New vacuum pump

bigpete638

I’ve been asked to find information on a replacement vacuum pump.  I couldn’t find a tag on the current one but need to order something with equal capacity.  So here I am coming to the experts yet again.  Hoping to change all traps as well as the install of the new pump.  Here are some pics.  All help and information is much appreciated.

bigpete638

I’m also still trying to figure out how to receive email notifications for replies.  I missed a few in the past that replied sometime later. 

mattmia2

click on the thing at the top right of the post to get notifications.

Is that a vacuum pump or just a condensate pump?

bigpete638

I’m actually not sure if it’s a vacuum pump as well.  

I did get an email notification.  Thank you.

JUGHNE

I have never seen one in my life but......"Pump 3&4...vacuum producer"
And also probably a boiler feed pump, not condensate pump.

retiredguy

That unit is a Skidmore Vacuum pump with a condensate dump or feed tank, could be either. The top 2 pumps are the vacuum producers and the lower (usually 2) are the condensate pumps. This is a rebuildable unit if it is not too old. I haven't worked on any for a few years since I am retired. If necessary, I can tell you how they work but there are guys that monitor this site that are experts on vacuum pumps, so "hold on" they will be along.

bigpete638

The unit is severely rusted and leaking profusely from the side.  Not even from piping.  I’m thinking a brand new unit will be needed.

kevinj_4

Did you look in the control panel???

I recently priced out a rebuild on an old skidmore, for a couple thousand more I sold them a new unit.

Now skidmore owns the warranty.

Send those pics to your skidmore rep, they can identify it.

bigpete638

I’ll look them up and send them pictures. Thank you.

Steamhead

Maybe @Pumpguy will chime in here- he's our resident vacuum-pump expert.

EBEBRATT-Ed

@bigpete638

Send Skidmore the pictures and the horse power of all the motors. Look inside the panel for any other information. And give them the job address. They will be able to find it

These are not stock pumps

They are built job specific, not a stock item

bigpete638

Thanks again for all the help.  We have several units on campus that need replacement.  Not to mention just about every trap.  I’m hoping they bring a sales rep knowledgeable in the equipment here.

retiredguy

I would recommend that you fix all the piping and system leaks first to insure a good steam and condensate integrity, then rebuild/replace all the steam traps, then replace or rebuild the vacuum pump systems. If the piping is bad or has leaks and the steam traps are bad, replacing the vacuum tanks would be a waste of time and could also harm the new vacuum units.

bigpete638

There is over 30 buildings here.  The piping should’ve been changed 30 years ago.  I wouldn’t know where to begin.  Asbestos is also an issue in many places.

jumper

bigpete638 said:

There is over 30 buildings here.  The piping should’ve been changed 30 years ago.  I wouldn’t know where to begin.  Asbestos is also an issue in many places.

Does each building have its own boiler? Or is steam distributed?

bigpete638

Each building has a steam generator.  They send out high pressure high temp. Hot water to all the buildings from the plant.

EBEBRATT-Ed

@bigpete638

Replacing or rebuilding the traps is a MUST.

If the traps are not fixed it will ruin the new vacuum pumps

#1 cause of bad vacuum pumps=bad traps

Pumpguy

This is a full duplex vacuum and condensate return pump package. The vacuum producers are water jet venturi types with a typical air capacity of 8 to 11 or so CFM per motor horsepower. Liquid ring vacuum pumps are more efficient, doing from around 12 to 17 CFM per motor horsepower.

If you can provide the HP of the condensate pumps, the size of the condensate receiver, and some info on the vertical and horizontal distance the condensate is being pumped to, and the pressure at the destination, I should be able to come pretty close for sizing. The condensate pumps currently fitted look to be substitute replacements, so how closely they were sized to the originals is a mystery.

For this equipment, the industry sizing standard for receiving tanks is a 1 minute storage capacity, so if sized according to that rule, and for example the lower tank holds 35 gallons, the rule would dictate 35 GPM for each condensate pump.

This assumes the existing unit was correctly sized to begin with, which is not always the case.

When considering the actual load of the building's radiation, the sizing standard is to survey the EDR of the building's radiation, and figure 1 GPM per thousand square feet of EDR.

Another approach is based on the steaming capacity of the boiler(s). Knowing the boiler horsepower, and/or steaming capacity in #/hr is always useful as well. Here again, this depends on how closely the boiler is sized to the condensing rate of the building's radiation.

As far as the air capacity of the vacuum pumps goes, the old standard was 1/3 of a CFM per thousand square feet EDR. This assumes no trap leakage so condensate is realistically cool, and no air leakage from atmosphere into the return lines. Hot condensate, say 175*F or higher can diminish, or totally kill the possibility of producing a vacuum. When customers tell me they have 190*F condensate coming back I tell them to just forget vacuum until they get that condensate temperature down to a realistic temperature. Turn off the vacuum pumps and run on FLOAT ONLY until they fix the traps and get the steam pressure down to a pound or 2 where it needs to be.

