Pigtail-Related Question

SusanC

Today boiler had just stopped night maintenance run a few mins. before setback recovery run started. Heard pop again followed by vaporstat chatter. Pipe from pigtail to vaporstat is very hot; I would say steam is getting to vaporstat.

SusanC

Possible problem in pigtail area?

While monitoring a steam boiler, installed in the Spring of 2007, I have noticed that occasionally there is a pop, pop/splat or sort of mini-explosion sound which I have determined occurs in the general area of the pigtail. Please note that the boiler has been cleaned and skimmed 2-3 times and is pretty clean. The pigtail is what I would describe as the horizontal design, meaning that it comes out of the side of the boiler horizontally, loops down and then extends up, so the direction change is 90 degrees, not the 180 degrees characteristic of pigtails that extend from the top of a boiler. There is a connector at the top of the vertical portion of the pigtail from which a vertical pipe goes up to the vaporstat, while a horizontal pipe goes out to a connector that has the low pressure (15 psi.) gauge mounted on top and the mandatory 30 psi. gauge on the end.

I am wondering if perhaps, under certain conditions, there is not enough water/condensation in the loop of the pigtail to prevent steam from sort of bursting through or maybe the opposite is happening and steam hits the water seal especially hard for some reason. After the pop the vaporstat chatters for a while and also the low pressure gauge may vibrate a little. The pop sound happens just as (possibly immediately before) the pressure starts to rise on the low pressure gauge.

I have been checking the pipe that leads from the pigtail up to the vaporstat and the pipe going out first to the low pressure gauge and then on to the 30 psi. gauge by hand to determine if, or how hot they feel. While the pigtail is hot the pipes connected to it normally are coolish to warmish, as I would think they should be; sometimes they get hot but not steam hot. I noticed after tonight’s pop, the pipes from the pigtail were pretty hot – probably were before the pop also, but am not sure I checked.

The first time I noticed this phenomenon for sure (might have occurred before), was after a several hour period when the boiler had not fired because it had been cleaned (professionally) (including blowing through the piptail) and then run awhile to check radiator vents, so the thermostat did not call for heat. Similarly it also has occurred during recovery after a small setback of 2 degrees. Because of this timing, I had thought maybe water dissipates from the loop when the boiler hasn’t run for awhile. Tonight the sound (an especially loud pop) happened in a different situation, occurring when the boiler had been on frequently, e.g. for 20 mins. or more every hour (1 cph thermostat) because of the extremely cold temperatures.

So far as I know, this has not been a frequent happening, but normally I pretty much monitor the boiler only in the AM during recovery from a 2 degree setback, so it might happen more frequently than I thought. In addition to generally disliking any explosive sound around the boiler or vibrations of boiler-related controls, I am specifically worried that this is likely to damage the vaporstat and also possibly the low pressure gauge. I would appreciate any information as to what might be causing this and suggestions regarding a remedy. Sorry about the length of this post; I was trying for an accurate non-photographic description.

nicholas bonham-carter

pigtail problem

i also have such an arrangement of gauge and vaporstat piping on my new peerless and i wonder if that mass of water in these pipes throws off the vaporstat reading but i have not heard any noise from it.nbc

SpeyFitter

Pigtail noise

I would try removing the pigtail and cleaning any and all crud out of it, with a piece of flexible wire or something similar. You may have a partial blockage, which is causing the noise, combined with thermal expansions in the pipe. While you're at it make sure that the pipes going to the vaporstat and gauge are completely clean also, and if you can, try to wash any crud out of the vaporstat and the gauge themselves. After you reattach the pigtail to the boiler make sure you fill it with water before assembling the rest of the stuff to it.

Blowing through the pigtail is not what I would call a professional cleaning. Also, the upper part of the pigtail and everything attached to it should always be much cooler to the touch due to the water in the pigtail.

Let us know what happens.