Federal Environmental, Industrial and Nuclear Supervision Service (Rostekhnadzor)
FEDERAL RULES AND REGULATIONS IN THE FIELD OF ATOMIC ENERGY USE
Approved by the Decree of the Federal Environmental, Industrial and Nuclear Supervision Service dated October 04, 2004 No. 6
STANDARDS
FOR STRENGTH CALCULATIONS OF EQUIPMENT COMPONENTS AND PIPELINES FOR MARINE NUCLEAR STEAM-GENERATING PLANTS WITH WATER-WATER REACTORS
NP-054-04
Effective
from 5 January 2005
Moscow 2004
UDC 621.039
STANDARDS FOR STRENGTH CALCULATIONS OF EQUIPMENT COMPONENTS AND PIPELINES FOR MARINE NUCLEAR STEAM-GENERATING PLANTS WITH WATER-WATER REACTORS. NP-054-04
Federal Environmental, Industrial and Nuclear Supervision Service - Moscow, 2004
These rules and regulations are intended for organizations and enterprises performing strength and durability calculations of equipment components and pipelines of marine nuclear steam-generating plants.
These standards apply to components of safety classes 1-3 as per General Provisions for Assurance of Safety of Nuclear Power Plants of Vessels of Marine Steam-Generating Plants with Water-Water Reactors - pressurized, operating at a coolant temperature not exceeding 623 K.
The standards set the general requirements to performing strength and durability calculations of equipment and pipelines at the stages of design, construction and operation of marine nuclear steam-generating plants, as well as to performing vibration resistance, vibration strength and cyclic strength tests.
First issue*.
Contents
Abbreviations - Conventional designations - General terms and definitions.General terms and definitions
1. General
1.1. Purpose and scope of application
1.2. Principles underlying the Regulations
2. Nominal permissible stresses
3. Selection of basic dimensions
4. Checking calculation
4.1. General
4.2. Stress Calculation Procedure
4.3. Calculation for static strength
4.4. Calculation for stability
4.5. Calculation for cyclic strength
4.6. Calculation for resistance to brittle fracture
4.7. Calculation for shock resistance
4.8. Calculation for vibration strength
5. Experimental assessment of vibration stability and vibration strength
6. Testing model samples and elements of full-size structures for cyclic strength
*Developed at the Scientific and Engineering Centre for Nuclear and Radiation Safety. The development was implemented with participation from N.I. Karpunin, I.I. Neshcheretov (Scientific and Engineering Centre for Nuclear and Radiation Safety), S.V. Yevropin, A.V. Tashkinov (Engineering Centre of Strength and Material Science for Nuclear Engineering Elements), V.M. Anoshin (OKBM Afrikantov).
Remarks from specialists of FSUE Krylov State Research Centre, JSC Iceberg CDB, structural units and inter-regional territorial districts were considered and taken into account at development.
Abbreviations
AO - abnormal operation
NO - normal operation
SGP - steam-generating plant
TS - technical specifications
Conventional designations
| - nominal wall thickness, mm |
| - design wall thickness, mm |
| - total increase in wall thickness, mm |
| - temporary resistance (strength limit) at design temperature Т. MPa |
| yield limit at design temperature T, MPa |
| - safety coefficient for strength limit |
| - safety coefficient for yield limit |
| - design temperature, K |
| - nominal permissible stress, MPa |
| - rated permissible stress in bolts and pins, MPa |
| - critical stress intensity coefficient at design temperature Т, МPa*m1/2 |
General terms and definitions
The following terms and definitions are used for the purposes of this document.
1. Amplitude of stresses is the half of the difference of maximum and minimum stresses arising in a cycle of stress variation.
2. Vibratory loads are loads from the hull structure and foundations of a vessel, caused by running vibration of the first and blade order, the disturbing force from a nearby mechanism and from hydrodynamic forces.
