Dave in QCA
Joined on May 6, 2010
Last Post on April 19, 2014
@ April 19, 2014 11:42 PM in Steam Radiators???Here is a handy table. Look on table 5, it will give you what you're looking for.
@ April 16, 2014 11:57 AM in lowering steam pressure in a industrial buildingThis is not a simple situation but it sounds like there would certainly be an opportunity for huge savings and your engineer is wise to want to proceed with a plan to reduce the building pressure.
You used to require high pressure steam not only because the load was higher, but because much of the power or process equipment required that pressure to operate. You no longer have that requirement. You only have the heating load which has been described to be 12 psi. While most system can operate on pressure as low as 2 psi, others are designed at 5 psi or 10 psi. Control valve sizing, steam/air coil sizing, etc., may have all been calculated at the 10-12 psi range, so keeping that pressure may be necessary if that is the case. Also, may buildings with higher pressure systems (5 psi) have condensate lines that rise above the steam device, and therefore need enough pressure to accomplish that lift.
The critical factors for this project would be to calculate the full steam load of the building heat load and line losses in the building. Then, it should be a simple calculation to determine the capacity of the steam main, operating at 12 psi. Can it deliver the needed quantity of steam. There will likely be a little line loss under full load conditions, but I would guess that 1-2 psi loss between the boiler and the building being heated would not present a problem. 10 Psi will probably work just fine.
As for your feed pumps, you indeed bring up an important issue. Those pumps are designed to push feed water from a tank at atmospheric pressure into a boiler at 90 psi. If the pressure is dropped to 12 psi, they will operate much differently. They will pump water much faster. While the operation will probably be no longer on the performance curve, it will be above the curve not below. Cavitation tends to be a greater problem either at high temperatures or at very high heads where the pump is barely able to move the water. You will have the opposite condition. However, if the pumps in use are still being manufactured, it might be worth getting a manufacturer's rep to run the proposed operation of the pumps by the engineers in their home office and see whether a problem would be anticipated.
Good luck as this moves forward.
@ April 16, 2014 11:24 AM in Am I venting my mains too fast?With the combination of Main and Radiator vents that you have on your system, One would expect the steam to reach the end of the short main quickly, at which time it will close. Steam will continue flowing down the long main and will actually speed up when the short main is heated. Before the steam gets to the end of the long main, flow into the radiators should be minimal. After the steam has reached the end of the long main, those vents will close, causing a slight increase in pressure, at which time flow into the radiators should be begin. For the most part, the flow into the radiators would be expected to be fairly even. THIS is what would be expected, bit obviously, its NOT what you're experiencing.
You indicate that you hear swishing in the long main. That is an indication of a huge problem. Water in the main will prevent steam from passing and when it does whoosh through, much of the steam will be condensed by the water. It would be similar to having a gate valve in the pipe and having is mostly closed. The system just cannot work correctly with water in that main.
You indicate that the boiler is over-sized, yet you do not mention that it short cycles. Does it? I am also unclear in your description of 5 minutes for the short main and 30 minutes for the long one. Is that the amount of time it takes for the steam to get to the end of the main, or the time it takes for the radiators to be fully hot?
You probably should also check the firing rate of the boiler. Many times, for various reasons, they do not fire at the rate on the rating plate. Make sure everything else that burns gas in your house is NOT running, operate the boiler, and count the usage in a minute by watching the needle on the meter that turns the fastest. The dial will tell you how many cubic feet of gas pass per revolution.
Also, I'm wondering how often your boiler cycles. Once per hour? More often? Less often? When the boiler starts a new cycle, how hot is that long main? Do you have a way to measure its temperature? Or, perhaps the air coming out of the main?
Reason being, while Gorton #2 main vents are incredibly fast when they're cold, the begin to close in the 130-140 range. If the air coming through them is 150 or above, you can be sure that they are completely closed. In my system, cycling once per hour, the mains with 1" insulation on them, even on cold rooms, never cool down to below 150 degrees F. So, in one of the trial setups in my system, I found the Gortons just didn't do the job the were supposed to, except on a cold start.
@ April 16, 2014 10:16 AM in Is my steam boiler way oversized?I operated a pair of large dual fuel boilers 25 years ago. At that time, the dual fuel option was not set up properly and I set out to make corrections and set it up so that the firing fuel could be changed with the flick of a switch, the way it was supposed to be. At that same time, we changed from firm service gas to interrupt-able, which saved 25,000 a year. These boilers were 238 HP Kewanee Scotch marine type, firing at around 9 Million BTU on high fire.
