Due to the above, the manufacturer suspected that the real cause of the failure was errors during the gluing of the joints. The sleeves were cut in half and the gluing quality was assessed in the designated areas.

The photo below shows the lack of chamfering of the right pipe edge, which is inconsistent with the pipe manufacturer's requirements described in the gluing instructions.

The photo below shows a missing layer of adhesive across the entire length of the pipe inserted into the sleeve, which is essentially the source of the leak. The pipe end was beveled, but not enough adhesive was applied.

The photo below shows a missing adhesive layer approximately ¾ of the way into the socket. The pipe end was beveled, but not enough adhesive was applied.

The photos below show sections of the joint showing a lack of adhesive at a depth of several millimeters. The shiny, scratch-free pipe surface is clearly visible, proving that the author did not interfere with the adhesive joint during the tests. 

To demonstrate the microscopic image of a properly executed joint, another fitting was examined. A thin line, darker than the adjacent sections, is clearly visible. This represents a properly applied adhesive layer.

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Some top seal manufacturers do add some useful data. They show more or less how the seal will behave during installation and operation. These pieces of information are not mandatory. Some designers use this data, but there is no guarantee that, for example, an inspector accepting the installation and calculations will agree with this approach.

Let's say that for the assumed class L 0.001. The value of "y" is read, in this particular case, as the intersection of the curve with the next higher tightness class - L 0.0001. And here it will be y = 6 MPa. We proceed similarly with the coefficient "m", which will give 11 MPa. These are very small values.

European standards have a completely different approach to the method of calculating the gasket and flange connection.

The graphs and tabular data for them are for informational purposes only. Using this data requires a lot of knowledge and caution.

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Until 2013, the Sh and Sc stresses were not limited by anything according to the following relationship:

Since 2014 Sh and Sc cannot be greater than 20 ksi / 138 MPa. This minor upper limit means that when we update old calculations with a high-strength material (duplex for example), they can suddenly stop working.

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In reality, we do not approach these values. We try to keep to 60-70% Sh. This is because permanent stresses belong to the basic stresses (ang. primary stress). Their impact is permanent, so any errors in assembly are irreparable. Additionally, exceeding the yield point by permanent loads is unstoppable due to the phenomenon of positive feedback.

The second, much more important issue is the phenomenon of lifting supports due to temperature expansion. If we have, for example, 90% permanent stresses, this is definitely too much. You have to be aware that if support F03 is lifted from the temperature (here T3), then it is switched off for GR+Max (P3). In such a situation, we have increased permanent stresses.

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Four operating modes     

Piping elements can operate in four operating modes marked with the letter A to D. Mode A (normal) is the normal operating mode, in which the system is to operate at full capacity. The typical design stress is SH._HMode B (upset) is an abnormal situation that the pipeline must withstand without having to repair it. The loading in this mode, in addition to the typical mode A load, is a basic earthquake. The typical design stress is 1.2 SH_HIn mode C (emergency) we have an emergency situation after the occurrence, the pipeline requires inspection because of visible large deformations. In this scenario, however, the pipeline remains intact. As for the load combination, in this case, exceptionally strong earthquakes can be expected. The typical design stress is 1.8 SH_HIn the last mode of operation (faulted), the pipeline is in a state of complete failure, although the required level is to remain more or less intact. The aim is to ensure that the destruction of the pipeline and its disintegration does not lead to a cascading increase in the size of the failure. Possible load combinations include a missile strike, an act of terrorism or an aircraft crash. The typical design stress is 2.4 SH_H.        

Component classes     

          The standard divides all pipeline elements into the following classes: Class 1 constructed in accordance with the principles of subsection NB, Class 2 in accordance with NC, Class 3 in accordance with ND, Class MC (metallic safety tanks) in accordance with NE, Class CS (main supporting structures) in accordance with NG. Section NF contains the principles of support construction and Section NF describes the principles for internal structures.

The question is what are the elements of classes 1 to 3 and how are they classified? This is the task of the safety department. Class 1 will include all systems (apparatus and pipelines) whose failure could lead to the most serious consequences. As a rule, these are the primary steam pipelines from the reactor to the turbine and the main cooling system. Class 2 includes the remaining systems of the main technology. Class 3 usually concerns auxiliary systems such as sprinkler systems, compressed air, flooding and water purification. All other pipeline systems not covered by the above classes are classless and can be designed on the basis of codes other than nuclear, for example from hour B31. An example would be building installations such as chilled water for air conditioning. 

Typical loads

          Designing a pressure element begins with a review of the possible loads occurring at the site of the system. Typical ones that must be considered first include:

• Internal and external pressure;
• Occasional impact loads
• Rapidly changing pressures;
• Weight under operating or testing conditions
• Wind loads, snow loads, vibrations and earthquake loads
• Reactions at supports
• Temperature influence

Design pressure

          This parameter is defined as not less than the maximum pressure difference between the inside and outside of the pipeline or between any enclosed areas of the pipeline that occurs under the most severe loading conditions in service limit A. The design pressure must include allowances for pressure surges, control errors, and system configuration effects such as static pressure. It is worth noting that this definition of design pressure includes surges that would otherwise be in the occasional range.

          The design pressure must be used in calculations made according to paragraphs NB-3221, NB-3227.1, NB-3227.2, NB-3227.4, NB-3228.1, NB-3228.2 and NB-3231. The specified working pressure at the relevant time must be used in calculations made according to NB-3222, NB-3228.3 and NB-3232.

Design temperature

          The design or design temperature shall not be less than the expected maximum average metal temperature through the thickness of the part under consideration for which Level A service limits are specified. If the component is locally heated, for example by induction or internal heat generation, the effect of such heat input shall be taken into account in establishing the design temperature. The design temperature shall take into account control errors and system configuration effects.

The design temperature shall be used in calculations in conjunction with the design pressure and mechanical loads. The actual metal temperature at the point under consideration shall be used in all calculations where the specified working pressure is required.

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Here, only the gasket reinforcement remains. The graphite has completely disappeared.

Graphite must be as little contaminated with sulfur and phosphorus as possible. How to test the purity of graphite? This is stated in the standard EN 14772 Flanges and their connections — Quality assurance control and testing of gaskets in accordance with EN 1514 and EN 12560 series standards.

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Ten projekt jest w trakcie spawania ale taka symulacja nie była wtedy zrobiona. Były za to tylko szacunki w/g DNV.

To jest model

To są wyniki prędkości z symulacji mechaniki płynów

I potem wyniki z mechaniki płynów były danymi do symulacji naprężenia

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