Webster Steam system with vacuum pumps

Double D

I have a Webster steam system with vacuum pumps. I have only done a very brief walk through. What would be the best way to see if the vacuum sides of the pumps even works? The only thing maintenance can tell me is that they run,, nobody ever questioned whether or not if they are working. The system has issues. There is some obvious knuckleheading done to the system. 

DanHolohan

Got pics?

Double D

I'll have pics after my next visit. Would you like to see more than just the vacuum side of the system?

EBEBRATT-Ed

@Double D

First thing to do is run the system and do steam trap survey and testing. Maintenance people can do this ....with the right tools and training

But you might be better off with a contractor or some companies that sell traps and parts, Armstrong, Barnes & Jones, Sarco, Tunstall etc do trap survey's


The reason I bring up traps first is they are most often neglected

And they will ruin the operation of a vacuum system fast

DanHolohan

Pics around the boiler is also helpful. Thanks. 

Double D

@EBEBRATT-Ed

Although I have not seen the system run, I have no doubt the buildings traps have been neglected. In the short time I was there I had noticed a condensate return pump ln a pit recently replaced was missing a check valve on the vent piping. When I mentioned the missing check valve, maintenance said he doesn't think there was ever one there. Then said I don't think they are on any of the vacuum pumps. When he took me around to the vacuum pumps, all of them had check valves on the vent side. They called the contractor back after the maintenance man installed the check valve. He said he didn't think It needed one because it only pumps condensate and it's not tied in with the vacuum pump. The maintenance man pointed out the path of piping and showed him where it Is tied in. Exactly the same as the picture in chapter 12 in Dan's book Lost Art. 

One of the heatexchanges for the theater has a Hoffman #79 used as a vent. Maintenance said it leaks. I said it shouldn't be there, it's acting as a vacuum breaker on a vacuum system. On another main in the same area, it looks like a crossover trap was remove and replaced with pipe plugs. They said there was some incredible hammering in that area before that work was done. My guess possibly failed crossover and the solution was to remove it.

The maintenance man who is there now was told to let the boiler pressure build 2-4lbs then go and turn the vacuum pumps on. I'm assuming this was their solution to get around operating the system with failed traps. 

When they asked me what should be done first, I told them their starting point would be to get the steam out of the dry returns. Verifying whether or not the vacuum pumps are working helps me with telling them where they stand with the system. I definitely wouldn't want to have steam destroy a newly repaired pump. 

Steam trap survey and test is on top of the list. I'll be fine doing a radiator/trap survey. The heatexchangers may be a challenge. In my area, if you were to ask a contractor to do a trap survey they would say "let me go to the truck and get a pencil" then drive away. 

Jamie Hall

I might point out that if you can provide adequate venting on the dry returns, the system will operate without the vacuum pumps. Not as well, but it will operate.

Replace that one failed crossover trap and look around for where they might have been others. The are essentiual.

It won't operate with failed traps...

Also when you get it operating, get the pressure down. Possibly way down. Look for water seals or locations where the steam main drips to a wet return. That can cause major problems...

DanHolohan

I’m wondering why the vacuum pump is there in the first place. It probably wasn’t there to start. Older vacuum systems didn’t have vacuum pumps. 

Double D

@DanHolohan The building was completed in 1939. I couldn't get anyone to give me an answer as to whether the fire tube boilers were ever coal fired. I mentioned the one vacuum pump but there are others in the system as well. They only have the one condensate return pump located in a small pit. For the time being it's the only picture I have.
Here is a link to the building.
 https://m.facebook.com/KleinhansMusicHall/ 

dopey27177

Vacuum pump;

To see if the vacuum pump works you need to do a dead end test.
Dead end test is done by closing the inlet valve into the accumulator and running the pump. First run one pump and see how high the vacuum will g, then run the other pump, after that run both pumps, hopefully you will reach the hg in the 20s. Shut the pumps off to see if the unit will hold vacuum.

That does not mean you will be able to reach a vacuum any where near the 20s. The old systems had pumps that ran from 2 -6 Hg, they were only used to remove the air from the system quickly.

If the pump makes vacuum the pump works. Next step is to pressurize the pump set. Fill the whole thing with water and check for water leaks where-ever gaskets are.


If this a vacuum system the vent from the condensate pump needs to be tied into the dry return.

Jake

Double D

@dopey27177 Thanks for the input. My guess is the vacuum pumps don't work or if they do they don't work well. I see there are issues with the system that are causing the vacuum to be broken. Addressing the vacuum pump issues were not on the top of the list. I just wanted to see if they even work. The inlet sides have isolation valves but they also have Hoffman vacuum breakers set to open at 10hg.

