Any pump experts out there?

[rScotty]

I worked with pumps during my 31 years as chemical engineer and have had a swimming pool for almost 30 years. That leaking packing sounds like your culprit because you say it leaks when shut down and almost stops when running. That clues you that it is actually sucking at the packing. This can be air on startup, and it is probably sucking air now while running.Ralph

I've have experience designing similar centrifugal pumps, and Ralph's idea sounds right to me. It might not be sucking air at the packing - but that is certainly the most likely place and the first place to look if you are happy with the suction hoses and connection. ALWAYS check the suction connection at the pump. Tighten it there or smear the outside of that connection with bathtub caulk. When you take it apart, it's not likely to be worth the hassle of changing any of the adjustments, there isn't much to go wrong or wear in that type of pump that doesn't involve packings and intake. Certainly nothing that would explain how it is running now. Like Ralph says, Id' bet it's heating up and sucking air somewhere. The time and heat heat also suggests the packing. These air leaks can be pinhole small but still cause big losses.
good luck, rScotty

 

[wolc123]

I think the more likely culprit is air building up in you suction piping. You probably have a foot-valve down at the end, in the creek, and you probably fill the pipe between the valve and the pump before startup. This gives you your short time of proper operation. As it runs, air likely begins to accumulate in high spots in the suction piping, reducing your effective suction head. THE SUCTION PIPING SHOULD HAVE A CONSTANT RISE TO THE PUMP, especially when pumping highly-aerated water like that from a running creek. This may mean you have to raise the pump to get it above the bank. Raising the pump will not affect the NPSH because you will still have the same difference between the water level in the creek, from which you draw, and the pond, to which you deliver. NPSH means Net Positive Suction Head and refers to the fact that a pump can not pull liquid, but only push it. Atmospheric pressure (around 34 ft) is what pushes the water into the pump. This means that, in theory at least, a pump may be able to "lift" water about 34 feet, into its suction. If there are any horizontally-installed reducers in the suction piping, they should be of the eccentric type, and installed so that there is no high spots where air can accumulate. The fact that your pump still operates properly for a time after startup is an indication that there is no problem with your impeller, or wear rings. If these components wear out, performance goes away until they are repaired.

 

[user.69169]

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Could someone explain why a bad packing could cause this problem? I simply don't understand. My simple understanding is that the packing is just a way to seal water from leaking around the shaft.
If this means anything, the packing drips briskly and steadily with pump off, and slows to almost a stop with pump running. Do packings get too tight or too loose with age? I should also mention that although I usually pump clean, clear water, I did pump a lot of sand inadvertently about a month ago. The suction end got half buried in a small sandbar after a storm, and I flipped the pump on without realizing this. I noticed what happened when I saw brown water coming out of the discharge. Thanks again.

Son you just diagnosed your own problem all the way.

Packings require a little attention over their life to keep them working right, that's why pump manufacturers welt to ceramic seals last 50 years. Seems they recognized people's mechanicle ability was falling off before the rest of manufacturing.

If that shaft is leaking the pump is sucking air and loosing ability to pump, ain't no way around that fact. She might have also taken some impeller wear, but looking at the part diagram I posted the link to the impeller is also available, sure hope you don't need that though cause she will cost. Even pumping what looks like clean water impellers do wear, so do the castings around the impeller.

When you tighten the packing gland a bit the problem of the leak might go away. Bring it up just a wee bit at a time or you'll ruin something for sure.

After you bring the packing up and shut the pump down it'll be a real good idea in the future to pop the endcap off the back end of the motor bearing and eyeball the back of the shaft. Generally the shaft has a screwdriver slot on a little pump like that you got, and you will want to use a screwdriver to turn it over before putting the power to the motor to be sure the packing ain't overtight. That packing also acts like a bearing right up close to the impeller in that pump.

Back when I went to driving truck we had little grease cups on the water pumps of the truck engine, and every day you'd give that greasecup a bit of a turn to keep the pump lubricated. Fellow told me one time a pump is a whole lot like a woman, you keep her maintained and she keeps you happy. You don't take care of either one and you got a big problem.

