Document YjgoyyV82peDOEjyveNeekbxO

Hoffman Valoes Specialties, Heating Differential Loop The Differential Loop is the safety device for maintaining a steady water line in vapor and vapor vacuum systems. It is entirely automatic', non-adjustable and has no moving parts to stick at a critical moment. Through its use water is permitted to rise in the return main a certain predetermined amount when the loop functions, blowing over a small quantity of steam which closes the No. 10 or 11 Valve installed on tie loop for venting the system and then compresses the air which is " bottled up" in the return main and builds up a pressure which prevents further rise of water in the vertical part of the return beyond the predetermined amount. As soon as this is accomplished, and the action is almost in stantaneous, the loop reseals and no more steam is blown over until the differential pressure is not maintained. It will be readily seen that, by Hoffman Differ the alternate blowing over and resealing of the loop, a constant differential ential Loop pressure will be maintained between the steam main and return main and also that by the main tenance of this differential regardless of how high the boiler pressure goes circulation will take place in a radiator which is turned on with the return main vent closed through loop action. Differential Loops are made in four sizes, having a capacity up to 15,000 sq. ft. of radiation. For larger systems the No. 4 Loops can be installed in a battery or the return mains divided so as to have their load come within the capacity of stand ard loops. No. 1 and No. 2 Loops should not be used where the low point' in the dry return is less than 24 in. above boiler water line; with the No. 3 and No. 4 Loops this distance must be at least 30 in: Loop No. A DIMENSIONS AND CAPACITIES OP LOOPS BcpE F G j K Capacity L Sq.Ft. Rad. w , w1 WS 1'// VS I/.* 26' 30H' m 3" 2000 w2 vs i'/.' 1'/.' I/.* 26' w 7H' 3". 3500 w3 vs I'/:" 2" \* 25" 32' 37%* 10" 3'// 7500 4 vs V 2* r IT 25' 32' 37y.' 10" WS 15000 460 j : s Hoffman Valves Specialties, Heating 461