Boiler modifacations

[johnp]

Is it ok to add some outlets to an existing boiler?

It's all sand blasted and checks out ok, but i wanted to add a couple water feed inlets since the original one is above the water level and had a copper tube running down the inside of the tank to be below the water level.

Or can i use a couple of the 3/4" inlets right at the bottom of the tank?

On the top sheet their is one 1" outlet and two 1/4" outlets. the 1" is for main steam and saftey valve, one 1/4" is for my pressure gauge and the other i was thinking about drilling out to 1/2" for my whistle. Would this be ok or could i run the whistle off the 1" main steam outlet?

John

[87gn@tahoe]

NEVER EVER run ANYTHING off of the same outlet as the safety valve. EVER

The pressure drop will give the safety an inaccurate reading of the actual boiler pressure.

You can have weld-o-lets welded into the boiler shell, but it must be performed by a competent welder I.E. a code pressure vessel welder at a code shop.

Remember, you are playing with a potential bomb.

[johnp]

Would it be ok if I added a 1/2" outlet for my safety valve and shared the 3/4" outlet for my whistle and main steam? Its only 21.4 sqft I think 90 pph.

[artemis]

Would it be ok if I added a 1/2" outlet for my safety valve and shared the 3/4" outlet for my whistle and main steam? Its only 21.4 sqft I think 90 pph.

Before you buy a NEW, sealed pressure relief valve rated for steam, contact the company's tech engineers to size the valve. Give them the type of boiler, sq.ft. heating area, steam pressure etc. They can readily calculate the approximate maximum quantity of steam produced. The discharge pipe size should be one size larger than the inlet.

And every time you blow your whistle the engine will slow and a large "slug" of water will surge into the engine and cause the connecting rod to bend, the crankshaft to twist and the cylinder head to be blown off.

There is a reason for all these DON'Ts
DON'T ignore any of them

[Lopez Mike]

It sounds like you are suffering from boiler connection inadequacy. It's a common disease.

One solution is to reserve single connections for certain VERY critical items like the safety valve, pressure gauge and the top connection of your sight glass. Then feed all of the other secondary needs like the whistle, blower, burner feed, feed water pump(s) and god knows what else in the future through a turret (manifold) with it's own dedicated shut off valve.

This is normal practice. Others on here with much more experience can elaborate on this and give specific recommendations.

My factory built Beckman VFT has about twice as many places to hook things up as I can conceive of using. I spent a few dollars on pipe plugs! But I am ready for anything!

Mike

[johnp]

In vertical firetube boilers the feedwater shall be introduced at a point not less than 12 inches (300 mm) above the crown sheet ...... feedwater shall not be introduced through the openings or connections used for the water column or gage glass


What does this mean? Is it ok to use the inlets on the bottom of the boiler for feed water? Hand,injector ,and cross head driven pump.

I am confused

[fredrosse]

The 12 inch rule is meant to keep cold feedwater away from the crown sheet (or, in the case of a typical VFT, away from the bottom tubesheet) so that thermal strains are minimized. These sections of the boiler receive the most intense fire heat, and are most succeptable to thermal stresses. If you use a lower elevation connection, then a tube inside the boiler shell must cary the feedwater up to the 12 inch elevation before releasing the feedwater into the main shell volume.

The water column is there to provide a reliable level indication, so only the gauge glass, try cocks, and pressure gauge should be connected there. If feedwater was pumped into the water column, then a pressure drop of only 1/4 psi in the feedwater flow from the water column into the boiler proper would give an indicated level that was 6 inches more than the true level in the boiler proper.

I think the rule prohibiting use of blowdown connections for feedwater is a thermal shock issue, but that is just my guess.

[johnp]

But then at 12" above on a 14" tank I might be above the water line.

I also have a tube which looks like it runs the perimeter of the tank inside under the top sheet. You can see both ends ending at each side of the 3/4" outlet what would this be?

[fredrosse]

I know of no rule that prohibits pumping feedwater into the steam space.

Could you describe the tube you mention a little more, are you saying it is mounted inside the boiler pressure vessel?

Perhaps this is what was typically called a "dry pipe" which is a long perforated pipe connected to the steam outlet connection. This pipe , mounted as high as possible above the boiler water level, minimized water carryover if there was significant splashing going on inside the boiler.

[Lopez Mike]

Fred is right. There is no reason not to pump into the steam space.

I have before me Locomotive Boiler Feeding Devices, (copyright 1934!) wherein is discussed a Duplex Top Check and Stop-Valve.

"The principle reason for placing the boiler check-valve on top of the boiler is that certain impurities in the feedwater, when it is delivered to the boiler below the water level, will form a hard scale on the sheets, whereas if the water is delivered into the steam space, the impurities will be deposited in the form of a mud that can be blown out."
"Also, the water in falling through the steam space becomes heated and does not have such a cooling effect on the sheets as when the water is delivered on the side of the boiler".

First I've heard of all this but it sounds good to me. Also, throwing around words like 'whereas' gives it a certain gravitas.

Mike