Section 6 Control and monitoring of main and auxiliary steam turbines

6.1.1 Control engineering systems are to be in accordance with the requirements of Pt 6, Ch 1 Control Engineering Systems.

6.1.2 All main and auxiliary steam turbines intended for essential services are to be provided with means of indicating the lubricating oil pressure supply to them. Where such turbines are of more than 37 kW (50 shp), audible and visual alarms are to be fitted to give warning of an appreciable reduction in pressure of the lubricating oil supply. Further, these alarms are to be actuated from the outlet side of any restrictions, such as filters, coolers, etc.

6.2.1 An overspeed protective device is to be provided for main and auxiliary turbines to shut off the steam automatically and prevent the maximum designed speed being exceeded by more than 15 per cent.

6.2.2 Where two or more turbines of a compound main turbine installation are separately coupled to the same main gear wheel, and one overspeed protective device is provided, this is to be fitted to the L.P. ahead turbine. Hand trip gear for shutting off the steam in an emergency is to be provided at the manoeuvring platform.

6.3.1 Where a turbine installation incorporates a reverse gear, electric transmission or reversible propeller, a speed governor in addition to, or in combination with, the overspeed protective device is to be fitted, and is to be capable of controlling the speed of the unloaded turbine without bringing the overspeed protective device into action.

6.3.2 Auxiliary turbines intended for driving electric generators are to be fitted with speed governors which, with fixed settings, are to control the speed within 10 per cent momentary variation and 5 per cent permanent variation when full load is suddenly taken off or put on. The permanent speed variations of alternating current machines intended for parallel operations are to equalise within a tolerance of ±0,5 per cent.

6.4.1 Where machinery steam turbines are fitted with automatic or remote controls so that under normal operating conditions they do not require any manual intervention by the operators, they are to be provided with the alarms and safety arrangements required by Pt 5, Ch 3, 6.4 Unattended machinery to Pt 5, Ch 3, 6.6 Auxiliary steam turbines, as appropriate. Alternative arrangements which provide equivalent safeguards will be considered.

6.4.2 Where machinery is arranged to start automatically or from a remote control station, interlocks are to be provided to prevent start-up under conditions which could hazard the machinery.

6.4.3 Where machinery specified in this Section is required to be provided with a standby pump, the standby pump is to start automatically if the discharge pressure from the working pumps falls below a predetermined value.

6.4.4 Where a first stage alarm together with a second stage alarm and automatic shutdown of machinery are required in the relevant Tables of this Section, the sensors and circuits utilised for the second stage alarm and automatic shutdown are to be independent of those required for the first stage alarm.

6.5.1 Alarms and safeguards are indicated in Pt 5, Ch 3, 6.5 Steam turbine machinery for propulsion purposes 6.5.2 toPt 5, Ch 3, 6.5 Steam turbine machinery for propulsion purposes 6.5.6 and Table 3.6.1 Steam turbine machinery: Alarms and safeguards.

6.5.2 Audible and visual alarms are to operate, and indication is to be given at the relevant control stations to stop or reduce the speed of the turbine(s) for the following fault conditions:

1. Excessive turbine vibration.

2. Excessive axial movement of turbine rotor.

3. Low vacuum in main condenser.

4. High condensate level in main condenser.

6.5.3 Reduction of speed may be effected by either manual or automatic control.

6.5.4 Means are to be provided to prevent the risk of thermal distortion of the turbines, by automatic steam spinning, when the shaft is stopped in the manoeuvring mode. An audible and visual alarm is to be provided at the relevant control stations when the shaft has been stopped for a predetermined time.

6.5.5 The following turbine services are to be fitted with automatic controls so as to maintain steady state conditions throughout the normal operating range of the propulsion turbine(s):

1. Lubricating oil supply temperature.

2. Condenser condensate level.

3. Gland steam pressure.

6.5.6 Prolonged running in a restricted speed range is to be prevented automatically, or alternatively, indication of restricted speed ranges is to be provided at each control station.

6.6.1 Alarms and safeguards are indicated in Table 3.6.2 Auxiliary engines and auxiliary steam turbines: Alarms and safeguards