The pumps have vacuum switches that are supposed to turn it on at 2 and shut it off at 8 but my guess it they don't work. It appears the turn them on and off manually. When the say they hear them go on and off after they turn the switches on,  My guess is they are hearing the condensate pump turning on and of by the float switches. Soon they will be turning the boiler on. After they take down all the scaffolding from replacing some of the fire tubes, I'll get pictures of the boilers and system.

Pumpguy

If you can get a decent vacuum reading on the gauge using the shut off test described by @dopey27177, then the next concern is the air volume removal capacity of the vacuum pump(s) in terms of ACFM.

If your system has air leaks and your pump has a very low air volume removal capacity, you will never reach a desired return line vacuum because there is more air leaking in than the vacuum pump can remove.

There is a very simple way you can measure the air removal capacity of your vacuum pump(s).

Simply take one or more 1" iron pipe caps and drill orifices in them and attach to the vacuum pump receiver tank. Then valve off the tank so the only source of air entering receiver tank is through these orifices.

Next turn on the vacuum pump(s) and record the size and number of orifices and the resulting vacuum showing on the gauge.

I have a series of tables showing orifice size, vacuum produced, and resulting ACFM volume capacity. Get this information to me and I will tell you what your actual ACFM is and what might be done to improve things. The attached file goes into more detail.

Another aspect of vacuum pump performance is condensate temperature. The attached file shows how increased condensate temperature decreases the maximum vacuum that can be achieved. Vacuum pumps don't do well with high temperature condensate.

The picture shown in the earlier post above is a condensate pump only. There is no vacuum producing function on this pump.

Double D

@pumpguy_2

Thank you for your procedure and input. The pump in the picture is a condensate pump only. When I return to the job I will take pictures of the vacuum pump. Confirming if the pumps even work helps me with telling them where they stand. I realize the failed traps need to be addressed first. This system has a mix of convectors and cast iron radiators throughout the building. The Theaters have very large blower coils. There's a lot of ground to cover looking for leaks or anything else in the system that would break vacuum, failed traps, check valves, air vents added over the years ect. From what maintenance is telling me, condensate temperature is very high.

Pumpguy

High condensate temperature is due to failed steam traps, operating with too high steam pressure, or both.

Double D

No doubt the system has failed traps but the 4+lbs they operate this system at isn't helping. With this being a vacuum system, will the large heatexchangers still need a higher pressure? 

Pumpguy

It depends on what steam temperature the heat exchangers were sized for.

I don't see where you mention how the heat exchangers are used. Are they for air handlers or for a hot water heating loop?

If these heat exchangers were sized using EDR rules, then for each EDR of the heat exchanger's rating, it will give off 240 BTU/hr of heat when surrounded by 70* F. air and filled with 215* F. steam, which just happens to be the temperature of steam @ 1 PSI. So I guess the heat exchanger would put out 100% of its rated heat output when filled with steam @ 1 PSI.

Steam @ 4 PSI would have a temperature of 224* F.

Double D

@Pumpguy
They are very large air handlers. You walk inside of them. You need a ladder to change all the filters. They've been operating the system this way for years. When maintenance says 4+lbs operating pressure, my guess is it's probably more. 

Pumpguy

Can you provide more info and pictures of your vacuum pumps?

With more info, I should be able to provide performance data and troubleshooting advice.

Double D

@Pumpguy

  I should be returning to the job shortly. Waiting for them to get past the firetube replacements. I'll get as much info and pictures as I can. Any help would be greatly appreciated. The only picture I have is one I took of a rating plate during a very quick walk through.

Pumpguy

Based on what I can see, and the image is a bit blurry so can't make out the Model number, and the other numbers are a bit fuzzy, the ratings of 45 GPM and 9.7 CFM of air, the air pumping capacity of this unit is way undersized.

If you can get a good vacuum on the receiving tank when valved off from the rest of the system, but very poor vacuum on the system, the vacuum pump(s) don't have enough air removal capacity to cope with the system load which is often air leaking in from atmosphere.

Now, there may be reasons why the air capacity of this unit is so low, so I'm responding with an open mind, but based on usual vacuum return systems I deal with and see, the CFM capacity of the vacuum pumps should have nearly the same number as the GPM of the condensate pumps.

So, based on the above, I I would be looking for vacuum pumps with an air removal capacity in the neighborhood of 45 CFM.

retiredguy

I do not know where you are located but I would recommend that you try to contact a commercial/industrial boiler service company to help with repairs that are needed with your system. When I see a condensate return pump like the one that was just installed it tells me that your system has been worked on and serviced by people who have no idea what they are doing and that your system has been in need of repair for a long time. My guess is that the vacuum pump and the whole system has not worked properly for a long time and that the building owner tried to "go cheap" with needed repairs. I would also guess that the cost to heat that building is now extremely high due to trying not to spend the money necessary to do the work correctly. I saw this scenario happen for 40+ years that I spent in the commercial/industrial heating service field. That Hoffman 79 vent is for a water system and not a steam system. That should be a #76 vent.