Set up and adjustment was a pretty complicated process as the the burners were fully modulating, not a simple hi-low operation. The first step required getting the oil firing correctly adjusted at hi fire, then at the low end of the modulating range. Second step was to adjust the air shutter linkage to provide the correct mixture of air through the full range of oil firing. The third step was to switch to gas and then adjust the gas firing rate to match the air shutter so that proper mixture was obtained all through the firing range.
While it does not sound too complicated, the process required a considerable amount of time. But, once it was done, fuel switching merely required a few steps to the boiler, turning the boiler off, turning the selector switch to the desired fuel, and turning the operating switch back to "on".
In your case, a dual fuel burner might be unnecessarily complicated and expensive. You could just save the old burner and of fuel oil prices ever get lower than natural gas, (not likely), you could simply install the old burner and you probably could change the nozzle and make it fire at the lower rate you need.
As for the option of 1 stage or 2 stage, I would opt for 2-stage, but there will definitely be a price difference. 2-stage firing would provide a benefit if your load varies from time to time because of some of the radiators being turned off and at other times, all of them being turned on. Also, if you frequently fire the system long enough to fully heat the radiators, this will cause the boiler to cycle off and on. This can be minimized in single stage firing by having a low pickup factor. But, if you do this, you will need to make sure that your main venting is good and fast and your radiator venting is slow, for example, no faster than a Hoffman #40. This arrangement will make your system slow to heat up, but it should be even and in most cases, on off cycling when fully heated will be minimized and may not occur at all.
Gas pipe size: You probably need 1 1/4" if running house pressure from the meter. 1" is too small.
When we bought our building, the boiler was a 1,050,000 BTU firing rate. We are on low pressure and there is a 2" main coming in from the street. The meter is a 2" meter, but the piping reduces to 1 1/2 to the boiler which is about 40 ft away. This piping was actually a little under sized. In addition to the 2" meter, there are 9 more meters connected to the incoming main, most are for kitchen stoves by 2 of them have forced air furnaces on them. It all works just fine and the pressures are adequate to deliver the required amount of gas.
@ April 16, 2014 9:39 AM in Dunahm Air Eliminator replacement availableI found a substitute for the Dunham Air Eliminator and wanted to post the information for all to see. Of course, it would also work for any system that used a float type air eliminator on the return piping of a 2-pipe vapor system, such as ARCO, etc.
The device is made by Spirax-Sarco, and is intended for use in hydronic systems to let air out of places where it might be trapped, but then closes via the float valve when water is present.
I do not know the diameter for the valve port passage and if it is too small, it might not provide for enough venting. However, if operated in vacuum by adding a swing check valve, venting becomes less of a concern.
@ April 16, 2014 8:46 AM in Replacement Dunham trapsNicholas, you have touched on a subject that mystified me for quiet some time. Does a thermostatic trap operate properly on vacuum and if so, how the heck does it do it?
First, your observations that the early Dunham systems did not use the 1E trap for crossover. That is correct, they used the the Dunham Air Line Valve. That device was actually a small version of a 1E type trap and the same thing as a paul type trap. In addition of it being used as a crossover trap at the end of steam mains, it was used on vacuum one-pipe systems as a retrofit, just like Paul systems. I supposed it worked fine because often in coal fired systems, steam was slow to build. Whatever the case, my guess is that Dunham discovered that they had a real big problem with unbalanced distribution, especially on partial steaming cycles. Thus, they started using "balancing plates" or orifices to even out and regulate the steam at the entry point of the radiators. They still used traps so the orifice openings must have been larger than they would be on an truly orificed system. About the same time, according to my reference books, they stopped using the air line valve as a crossover trap and instead started using the 1E. Of course, a 2E would be even faster.
VACUUM ? If you look at the cap on a 1E trap, you will see that it is rated from 25" vacuum to 10 psi steam, actually some early Dunham 1E traps are marked to 25 psi steam. How does it work? That steam at 25" vacuum is not very hot at all!
It took a long time for me to wrap my head around it, but eventually found an explanation somewhere in one of the Dunham books, or at least I think that is where I found it. Here it is. You have to realize that the thermal disc in the dunham trap is flexible, somewhat like a balloon. When the temp of the disc is hot enough, around 180 or 190 at atmospheric pressure, the alcohol will vaporize, causing an increase in pressure inside the disc, therefor expanding the disc and closing the trap. Now, if the the system pressure is 10" Hg vacuum, the flexible capsule will expanded because of the low ambient pressure, transferring the forces of the vacuum to the contents of the disc as well, and lowering the flash point of the alcohol inside the disc. Thus, the closing temperature of the trap adjusts according to the surrounding pressure/vacuum so that the closing temperature is lower than the actual temperature of the steam at that same temperature.
Nicholas, I forget about the detail of the Dunham system you're working on. Does it have an air eliminator? a return trap? any other original boiler room apparatus, such as a differential controller, etc?
