The control of cooling or heating water flow is critical to maintaining the desired temperature of process fluid in a heat exchanger. The traditional loop relies on the temperature measurement of the process fluid on the outlet of heat exchanger and using this to generate, via a controller, a setpoint for the valve. This setpoint is traditionally in % opening. This, however, is not the most efficient form of control due to inherent loss of control quality over the loop involving many individual components, such as temperature sensor inaccuracy, lag within PID of controller to generate setpoint, valve hysteresis, communication delays, etc.
FOCUS-1, as the 1st integrated control and measurement device, can provide different possibilities of control that make the traditional loop design redundant. Simplest and most common form of control with FOCUS-1 is using ‘Flow as a Setpoint’. In this case, a 4/20mA signal equaling the desired flowrate is sent to FOCUS-1 device, with for example 4mA being the lowest permissible flowrate, 20mA being the highest permissible flowrate, and 12mA being 50% of the permissible flowrate range. With the use of this control philosophy, SRC was able to achieve faster and better flow control of the cooling water across the heat exchanger.
The added value of such a multi-parameter control and measurement device was visible, when SRC identified that the cooling water flow needed across the loop was much higher than the design. Such information is sometimes simply not available in traditional loops due to the lack of flow meter and current valves not providing the necessary feedback to DCS.
As was demonstrated at SRC, FOCUS-1 truly shines new light on the process loops of today!
