Conventional Servo System to Direct Drive Actuators Why Does It Matter?

Abstract

This paper discusses the development of Actuators over a period of time. The purpose of an Actuator (servo system) is to operate steam turbine control valves. With the increasing demand for better control of steam valves and depleting support for conventional servo system, there has been a gradual shift to Direct drive Actuator. The conventional servo system consists of an E/H Actuator along with pilot valve, power cylinder and a complex system of linkages. The introduction of direct-drive actuators enables the Turbine OEM’s to completely eliminate the application of pilot valve and power cylinder and redesign the system for less space, better reliability and low maintenance. The major issue with conventional system is the large number of bearings, linkages and moving parts which had resulted in multiple failures over time and the complexity of the system which makes it very difficult to analyze the root cause of these failures. This paper presents the above failures and how the direct-drive actuators solves the issue by allowing OEM’s to design the system with minimum components and better analyze the system leading to high reliability and better optimization of the limited space around Turbine. This paper also discusses other factors which make the system highly reliable and redundant. While the users experience many benefits, it is also important to understand the issues associated with direct Actuators. The paper also lists these disadvantages along with