Section 7 Tests and equipment

7.1.1 All solid forged H.P. turbine rotors intended for main propulsion service where the inlet steam temperature exceeds 400°C are to be subjected to at least one thermal stability test. This requirement is also applicable to rotors constructed from two or more forged components joined by welding. The test may be carried out at the forge or turbine builders' works:

1. after heat treatment and rough machining of the forging; or

2. after final machining; or

3. after final machining and blading of the rotor.

The stabilising test temperature is to be not less than 28°C above the maximum steam temperature to which the rotor will be exposed, and not more than the tempering temperature of the rotor material. For details of a recommended test procedure and limits of acceptance, see Rules for the Manufacture, Testing and Certification of Materials, July 2022. Other test procedures may be adopted if approved.

7.1.2 Where main turbine rotors are subjected to thermal stability tests at both forge and turbine builders' works, the foregoing requirements are applicable to both tests. It is not required that auxiliary turbine rotors be tested for thermal stability, but, if such tests are carried out, the requirement for main turbine rotors will be generally applicable.

7.2.1 All rotors as finished-bladed and complete with half-coupling are to be dynamically balanced to the Surveyor's satisfaction, in a machine of sensitivity appropriate to the size of rotor.

7.3.1 Manoeuvring valves are to be tested to twice the working pressure. The nozzle boxes of impulse turbines are to be tested to 1,5 times the working pressure.

7.3.2 The cylinders of all turbines are to be tested to 1,5 times the working pressure in the casing, or to 0,2 MPa, whichever is the greater.

7.3.3 For test purposes, the cylinders may be sub-divided with temporary diaphragms for distribution of test pressures.

7.3.4 Condensers are to be tested in the steam space to 0,1 MPa. The water space is to be tested to the maximum pressure which the pump can develop at ship's full draught with the discharge valve closed plus 0,07 MPa, with a minimum test pressure of 0,2 MPa. Where the operating conditions are not known, the test pressure is to be not less than 0,34 MPa, see Pt 5, Ch 14 Machinery Piping Systems.

7.4.1 Indicators for determining the axial position of rotors relative to their casings, and for showing the longitudinal expansion of casings at the sliding feet, if fitted, are to be provided for main turbines. The latter indicators should be fitted at both sides and be readily visible.

7.5.1 Main and auxiliary turbines are to be provided with bridge weardown gauges for testing the alignment of the rotors.