Our Toyne Rescue Pumper has a rearmounted Waterous CXVK 1250 pump. Since day 1 upon engaging the pump there has been a "cavitation" type, gravelly sound. This sound is immediately reduced upon opening the tank to pump valve and is completely quiet when circulating water.
The reason this is an "issue" now is that after replacing the mechanical seal during the annual service test, they still could not hold the dry prime. This is a minor issue operationally as the engine doesn't even carry suction hose, it's an in town attack engine with no chance of drafting, but to not be capable is indicative of an issue that can only get worse.
Some tests and results so far:
1. Leave the T2P open all the time. This reduces the noise created about by half. This is one step that's likely to become a permanent procedure as we run a wet pump 24/7/365.
2. Drain pump, dry prime with pump out of gear. Engage pump. Zero noise. Once water had been circulated the noise returned upon returning the pump to idle and closing all valves.
3. With pump engaged and re-circulating supply positive source through a gated intake. Sound immediately goes away completely.
4. While the pump is engaged and the noise is worst, engage the primer. This had no effect on the noise.
We were thinking the pump is getting air somewhere, but there's no viewable leaks? Thoughts, ideas, tests, comments?
I've worked with a lot of rear mount PTO pumps with the same noise. I think it has something to do with the driveshaft configuration with a rear mount. They all make a lot of noise which goes away as soon as the pump gets flooded and there is a load on the pump shaft. Can't help on the leak except to mention that our mechanics will sometimes use compressed air in the pump to listen for the leak.
Obviously, as you say, air is getting into the pump somewhere. Is it possible that the prime valve is stuck partially open? Your comment about the "gravelly" sound plus all of the things that make it come and go make me wonder. See also PM.
Several things come to mind when dealing with a Waterous Pump. ChiefEng made a valuable suggestion. Over the years I have encountered MANY improperly adjusted primer valves. Most times the microswitch makes contact, and runs the primer pump, but the valve on the vacuum line between the primer and the main pump stays shut. If you are getting a prime (shows 20 inches or so of vacuum, but then leaks off rapidly, try one or more of the following. 1. Drain the pump completely, but be sure the tank is full and the T to P and the Tank fill are both closed. Then operate the primer until you get at least 15 to 20" of vacuum. Shut the engine down and leave the pump out of gear. Crawl under and rig and listen for air leakage. Some notorious locations are: a. Packing (Might not have been reinstalled properly. b. Main drain - Never open a Waterous main drain under pressure. The O-rings sealing the main drain can be blown off the operating shaft and it is easy to do this. c. If equipped with an automatic relay relief valve, check the outlet and listen for an air leak. If leaking, vap this off for the vacuum test, but be sure to remove the cap before returning to service. If there is no sound from under the rig, then climb up and listen in the tank fill hole. A leaking tank fill line that enters the top of the tank can allow air to enter the pump through a bad valve. d. if all else fails recheck the pump to be sure it is still dry. A pump full of water indicates a bad tank to pump line. To do these tests you should have a vacuum gauge that has at least 2 inches per division resolution. Trying to use the pumper vacuum indicating gauge is usually not good enough for this test.
Noisy drive line is pretty common on a whole lot of set-ups. Usually near the thrust coupling at the input to an outboard gear case. (PTO driven pumps)
Thanks guys, we have pulled a dry prime ourselves and short of having a quality gauge the panel intake gauge shows very little if any loss over 10 minutes or more. I thought I heard a leak and when I got my "second set of ears", he couldn't hear anything, when I put my head back in, nothing, and nothing since. Found our test gauges had been misused and inoperable this morning so I'm looking for another test gauge or the truck may be going back to the pump man anyway, it seems we hadn't thought about the thermal relief and he's installing one given we're pretty certain we know when we damaged the seal. While the thermal relief doesn't take the place of proper training, it appears redundancy is the safest bet given the costs.
That isn't by any chance a chain driven pump is it? We have one on a older truck that is, (can't remember the brand) but it always goes away once you start bringing the RPM's up and put a little load on it. Never had any effect on the operation. If it is a chain driven pump I'd speculate that it's just a little slack action like ours, it does have a sound like gravel. Just a normal sound for us.
Quick update/side note:
We finalized a training bulletin to ensure all shifts and personnel were conducting the same exact checks using the same exact procedures, daily and weekly. During the hands on training for my shift we noted again that:
1. After pulling a dry prime test the pump lost zero psi during the 5 minute time
2. We then opened the T2P and flooded the pump before engaging it.
3. Now we engaged the pump shift and pump and found that the "normal junky sound" upon engagement (prior to bring the engine off idle and opening the recirculate valve 50% or more) is gone. The pump purrs leading us to believe the "normal junky sound" is air causing cavitation.
The perplexing part is that the pump runs smooth and quiet until it's brought to idle, disengaged, then re-engaged at which point the cavitation sound reappears. The T2P remains open from the time it's opened after the dry prime test throughout. We're baffled as to where air might be coming in from, as I said the pump does the dry prime perfectly????
I suspect this is possible, I'm not sure how we'd check this? Would it be possible for the prime valve to be partially stuck open and still allow a dry prime repeatedly?
Originally Posted by chiefengineer11
I must say the training bulletin was enlightening. In the past we relied on senior personnel to instruct probies on the routine daily/weekly checks and we've found that over the years some things seem to get lost. The older personnel seem to have a more detailed lengthier process and the newbies check fewer items. This bulletin certainly opened a few sets of eyes. Most of us had not been testing our Waterous Relief valves in accordance with their manual, instead following the Hale procedure which leaves out steps due to the different design.
Does the intake side of the plumbing in your pump have a "high spot" somewhere? Specifically, an elbow or some such high spot above the level of your impeller(s) from which water can drain?
It sounds like you have no issues when under positive pressure (open T2P with gravity, or the source mentioned in your second post.) You may have a spot too high up to be flooded by the negative pressure of your impellers. When you flood the pump out, the sound goes away. When you let it rest, and the high spot drains to wherever, you have a pocket of air which is being cavitated.
Do you find that the sound goes away when you simply increase the RPMs? If so, that may be your impellers building the necessary suction to push out the trapped air.
Does the sound go away when you let it idle for a minute or two? If so, you may simply finish off the air pocket at that time and are getting full water flow.
It would also explain the inability to hold a dry prime. In a vacuum with a void, the vapor pressure of the water in the pump will increase and give you pressure drops. Not likely as bad as an actual leak, but pressure drops none the less.
It's very doubtful unless it's a very small one, the two suction lines are direct into the pump at the same level, in fact you can see the impeller though the steamer opening and the gated suction is in the same plane just to the right and enters into the same line.
Originally Posted by gonzo25nj
The noise changes when the RPM's are increased, but sound similar but faster(?)
Originally Posted by gonzo25nj
Does the sound go away when you let it idle for a minute or two? If so, you may simply finish off the air pocket at that time and are getting full water flow.[/QUOTE]No at idle it seems to remain unchanged.
It actually holds a dry prime which adds to the "baffle factor".
Originally Posted by gonzo25nj
Thanks for the questions and thoughts, keep them coming.:)
And what the heck does radon pumps have to do with this thread?
Originally Posted by reaganfleming1
Mike: Check his total replies on this forum. He must be just a kid with very little to contribute to the discussion. Maybe by reading the old threads and taking the time to try to understand some things discussed on here, he might learn a few things. His latest comment concerning hydraulic generators was equally off the mark concerning the discussion.