We recently upgraded the controls of steam boiler feed water system at Toronto Western Hospital. The existing controls was originally built at the time of boiler construction, using pneumatic control valve with level switch to control the water level of the condensation tank and the deaerator tank. However, over the time, some of the control lost its functionality and the operator had to switch to manual control mode.
The boiler feed water system is comprised of two condensation water tanks that collect the condensation water from each mechanical room. Domestic cold water makeup is installed to supply additional water to maintain the condensation level at a specific setpoint. Three condensation pumps then pump the water to the deaerator tank, which also has a domestic cold water supply valve as a backup in case of emergency. From the deaerator tank, the boiler feed water pumps will supply the water directly to the steam boiler to generate steam.
There were some issues with the existing level gauges on both the condensation tank and deaerator tank. They were glass tube gauges, which did not provide a clear indication of the water level and also lacked of height level indication. To address this issue, we installed new 56” and 75” stainless steel level sensors that come with plastic orange flags to indicate the water level. These new sensors also provide a 4-20mA signal to the building automation system, which allows for improved monitoring and control of the water levels in the tanks.
We also replaced and upgraded the some controls valves from pneumatic to electrical was based on several factors. While pneumatic actuators have been traditionally considered simple and reliable, they can be impacted by the pneumatic line pressure, leading to low accuracy control. Also, sometime it is hard to find the exact replacement parts. Using a similar parts will cause more control issues.
By upgrading to electrical actuators, we were able to achieve several benefits, including improved control precision, standardization of power supply, and easy integration with the building automation system. Additionally, the better operability of electrical actuators allowed us to streamline maintenance and minimize the downtime.
With the integration of the valve control and pump speed control, we are now able to maintain the water level in the condensation water tank and deaerator tank with greater precision and accuracy. Prior to this upgrade, the pneumatic control system was incomplete, requiring the shift engineer to manually check the system every two hours to ensure the water level remained at a safe level. Additionally, the shift engineer was responsible for manually rotating the pumps to equalize their operation time. With the new control system, we have automated the water level control, supply water pressure control, pump rotation, and pump failure switchover processes. As a result, the shift engineer can now check and review the system from the BAS front-end, improving the system’s reliability and reducing the shift engineer’s workload. Overall, this upgrade has greatly enhanced the efficiency and effectiveness of the boiler feed water system, providing greater control and better reliability.
The fully automated system has been running smoothly for a couple of weeks. Appreciate the outstanding support from the TWH facility throughout the entire project including Chief Engineer, Facility Manager and all shift engineers.
Energy efficiency projects not only help reduce operating costs but also contribute benefit to the facility operation. Looking forward to more potential opportunities to improve the efficiency and continue to make a positive impact on the environment.