Pump damages

[andrewschools]

Hi everyone,

I have a couple of questions regarding pump operations and causing damages to your pump. I was wondering how sever any of the things listed below are to the health of your pump.

1. Running the pump without any water in it – pump idling.
2. Running the pump with “Tank-To-Pump” but without “Tank Fill” or any discharges – pump idling.

I know none of this is a good thing, but I was wondering how sever they are.

Thanks,
Andrew

[osh599]

Pump Damages

I'll try to answer your question for you.

First by running your pump without any water moving will damage the impeller which is desiged to have water flowing through the pump which helps keep the piping cool. If the impeller is not having any water flowing through it then significant heat will build up and ruin your piping.

Second by not having the recirculation valve open while your "tank to pump" valve is open will cause the water inside the pump to heat up. This could eventually cause the water to boil which in turn will cause heat damage to the pump plumbing. Fire pumps are not designed to handle heat internally.

One way that I use to check the temperature of the pump is to feel the steamer pipe that is accessible outside of the pump panel. If the temperature is starting to get warm then you need to get water moving before the piping gets too hot.

If you see steam rising from the hoses when flowing water then you are not recirculating enough water to cool the pump.

Another thing to keep in mind when recirculating water in your pumps is the following;

For a pump to have adequate recirculation, the water moving inside the pump needs to equal half the capacity of the pump.

Example: 1500 gpm pump needs at least a 750 gallon tank to recirculate for proper cooling.

I hope this helps...

[rfdlou]

pump damage

Avoid both conditions #1: Running dry will damage pump packing & shaft as water is used for lubricating & cooling

#2: Running without passing any water through the pump will overheat the water & pump. Get it hot enough & the temperature relief valve should open (the outlet with the sign that says "Do not cap") most have a pump cooler valve that must be opened to circulate water.

[NBChopper]

Do not ever run the pump dry,
Like what has been previously posted, running the pump dry will cause heat buildup within the pump. as heat builds, the clearance between the
impeller(s) and wear rings will get smaller and eventually the wear rings will contact the impeller. When this happens, one of two things will happen, either you will stall the engine, or the engine will bog down briefly and then you will spin the wear rings in the pump body. In both instances you have just made yourself a hefty repair bill and a truck out of service for some time.

Also by not circulation water, you are essentially dead heading the pump, causing cavitation, this will cause premature pump failure due to cavitation at the impeller, in addition to the heat buildup.

rfdlou, the "discharge" that says "Do not cap" is the intake "Dump Valve" or Intake relief valve. Not the temperature relief valve.

NBC

[andrewschools]

Hi guys,

Thanks for the responses, it’s greatly appreciated!

Thanks,
Andrew

[FWDbuff]

Another thing to keep in mind when recirculating water in your pumps is the following;

For a pump to have adequate recirculation, the water moving inside the pump needs to equal half the capacity of the pump.

Example: 1500 gpm pump needs at least a 750 gallon tank to recirculate for proper cooling.

I hope this helps...

Never heard this. Can you expand?

[NewJerseyFFII]

Avoid both conditions #1: Running dry will damage pump packing & shaft as water is used for lubricating & cooling

#2: Running without passing any water through the pump will overheat the water & pump. Get it hot enough & the temperature relief valve should open (the outlet with the sign that says "Do not cap") most have a pump cooler valve that must be opened to circulate water.

To: rfdlou, Do you have any updated information on your departments new Rechassis Seagrave Aerialscope apparatus. Is it back from the factory and do you have any pictures of the 75' Scope !......

[Catch22]

1. Running the pump without any water in it – pump idling.

As has been stated, not a good idea. You're asking to destroy your impellor, or even worse the pump itself. Last I knew it took around $4,000 to replace the impellor. If you tear up the impellor housing, you just screwed the pooch and you're looking at a new pump.

2. Running the pump with “Tank-To-Pump” but without “Tank Fill” or any discharges – pump idling.

Some physics come into play here (I'm not a physicist, so bear with me if I screw this up). You have water under pressure and heating up. As you add pressure to water, you drop it's boiling point, causing it to boil at lower temperatures. When you have water boiling inside the pump, you have just caused "cavitation," which is not good.

I posted some pictures I tracked down of pump damage that can be caused by these two issues.

[GreggGeske]

Avoid both conditions #1: Running dry will damage pump packing & shaft as water is used for lubricating & cooling

#2: Running without passing any water through the pump will overheat the water & pump. Get it hot enough & the temperature relief valve should open (the outlet with the sign that says "Do not cap") most have a pump cooler valve that must be opened to circulate water.

Just to clarify, the "Do Not Cap" connection is more than likely an intake relief valve opening to atmosphere and not a thermal relief opening. The intake relief valve will open when the incoming pressure rises above what the setting is. If you apparatus is equiped with a thermal relief valve it can be plumbed to atmosphere or back to the tank.

The big concern about "dead-heading" water in the pump is the possibility of scalding burns at the end of the nozzle or at pump connections. The thermal relief valves I have been involved with will start to move water at 120F degrees. Provided the operator has fresh water coming into the pump it should cool. Damage can be caused to the pump from "dead-heading", but are easier and less costly to fix than human injuries. Just practice and preach anytime the pump is engaged we should have water in and water out.

