Vol-3 Issue-3 2017 IJARIIE-ISSN(O)-2395-4396 5413 www.ijariie.com 1746 PROCESS CONTROL LOOPS A Review Article Lalit Goswami 1,2 , Shagun Malhotra 3 1 Department of Electronics & Communication Engineering, Delhi Technological University, New Delhi. 2 Advanced Materials & Devices, CSIR-National Physical Laboratory, New Delhi 3 Electronics Design Engineer (R&D Deptt.), Vinytics Peripherals Pvt. Ltd, New Delhi, India ABSTRACT Process control refers to the methods that are used to control process variables when manufacturing a product or controlling any parameter. In today’s modern plants, to achieve control, several elements are coordinated together to achieve the control objective. Process control is an engineering discipline that deals with architectures, mechanisms and algorithms for controlling the output of a specific process within a desired range. In any instrumentation system, the control objective can be accomplished by designing proper control system for a specific purpose. Control can either be manual or automatic. Manual control involves the controlling process parameter to a specific value using human intervention. In automatic control, no human intervention is required rather sensors, controllers, actuators and other control elements are used to automatically control a system to maintain the system parameters to desired levels. This paper will explain the process control and different types of control loops. Keyword: - Process, Control loops, Basic control loops, Advance control loops. 1. INTRODUCTION The term control means methods or means used to maintain parameters in any system to have specific or desired values. Process control refers to the regulation of a process variable so as to maintain a desired output level. The aim of process control instrumentation is to measure, indicate, and or control a process. For thousands of years, processes were controlled manually by humans with the necessary skills or expertise. A person or group of persons observed the process; determined the control actions required, and manipulated the variable or variables necessary to achieve satisfactory product. Due to the subjective nature of this control mechanism, the product quality varied widely and overall efficiency was often poor. Modern production systems use automatic control systems where control is carried out with minimal or without human intervention. Control processes use basic elements that include a sensor (primary element), controller, transmitter, and a final element. Product quality is high and consistent and the overall process efficiency is often near optimum. The role of a process technician in industrial production today is mainly to monitor and maintain automated processes. Simply stated, the term control means methods to force parameters in the environment to have specific values. [1] 2. IMPORTANCE OF PROCESS CONTROL Process control engineering is an important tool for the operation and monitoring of an automated complex process. This technology is the tool that enables manufacturers to keep their operations running within specified limits and to set more precise limits to maximize profitability, ensure quality and safety. Here process parameters are measured, monitor and control using various control schemes as explained in the later sections. 2.1 Process Usually Process means a system that is under observation, in which one or more parameters are maintain to the desired value known as process variables. Process as used in the terms process control and process industry, refers to the methods of changing or refining raw materials to create end products as shown in the Fig-1. Process industries include the chemical industry, sugar industry, the oil and gas industry, the food and beverage industry, the pharmaceutical industry, the water treatment industry, and the power generation industry. [1,2,5]