@ April 11, 2014 5:11 PM in Radiator air vent preference?Here is a diagram of the Hoffman #40
Here is a view of the insides of the Gorton
Note: They both have a float. The Hoffman closes suddenly when steam is present in the vent. The Gorton closes more slowly but at much cooler temperatures, generally as stem is getting close the vent, the last air coming out of the radiator is probably warm enough to close the vent.
@ April 11, 2014 1:32 PM in Radiator air vent preference?I prefer the Hoffman #40 because they are nice and slow and because of that, tend to help a system heat up smoothly with balanced steam distribution.
The varivalves are just way too fast and don't have any provision for dealing with condensation in the valve body. As Chris said, the Hoffman 1A adjustment mechanism is so poorly designed it is difficult to get any kind of adjustment set correctly, and on many system, they perform the best if their set as close as possible to the rating of a #40.
I have observed that most systems, if piped properly in the first place, the radiators will heat up proportionately with #40 vents. That is, both small and large radiators will heat the same percentage on a partial steam cycle, even though they are using the same sized vent.
@ April 11, 2014 1:23 PM in Is my steam boiler way oversized?Just wanted to let you know that I have an oversized boiler similar to yours, except mine is a Weil-McLain 680. I really only needed a 580, which will allow for future restoration of parts of the steam system that are not currently connected. Because I wanted a 2 stage burner, and WM had only approved a 2-stage burner on a 680 and larger, that is what I ended up with. At the present time, it is firing on Low Fire, a little less that 50% of its full rating. It works great! 82-83% efficiency and 34% less than my old gas boiler.
As a general rule of thumb, most power burner boilers can fire at 50% with little loss in efficiency and sometimes, actually more efficient that firing at 100% of capacity.
As second benefit, it doesn't work the boiler near as hard and you'll probably find that it will have a longer life as a result.
If it were my boiler, I'd convert to gas and tune the thing at 50% of it's full rating ASAP. I would not bother taking sections out, it's too much bother and cost (new jacket panels) and not really necessary.
@ March 25, 2014 5:56 PM in Vaporstat sticking / biasing after vacuumI have two vaporstats on my system. One is an old style and the other is a new type. The vaporstats are subjected to pressure occasionally as high as 14 oz and vacuum as high as 9" Hg. It has not had any effect on either device.
@ February 28, 2014 9:36 PM in Pickup factor. Help me understandThis is a somewhat difficult subject to understand and its an even more difficult subject to explain. I have to bow to Jamie for his analogy to the accelerating car, it is excellent!!! I had never thought of it in that way before, but it's spot on!
I'm going to jump in and give my 2 cents too and see if I can help to make it easier to understand too.
The "pickup" factor is actually two separate factors that have separate purposes. First, the piping loss factor takes into consideration that piping will give off heat and in doing so will condense steam, even after it is fully heated up. So, in order for a boiler to be able to maintain a fully heated system of radiators and piping at full temperature and and maximum output, the heat losses or emission of the radiators and the heat losses of the piping must be matched by the output of the boiler. The amount of heat loss from an average piping system that is insulated is estimated at 10% of the capacity of the radiators. So, if the radiators on a system add up to 200 Sq Ft, the piping losses can be estimated to be equal to an additional 20 Sq Ft of radiation.
But, the piping loss factor only takes into consideration the piping losses of a fully heated system. Steam systems by their nature are difficult to heat up in an even manner. By comparison, a hot water system uses a 15% piping loss and pickup factor, or only 5% pickup. The result is that old gravity hot water systems with huge cast iron radiators are very slow to heat up, but they do eventually heat up. In the heating process, all of the radiator will heat up gradually and all at the same time. Starting from stone cold, to luke-warm to warmer, and eventually hot, if the boiler has been firing continuously. The key point is that the radiators throughout a well designed system will heat uniformly.
This is not the case with a typical steam system. On a steam system, an additional pickup factor of 24% on insulated piping is needed. On a typical steam system what would happen with a boiler sized too small to give adequate pick-up, some radiators will heat first, and others later, sometimes not getting any steam at all until other radiators are blazing hot. The negative effects of unbalanced steam distribution are especially undesirable in mild weather when steaming cycles are short and only partially heat the radiators. Undersized boilers in these situation will often leave some of the radiators with no steam at all.
Fast vents on steam mains will improve the likelihood that steam will arrive at the radiators at the same time. Slow, make that VERY slow radiator vents will further improve even distribution. Actually, I have seen some cases where marginally sized boiler worked just fine, but the size of the mains were small, reducing the amount of heat loss and the vents were all Hoffman #40s, which are pretty slow.
