3.7　Special Instruments

3.7.1　The turbine rotor corresponding to the iron core of electromagnetic sensor shall have flat and smooth cam edge，the clearance among different parts and the installation and adjustment shall meet the requirements of the manufacturer's technical document.

3.7.2　The installation clearance between the eddy current sensor and the tested metal shall be determined according to the linear midpoint position defined by the output characteristic curve that is given in the product technical document.The type and length of the high-frequency cable connected between the sensor and transmitter shall not be changed at will，the high-frequency joint shall be sealed in thermal shrinkable sleeve and also shall be insulated and ungrounded.The ambient temperature at the installation site of transmitter and whether the transmitter is ungrounded or not shall meet the requirements detailed in manufacturer's product technical documents.

3.7.3　The installation of rotational speed measuring sensor shall meet the following requirements：

1　The installation clearance between the end surface of magnetic-resistant sensor and the top of the speed measuring gear shall meet the requirements detailed in product technical document.

2　The clearance between the end surface of eddy current sensor and the measured shaft shall be determined according to the even surface of shaft if the shaft is marked as notch，and shall be determined according to the convex surface if the axis is marked as convex.

3　The mounting support of sensor shall have adequate stiffness to prevent deformation and also shall have anti-loose measures.

3.7.4　The installation of electromagnetic sensor and eddy current sensor or transmitter used for measuring the axial displacement and differential expansion shall be in accordance with the requirements of product technical document，the rotor shall be pushed to make its thrust disc abut upon the working or nonworking thrust segment surface，and then the gap adjustment shall be made.The central axis of sensor shall be perpendicular to the measuring surface.

3.7.5　The installation position of the eddy current sensor used for measuring the eccentricity of principal axis shall meet the requirements of product technical document.The support for installing sensor shall have adequate stiffness to prevent deformation，and the sensor shall be firmly fixed on the support.

3.7.6　The electromagnetic speed sensor and piezoelectric speed sensor installed on the finished surface of bearing pedestal to measuring the absolute vibration of bearing pedestal shall adopt rigid connection.Where the bearing pedestals of generator and exciter are required to be insulated against ground，the sensor shell shall be ungrounded.

3.7.7　The installation of such eddy current sensor or eddy-current magnetic-resistant combined sensor used for shaft vibration measurement shall meet those specified in 3.7.5 of this Part.

3.7.8　The installation and zero position adjustment of thermal expansion sensor shall be carried out when the steam turbine is at room temperature，the installation position of valve position travel sensor shall make the electric zero position be consistent with the mechanical zero position.