A burn rate control valve for gas fired heaters in the form of a 1/4 turn ball valve having two flow passages through the valve member in which one flow passage is for full gas flow and the other flow passage is smaller in diameter for low gas flow in order to provide a full burn rate or a low burn rate....http://www.google.fr/patents/US5653220?utm_source=gb-gplus-shareBrevet US5653220 - Burn rate control valve for gas fired heaters