3. Hydraulic test is loading of equipment or pipelines with pressure for their strength and air-tightness to be checked after manufacture, assembly, the period of operation, repair or replacement of equipment.
4. Group of categories of stresses is the totality of categories of stresses causing a certain limit state.
5. Durability is the property of equipment or pipelines (and SGP, as a whole) to remain operable till the onset of a limit state.
6. Tightening of bolts and pins is loading of equipment or pipeline caused by assembling of threaded connections.
7. Reactor power change is an operating mode in which a transition occurs from one steady-state mode of reactor operation to another (with the exemption of the start-up and shutdown modes).
8. Category of stresses is the type of stress distinguished based on a feature (by the type of distribution diagram; by the extent of the zone of action; by the type of loading causing the stress in question, etc.).
9. Criterion of limit state is a feature, or a totality of features of a limit state of elements established by regulatory and (or) engineering (design) documents.
10. Assigned service life is the designed calendar duration of operation of a SGP (or elements thereof), on attainment of which further operation of equipment or pipelines (and the plant, as a whole) may only be continued upon a special decision to be made based on substantiation of safety of such operation.
11. Anticipated operational occurrence is any disturbance in the SGP operation with deviation from the established operation limits and (or) conditions.
12. Normal operation is operation of SGP within the designed operation limits and conditions.
13. Shutdown is an operating mode in which the temperature and external loads in the SGP vary from the values of parameters of any operating mode to the initial values of parameters of the subsequent start-up mode.
14. Steam-generating plant is a part of a marine nuclear power plant comprising a reactor, equipment, the primary and secondary circuit pipelines, and a steam generator.
15. Half-cycle of stress variation is continuous variation of stress from the maximum (minimum) value to the minimum (maximum) value.
16. Limit state is the state of elements, at which their further operation is unacceptable or inexpedient, or bringing them back to an operable condition is impossible or inexpedient. Once elements come to a limit state, their operation must be temporarily suspended, or definitively terminated (they will be withdrawn from operation for repair or decommissioned).
17. Start-up is an operating mode, in the process of which external loads and temperatures in the SGP vary from initial values to values corresponding to the steady-state mode. During start-up, the temperature and external loads may exceed the values corresponding to the steady-state mode.
18. Operable condition, operability is the state of elements, at which the values of all the parameters characterizing the ability to perform assigned functions meet the requirements of regulatory and (or) engineering (design) documents.
19. Design pressure is the maximum overpressure acting on the equipment or pipeline used in the calculation for selection of basic dimensions at which the operation of this equipment or pipeline is allowed under the NO.
20. Design temperature is the temperature of the wall of equipment or pipeline equal to the maximum arithmetic mean of temperatures on its outer and inner surfaces in one section at the SGP steady-state operation mode at the maximum capacity.
21. Service life is accumulated operational time of equipment or pipelines from the beginning of their operation or resuming the same after repair till transition to the limit state.
22. Steady-state mode is an operating mode in which the loads and temperature remain constant within ±5 % of nominal values stipulated in the engineering (design) documentation.
23. Impact load is a load characterized by its short duration (5-200 msec).
24. Conventional elastic stress is a stress beyond elasticity the value of which is determined in accordance with the Hooke's law.
25. Operation of the emergency protection system is an operating mode in which there is a change in temperatures and external loads (towards both increasing and decreasing) from their values in the steady-state mode, start-up, or shutdown, to the corresponding intermediate values.
26. Running vibration of the blade order is vibration of the hull with a frequency multiple of the speed of the propeller shaft at full speed and in the reverse mode.
27. Running vibration of the first order is vibration of the hull with a frequency equal to the speed of the propeller shaft at full speed and in the reverse mode.
28. Cycle of stress change is a change in stress from the initial value to the final value equal to the initial one, at which one maximum stress value and one minimum stress value is reached.
29. Operation conditions are conditions for the quantity, characteristics, operability and maintenance of equipment and pipelines as well as the SGP as a whole required for operation without any deviations from the operation limits.
