fuel savings. The cost to go to a 2-stage pump was only about $1500, which should pay for itself in a couple of years. Also less noise since the engine rpm's are lower.

[kuh shise]

johnsb: Thinking by your purchasing group is correct; however, if you have a 2 stage pump on a hydrant relaying to a 2 stage feeding a preconnect, the following pressures are likely to occur. A 2 stage pump at idle in the pressure mode will probably develop about 80 psi at idle. Then with a 60 psi hydrant, the output of the relay engine at idle will be 140 psi. You will have less than 10psi loss using 5" supply line, so the intake at the attack engine will be 130 or more. Finally with the attack engine at idle, the line pressure will be 210 psi. In this case, changing both engines to volume will result in higher engine rpm thus solving the problem of low voltage from the generator running the warning lights.
Another possibility is to take the relay engine out of gear and allow the hydrant to push the water right through the pump. A two engine relay provides a degree of safety should the attack engine go down, the relay engine can boost pressure to (185 psi) pump through the attack engine and supply the lines.

[johnsb]

johnsb: Thinking by your purchasing group is correct; however, if you have a 2 stage pump on a hydrant relaying to a 2 stage feeding a preconnect, the following pressures are likely to occur. A 2 stage pump at idle in the pressure mode will probably develop about 80 psi at idle. Then with a 60 psi hydrant, the output of the relay engine at idle will be 140 psi. You will have less than 10psi loss using 5" supply line, so the intake at the attack engine will be 130 or more. Finally with the attack engine at idle, the line pressure will be 210 psi. In this case, changing both engines to volume will result in higher engine rpm thus solving the problem of low voltage from the generator running the warning lights.
Another possibility is to take the relay engine out of gear and allow the hydrant to push the water right through the pump. A two engine relay provides a degree of safety should the attack engine go down, the relay engine can boost pressure to (185 psi) pump through the attack engine and supply the lines.

You are correct on that, in fact we've had that happen. They were teaching the newboys in the acadamy to pump in series, something we rarely did on the streets due to LDH and lots of hydrants. Unfortunately, we in the real world didn't know they were teaching the new guys to do that. Before, it was only done when an engine was ordered to do that, and we had single stage pumps. Our truck will run around 80 psi at idle with the 2 stage.

[FIREMECH1]

I need some literature on pumping in RPM mode with a pressure governor. We had a discussion on pumping in RPM mode and it was brought up anytime you flow large GPM's pump in RPM mode. RPM mode is not volume. It is a single stage pump. My understanding is you use RPM mode in drafting operations, if you are relaying water, or if the pressure gauge is not working properlly.

Being your pump is a single stage, the thing you need to watch is your RPM's. Volume has no operation or control. Your volume will be whatever your RPM's are. The more your RPM's, the more the volume to pump capability.

On a 2 stage pump, everything changes.

FM1

[16Scott]

E Smith-

I have worked extensively with both Class 1 and FRC governors. There was little training literature and I learned most of what I know from factory reps followed by trial and error. Both behave the same, although I do prefer the FRC over the older Class 1 Captain. I have not used the newer Class 1 devices but they look to be much improved.

You are correct - RPM mode is for drafting, supplying another pump, and in the event of a governor pressure sensor failure. I also change from PSI to RPM when charging large lines, but then I switch back to PSI. Otherwise I always use PSI when I am the "attack engine." Supply apparatus (engines or tankers) should always use RPM and let the attack engine manage pressure (in PSI mode).

Governor operation changes little regardless of single stage or 2-stage pump. Some engineers confuse the two "modes" of governor operation with two "stages" of a centrifugal pump. There is no correlation and each device operates independantly of each other.

I hope this helps.

[Rescue101]

E Smith-

I have worked extensively with both Class 1 and FRC governors. There was little training literature and I learned most of what I know from factory reps followed by trial and error. Both behave the same, although I do prefer the FRC over the older Class 1 Captain. I have not used the newer Class 1 devices but they look to be much improved.

You are correct - RPM mode is for drafting, supplying another pump, and in the event of a governor pressure sensor failure. I also change from PSI to RPM when charging large lines, but then I switch back to PSI. Otherwise I always use PSI when I am the "attack engine." Supply apparatus (engines or tankers) should always use RPM and let the attack engine manage pressure (in PSI mode).

Governor operation changes little regardless of single stage or 2-stage pump. Some engineers confuse the two "modes" of governor operation with two "stages" of a centrifugal pump. There is no correlation and each device operates independantly of each other.

I hope this helps.

Correct with an IMPORTANT safety reminder. In RPM you do NOT have the "relief" offered by the transducer when used in pressure mode. Therefore you need to be very careful when operating in Rpm since the system is sensing Rpm change NOT pressure change.You can liken it to running an older Pump with the relief valve screwed in tight. Doesn't affect OUTPUT,but it will raise hell with things if somebody shuts the line down quick.

[syndrella thomos]

Single Stage pump means you are not changing from pressure to volume like a two stage.

[FyredUp]

Single Stage pump means you are not changing from pressure to volume like a two stage.

Um, Duh?

The topic is about a pressure governor and they operate in either RPM mode or Pressure mode. In RPM mode the governor maintains the set RPMs of the engine, in Pressure mode the governor maintains the set pressure of the pump.

[GTRider245]

Single Stage pump means you are not changing from pressure to volume like a two stage.

Drafting is how they test a pump at the factory so whom ever told you RPM is not volume is mistaken. I would suggest going to Hale or Waterous website and looking at their documentation or the manufacturer of the pressure governor.

Depends on how you look at it.

Some people have the misconception that with the EPGs pressure mode equals pressure stage and RPM mode equals volume stage. Of course, anyone with (un)common sense knows they have absolutely nothing to do with eachother, but the confusion still exists.

So in theory, if someone were to tell him RPM mode was not the same as volume stage on a two stage pump, they would be correct. Being as a single stage pump is always pumping in volume, they could also be incorrect. Not being there for the conversation I don't know what the case actually was.

Pressure governors are nice, but I still prefer a manual throttle and relief valve. Two stage Waterous. For the reasons already stated above. Not to mention it forces guys to actually learn how to run a pump and not just press buttons, pull levers and wait for the computer to kick in.