Pumpguy

Vents are not used on vacuum return systems. The air removal function is handled with mechanical air removal by the vacuum pump(s).

Even when the vacuum pumps are turned off and the vacuum switches placed in FLOAT ONLY mode, air is vented through the pressure relief vent off the vacuum pump's receiver tank.

Where condensate pumps are used as mechanical lift or supplemental boost, the receiver tank's vent should be piped to a vacuum return line, and not simply out to atmosphere. The attached file shows the piping arrangement.

Double D

@retiredguy

 Thank you for your input. This is a city owned property and has been since 1939. I'm not thinking money is an issue here. The tenant is non-profit and has the ability to get funding for whatever is needed.
    All of our local commercial/industrial contractors have worked on this system over the years. A property management group was hired recently to put together a plan to upgrade the boiler plant, steam system and controls. Boilers would consist of 4 Cleaver Brooks CBT-40 boilers and replacement of the vacuum system. (No mention of vacuum only condensate return system pumps) They asked me to meet with them to see what I thought. After a very brief view of the system and a description of how it is operating, I told them they need to address the issues with the system or the entire project will just be a waist of money. 

 There are other issues with this system that I have not mentioned. One example, over the summer they hired one of the local commercial/industrial contractors to remove the pneumatic zones on over 40 radiators and replace them with electronic. When they showed me the work that was done, I researched the zones they used. They took out full port zones and installed hot water zones. When I told them they won't work due to a flow restriction they called the contractor who did the work. When he looked at the zones, he said they are the wrong ones for the system and they will replace all of them with the correct zone at no charge. 

Unless there's someone willing to fly in and work on this system, it's looking like I'm all they have for now.

I can totally relate to same scenario and I'm coming up on close to the same number of years.

Double D

@Pumpguy

Thank you again for your input.
My area used to have a Great rep for these systems. He is now retired. I have not had any dealings with his replacement so I'm not sure how much he knows or how much help he can be. 

  Your input is very helpful. If they replace these pumps, my guess is they will be replaced as Dan says in chapter 12 of Lost Art, the "Label Method" (also known as "Give'Em What They Got" Method)
 I'm not thinking there will be a problem getting a local contractor to do the replacement. I think they will need to be told what will work.

retiredguy

Depending on the size of this project and your location it would be a wise decision to hire a "heating engineer" schooled in older steam systems. He would lay out the whole project so that most of the guess work would be eliminated and the job would be done right. Look for an older engineer since most of the younger ones are most likely schooled in hot water systems. Where I live north of Pittsburgh, Pa. we had numerous old time engineers that were schooled in steam systems. Many of them are retired like me but there are still a few good ones left.

Double D

@retiredguy

  My guess is they would want me to find this engineer you're suggesting. If it is actually possible to find one, I'm sure they could be kept very busy. There are other buildings with the same scenario. 

 This project is in Buffalo NY. The building is Symphony Hall home of the Buffalo Philharmonic. Is there anyone in that region you could suggest? 

 

Pumpguy

Sounds like this is a lost cause when it comes to doing things to heat the building in the most efficient manner possible.

Best of luck, and feel free to contact me directly if you think I can be of assistance in the future.

Double D

@Pumpguy

I still need to get ahold of the new local rep. to see what he knows. Is there something more than a radiation survey needed for sizing? Radiators and convectors I could do in my sleep. The heatexchangers I might need some help if there are no rating plates.

retiredguy

@Double D; you could call the H F Lenz company at 814-269-9300 and ask if they service the Buffalo area. If they do not they could probably recommend a near-by engineering firm.

Double D

@retiredguy

Thanks for the info. I'll see where I can get with that number. If nothing else at least the other project won't happen. For the time being they're going to stay with what they have until this can get sorted out.

Pumpguy

For correct sizing of a vacuum condensate return pump, its best to know how much steam is being condensed from the radiation the new pump set will serve.

This would usually be expressed in #/hr. If we can determine the #/hr, divide that by 8.33 to get Gallons Per Hour, then divide by 60 to get GPM. This is that system's evaporation rate.

For the condensate pumping function, a factor of 2 X the evaporation rate is usual for sizing Duplex units with 2 condensate pumps. For a Simplex unit with one condensate pump, 3X the evaporation rate is often used.

When it comes to sizing vacuum pumps, everything depends on the condition of the system; how air tight it is, and the condensate temperature. There is no certain formula to determine what size vacuum pump to use. It takes sound judgement and experience.

The pounds per hour calculation described above can be converted to square feet of Equivalent Direct Radiation; EDR.