 

[jbarker855]

Well fellas, I have to say that the depth and breadth of knowledge here at TBN never fails to amaze me. I believe you guys are right-on about the bad/loose packing. It makes perfect sense. Difficult priming. Pumps good at first and then falls off as packing heats up and starts sucking air. Also, the packing leaks when the pump is off, further suggesting the packing is too loose. Thanks for the help here. It's a little embarrassing I didn't see how bad packing could cause air leak and poor output.
The bolts holding the packing in are completely shot. No getting them off without cutting them. But they will be easy to replace, as they will just fall right out when I cut them. I will get new bolts, tighten them up slowly and gently, making sure not to over-tighten. If that doesn't work, I will try getting new packing, as I suspect this packing hasn't been replaced in many years. I'll let you know how things work out. Thanks so much.
-Jay

 

[Egon]

Consider installing new packing right away. Gives you a look at the shaft condition and will be easier on the shaft if some sand got stuck in the old packing.:thumbsup:

Some packing comes in rolls, others is precut and the joints are staggered when installing. It also comes in many different types for different usage.

A little tool with a hook on the end, another with a corkscrew type end and needle nosed pliers are usually the type of tools required for packing removal.

Flashlight and mirror may also help for inspecting the shaft.

Course, considering the number of years since I've repacked a gland ever thing about doing it may be different!

 

[jbarker855]

Well I decided to just replace the packing. Bought a little packing puller to help with the job. Unfortunately, I destroyed the lantern ring in the process. To be honest, I knew it was in there and I reallly wasn't too careful with it. Figured I'd just buy a new one. Well before you read farther, guess how much a new lantern ring from Crane-Deming is.....10? I thought maybe $20 at the high end. Nope. New lantern ring- $100. I was shocked but felt I didn't really have a choice. So now it is all back together and working great. I still have a concern though. Instructions from pump owner's manual said after putting packing in, tighten up gland bolts to cinch it all in there, and then back off them. This is what I did, but even with bolts backed all the way off now, I don't get much of a drip at the gland with pump running. Manual states it should drip slowly while running so as to keep packing cooled. Maybe as it wears in, it will start dripping a bit, but the no-drip makes me a little concerned. The shaft turns easily by hand. I have run it for about 10 minutes, and the shaft gets warm, but not hot. I have not run it for a prolonged period of time yet. By the way, it pumps better than it has in years. Thanks again guys.
-Jay

 

[Egon]

The shaft turns easily by hand. I have run it for about 10 minutes, and the shaft gets warm, but not hot.

That sounds like it's working OK and the shaft is good.:thumbsup::thumbsup:

 

[jbooth]

I'm a bit late with this info. Unless your lantern ring is piped back to the suction, discharge, or poses as a leak off port, you could probably have eliminated it.

It is possible to help cool new packing on the breakin period with an external source of water placed on the external parts of the stuffing box and pump shaft. We used this method in some of the old fossil power plants that still used packing. Even the newer seals had built in coolers on them.

Another thing that might be beneficial as your new packing wears is to apply a small amount of water pump grease through the lantern ring leakoff ports.

If your pump has a tubing on the leak-off port piped to the suction it will reduce the pressure your packing is exposed to. If the port is connected to the discharge it is for water lubricating the packing.

I worked power plants for 40 years prior to retiring and had a lot of expierence with pumps. I thought you were getting good advice. Hope my tardiness didn't cause you to spend the $100 for a needless lantern ring.

 

[jbarker855]

A little update-
I tried running the pump a little longer, and the shaft got too hot to touch. Now I don't really have any idea how warm it used to get when it was running fine, but I was still concerned about the fact no water was dripping from the packing. So I took the darn packing out again and repacked it, but looser this time. Still no drip. Then it finally hit me. I sucked a bunch of sand in one day. The lantern ring is plumbed to the pump discharge as a water source by a small copper line. The line must have got plugged with debris, the packing overheated, and then started sucking air and failing to pump. I took the line off that was feeding the lantern ring, and EUREKA! The line was plugged with sand. I cleaned it all out, put it back together, and the pump ran great for over 6 hours today, and the shaft was barely warm. I get the nice slow steady drip from the gland that the manual insisted I should have. Now the pump is back in action!.......though I noticed the bearing housing on the motor side of the pump is quite warm to touch. Certainly unrelated problem, but I will have to look into it soon. Thanks again all.
-Jay