30. Operation limits are the values of parameters and characteristics of the state of equipment and pipelines (as well as those of the SGP as a whole) established in the nuclear power installation design for normal operation.
1. GENERAL
1.1. Purpose and scope of application
1.1.1. Federal rules and regulations "Norms for strength calculation of equipment and pipelines of marine nuclear steam generation plants with water-water reactors" (hereinafter, the Rules) shall be applied in the substantiation of the strength and durability of structural elements of equipment and pipelines of marine nuclear SGP.
1.1.2. The norms shall apply to components of safety classes 1-3 according to the classification of the General Safety Provisions for Nuclear Power Installations of Vessels of marine SGP with water-water reactors under pressure operating at a coolant temperature not higher than 623 K, including pressure vessels, pump housings, valves and pipelines of SGP.
1.1.3. The norms shall not apply to the following SGP components:
§ fuel elements and assemblies;
§ rods of the control and protection system;
§ components of reactor plant internals;
§ electromechanical equipment;
§ supports and hangers of equipment and pipelines;
§ components located in shell parts of equipment and pipelines for examination of their operability;
§ packing gaskets and non-metal components of sealing assemblies.
1.1.4. The standards set the general requirements to performing strength and durability calculations of equipment and determination of service life of equipment and pipelines at the stages of design, construction and operation of marine nuclear steam-generating plants, as well as to performing vibration resistance, vibration strength and cyclic strength tests.
1.1.5. Strength calculations for equipment and pipelines at the stages of construction and operation must be performed in the following cases:
§ at least one of the values of the mechanical characteristics of the material exceeded the values used in the calculations at the design stage;
§ a change is established of conditions of mutual interaction of equipment, pipelines and support structures (jamming, take-up of clearances, etc.);
§ defects are found with dimensions exceeding the allowed dimensions set by the current regulatory documents and (or) engineering, process and operational documentation;
§ a value adopted for design, wall thinning of equipment or pipelines due to general or local corrosion or erosion has been exceeded;
§ the values used in the design, the values of loads on the equipment and pipelines at NO and (or) AO, or the stiffness characteristics of supporting structures have changed by more than 5%;
§ the actual number of NO, AO modes or tests exceeded the designed values;
§ the maximum permissible value of the cyclic metal damage allowed by the engineering documentation has been reached (or exceeded) in any area of equipment or pipeline.
1.1.6. Methods of performing calculations for the selection of basic dimensions, substantiation of strength and service life of equipment and pipelines must be stipulated in the documents of organizations involved in the design and manufacture of equipment and pipelines approved by the Federal Service for Nuclear Supervision.
1.1.7. The norms do not regulate methods of calculation of forces, temperature fields or stress-strain state. These methods must be selected by the organization performing the relevant calculations, and the software used in this case must be certified.
1.2. Principles underlying the Regulations
1.2.1. The norms use the principles of strength assessment for the following limit states:
a) viscous or brittle destruction;
b) plastic deformation throughout the cross section of the structural element;
c) loss of stability;
d) the occurrence and accumulation of residual changes in shape and dimensions, leading to the impossibility of operation of the structural element;
e) the appearance of microcracks under cyclic loading.
The calculation of the specified limit states must be carried out using short-term, and for parts made of titanium alloys - long-term characteristics of strength and ductility of materials.
1.2.2. The calculation of strength of equipment and pipelines must be carried out in two stages - calculation for selection of basic dimensions and checking calculation. When assessing the strength of equipment and pipelines, both the requirements of calculation for selection of basic dimensions and the requirements of checking calculation shall be fully satisfied. At the operational stage, it shall be allowed to skip the calculation for selection of basic dimensions.
1.2.3. When performing calculations for selection of basic dimensions, the (internal and external) pressure applied to equipment and pipelines is taken into account, and for bolts and pins the tightening force is additionally taken into account.
