Water freezing in hydrant/ valve pits in very cold climates

[abccba7531]

Hi,
We have dry type hydrants in valve pits covered with access manhole ductile iron cover. This is underground type hydrant. there is no heat tracing or winterization of the pits. The pits are concrete type.

The barrel of the hydrant is automatically drained after use. but there is an elbow piece below the hydrant (similar to a duck foot bent) which is filled with water normally and is made of carbon steel. this connects to a Hdpe pipe. The elbow and portion of Hdpe pipe are in the pit. the pit is below ground.

The ambient conditions are as low as -35 deg.c during winter.The piping is installed below frost line but in the pits the pipe and hydrant are exposed, but the pit is covered with manhole.

My question :

1) can water in the elbow piece freeze since water is stagnant from the ring main network? ( ie through convection and heat transfer through air)

2) similarly, we have isolation valve pits in which the valves are metallic. The pits are again covered with manhole. Can localized freezing of water in the valves occur? we have no electrical heat tracing in any of the pits.

3) is there a calculation method for these conditions of heat transfer?

Thanks.

 

[MiketheEngineer]

Yes
Yes

Not sure

 

[chicopee]

The water in the elbow piece will freeze by conduction of heat transfer thru the metallic barrel. I supposed, before the onset of winter,you can apply an antifreeze solution in the elbow piece and also stuff the pit with styrofoam blocks. You can estimate a temperature profile along the barrel by assuming an underground constant temperature on one end and an ambient temperature with a certain wind velocity on the other end of the hydrant with the pit insulated.

 

[dvd]

This is a topic that has been researched and published. You should not re-invent the wheel here. Do a literature search.

You could start at a site such as:

http://www.crrel.usace.army.mil/

Find any paper somewhat related to the topic and look at the references list for more ideas.