3　Installation of Sampling ﹠ Sensitive Element

3.1　General Provision

3.1.1　The sampling and sensitive element shall be installed on such process equipment or process pipeline that are able to actually reflect the parameters of measured medium，and are convenient for maintenance and overhauling and uneasy to have mechanical damages.

3.1.2　The sampling and sensitive element shall not be installed nearby manhole，observation hole，explosion door or blowdown door.

3.1.3　The hole opening，welding and heat treatment work of sampling element shall be carried out before the cleaning and sealing test of pipeline lining or thermal equipment.The hole opening and welding shall not be carried out on the thermal equipment that has been sealed and insulated，if they must be carried out，corresponding measures shall be taken and approval procedure shall be transacted.

3.1.4　The hole opening and the installation of sampling element shall be not carried out on the supervision segment of steam pipeline.

3.1.5　The material of sampling element shall conform to that of thermal equipment or pipeline，and the sampling element shall be provided with the certification of fitness.

3.1.6　Before and after installation，the alloy steel part and the source pipe must pass the spectral analysis and recheck，and the relevant records shall be made.

3.1.7　The welding and heat treatment of high pressure and high temperature system shall meet those specified in"The Code of the Welding for Power Plant"（DL/T 869）.

3.1.8　The hole opening in the thermal equipment and pressure pipeline shall adopt the machining method；the hole opening in air pressure pipeline may adopt the gas flame cutting method，however，the orifice shall be polished to be smooth and clean.

3.1.9　When installing the sampling element，the socket and stub pipe shall not be set in the weld or heat affected zone.

3.1.10　The material of the gaskets for sampling element shall be selected in accordance with those specified in Appendix C.

3.1.11　According to the flow direction of medium，the distance between two adjacent measuring points shall be larger than the outside diameter of the measured pipeline and shall not be less than 200mm；where the pressure sampling element and the temperature measuring element are installed at adjacent positions in the same pipe section，the pressure sampling element shall be installed in front of the temperature measuring element.

3.1.12　On the same cross-section pipe wall of the high-and medium-pressure pipeline，only one hole is allowed.

3.1.13　The sampling elements for pressure，flow and composition analysis under high-and mediumpressure shall be welded with additional sampling stub，the installation of sampling stub shall meet those specified in Section 3.3 and Section 3.4 of this Part，and the exposed length of the sampling pipe shall exceed the insulating layer.

3.1.14　The sampling valve shall approach to the measuring point，be convenient for operation，be firmly fixed，and shall not affect the hot-state displacement of the main equipment.The type and specification of sampling valve shall meet the design requirements.

3.1.15　The sampling valves of the high-and medium-pressure thermal system shall be connected by welding，and that of other systems should be adopted with the external screw thread connection.The cutting sleeve type joint shall not be adopted in front of the sampling valve.

3.1.16　The sampling valve shall be installed before the pressure test of thermal system and also shall be involved in the sealing test of the main equipment.

3.1.17　The sampling element or sensitive element，after being installed，shall be set with label plate indicating the design number，name and purpose.