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Pipe shaking

MarkYS Member Posts: 2
Hi all,

I have a one pipe steam system. The boiler was installed in 1996, and I bought the house in 1999. Since then, the system has been working fine till recently: a shaking problem was noticed.

The piping from the boiler to the main consists of 3 parts. The lower part goes up vertically from the boiler and is about 3 feet long. The second part is a 135 degree upward turn. The third part goes up in the direction of the 135 degree turn and is about 1 foot long to reach the beginning of the main. Then it connects to the horizontal main through a 90 degree turn. Recently, when the boiler fired up from a cold start, shaking was seen in the beginning of the main. It began approximately at the time the 135 degree turn of the riser became hot and stopped when the beginning of the main became hot. Also found was that the hanger at the beginning of the main was loose, and the nail holding the hanger was movable in a crack half inch from the bottom of the joist.

A tech came and said that it is normal to have a little shaking because of expansion and contraction, but not this much. He replaced the hanger, and made it a bit tight to reduce the shaking, but not firmly stabilized, he explained, because it has to move a little bit. Now the shaking is smaller. He pointed out there is no header and the 4 feet boiler-to-main riser with its 135 degree turn is also wrong. He concluded that the wrong piping is the cause of larger than normal shaking, and without making it right, the hanger will fail again, or cracks may occur in this region of piping, because of the strong shaking force. So, he suggested changing the piping.

To get a second opinion, I asked another tech to look at the problem. He said the following: Steam goes fastest in the beginning of the piping from the boiler. When it goes through the 135 degree turn of the riser and then through the 90 degree turn to the main, it changes direction and its speed slows down, causing vibration. The hanger, providing a restraint, reduces the vibration here and its progression downstream through the main. The piping has no header, but the long riser allows water to go down back into the boiler. The 135 degree turn is important because it absorbs movement associated with expansion and contraction to protect the boiler. In short, this piping is acceptable and the small vibration is bearable to the piping.

They had different opinions. What should I do?

Any help would be greatly appreciated.



  • Unknown
    edited March 2010
    Steam goes fastest in the beginning of the piping from the boiler.

    Steam goes to the "fastest" point air is vented from,, (you could have 3-3" pipes), but if the air is NOT vented from them(rads), smaller pipe sizes(if vented) will get there first.

    I would advise having a GOOD steam-man look!   ;-)

  • clean boiler

    Steam piping should never visibly shake.  Its operates at so a low pressure, no matter how fast its moving it will not violently shake a pipe.  Hire a plumber, one that knows about steam heat.  Ask them to skim the boiler and clean the gauge glass.  When the boiler is flooded the piping around the boiler will shake.  If the boiler was flooded you need to asses the reason why.  Either the feed valve is passing water, or the boiler is so filthy its throwing water up into the mains.   Dont let anyone tell you its normal for steam piping to shake, thats not an acceptable answer.  Usually when a system is dirty or the mains are flooded you will get alot of banging noises.
  • MarkYS
    MarkYS Member Posts: 2

    Hi Dave and Mike,

    Thank you very much.

    Dave: Does 3-3” mean 3 inches pipes? The riser and main are 2 inches in my steam system. From what Mike wrote, my understanding, if correct, is that a 3 inches riser is better (please see below). Looking at the riser-boiler junction, it seems to me that only a 2 inches pipe can be screwed into this boiler. I will try to find a good steam man.

    Mike: Now I got the concept--“Steam piping should never visibly shake”—from you. Also, you made the following important points: 1. “Skim”. Last year, the service person told me that he flushed the boiler, and the water in the glass tube looked less brownish and muddy than previous years. I don’t remember if he used the term “skim”. Just now, I searched this site for “skim” and got the concept about it. It is different from a simple flushing. So, good looking water without good skimming doesn’t indicate a good quality. No skimming has ever been done since we bought the house in 1999. I don’t know if a good skimming was done during 96-99 (the boiler was installed in 96). 2. “the boiler is so filthy it is throwing water up into the mains”. So, bad water not only can enter this riser, but also can leave this 4 feet high barrier behind. 3. “when the boiler is flooded, the piping around the boiler will shake.” During the first service in 99, the tech told us some “Don’t ”, including “don’t let the water go above the water line”. Since then, we have been careful and water has never been above the line. However, this doesn’t mean that boiling water of bad quality cannot flood the riser. Looking at the riser in the basement, it looks like a thin, tall extension of the boiler. It is so thin that it can be easily flooded by bad water when boiling. And the pipes around this upper chamber of the boiler now start to shake. So, Mike, most likely, you found the source of the problem and gave a prescription targeting right at the source. 4. “Usually, when a system is dirty…you will get a lot of banging noises.” No banging noises have ever been heard in the pipes since we moved into this house. This is probably because the bad water has been unable to overcome the height of the riser yet, but shakes the pipes around. However, a good skimming needs to be done to prevent the water from getting worse and getting into the system some day. With these points in mind, I will know how to look for a good steam heat man to get the job done correctly.

    I will let you know about the result.

    Thank you very much again.

This discussion has been closed.