In Europe, in 2001 the new standard EN 1591 for strength and tightness proofs of bolted flange connections (BFC) of floating type flanges was released. In addition, the German nuclear code was revised regarding the calculation of BFC. With this standard not only the floating type but also the metal-to-metal contact type of flanges (MMC) can be treated. Additionally, the ASME code is the basis for the flange calculation in the European standard EN 13445, which is the standard for unfired pressure vessels. In compliance with the goal of the calculation, the different calculation codes can be used. There must be a differentiation between the design of the components, the determination of the prestress values for assembly, the stress analysis and the tightness proof of the BFC. First, all parameters which influence the function of the bolted flange connection are considered. In a second step, the range of use of the different standards and the calculation algorithm are discussed.

Against the background of the reduction of fugitive emissions, the demands on industry are increasing, steadily. In Europe the Integrated Pollution Prevention and Control (IPPC) directive [1] determines emission levels for different industrial facilities. Member countries must adopt these specifications into national guidelines like in Germany the TA-Luft (“Technical Instructions on Air Quality Control”) [2]. In addition, the German VDI guideline 2440 (“Emission control - Mineral oil refineries”) [3] gives more detailed procedures to meet the requirements. Apart from this qualification test in VDI 2440 in Germany, some other (more comprehensive) test procedures are established worldwide to examine the mechanical and tightness behavior of the packing material in valves. These test procedures are e. g. API 622 [4] or ISO 15848-1 [5]. The different test parameters of these test standards are compared in this paper with the ones of the VDI guideline 2440. Also, some typical test results of the VDI 2440 testing shall be illustrated and discussed in respect on the transferability to the other standards. Because the test procedures in the standards are different, it is not possible to perform the test on the same testing device. Especially the added requirement in ISO 15848-1 to measure the tightness of the body joint, leads to additional requirements on the testing equipment. In addition to the well-established test rig for the characterization of the mechanical and tightness properties of the packing material, a new testing device for valves is introduced. With this equipment, the stuffing box packing and the body seal of valves can be tested. The measurement of the friction forces during the stem cycles and the determination of the tightness characteristics (with Helium or Methane) are in the focus of the investigations of this test bench.

The demands on industry to reduce fugitive emissions are increasing, steadily. For the European Union the Integrated Pollution Prevention and Control (IPPC) directive determines emission levels. Individual countries can adopt even tighter legislation like the TA-Luft (“Technical Instructions on Air Quality Control”) in Germany. E. g. the TA-Luft gives specific emission levels for valves according to the German VDI guideline 2440 - Emission reduction in oil refineries. In industrial applications in which the demands of the TA-Luft have to be met only certified sealing materials can be used in future. There are several requirements the sealants must fulfill, the most important in this respect is the tightness proof in a first-time test according to VDI 2440. In this objective, new packing materials were developed to be in compliance with the TA-Luft needs. The knowledge of the material characteristic is the basis for the improvement of the tightness capability and therefore for the reduction of fugitive emissions. But in almost the same manner the mounting procedure of the packing rings is important. It is necessary to perform the mounting procedure in two steps: a pre-deformation step (high stress level for seating) and a prestressing step (stress level must meet tightness requirements). Mounting by use of torque wrenches is time consuming, if this 2-step procedure is followed. Thus, mounting by use of hydraulic tensioner becomes effective. In the paper the most relevant packing material characteristics and the necessary tests to determine these characteristics are summarized. Then the mounting tools for hydraulic tensioning are introduced. Finally, some results of packing tests according to VDI 2440 are presented.

To study the effect of temperature on the tightening characteristics of gaskets, leak rate tests were performed using a servo-hydraulic test equipment (short term temperature exposure). According to the tests the tightening behaviour of gaskets made of fibre based sheet material improved with temperature due to additional deformation of the gaskets during the test. In tests with camprofile gaskets with graphite layers there was no significant additional deformation of the gasket thus the leak rates showed no difference between room temperature and elevated temperature. Regarding long term exposure to temperature it is expected that with a lot of gasket materials the leak rates increase after a certain aging period. It is too expensive to study these effects with complex servo-hydraulic test rigs. Therefore a more simple test rig was developed that can be loaded in hydraulic test rigs (to determine leak rate vs. gasket stress curves) and that can be exposed to temperature in an oven or by a special heating device.

The Nuclear Power Plant KKG in Gösgen, Switzerland was designed according to the ASME Boiler and Pressure Vessel Code. The ASME BPVC, Section III, Appendix 11 regulates the flange calculation for class 2 and 3 components, it is also used for class 1 flanges. A standard for the determination of the required gasket characteristics is not well established which leads to a lack of clarity. As a hint different y and m values for different kinds of gasket are invented in ASME BPVC Section III [1]. The KTA 3201.2[2] and KTA 3211.2[3] regulate the calculation of bolted flanged joints in German nuclear power plants. The gasket characteristics required for these calculation methods are based on DIN 28090-1[4], they can be determined experimentally. In Europe, the calculation code EN 1591-1 [5] and the gasket characteristics according to EN 13555[6] are used for flange calculations. Because these calculation algorithms provide not only a stress analysis but also a tightness proof, it would be preferable to use them also in the NPP’s in Switzerland. Additionally, for regulatory approval also the requirements of the ASME BPVC must be fullfilled. For determining the bolting up torque moment of flanges several tables for different nominal diameters of flanges using different gaskets and different combinations of bolt and flange material were established. As leading criteria for an allowable state, the gasket surface pressure, the allowable elastic stress of the bolts and the strain in the flange should be a good and conservative basis for determining allowable torque moments. The herein established tables show only a small part according to a previous paper [7] where different calculation methods for determining bolting up moments were compared to each other. In this paper the bolting-up torque moments determined with the European standard EN 1591-1 for the flange, are assessed on the strain-based acceptance criteria in ASME BPVC, Section III, Appendices EE and FF. The assessment of the torque moment of the bolts remains elastically which should lead to a more conservative insight of the behavior of the flanges.