[rfdlou]

Pump Damage

I had a brain f—t. The “Do not cap” outlet is the intake relief. Says so on the tag.

To New Jersey FFII the truck is overdue Sept.06. New factory & other problems @ graves. Inspection trip end of Feb. maybe.

[Catch22]

Just to clarify, the "Do Not Cap" connection is more than likely an intake relief valve opening to atmosphere and not a thermal relief opening. The intake relief valve will open when the incoming pressure rises above what the setting is. If you apparatus is equiped with a thermal relief valve it can be plumbed to atmosphere or back to the tank.

You hit the nail on the head there. My career department has several quints with the same valve on the discharge side of the pump, on the stick piping, to keep guys from over-pressuring the stick (I assume). A thermal relief valve only has a 3/8" line coming out of it. Just enough to bleed off some water and let fresh water in (assuming there's a way for it to come in). The guy I took Hale's pump mechanic class from suggested installing the hose about waste level on the pump panel, so the operator knows the pump's too hot.

[emripp]

As has been stated, not a good idea. You're asking to destroy your impellor, or even worse the pump itself. Last I knew it took around $4,000 to replace the impellor. If you tear up the impellor housing, you just screwed the pooch and you're looking at a new pump.



Some physics come into play here (I'm not a physicist, so bear with me if I screw this up). You have water under pressure and heating up. As you add pressure to water, you drop it's boiling point, causing it to boil at lower temperatures. When you have water boiling inside the pump, you have just caused "cavitation," which is not good.

I posted some pictures I tracked down of pump damage that can be caused by these two issues.

When you add pressure to water, you increase its boiling point. When you reduce the pressure, then the boiling point is reduced.

Ed

[Catch22]

When you add pressure to water, you increase its boiling point. When you reduce the pressure, then the boiling point is reduced.

Ed

Knew I'd screw it up. This is why I review material prior to teaching hydraulics class.

[kuh shise]

Shaft and packing damage

The type of packing/seal system on a fire pump determines how quickly damage will occur when operating without water in the pump. Example: Ceramic / carbon seals can withstand a greater amount of abuse since the carbon contains graphite, a natural lubricant. A standard packing gland using graphite impregnated packing rings (3 or 4) a lantern ring and a final packing ring in direct contact with the impeller shaft might be able to endure 5 minutes or so before enough heat is generated due to friction. Try an experiment... Place the palms of your hand together, apply some pressure and rub them vigorously for 10 to 20 seconds. You will soon reach a surface temperature on the palm of your hand where it becomes uncomfortable to continue due to heat. That temperature should be slightly over 115 degrees F. I generally think of this as about 1 degree F per second. therefore in about 5 minutes or a little more you could reach surface temperatures opproaching 400 + Deg. F. When the graphite breaks down the friction from the packing will increase rapidly causing excessive wear on either the packing seal or the impeller shaft. Water from the pressure side of the pump is directed through a small tube and into the lantern ring. Because the eye of the impeller is at a lower pressure the water flows under the packing rings next to the pump shaft cooling and lubricating the packing. When my students learn to prime pumps, they are taught that it is possible to get a prime without turning the pump shaft (But it is more difficult because there is no water to help seal the packings).

Keep water flowing through your pump. The water is also subject to the same friction / temperature rise that the packing exhibit. The engine horsepower must be dissapated. If you don't move water the only place this energy can go in into producing heat. (law of physics about not being able to create or destroy energy) Generally I like to keep the tank fill cracked, unless I'm working in cold weather and don't want to be standing on Ice while being supplied by a relay or hydrant. You should expect to cause some damage to the fill valve over time because of the high speed water flow across the valve, but is is a lot cheaper than a pump. We are talking years and many hours to cause this. If you forget to circulate and the steamer cap gets too hot to touch. Shut Down! If you aren't flowing water to the fireground, then you should be able to get a different engine to supply the watch lines or overhaul lines. The danger with rapidly cooling a fire pump is chilling one part of the casting while another part is still hot. Cast iron has a high compressive strength and is a great pump body, but it can not stand transverse rupture stresses. If a narrow part of the casting cools quickly, whil another part of the pump stays expanded from the excess heat you can expect to be replacing the pump. Some pumps use a snap ring and roll pin to keep the anti-swirl device from turning on the impeller shaft. (shaped like a hand in the eye of the impeller to direct the water into the pump) The area of attachment is very thin with both sides exposed to water. this area quickly cools and causes the casting to crack. The pump is shot. Also if you still operate old Mack CF's with Waterous pumps, the casting was drilled and tapped in the first stage of the pump and a 1" tank fill line attached at that point. If you are operating in the pressure mode, even with the tank fill cracked, you are not circulating water through the second stage of the pump. I recommend setting the relief valve right at your desired discharge pressure and SLIGHTLY increasing engine rpm until the relief opens thus keeping water flowing through the second stage. As you can readily see, it is essential that pump operators be extremely knowledgable about their equipment.

[Rescue101]

And DO NOT depend on a thermal relief to protect your pump,earlier versions DID NOT have this feature.I won't spec a pump without it however,it's a good safety.Keep water moving and your pumps live a LOT longer. T.C.