Help with oil combustion settings

[RayPlumb]

Looks like not solved this problem yet. Started sooting up again after week, still mainly around the nozzle and blackening the photocell ...lockout.. Ive checked the nozzle again and back to a small squirt at end shut down. Presume drawing air in somewhere, but it is on a tigerloop. This should bleed air out, but could air still be drawn into the nozzle oil line causing it to compress and then squirt when expanded.?
New issue today was tigerloop was empty boiler been off for day and half. No sign of leaks presume check valve passing ?. Could this draw in air..?
Phoned grant Friday for advice and the tec said the cleaning door seal could of compressed over the years and caused the door to sit further in causing the long drip plate just under the tubulators to touch the door insulation causing the an air flow restriction which end in sooting.. There is some evidence of this with a black soot line on the door insulation.
But would this cause sooting on nozzle and photocell?
Turning into nightmare...

 

[SJB060685]

The door seal problem is known yes. Trying cutting a shallow 25mm grove into the insulation to allow proper passage of flue gases.
The tiger loop sounds like the NRV has failed. Either put a small 10mm NRV on the suction line before the loop or replace the loop with a current regs metal one. It is possible the oil feed line and flexi is drawing in air. See through hoses help to diagnose this problem.

 

[RayPlumb]

So went out today and tiger loop still holding oil after a day ( burner been off).
Cut chanel in door insulation and added some more door seal rope around seal.
Removed the burner and checked electrodes and while it was out. With a container of oil checked the burner. Littler after squirt. Flushed out air in nozzle oil line. Ran on and off quite a few cycles and no after drip or squirt at shut down. No evidence of any oil leak on oil line from tigerloop to burner, so presume the day it was empty it had drained back to tank.
Added a non return valve just before tigerloop on supply side. Also added a clear oil hose on the suction side to pump.
Connected all up and flushed all air out oil lines with coil disconnected. Clear oil suction hose nice and clear with no air flowing through. Although every 1.5 - 2 minutes a small bubble comes through the return line.. ran for about 10 min and still small bubble every 1.5 - 2 min. The flow hose is still clear no air. (although flow rate quite high would I even notice?)
Could it be cavitation in the pump ? or is there a small leak sucking in air. Is it enough to worry about. ?
There is two isolation valves on the suction and return, but cant see any leaks.?

 

[SJB060685]

What’s the total suction height from base of tank to burner? As you know a tiger loop or any other deaerator is a sub gravity system. I think at about -0.4 bar gases can be extracted from the fuel, that’s the purpose of the deaeration. If the suction head is more than 3.5-4m this can happen.
An air bubble appearing in the return chamber rather than the feed chamber still suggests a leakage after the loop and before the pump inlet, the return is pressurised.

 

[RayPlumb]

What’s the total suction height from base of tank to burner? As you know a tiger loop or any other deaerator is a sub gravity system. I think at about -0.4 bar gases can be extracted from the fuel, that’s the purpose of the deaeration. If the suction head is more than 3.5-4m this can happen.
An air bubble appearing in the return chamber rather than the feed chamber still suggests a leakage after the loop and before the pump inlet, the return is pressurised.

The tank is about 10 mtrs away from the tigerloop and burner is about 1 mtr above the bottom of the tank. Flow rate through oil line is quite good, but slows a bit through fire valve, but more than burner nozzle would need.

 

[RayPlumb]

What’s the total suction height from base of tank to burner? As you know a tiger loop or any other deaerator is a sub gravity system. I think at about -0.4 bar gases can be extracted from the fuel, that’s the purpose of the deaeration. If the suction head is more than 3.5-4m this can happen.
An air bubble appearing in the return chamber rather than the feed chamber still suggests a leakage after the loop and before the pump inlet, the return is pressurised.

So if there is no air in the clear inlet hose could that rule out all before the hose including the isolation valve. Which would only leave the connection of the clear hose to the pump and the new pump itself.

 

[SJB060685]

If the tank base is only 1m below the burner then most of the time when the tank is full/near full the suction line will be under a positive pressure. Only the oil line above tank fill level would be subject to less than atmospheric pressure. That’s where you would expect air being drawn in.
I’ve always approached like this. If air/bubbles can be seen entering the bottom chamber of loop from tank then there’s a leak somewhere between tank outlet and loop entrance. If no air/bubbles at that point it any air ingress would be on the suction side of the pump.

 

[RayPlumb]

If the tank base is only 1m below the burner then most of the time when the tank is full/near full the suction line will be under a positive pressure. Only the oil line above tank fill level would be subject to less than atmospheric pressure. That’s where you would expect air being drawn in.
I’ve always approached like this. If air/bubbles can be seen entering the bottom chamber of loop from tank then there’s a leak somewhere between tank outlet and loop entrance. If no air/bubbles at that point it any air ingress would be on the suction side of the pump.

The only connections that would be under negative pressure it the check valve I installed below the tiger loop.
Bubbles definitely entering from the side where the return pipe enters the tigerloop. I did tighten all the suction side connections, could pressure test but would that not necessarily show up if it a suction issue. Looks like a revisit...

 

[SJB060685]

Metal braided hoses? And have you swapped them out? Common failure and should be replaced every service, tagging with date as well.

 

[RayPlumb]

Metal braided hoses? And have you swapped them out? Common failure and should be replaced every service, tagging with date as well.

Yes. Swapped both hoses out first visit with long life hoses. then swapped suction hose for a clear hose.