Rubber Gasket Quality Inspection Standards
1. Scope
This document is applicable to the company's inspection of semi-finished heat exchanger gaskets and warehouse-in inspection and delivery inspection of finished products.
2. Inspection items
2.1 The physical properties of the heat exchanger gasket material (tensile strength, elongation at break, 100% modulus).
2.2 Gasket hardness and compression set;
2.3 Gasket length, thickness and size;
2.4 Appearance quality of gaskets;
3. Quality requirements
3.1 Appearance
3.1.1 Gaskets made of the same material should have uniform appearance.
3.1.2 The color and luster of the gaskets should be uniform and have no defects such as impurities and bubbles.
3.1.3 The main sealing surface of the gaskets should be flat and smooth and have no defects such as impurities, bubbles and dimples that affect the sealing.
3.1.4 The unilateral dislocation of the gasket cross-section should be no greater than 0.2mm. The height and depth of the surface defects should be no greater than 0.2mm, the length shall not exceed 2mm, and the width shall no exceed 1.5mm.
3.2 Size and tolerance
3.2.1 The gasket size should conform to the stipulations of the drawing (processed with drawings supplied by customers).
3.2.2 The gasket thickness should have no minus deviation, and the positive deviation should meet the stipulations of Table 1.
Table 1
Item | Heat transfer area of single plate α，m2 | |
≤0.7 | ＞0.7 | |
Thickness Tolerance | +0.2 0 | +0.25 0 |
For heat exchanger gaskets with single plate heat transfer area of less than 0.7m2 (including 0.7 m2), the thickness tolerance is (0 ~+0.20) mm; otherwise, the thickness tolerance is (0 ~+0.25) mm;
The thickness tolerance of the one seal, two seals and the main sealing face of single gasket shall meet the stipulations of Table 2.
Table 2 Tolerance of Molded Products
公称尺寸 （垫片厚度）Nominal Size(gasket thickness) | 0～4（including 4） | 4～6.3 | 6.3～10 | 10～16 | 16～25 | 25～40 |
公差数值Tolerance Value | 0～+0.1 | 0～+0.12 | 0～+0.15 | 0～+0.2 | 0～+0.2 | 0～+0.25 |
Check the standard thickness of each type in Appendix 1: Look-up Table for Plate Heat Exchanger Gasket Type and Thickness.
3.2.3 The unilateral length of the gasket should not have positive tolerance. The absolute value of the negative tolerance shall not be more than 3‰ of the unilateral length, and no greater than 4 mm.
3.3 Material
The physical properties of the material shall conform to the stipulations of Table 3.
No. | Property | Requirements | ||
NBR | EPDM | FKM | ||
1 | Shore A hardness | 75±5 | 80±5 | 80±5 |
2 | Minimum break strength | 13 | 12 | 10 |
3 | Minimum elongation at break | 250 | 150 | 120 |
4 | Minimum tear strength Crescent-shaped | 30 | 20 | 15 |
5 | Maximum compression set 100℃×70h 150℃×70h 200℃×70h |
25 |
30 |
35 |
6 | Air oven aging test 100℃×70h Variation in Shore A hardness Maximum change rate of break strength 150℃×70h Maximum change rate of elongation at break Variation in Shore A hardness Maximum change rate of break strength 200℃×70h Maximum change rate of elongation at break Variation in Shore A hardness Maximum change rate of break strength Maximum change rate of elongation at break
|
0～+15 -20 -35 |
-5～+10 -20 -30
|
-5～+10 -20 -30 |
4. Test method
4.1 Visually check the appearance quality of the gasket.
4.2 Check the cross-section quality and section size of the gasket by cutting anatomy method.
4.3 Test the thickness of the gasket by thickness gauge. The testing points should be uniformly distributed, including 4 points at each end and 2 points at each seal. Check 3 points per meter on the straight line on each side (when the straight length is less than 1m, calculate according to 1m).
4.4 Test the gasket hardness on the whole gasket with a durometer. The testing points should be uniformly distributed, including 4 points at each end and 2 points at each seal. Check 3 points per meter on the straight line on each side (when the straight length is less than 1m, calculate according to 1m)
4.5 Test the shape and length of the gasket with corresponding plates. Place the gasket in the corresponding plate gasket groove, and measure the relative size over tolerance by vernier caliper. Adopt different testing methods for different installing forms. Check the standard length of each type in Appendix 2: Look-up Table for Plate Heat Exchanger Gasket Type and Length.
4.5.1 clip on type gasket:
Fig.1 Fig.2 Fig.3
Clip on type gasket is as shown in Fig.1, and the M series, BR series and part of F series belong to the hook buckle installing form. When doubling plate, the semi-finished products with trimmed flash are tiled in the plate gasket groove, as shown in Fig. 1. The position structures of the gaskets in Fig. 2 and Fig. 3 are accurately placed in the plate gasket groove. The conjoint ratio of the two ends and the straight gasket in the plate gasket groove is observed. The numerical value of the dimension deviation is measured by vernier caliper, and the results of doubling plate are recorded faithfully in the Gasket Product Quality Tour-inspection Form.
4.5.2 button lock type gasket:
Fig.4 Fig.5 Fig.6
button lock type gasket is as shown in Fig.4, and the NT series, S series and part of F series belong to this installing type. When doubling plate, the semi-finished products with trimmed flash are tiled in the plate gasket groove, as shown in Fig.4. The position structures of the gaskets in Fig. 5 and Fig. 6 are accurately placed in the plate gasket groove. The conjoint ratio of the two ends and the straight gasket in the plate gasket groove is observed. The numerical value of the dimension deviation is measured by vernier caliper, and the results of doubling plate are recorded faithfully in the Gasket Product Quality Tour-inspection Form.
.
4.5.3 lock in type gasket:
Fig.7 Fig.8 Fig.9
Lock in type gasket is as shown in Fig.7, and the VT series and GEA such as N40 belong to this installing type. When doubling plate, the semi-finished products with trimmed flash are tiled in the plate gasket groove, as shown in Fig.7. The position structures of the gaskets in Fig. 8 and Fig. 9 are accurately placed in the plate gasket groove. The conjoint ratio of the two ends and the straight gasket in the plate gasket groove is observed, and then the gaskets are fixed in the gasket groove to observe the conjoint ratio again. The numerical value of the dimension deviation is measured by vernier caliper, and the results of doubling plate are recorded faithfully in the Gasket Product Quality Tour-inspection Form.
.
4.5.4 glue type gasket:
Fig.10 Fig.11 Fig.12
Glue type gasket as shown in Fig.10, and the Tranter GL, GX and GC belong to this installing type. When doubling plate, the semi-finished products with trimmed flash are tiled in the plate gasket groove, as shown in Fig.10. The position structures of the gaskets in Fig. 11 and Fig. 12 are accurately placed in the plate gasket groove. The conjoint ratio of the two ends and the straight gasket in the plate gasket groove is observed. The numerical value of the dimension deviation is measured by vernier caliper, and the results of doubling plate are recorded faithfully in the Gasket Product Quality Tour-inspection Form.