Understanding that replacement vacuum pumps these days are for old buildings, the load on the vacuum pumps is always higher, so I recommend a full ONE (1) CFM per thousand square feet EDR. Systems with duplex vacuum pumps with controls that can pull both vacuum pumps into operation under peak load conditions can be sized a bit lower, say 0.75 CFM per thousand square feet EDR.

One thing is certain, within practical limits, you can't put in too big a vacuum pumps. Oversize vacuum pumps will just run for a shorter time period to cycle between the on and off settings of the vacuum switches. For a given system, the off time for the vacuum pumps will be the same.

So, with all this rambling, if you would like my input on your particular system, feel free to contact me to discuss your particulars and I'll see what we can come up with.

Edit: Condensate tank construction.

While I have this platform and can stay on topic, I should add some comments about condensate tank construction.

The example shown here is of welded carbon steel construction. Typical wall thickness is 3/16" and is the lowest cost option.

Traditional tank construction is cast iron which has a thicker wall and is more corrosion resistant. Some manufacturers offer a 20 year replacement warranty against corrosion failure. It is not unusual to see cast iron tanks that are nearly 100 years old and still perfectly sound.

So long as the condensate is kept mildly alkaline with a pH around 8.5 or so, they can last forever. If the condensate is allowed to go acid with a pH lower than 7, the acid will leach out the iron from the casting and leave a matrix of free carbon behind. This matrix has the appearance and texture of a soft lead pencil.

Some manufacturers offer stainless steel tanks. While I have never seen a corrosion problem with these, I have been told that condensate with chemicals added that end in "ide" can cause corrosion problems.

bigpete638

We had a very hard time ordering material to keep it simple.  A couple weeks ago we finally got a shipment of traps in so this summer will be very busy.  Much of the lines are covered in asbestos which also makes us reluctant and there are pretty severe leaks in some areas.  Very difficult to tackle these issues.  The last time there were trap replacements for SOME of the buildings was in 01.  It’s very easy to feel overwhelmed but we’re doing the best we can.

The Steam Whisperer

I've eliminated a number of vacuum pumps by converting the system to orificed supply valves, if the radiation is oversized for the max. heat load. Most radiation can run at about 60% capacity on the design day, so the piping only needs to carry 60% of the load it was designed for as a vacuum system. Cutting the load will allow the system to run with the smaller piping used for vacuum systems. This also eliminates the traps on the radiators...getting rid of another maintenance headache.
I'd use anyone but Skidmore for the pumps.... I and a number of others on this forum have had really bad experiences with them. Probably thier largest competitor, Shipco, has had several record breaking sales years in a row with thier vacuum pumps...... and Skidmore's attitude is probably the reason why.

bigpete638

I’m clearly in the presence of greatness from the members here.  I really appreciate everything.  Things were tough before but now there is an even larger budget cut.  Somehow we started getting material.  Probably because half the buildings didn’t have heat.  The current situation causing the absence of students has been the only saving grace.

bigpete638

I will bring this information up with my partner and the engineers to come up with a game plan.  I can’t thank this site enough.

EBEBRATT-Ed

@bigpete638

Sounds like you have a long haul ahead of you. When systems get neglected it's a long road back.

Here's the story

The traps get neglected and blow steam.

This ruins the vacuum pumps &

causes excessive make up water which shortens the boilers life, rots out the return piping etc etc

It's always cheaper to maintain but making the powers that be believe is another story.

They will usually let it go until the system is trashed then beg for donations to replace the system

Wishing you a lot of luck I think your gonna need it

bigpete638

They’ve been dumping condensate in several buildings for years now.

retiredguy

What you can now be a witness to is that fresh water is one of the worst things to introduce into a steam boiler. Excess fresh water, without the necessary deaereation and treatment will kill the whole system.

Steam boilers, both high and low pressure, can run on 100% fresh water if the boiler plant has a good Deaerator and the necessary water treatment. Without that, your system is doomed. If I were the head of that campus and I am guessing that it is a school, I would be asking the government for emergency funding to install a whole new system in all the buildings, which you will be doing soon enough anyway. If the money is available I would be asking for as much as I could get since the interest rates are as low as they have ever been. As the system deteriorates, it may get to a point where the boilers will not be able to satisfy the steam load of the campus. I have seen this many times as the cold fresh water consumes too much of the steaming capacity of the boilers. A new system will reduce the fuel usage, the water usage cost, the labor cost, the wasted money spent on your attempt to keep the system running, and will increase the comfort level of all the spaces. A new vacuum pump is the least of your worries and probably not a good way to spend money at this time. You have too many other problems.

My 2 cents.

bigpete638

It falls on def ears at this school.  Think they began talking about a new plant ten years ago.  Still nothing came of it.  The magnitude of the job to replace all piping would be enormous for the entire campus.