1.2.4. As the main mechanical characteristics of the materials used in determining the values of the nominal allowable stresses, temporary resistance (tensile strength) and yield strength are taken. Nominal allowable stresses should be set to these characteristics by introducing appropriate safety factors.
1.2.5. The values of safety factors shall be assigned on the basis of long-term practice of design and engineering, taking into account the experience of operation of equipment and pipelines.
1.2.6. When choosing the basic dimensions, the strength should be evaluated according to the following limit states: ductile fracture, plastic deformation spread over the entire cross-section of component, loss of stability, and achievement of limit deformation.
1.2.7. The checking calculation must be carried out for equipment and pipelines with selected basic dimensions or based on actual dimensions.
1.2.8. In the checking calculation, one should take into account all the loads acting on the structure (including loads from thermal effects) and consider all modes of operation.
1.2.9. The checking calculation shall comprise:
a) сalculation of static strength;
b) calculation for stability;
c) сalculation for сyclic strength;
d) calculation for resistance to brittle fracture;
e) calculation for shock resistance;
f) calculation for vibration strength.
1.2.10. The checking calculation for static strength is carried out for determination of the fact that at all values of loads and temperatures in the design SGP operation modes the stresses in the component would not exceed the permissible values determined by the limit states indicated in subitems a) and b) of item 1.2.1.
1.2.11. The calculation for stability shall be held to determine the permissible loads, an excess of which would cause the loss of stability of structural elements of equipment and pipelines.
1.2.12. The calculation for cyclic strength shall be carried out for preventing emergence of microcracks in structural elements of equipment and pipelines which are under the effect of cyclic loads. Permissible stress amplitudes are determined on the basis of the characteristics of fatigue failure resistance, which generally depend on the temperature, time, parameters of the working medium and neutron fluence, with the introduction of safety factors based on the number of cycles and on stresses. As a result of the calculation for cyclic strength, the permissible number of repetitions of operation modes and hydraulic tests shall be set for the specified values of loads and the assigned operation period.
1.2.13. The calculation for brittle destruction resistance shall be carried out by methods of fracture mechanics. On the basis of this calculation the impossibility of destruction of elements in the presence of the postulated defect (crack) within the assigned operation period shall be confirmed, and the temperature modes of hydraulic tests within the assigned operation period shall be determined.
1.2.14. Shock resistance of equipment and pipelines shall be assessed based on two limiting states. The first of them is characterized by the achievement in the most stressed areas of equipment structures and pipelines of a specified plastic deformation, and the second one - by the achievement of linear or angular displacements, at which it is possible to disrupt the operability of the components.
1.2.15. The calculation for vibration resistance shall be carried out in order to reduce the parameters of vibration loading on equipment and pipelines by adjusting the frequency of natural vibrations from the disturbing frequencies of the vibration source. The acceptability of vibration loads may be confirmed by experimental and (or) calculated method in the calculation for cyclic strength.
1.2.16. Reduced stresses to be compared with the permissible ones should be determined in accordance with the maximum shear stress theory with the exception of calculation of resistance to brittle fracture when the reduced stresses shall be determined in accordance with the maximum normal stress theory.
1.2.17. Calculation of stresses, without taking into account concentration, is carried out in the assumption of a linearly elastic behavior of the material, unless otherwise indicated. In assessing the strength outside the elasticity limits it is necessary to use conventional elastic stress.
1.2.18. The data obtained as a result of the checking calculation (stresses, stress intensity factors, cyclic metal damage, etc.) shall be compared with the corresponding permissible values.
1.2.19. In the calculations for selection of basic dimensions and in the checking calculations, an increase in the strength and yield limits under the action of neutron fluence should not be taken into account. The reduction of ductility and brittle fracture resistance characteristics should be taken into account in the relevant calculations.
