WARD: INCREASING THE CAPACITY OF STEAM HEATING PLANT. asa 
These pipes connect low enough to run through a tunnel nearly 
1000 feet long to and from the library. The steam pipe starts into 
the top of the tunnel and gradually descends to the middle at the 
far end where the return pipe starts and descends to the bottom at 
the end of the tunnel as shown. 
After a trial of two winters, it was found necessary to maintain 
a greater pressure in these pipes than in the mains leading to and 
returning from the buildings which are nearer and on a higher 
level, the natural draft being upward. 
Propositions were made by reliable firms, which would have 
reached the required end, but they were expensive both in first 
cost and in operation. 
The writer’s plan which was put into operation 1s: 
First—a regulating valve, Fig. 2, placed in the ro-inch main at 
A (see Fig. 1) to form a back pressure at that point to any desired 
amount (say 5 pounds) which can be regulated by the weight W. 
Big. 2. 
Thus the back pressure will fill the long pipes leading to the 
library with steam at a pressure of 5 pounds or any desired amount 
to overcome the difference between its heating capacity and that of 
the remaining buildings. Then as the pressure rises it is permitted 
to pass through the regulating valve so that when the back pressure 
is 10 pounds, the pressure beyond the valve is 5 pounds. If this 
should heat the library too much the weight can be placed back a 
notch and the back pressure reduced by allowing the _ boiler 
pressure to reduce, and the temperature of the other buildings will 
not be changed. These valves are used successfully in many 
places similar to this. In our case, however, the return main will 
have an equal pressure effected by the necessary connection to the 
