In manufacturing, a continuous process is a method that is used by manufacturing or production companies to churn out the greatest quantity of a product over the least time. This is consistent, constant, and uninterrupted, in contrast to batch processing. Manufacturers most often use this type of process in the manufacture of chemicals, drugs, and glass, as well as in the refining process for crude oil. A continuous process plant is designed so that there is a seamless flow of the product from one machine or robot station to another through the production process. Software programs and complex equipment that collect feedback from different stations regulate the rate of flow through the system, controlling the rate of production closely.
Timely maintenance on a continuous process system is essential. The system is set up in a serial configuration, with a dynamic progression of the product through the factory. Any failure in one machine delays the supply chain both upstream and downstream of the defective machine. Although the continuous process system is automated, human input and management keeps the process moving forward as planned. These systems require a substantial investment in system design, transducers, controllers, and complex machinery to achieve the desired goal of production around the clock.
Most continuous process systems use a proportional-integral-derivative (PID) controller. A PID controller collects feedback from various checkpoints in the system and runs through three calculations. The proportional calculation detects an “error” by comparing a measured output value to a predetermined set point. Integral calculations average the most recent errors to assess trends, while derivative calculations examine the rate of change of the error. The controller uses the weighted sum of the three calculations to adjust the system by altering a control point such as the speed of a conveyor belt, the position of a valve, or the temperature of a heating element.
The production method that a given plant uses depends on the product. Continuous-flow production requires products for which the same level of quality can be reliably achieved as long as the process of manufacture and the ingredients are unchanged. If the product quality varies significantly, batch production allows quality testing of a limited amount of product. While batch production requires less initial capital investment and can be adjusted according to market demand, it requires downtime between batches for reconfiguring and testing. Continuous process production lowers the manufacturing costs by eliminating downtime.
