File:Doug Alkire 5300 5.jpg

Three safety valves bleed off steam when the pressure in the boiler taps 140 pounds.

http://books.google.com/books?id=TNQDAAAAMBAJ&pg=RA1-PA147&lpg=RA1-PA147&dq=Doug+Alkire+IBLS&source=bl&ots=YSDIHeFmhn&sig=NKenBwiFm9LV2GIwIxVNyHTJki0&hl=en&sa=X&ei=IFQMUe6JD4SvqgHfooCgBA&ved=0CDkQ6AEwAg#v=onepage&q&f=false