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0426T368 SPECIFICATION OF GRAPHITE GASKETS FOR SECONDARY AND AUXILIARY PIPING SYSTEM REV A
13/19
SPECIFICATION OF GRAPHITE GASKETS FOR
SECONDARY AND AUXILIARY PIPING SYSTEM
1 PURPOSE
This specification is applicable for sealing gaskets for flanges used in piping of the Nuclear Steam Supply System (NSSS) and Balance of Nuclear Island (BNI) systems of the 2×1000MWe PWR plant at FUJian fuqing nuclear power plate phase 1 project(FQNPP1) and sets forth technical requirements for material, design and acceptance of nuclear classified graphite gasket.
2 APPLICABLE DOCUMENTS
RCC-M(2000 and 1st Addendum 2002) Design and construction rules for mechanical
components of PWR nuclear islands
ASMI/ANSI B16.5 Pipe flanges and flanged fittings
ASMI/ANSI B16.36 Pipe flanges and flanged fittings with measured aperture 0426T102 Specification for identification and marking of piping and pipe supports
0426T104 Finish and protection of materials for auxiliary and Secondary System Piping
3 MATERIALS 3.1 Graphite filler
The graphite used for filling is made of expanded graphite of high purity with approval from PMUC.
Chemical Composition of Graphite(raw material): Carbon content Ash content
> 99,5% ≤ 0,5%
Total sulphur content < 200 ppm Halogens content <200 ppm. Leachable (Extractible) Chloride <30 ppm Leachable (Extractible) Fluoride ≤50 ppm
CHINA NUCLEAR POWER ENGINEERING Co.Ltd
0426T368 SPECIFICATION OF GRAPHITE GASKETS FOR SECONDARY AND AUXILIARY PIPING SYSTEM REV A
14/19
Mechanical properties of raw graphite material: Tensile strength
≥ 4,5 Mpa
≥ 170 Mpa
Compressed strength 3.2 Graphite tape Raw material density 3.3 Locating ring
0,9 ± 0,1 g/cm3
The crushing limiter and the expansion limiter (outer ring and inner ring) of the stamped expanded graphite metal-to-metal gasket are made of Z2CND17-12 austenitic stainless steel. They are procured according to the M3307 (for sheets) with a RCC-M Class 2. Chemical composition and mechanical performance refers to Table 1 and Table 2. Checking the elasticity limit at 350° C is requested. Table 1: Chemical composition for metallic sheets
CHEMICAL COMPOSITION for metallic sheets (following RCCM 2 standard M3307) Stainless steel nature Designation AFNOR C % Si % Mn% P % S % maxi maxi maxi maxi maxi Cr % Ni % Mo % Cu % maxi SS 18-10 with Mo Z2 CND 17-12 0,030 1,00 2,00 0,030 0,015 16,00 10,00 2,00 to to to 1,00 19,00 14,00 2,50
Table 2: Mechanical performance for metallic sheets
MECHANICAL PERFORMANCE for metallic sheets (following RCCM 2 standard M3307) MECHANICAL CHARACTERISTICS Stainless steel nature AMBIANT TEMPERATURE Designation AFNOR Rp0,2 min (Mpa) 175 Rm min (Mpa) 490 A% (5d) min thickness (mm) > 3 45 ? 3 40 - KV Min (J) At 350 °C Rp0,2 min (Mpa) 105 Rm min (Mpa) SS 18-10 with Mo Z2 CND 17-12 382
4. SKETCH AND DIMENSION OF GRAPHITE GASKET 4.1 Sketch of graphite gasket
Graphite gaskets consist of one stamped high purity expanded graphite rings with strict controlling of volume and density which purpose is to ensure the sealing, plus one inner ring and one outer ring made of RCC-M stainless steel. Both inner and outer rings ensure the support
CHINA NUCLEAR POWER ENGINEERING Co.Ltd
0426T368 SPECIFICATION OF GRAPHITE GASKETS FOR SECONDARY AND AUXILIARY PIPING SYSTEM REV A
15/19
of the expanded graphite ring. The function of one of the stainless steel ring is to act a crushing limiter to avoid over tightening of the gasket.
Dimension of graphite gaskets shall be decided according to dimension of connecting flanges specified by ANSI B16.5，ANSI B16.36, and to ensure matching with flanges. Fig 1: configuration sketch of graphite gasket
4.2 Dimension of graphite gaskets
Φd1 shall match the inner hole of the relating flange. The effective sealing surface is between Φd2 and Φd3. Φd4 shall be less than inner diameter of bolts for flange.
CHINA NUCLEAR POWER ENGINEERING Co.Ltd
0426T368 SPECIFICATION OF GRAPHITE GASKETS FOR SECONDARY AND AUXILIARY PIPING SYSTEM REV A
16/19
Table 3: dimension of graphite gasket DN d1 15 20 25 40 50 65 80 17(15) D2 d3 23 31 38 48 69 84 95 115 e E d4 150Lb 300Lb 600Lb 900Lb 1500Lb 2500Lb 52 66 73 94 107 127 146 178 213 248 304 357 418 481 535 592 650 771 52 66 73 94 107 127 146 190 237 262 316 396 453 488 561 609 679 786 62 69 78 97 139 160 166 203 244 285 354 431 494 517 571 634 695 833 62 69 78 97 139 160 170 205 250 280 348 430 515 575 637 698 752 896 69 75 84 116 141 163 192 231 276 312 382 471 543 4.4 3.2 46 4.4 3.2 56 4.4 3.2 66 4.4 3.2 84 4.4 3.2 100 4.4 3.2 119 4.4 3.2 132 4.4 3.2 170 4.4 3.2 194 4.4 3.2 219 4.4 3.2 276 6.6 5 6.6 5 6.6 5 10 8 10 8 10 8 336 406 446 510 545 602 713 23.7(21) 30 29.7(27) 36 50.7(42) 57 65.7(56) 72 76.7(67) 83 90(83) 99 100 110(99) 150 161 250 265 350 360 400 407 450 454 119 135 174 194 285 305 390 410 484 514 125 140(129) 149 165 200 212(205) 225 245 300 318(308) 338 358 431 461(456) 6.6 5 500 508(500) 538 576 600 610(606) 642 682 Note: 1. Values in brackets indicates dimensions of gaskets whose pressure grade is 1500Lb and 2500Lb.
2. The other data could be adjusted accordingly except d1 and d4 in the table.
5. DESIGN REQUIREMENTS 5.1 Designing parameters
Class grade of gasket shall be determined according to grade of the flanges. The designing parameters are showed in Table 4.
CHINA NUCLEAR POWER ENGINEERING Co.Ltd