Water Bath Heaters are commonly found on Northern Gas Networks’s existing sites. They currently provide heating to approximately 50% of the sites where preheating is required. They are usually between 30 and 40 years old. Burner capacity can range between 210kW up to 2,330kW per WBH.
Operation of the units is simple as the burners are usually either ‘on’ or ‘off’. Variances occur where some WBHs have 2 or 3 burners and some burners have ‘high’ and ‘low’ fire. WBHs are usually installed in pairs with one WBH capable of providing sufficient energy to heat the peak load of the gas stream. Gas flow usually passes through both WBHs simultaneously. The burners are controlled by the monitoring of the downstream gas temperature. As gas passes through both WBHs simultaneously, the first WBH fires at a set point slightly higher than that of the second WBH. By controlling in this way, should a problem occur with one burner, the other will automatically pick up the load. However, if both WBHs are regularly firing due to the requirements of the peak demand, energy is lost as thermal energy to atmosphere (kW) and to the gas stream by overheating it above 0°C (kW).