The negative aspect of using the 34% piping and pickup factor for insulated mains or the 50% piping and pickup factor for uninsulated mains, is that on long cycles, when the system becomes fully heated, the boiler will start cycling off and on because of pressure. It is just a part of the beast. Of course, as has been mentioned, two stage firing is a great benefit in this situation.
It should be noted that in two pipe systems, when inlet orifices are installed on the radiator, since they separate the radiator from the boiler and main pressure, the pickup factor can be omitted. Only the piping loss needs to be factored. Also, according to writing by Dave Bunnell, aka, the Steam Whisperer, if very slow vents are used on one pipe systems, the pickup factor can sometimes be omitted as well.
Hope this is helpful. on some level.
@ February 6, 2014 9:54 AM in An Epic Tale: I hear the Trane a comin'!Colleen, Now you're really having fun! And, staying warm too! I don't know how you have tolerated not having heat for so long!
Regarding your main vent. That little vent on top of your return trap is not the ONLY vent is it? I was thinking that you had a mercury pot on your system. If so, the venting is running through that pot.
@ February 4, 2014 10:27 PM in MegaSteam short cycling on pressuretrolWhen the boiler runs an extended time and the radiators become fully heated and the pressure builds up, the pressuretrol shuts the boiler off until the pressure drops, which will occur quite quickly, as you have reported. This is completely normal. In most normal cycles, except when it is extremely cold, this will not occur.
@ February 2, 2014 1:51 PM in remove insulation on one pipeAs I recall, this saga has been going on a LONG time. Too bad for such an attractive building in a great Chicago neighborhood, that it is proving so difficult to get something that should be simple accomplished.
Running my building in Davenport with a set point of 71. Yesterday I checked and the south 1st floor was 71, the north first floor was 72. The third floor was 72. Of course it was a cloudy and there was no solar gain on the south side. But I have to tell you that we get zero complaints about temperature. The system works great. And, since it was balanced, and a new boiler installed, which happens to be a smaller version of yours, it being a Weil-McLain 680, our bills have dropped by 33%.
How much money has been wasted by over heating parts of your building? How is the undesirable heat affecting property values?
@ February 2, 2014 9:14 AM in remove insulation on one pipeTaking the insulation off of the steam main is somewhat equivalent to installing a small radiator in the space. The steam main will condense more steam with it bare than with it insulated, but normally that will not cause a problem. Many systems operate with uninsulated mains because heat is needed in the space where the mains are located.
It would cost less to leave the basement space unheated, but if for whatever reason that is not acceptable, the operating cost difference is that you're now providing a little heat to that basement space.
@ February 1, 2014 3:39 PM in Gorton Main Vent SurveyGerry, I was really hoping that you would jump in on this topic.
What brought it to my attention as watching my system a few years ago, before the boiler install and going back to crossover traps. I had timed how long it took for steam to get to the Tekmar condensate or end of main sensor. Then, at a later time, on a warm start, I was timing it again. I thought the steam would never arrive! I felt the G2, and it was warm, but not hot. And, it was closed. I quickly removed it from the antler and air came rushing out! In a short time, the steam had arrived. I thought I had a faulty G2, but then after research and finding your data, learned that it was never going to be open at the temperature of my mains and the air in the mains. This has been bothering me ever since.
As Dan says, there's a lot of real smart people on here. It will be interesting to see ya'all figure out.
@ February 1, 2014 3:18 PM in An Epic Tale: I hear the Trane a comin'!I'm so glad to hear that your project is coming to completion, and it sounds like you have lucked out in finding someone who loves steam to help you finish up! I'll be waiting for more news.
@ February 1, 2014 2:31 PM in Gorton Main Vent SurveyJamie, yes, you'res is working like a charm I'm sure. In frustration resorted to going back to Dunham/mepco 1E traps as crossover traps. One vent point on the return, an open pipe with a swing check on it. It also is working like a charm! In this spell of real cold weather, the system was dropping to 8" vacuum between cycles. No worry about getting the air out when it can't get back in.
@ February 1, 2014 1:18 PM in Setting Vaporstatit is standard on the lgb-6 and above. But, their would be the ability to order other control options, so its impossible to say "ALL". check your wiring diagram. Check the second gas valve. If it has 3 wires coming out of it instead of 2, like the first gas valve, you know you got the two stage valve.
@ February 1, 2014 12:33 PM in Setting VaporstatI've never come across one set up as 2 stage. Most don't know it is even on there.
@ February 1, 2014 12:30 PM in Gorton Main Vent SurveyThe temperature range of the Hoffman 75 is essentially the same as a thermostatic trap, being driven by a capsule filled with an alcohol mixture. The range is 180-190F. Like the thermostatic steam trap, it pretty much stays open until steam is present.