3.4　Materials

3.4.1　The construction materials of rotary machines shall comply with the following requirements:

1　The material requirements for the pressure-containing parts and other main components of rotary machines shall be specified in the inquiries or datasheets，final material selection shall be specified in the proposals of the manufacturers，and specific material codes shall be indicated in the datasheets.

2　Welded pressure-containing parts shall be subject to post weld heat treatment and nondestructive test.

3　Except for cast steel parts，repair welding shall not be made on all pressure-containing cast parts.If repair welding is required for cast steel parts，it shall comply with Article 11.2.3 of this code.

4　If the specified minimum design metal temperature is lower than-20℃，low temperature impact test shall be made for the base metal and welds of all pressure-containing steels except for austenitic stainless steel.

5　If chlorides are present in the medium，the component materials in contact with the medium should not be aluminum and austenitic stainless steel.

6　When the medium contact with copper and then generate explosive copper compounds，copper or copper alloy shall not be used to fabricate the parts.

7　The materials exposed in acid environment or wet H2S-containing environment shall comply with the requirements specified in the current national standard GB/T 20972.1 Petroleum and Natural Gas Industries-Materials for Use in H2S-containing Environments in Oil and Gas Production-Part 1：General Principles for Selection of Cracking-resistant Materials.

8　Gaskets and seal rings shall not contain any asbestos.

9　Hygroscopic materials shall not be used for sound insulation materials.

10　Material corrosion-resistant performance should not be enhanced by using surface plating and surface coating.

11　Materials for lube oil，seal oil，seal flushing and dry gas seal piping and fittings shall be 304 or 316 stainless steel.

12　For the welds that are impossible for inspection during fabrication or after fabrication，separate quality control methods shall be determined.

3.4.2　In addition to the requirements specified in Article 3.4.1 of this code，the construction materials of pumps shall also comply with the following the requirements:

1　Cast iron shall not be used for pressure-containing parts of pumps for toxic，flammable and explosive liquid services.Cast iron shall not be used for centrifugal pumps and rotary pumps for toxic，flammable and explosive liquid services，including seal less centrifugal pumps，and their bearing housings.

2　Unless otherwise specified，the corrosion allowance of pump casings shall be at least equal to 3.0mm.

3　The liners of canned pumps shall be made of nonmagnetic materials and shall have good corrosion resistance and high strength，stator liner should be Hastelloy alloy，its minimum thickness shall be 0.4mm and corrosion allowance shall be 0.15mm.The containment shell of magnetic drive pump shall be high-resistivity materials，Hastelloy alloy and titanium alloy should be selected，its minimum thickness shall be 1mm and its corrosion allowance shall be 0.4mm.For medium-and lightduty magnetic drive pumps used for medium service with temperature lower than 120℃，their containment shells may be non-metal materials such as plastics or ceramics.

4　For non-metal pumps，their allowable working temperature shall meet the special performance requirements such as material thermal expansion coefficient，high temperature"creep"of plastic materials and low temperature cracking.The maximum allowable working temperature of non-metal pumps shall be 60%-70% of the ultimate heat-resistant temperature of the materials.

5　The diaphragm materials of pneumatic diaphragm pumps shall have reliable chemical stability，and the working temperature shall be less than the ultimate heat-resistant temperature of the diaphragm materials.

3.4.3　In addition to the requirements specified in Article 3.4.1 of this code，the construction materials of agitators shall also comply with the following requirements:

1　The corrosion allowance of agitator shafts and impellers shall be at least equal to 1.0mm.

2　The agitator impellers and shafts contacting with mediums shall be not lower than materials grade of the vessels.

3　Lock nuts，spring washers，lock pins and metal lock wires shall be austenitic stainless steel or higher materials.The material grade of lock nuts and spring washers contacting with the medium shall be not lower than the agitator impellers.The metal lock wires contacting with the medium should be titanium.

3.4.4　In addition to the requirements specified in Article 3.4.1 of this code，the construction materials of compressors shall also comply with the following requirements:

1　The casing materials of centrifugal and rotary compressors for flammable and toxic gas services shall be at least carbon steel.

2　The casing materials of centrifugal compressors for air or non-flammable gas services may be ductile iron；however，the maximum outlet pressure of the compressors shall be less than or equal to the maximum allowable pressure of PN50 flanges at the delivered medium temperature.

3　The casing materials of rotary compressors for air or non-flammable gas services may be ductile iron；however，the maximum outlet pressure of the compressors shall be less than or equal to 1.0MPa，and the maximum outlet temperature shall be less than or equal to 250℃.

3.4.5　In addition to the requirements specified in Article 3.4.1 of this code，the construction materials of steam turbines shall also comply with the following requirements:

1　For steam pressure of greater than 0.52MPa（G）or steam temperature of higher than 230℃，all the pressure-containing parts shall be of steel.

2　For maximum steam temperature of higher than 410℃，all the pressure-containing parts shall be of alloy steel.

3　Material for turbine shafts and wheels shall be forged steel.

4　The nozzles，closing pieces，rotating and stationary blades，shrouding，and steam strainers should be of 11% to 13%chromium steel，titanium，or nickel-copper alloy.

3.4.6　In addition to the requirements specified in Article 3.4.1 of this code，the construction materials of expanders used in the following plants shall also comply with the following requirements:

1　For expanders used in air separation plants，the main shafts shall be alloy steel，the impellers shall be cast aluminum and wrought aluminum，and they shall be subject to anodic oxidation treatment after fabrication.

2　For expanders of flue gas energy recovery unit used in catalytic cracking plants，the materials of main parts of expanders at various inlet temperatures shall be selected in accordance with Table 3.4.6.

3　If the fluid contains dust and particles，anti-erosion measures shall be provided to mitigate erosion to guide vanes and stator vanes.

4　480m/s.In air separation plants，if the expander impellers are aluminum，the linear speed shall be less than or equal to 270m/s，if the impellers are wrought aluminum，the linear speed shall be less than or equal to 480m/s.

3.4.7　In addition to the requirements specified in Article 3.4.1 of this code，the construction materials of gas turbines shall also comply with the following requirements:

1　The material of fuel gas pipes within gas turbine unit shall be at least 316L stainless steel，and pipe welds shall be 100%NDT tested.

2　The internals of fuel gas filters shall be of stainless steel.