Boiler life expectancy

We have a Tarm wood gasification boiler that we use for heat and domestic hot water year round. We also have a kerosene boiler that sits beside it and is only used when the wood boiler needs to be serviced, so it only goes through maybe 20 gallons in a typical year. The boiler is about 20 years old. The pump on the gun stopped working recently and I have been getting conflicting advice about what I should do. One option is to replace the pump for about $50 on ebay, some say that the whole thing is so old that it doesn't make sense to do that. Option 2 is to replace the gun, $400+ probably. Option 3 is to replace the whole boiler, some have told me that it will be deteriorated inside and need to be replaced soon anyway, others say that they do not deteriorate inside because it is a closed loop with no oxygen. I do not know what the cost is for this option but likely at least $2k. Any advice will be much appreciated.
Zach

The life of the boiler should be related to the quality of the water in it. I would get someone in your area to inspect it that works on them.

The life of the pump and gun should be related to the quality of the fuel.

I have seen cast iron 'boilers' still working after 150 years, but the pump nozzles and transformers on the burner only last a couple seasons. If your boiler is not cast, but welded plate, if the smoke gas and water stay in their place, just give it a very close inspection. Agh, btw, I have taken a delivery of misery, thick , brass filings, and just plane crud, so before you tear into or spend money on anything, check your filters, at the tank, and the little one inside your pump. They are the usual suspects, and needs to be done every year anyway- a $20 fix, if you do it yourself. Good luck!

Does the kerosene boiler stay warm or does it get cold between uses? If it gets cold and there is domestic water running thru it it will get condensation which leads to rust and shortened life. Has it had boiler treatment in the water that stays in it? if not it has been deteriorating inside. If it has been kept warm and has had treatment it should have many years left in it.

The kerosene boiler stays hot all the time since the water from the
wood boiler flows through it. The domestic hot water preheat coil is
in the wood boiler, and there is also a boiler mate hot water heater
tank that either boiler can send water through. I have not put boiler
treatment in the water, the water is plumbed right into it so I can
open a valve and it will raise the pressure as needed. Is there a way
to check the boiler to find out what the inside is like? Thank you
very much.
Zach

Thanks, I do change the filter on the line regularly and have changed it now, but when I open the bleeder and hit the reset button it doesn't even push out foam. I didn't know there was a filter inside the gun itself. We bring our kerosene in a 5 gallon can so I think it is pretty clean, the tank would only hold 30 gallons and we never fill it all the way anyway since we don't use that much.
Zach

If the boiler feed is demin water, no oxygen ingress and the ph level maintained. The fire side of the boiler is then limiting factor.

The quality of the water is exactly correct. Closed loop doesn't eliminate the oxygen. Remeber water is 2H2O. Unless you treat with an oxygen scavenger, the piping could be severely pitted.

We use hydrazine and morphaline to scavage 02 from boiler
feed water. Just stay upwind of the stuff and don"t spill any on
your clothes or skin. There are other less toxic products out
there.

Open loop or closed loop?

Are you sure the pump is turning, There is a rubber coupler inside the fan basket that connects the burner moter to the pump. Some were cast ended that were compressed on to the rubber part, some had a male hex fitting cast in the end that the rubber slid over. These were held in place with allen set screws accessable thru a spot in the fan basket. Still others simply had a plastic ended coupling that slid on the moter and pump shaft and drove off the flat portion of the shafts. The last type were more prone to fail as the plastic would round out on the shaft. As to the filter inside the pump it is a very fine mesh screen and if I recall can be accessed by removing the bolts in the end of the pump and pulling the housing. Be carful on the gasket. Use a good fuel resistant sealer to put it back together. Large shaft pumps were 1750 rpm and small shaft were 3450 rpm as I recall. Unhook the fuel line to the nozzel and put it in a can. When I worked on them I had a hose I used to check flow in a can, needs to be pretty strong flow, and a gage set up for checking pressure. I set the gage up on a tee so I could check pressure with it connected to the nozzel as the burner was running to get real time pressure under normal running conditions. It should read 100 psi if I recall. It seems you could usually feel and somtimes even hear a vibration on the bad coupler deal. Not always but most of the time.
And this is worth what you paid for it and is from memmory based on somthing I haven't worked on in close to 30 years.
Angle Iron

Zach,

Our house has an older Tarm boiler than yours. I installed it in 1977, pulling out the cast iron American Standard boiler that had been new in 1973. A friend wanted to buy the American Standard, and installed it in his farm house next to his Tarm "add on" unit. All 3 of these boilers are working fine today, and the 2 that have fuel oil burners are still using their original burners. With the small number of gallons of oil you burn per year, your burner does not have many total hours on it. I have seen many burner guns exceed 20,000 hours of burn time on them. I highly doubt that your oil pump is shot. As others have suggested, check for oil flow to the pump, check the filter and pump screen, and check the plastic drive coupling that drives the pump. Your pump has an 1/8" pipe plug that can be pulled and a pressure gauge temporarily put in its place. The pump pressure to the nozzle is adjustable with the screw and locknut on the pump. A sticker on the side of the pump tells which port does what. An airlocked pump will not pump oil or develop pressure. A single oil supply line to the pump can be difficult to purge the air from, and maybe you have some piece of rust or insect part blocking the oil line at the base of the oil tank. A double line oil supply to the burner will self bleed, but will still shut down about every 30 seconds (press the reset button again until you have good steady fire).

And yes, there are poor quality boilers that can corrode through the firebox in less than 5 years. I suspect that boiler steel is different from mild steel plate.

Good luck in fixing the problem.

Paul in MN