... (Wet-Back) 4.Safty Control System Product Features of WNS Oil/Gas-fired Steam Boiler1. This horizontal wet-back boiler features ... ’s operation;6. Multi-layer protection on pressures, temperature, water-level and burner itself keeps the boiler to run safely and ... . It is widely adapted to various fuels, including light oil, heavy oil, residual oil, natural gas, coal gas, and liquefied petroleum gas;8 ...