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 last years there has been a great effort on research and development on gasket testing for bolted joints in Europe and in North America. In Europe, a new standard for the calculation of flanged joints (EN 1591) was developed by the Technical Committee TC 74 of the European Committee for Standardization (CEN). This standard requires gasket factors which must be determined in accordance to the testing standard EN 13555. In North America, the ASTM Committee F03 on Gaskets was established to implement PVRC developed gasket test procedures in the code. Since many companies are operating worldwide, there is an interest in “harmonized” gasket testing procedures to minimize the costs and to raise the effectivity of the tests performed. Several information exchange meetings on gasket constants and gasket testing have been held, and there have been many discussions concerning the difference between the European and the American test procedures. Up to now, only the test procedure for leakage tests has been “harmonized”. Although there are still some differences in detail, the European gasket constants as well as the PVRC parameter can be determined with the new definition of the test procedure, theoretically. In this paper some tests are evaluated in both ways, the results show some mismatch. More tests (with several gasket materials) are necessary to prove the reliability of this procedure.

In the EnBW nuclear power plant Neckarwestheim, the “Integrity Concept” is applied to important piping systems. As basis of this concept is an existing quality according to the requirements this has to be proven (e.g. during design and manufacturing) or verified (after a period of operation). This means for example that the material characteristics are as demanded, the construction is appropriate in detail and there is a fault free status. Possible causes of damage mechanisms in operation (loads, environment, degradation of material behavior) are either excluded or controlled, i.e. analyzed and assessed according to the requirements (standards). Within the scope of the “Integrity Concept” fracture mechanics analysis is a redundant measure. In the state of design, already, the assessment of a postulated crack is necessary to produce a “fault-tolerant” component and to determine effective non destructive test regions, methods and test intervals, so that possible consequences of damage mechanisms like cracks can be detected in an early stage. The size of the postulated crack envelopes the detectable crack depending on the resolution of the non destructive test method used during the manufacturing process and in operation. Using the operation loads the growth of the postulated crack is analyzed and assessed. Additionally, it is shown that the size of a through wall crack is safe below the critical crack size. Furthermore, it is demonstrated that the maximum loads in operation as well as in emergency and faulted conditions are below the collapse load. The high quality of the systems as produced has to be guaranteed in operation using redundant measures. Ageing phenomena have to be controlled concentrating on the relevant causes of possible damage. In most of the cases, damage mechanisms are caused by local effects; consequently, these local effects (like loads, water chemistry etc.) have to be monitored, evaluated and assessed regularly. Thus the knowledge about the system is permanently increased. Inservice inspection and testing are redundant measures to safeguard integrity. The efficiency of the entire procedure has to be assessed, periodically, taking into account the actual state of knowledge. Following this procedure the safety margin of the systems and components can be verified (and demonstrated) at every stage of operation. If the “Integrity Concept” is applied consequently there is no reason to restrict the application e.g. to certain systems or to nominal diameters > 200 mm. Furthermore, as fracture mechanics analysis is a tool to control a postulated extreme case (that can not occur if the analysis is correct) it is obvious that a special leak detection system is obsolete because it does not increase safety. Therefore it makes no sense to analyze leak rates etc.