System Solutions — Hype or Prerequisite for Tangible Monetary Benefits?
Valve Terminal Versus Individual Solenoid Valves
Figure 1 shows the production installation in a fine chemical plant taken as the basis for the comparison. It covers an area of approx. 20 x 20 m, is 15 m high (4 levels) and produces skin-care products and detergents. The installation is controlled by around 100 valves, mainly ball valves of nominal sizes most between 25 and 50 mm. The installation is equipped with individual valves and limit-switch boxes on the drives. The calculation has been done on the basis of existing cabinets in the installation.
The solenoid valves are mounted directly on the actuator via Namur interfaces. The solenoid valves and end-position switches are connected to the field bus via remote I/O’s.
The architecture is similar with a valve terminal. The field bus node, remote I/O’s and solenoid valves form a unit as a decentral control level. When valve terminal technology is used rather than an individual-valve concept, there is, for example, no need for a binary output on the remote I/O unit to control individual valves, or any of the associated wiring, installation work, etc.
The valve terminals have been located within the installation in a way that process requirements for opening/closing times of the process valves are fulfilled.