Heating Help

Expandtion rate of black pipe

 schd#80 ,in a 100psi steam system,room temp will be 45-50* and then the pipes get heated up to operating temp.The customer is talking about redundant low water cutoff, and boiler  operating controls [ 3 ].The  supply pipe comes out the top of the boiler, goes up 15', 90* ell towards the wall [ 15' ],then another 90* along the wall for 40' then a 90* out to the 14,000 gal production tank for 20' and one last 90* down to the top of the tank [3' ] . Should swing joints be used here?Thanks.

yes

they should

temperature expansion coefficient = .0000065

.0000065 inches per inch x degree Fahrenheit change.
So 100 feet of carbon steel pipe with a 130F degree change will expand 1 inch. 
.0000065 x 1200 inches x 130 degrees = 1.014 inches. 
sidenote:
PVC's temperature expansion coefficient is .000028 which means it expands 4.3" under the same conditions. 

thought that was interesting

Temp

What is the temp of the steam @ 100psi?

Boiling point @ 100 PSI

Boiling point of water @100 PSI is 328 degrees F.

Here's The Expansion

Watch what values you're pulling off the steam tables. The real world works in pounds per square inch GAUGE. Many, many steam tables list values in pounds per square inch ABSOLUTE.

I use Spirax Sarco's book "Hook-Ups" a lot for steam systems like this one.

Temp rise X 0.00804 = inches per 100 feet.

Temp rise on steam line: 338-45 = 293

293 X 0.00804 = 2.36 inches per 100 feet.

Your longest run is 40 feet, so:

2.36 X 0.4 = 0.94 inches.

You've got several 90* elbows in your system, with some relatively long runs of pipe, so there's lots of flex. I'd just cut that 40 foot run 1/2 an inch short, and cold spring it when doing-up the last union or flange.

Make the riser off the boiler high enough that you can slope the horizontal line to the tank about 1/2" in 10 feet, and locate a drip tee & trap on the bottom of the drop to the tank, ahead of the control valve.