For vacuum pumps, especially those installed in older buildings, the rule is 1 CFM per thousand square feet EDR. Back in the days when the steam systems were new, a capacity of 1/3 of a CFM per thousand square feet EDR was adequate.

One thing is certain; within reason, it is difficult to install too large a vacuum pump.

For condensate pumps, the rule is 1 GPM per thousand square feet EDR. Or, you could just go by the nameplate of the old unit and hope it was sized correctly, and is still close for the current load.

Double D

 If I were to have any involvement in this building, I would want to know the total square feet of installed radiation. I do radiation surveys for almost every job I've ever worked on. System piping is buried in many areas in the building but the radiation is fairly accessible. 

Pumpguy

@Double D Totally agree. With those large air handlers, that may be difficult. From the way I'm reading this thread, the task of actually sizing the load will be totally ignored.

Double D

@Pumpguy

Nobody went through the building looking at the installed radiation.
Sizing for the load was totally ignored in the proposed replacement. They will remove the existing 100hp firetube boiler and install 4 40hp Cleaver Brooks modulation system. It always sounds great in a proposal. 

The large air handlers will definitely be a challenge. They are a major part of the systems load. I posted a link to the building. If you're able to find it you should be able to get a rough idea of the size.

Pumpguy

Vacuum condensate return pumps for 2 pipe steam heating systems are sized in 2 basic ways; the condensing capacity of the load, which we have been discussing, or the steaming capacity of the boiler(s).

Using 100 HP boiler @ 2X the steaming capacity = 13.8 GPM. At 3X the steaming rate, the required condensate pumps would be 22.1 GPM.

If we figured all four 40 HP boilers firing, @ 2 X the steaming rate would require 22.1 GPM. @ 3 X the steaming rate we would need 33.2 GPM.

So that puts us close to the capacity of the existing vacuum pump set in terms of handling condensate, but that still leaves us with sizing the air removal capacity of the vacuum pumps. And there, bigger is always better.

Double D

@Pumpguy

A good starting point would be to get the total installed radiation.

I'm in the process of trying to get ahold of the new rep in the area. I'll see where that goes after we discuss the job.

Information you've provided helps in case he turns out to be someone who is just looking to give them what they got.

Thank you for your input, it's very helpful.

Double D

Just a short visit today. Firetube repair isn't finished yet but I was able to get a few pictures. Very interesting day. You'll see

Double D

After looking at the first few pics you'll see why I was surprised to hear that blower coil heats. I'm curious to see for myself tomorrow when the boiler is up and running after a firetube repair.

Pumpguy

Umm...... You have a problem with that low return coming out of the heat heat exchanger. As piped, you have a water seal in the return line that would require an upstream pressure to push the condensate up into the receiving tank. To maintain a vacuum on this line, you would have to have continuous operation of the vacuum pump to keep that low return drained of condensate.

Also, keep in mind that VACUUM DOES NOT SUCK, PRESSURE PUSHES. To provide a source of atmospheric pressure to push the condensate through that up sloping return line, you would need a vacuum relief valve in that return line so when the vacuum in that line reaches 8" Hg. or thereabout, the valve will open and atmospheric air will enter and push the condensate uphill. .

To get this properly piped, best way is to locate the vacuum condensate return pump lower so you have a gravity drain from the outlet of the trap to the inlet of the condensate tank. Unless there is a near-by location that is lower, you would need to locate that pump set in a pit.

Double D

@Pumpguy

Now you can see why I said an interesting day. Some of the things I tell them are things that none of the contractors who have worked on the system have said. 

That condensate return pump is sitting on 2 4" steel I beams. If I remove the beams, set it on the basement floor and use a straight-through trap, I can get gravity flow to the receiver. The atmospheric vent on that tank is not connected to the vacuum pump.

Did you see the rating plate I took a picture of showing the main vacuum pump? 52CFM That pump pulls the system into a vacuum all the way to the smaller one I originally posted. The pump I originally posted does not handle very much of the radiation in the building.

You can see where the vent pipe on the pump in the pit used to run and connect to the inlet of the vacuum pump but for some reason the installer felt atmosphere was good enough. I'm not getting the idea that anyone who has ever worked on this system ever addressed it as a vacuum system.

Pumpguy

You can confirm the 52 CFM rating by checking the horsepower of the motor. A 52 CFM vacuum pump would require a 5 HP motor.

A pressure vent line with check valve would come off the lower condensate receiver, not the upper hurling chamber. It could even be connected to the basket strainer just upstream of this receiver. I am not seeing any provision for a pressure vent in any of the Domestic / Hoffman books I have.

Where you have a separate condensate pump out in the system of a vacuum return system, the condensate pump's atmospheric vent should be tied into a vacuum return line, not just to atmosphere.

That said, this is a common error I see. When just vented to atmosphere, that part of the returns would not see any vacuum.