40 year old oil line issue

EBEBRATT-Ed

So if you look at my other post "New Smith 28 Steamer" this issue had to do oil piping with that same job.....40 years ago. This wwt plant was built in"78" and had 2 Smith 3500s with PF oil burners. If you look at the pics you will see one of the original boilers still in service and overhead oil lines to the oil transfer pumps sitting on the boiler room floor.

There was a local guy here now retired who did start ups for Smith and he had an excellent reputation..good guy. He was having a problem keeping these burners running. He called me for help because I worked for the PF rep.

So underground tank, 2 transfer pumps (1 is a back up) overhead loop to feed both burners and then back to the tank with the return. The pumps were pumping, we even turned both of them on but little to no oil pressure in the loop.....starving the burners.

I even took a pressure gage out of the discharge oil line with both pumps running and got no oil!

The problem was the oil return line ran to the bottom of the oil tank. Believe it or not the return line created a siphon on the overhead loop pulling it into a vacuum. It was pulling oil out of the loop faster than the pumps could fill it.

I told him he had to put a back pressure valve on the return line. A vac breaker would probably work as well but has leak potential.

He went out to his truck and came back with an old 1" gate valve, better than nothing. There was a union near by so we piped it in. Started the pumps and throttled the valve to get a slight pressure on the loop.

He said he would get a back pressure valve and install it.

So when we recently got this boiler replacement job I asked my coworker "look over by the transfer pumps and see if he put a backpressure valve in", "no he said, the gate valve is still there".

You can see it in the pictures above the transfer pumps.

It's an issue that happens very rarely (the siphon) and you usually only find it on jobs that have transfer pumps. In 45 years I have had this problem only 4 times

Jamie Hall

Your old guy was a man after my own heart -- "So when we recently got this boiler replacement job I asked my coworker "look over by the transfer pumps and see if he put a backpressure valve in", "no he said, the gate valve is still there"." It worked -- why bother to change it?

EBEBRATT-Ed

@Jamie Hall only because your not supposed to throttle with a gate. We used to put a simple spring loaded back pressure valve like a relief valve but with better control on the return line if we had that issue. Watson McDaniel makes then.

Guess it worked for 45 years so I'm not changing it. They have since removed the old underground tank and installed a new tank above ground (double wall) so the siphon is probably gone

Just a side note. This plant is right next to a huge university power plant. I asked the guy yesterday "why didn't you put gas in here"

He made a face.

A gas line runs over to the power plant but the university paid for it to be installed and won't let the WWT plant tie into it. Guess it's to far to run there own line out to the street.