The 25 steps in the repair of a vacuum steam system

HeatingHelp

The 25 steps in the repair of a vacuum steam system

The 25 steps in the repair of a vacuum steam system

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Mike_vernon

Gotta love the ending Dan. I see you have a sense of humor as well

DanHolohan

Thanks!

clammy

A lesson that to this day still occurs and for the smart ones who come across them should quickly reply as I do Especially w building management companies . I have to go get a bigger screw drive and proceed to your truck and leave when they phone your cell and you inform them that you need to purchase a bigger screw drive they ll get the hint . Some times u have to accept what u cannot change and waste no further time and move on . Some times you have to realize that they are driven by the hope of a miracle wigit or a wave of a magic wand or screw drive unfortunately this is never the way the stories end . Thanks for the excellent reminder and refresher on the Buddhist theory of cause and effect and the cause of all suffering , the lack of knowledge and desire of wanting . Peace and good luck clammy

JohnNY

I have to admit, the picture caught my eye more than the story this time. That Liquor Store sign is famously still hanging outside an old storefront on West Broadway in Tribeca, NYC. I used to live about 4 blocks from there. The space was empty forever and was very well preserved inside with many old bottles still sitting on the bar. At some point around 2007 I'd say, J. Crew took the space, cleaned it up, but preserved a great deal of it including the old bottles though they polished them and partially filled them with colored waters. The staff in there, on purpose, was a bunch of hipsters in their 20s. All of them rail thin with very deliberate haircuts. I used to go in to buy some new shirts or sweaters seasonally and depending who was around, the staff would pour shots of either Smirnoff vodka or Jack Daniels to anyone who looked like they wouldn't rat them out. They knew what they were doing. Turn the music up, get the customers a little drunk and watch them spend money. The store closed even before covid made its neighbors close too and so the space and nearly all the retail on the block is empty again but the sign is till there. When it was a clothing store it was still then (and I'm guessing forever will be) known as The Liquor Store. Even in their advertising, J. Crew alternately referred to it as their Men's Shop or The Liquor Store depending if the ad was national or local. We had fun in NYC years ago and as it always has throughout history, it's changed now, and I wouldn't be comfortable wearing the clothes The Liquor Store used to sell. It's good to have little triggers to fun times. Thanks, Dan.

Pumpguy

26th step?

Our story above tells us this is a large system, the vacuum pump has been installed for a long time, and has been recently overhauled. It also tells us a boiler feed pump set with receiver tank vented to atmosphere has been installed.

We discovered that condensing steam in the boiler and steam header caused an induced vacuum which sucked the feed water out of the boiler feed tank, flooding the boiler and steam lines. So we added motorized valves to solve this problem and now all is well with the world, right?

Well..... Maybe not. Let me explain.

While some vacuum condensate return pump sets are designed to discharge condensate from atmosphere, these are frequently on smaller systems.

A typical large capacity vacuum condensate return pump package will have separate pump and motor assemblies for pumping condensate and another for producing vacuum. The vacuum is applied to the receiving tank that collects the condensate so the condensate pump has a vacuum on its suction side.

Like all condensate pumps, these have check valves on their discharge to prevent back flow of fluids when the pump is not running. But check valves, like steam traps are mechanical devices and do wear out.

When a check valve on a condensate pump's discharge wears out, condensate will back flow into the receiver, causing the pump to short cycle. The operator notices the short cycling and comes to the conclusion the check valve is leaking and replaces it.

But in our example, we're discharging into a vented boiler feed tank. Typically the run of piping between the discharge of the condensate pump (discharging from vacuum) and the boiler feed tank is short so the first fluid leaking past that bad check valve is condensate, but when that's gone, the next fluid leaking past that bad check valve is air, and that's where the trouble begins.

At first this back flow of air is low enough to be vented off through the little copper tube venting the pump's shaft seal cavity, but eventually this back flow of air is enough to push the condensate out of the pump's volute and now the pump is air bound.

In this air bound condition, the pump is operating but not pumping because there is not enough condensate in the volute. The condensate receiver continues to fill and then gets get carried over to the vacuum pump which discharges it out to atmosphere, same as it does with air and vapor.

So the operator sees this and thinks there's a problem with the condensate pump; its not pumping. And when it does pump, the seal is leaking. So they take the pump apart and can't find anything wrong with the pump but order a new seal and impeller just to be safe.

The new parts are installed and the pumps turned on but the same thing happens; the pump spins but doesn't pump. Out of desperation he changes the old check valve and the problem goes away. Hurray! Problem solved .......for a while. Check valve wears, starts leaking, and problem comes back.

The usual piping arrangement for boiler feed pump tanks is to have their fill connection at the top, and of course the vent is at the top too. This give us a perfect path for air to push through the leaking check valve, pushing the prime out of the condensate pump and cause it to become air bound.

The real and permanent solution to this air bound condensate pump problem is to come up with a piping arrangement to provide A PERMANENT WATER SEAL ON THE CONDENSATE PUMP'S DISCHARGE PIPING. This can be done is several ways.

1) Fill the boiler feed tank FROM THE BOTTOM.

2) Install an internal submerged outlet pipe inside the boiler feed tank. The outlet of this internal submerged pipe should be below the tank's minimum water level.

Whenever I sell a boiler feed unit where this possibility exists, I include an internal submerged outlet pipe.

3) Revise the piping connecting the condensate pump's connection to the boiler feed tank so there is always a water seal present.

If the boiler feed tank is elevated, simply install a tee in the vertical run of pipe, the branch of which is connected to the boiler feed tank's drain tapping.

If the boiler feed tank is on the same level as the vacuum pump, before connecting to it's top inlet, run the pipe down to the floor, install an elbow and a tee, and then back up to it's inlet. On the branch of the tee down at floor level, run a pipe to the boiler feed tank's drain connection.

Each heating season I get several calls describing this problem and asking for a solution. Attached is the file I send them.

I hope this comment is informative and helpful to others.

GGross

"You do this in defiance of logic,mechanical history and physics. You do it because it’s cheap."

I just might take this and add it on instead of a disclaimer on certain quotes.

DanHolohan

Thanks for adding great stuff to my story, guys!