tailieunhanh - Intro to Marine Engineering 2E Episode 12

Tham khảo tài liệu 'intro to marine engineering 2e episode 12', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | 320 instrumentation and control Bridge control Equipment operation from the machinery control room will be by a trained engineer. The various preparatory steps and logical timed sequence of events which an engineer will undertake cannot be expected to occur when equipment is operated from the bridge. Bridge control must therefore have built into the system appropriate circuits to provide the correct timing logic and sequence. There must also be protection devices and safety interlocks built into the system. A bridge control system for a steam turbine main propulsion engine is shown in Figure . Control of the main engine may be from the bridge control unit or the machinery control room. The programming and timing unit ensures that the correct logical sequence of events occurs over the appropriate period. Typical operations would include the raising of steam in the boiler the circulating of lubricating oil through the turbine and the opening of steam drains from the turbine. Programming and timing unit .Safety checks Figure Bridge control of steam turbine plant Instrumentation and control 321 rhe timing of certain events such as the opening and closing of steam valves must be carefully controlled to avoid dangerous conditions occurring or to allow other system adjustments to occur. Protection and safety circuits or interlocks would be input to the programming and timing unit to stop its action if for example the turning gear was still engaged or the lubricating oil pressure was low. The ahead astern selector would direct signals to the appropriate valve controller resulting in valve actuation and steam supply. When manoeuvring some switching arrangement would ensure that the astern guardian valve was open bled steam was shut off etc. If the turbine were stopped it would automatically receive blasts of steam at timed intervals to prevent rotor distortion. A feedback signal of shaft speed would ensure correct speed without action from the main control .