Double Pitch Drive Chain,Standard Curved Plate Transmission Conveyor Chain,Conveying Double Pitch Transmission Chain,Steel Plant Double Pitch Transmission Chain Changzhou Donghu Chain Transmission Technology Co., Ltd. , https://www.dhuweldingchain.comPlumbing installation commonly used in a valve for deflation, the heating system in the process of water will have gas into the heating pipe, when the gas is congested, it will cause the heating is not hot. So to set the valve for the exhaust gas , So that the water circulation smooth