1.2.20. The possible corrosive effect of working media should be taken into account both when choosing the basic dimensions (an increase to the wall thickness) and during the checking calculation.
1.2.21. It shall be allowed to substantiate the strength of structural elements of equipment and pipelines through experimental studies, methods and programs which must be established in the documents of organizations involved in the design and manufacture of equipment and pipelines approved by the Federal Service for Nuclear Supervision .
2. NOMINAL PERMISSIBLE STRESSES
2.1. Nominal permissible stresses at the design temperature T must be determined based on temporary resistance and yield limit of the component material.
2.2. The value of the nominal permissible stress [a] should be taken equal to:
■ for components other than bolts or pins,
where |
|
|
|
| for equipment and pipelines loaded with internal pressure, as well as those made of titanium alloys and loaded with internal or external pressure; |
|
| for equipment and pipelines loaded with external pressure (except for those made of titanium alloys); |
§ in bolts or pins from pressure and tightening forces
where n0.2 = 2.0.
2.3. The values of characteristics of materials used in determining the nominal permissible stresses should be taken according to the relevant regulatory documents, national standards or technical specifications for the corresponding assortment.
2.4. In the absence of characteristics of materials at design temperatures in regulatory documentation, as well as in the case of pilot application of materials of new brands or semi-finished products manufactured by a new technology, the design values of the necessary characteristics must be established on the basis of experimental studies. The adopted values must be agreed with the relevant material science organizations.
3. SELECTION OF BASIC DIMENSIONS
3.1. When performing a calculation for selection of basic dimensions, the design loads are the design pressure and tightening forces for bolts and pins. When calculating the pins of the sealing unit, the pressure of the hydraulic tests should be taken into account.
3.2. The designed wall thickness must be determined without taking into account the thickness of the anti-corrosion deposited or cladding protective layer,
3.3. The total increase in the design thickness of the component of structure is defined as
С = С1 + С2 + С3.
3.4. The addition of C1 should be taken as a negative tolerance for wall thickness; its value should be set in the engineering documentation.
3.5. The increase of C2 is a process one, designed to compensate for the possible thinning of the component during manufacture. The value of this increase is set by the design (engineering) organization in agreement with the manufacturer and shall be indicated in the engineering documentation.
3.6. The increase C3 takes into account the corrosive influence of working medium on the material of the components of structure under operation conditions. The value of this increase shall be taken according to the relevant regulatory documents.
3.7. The assumed nominal wall thickness S shall satisfy the condition
S ≥ SR + С.
3.8. The value of the designed wall thickness must be determined from the condition of non-admission in
the structure of limit states specified in sub-items a) - c) of paragraph 1.2.1, with consideration of strength reduction factors caused by holes or welded joints in the structural component.
3.9. Strength reduction factors as per paragraph 3.8 should be determined in accordance with the provisions of relevant regulations.
3.10. The calculation for selection of basic dimensions may be carried out with use of software.
4. CHECKING CALCULATION
4.1. General
4.1.1. The checking calculation at the design stage must be carried out after the calculation for selection of basic dimensions.
4.1.2. The checking calculation should be performed:
§ for nominal dimensions - at the stage of design;
§ for actual dimensions - at the stages of construction and operation (should it be necessary to perform calculations as per 1.1.5).
4.1.3. The checking calculation should be performed with taking into account all design modes of operation.
4.1.4. During the calculation, the following loads must be taken into account:
§ internal and (or) external pressure;
§ loads from tightening of bolts and pins;
§ the weight of a product as such and its content;
§ additional loads (weight of attached products, including pipe insulation, loads leading to deformation in the manufacture and installation, etc.);
§ forces from reactions and displacements of supports and pipelines;
§ thermal impacts;
§ vibration loads;
§ impact caused by ship collisions and other navigational situations (the vessel being stranded, collision with rocks, icebergs, etc.).
4.1.5. The main design modes of operation are:
§ steady-state mode;
§ start-up;
§ tightening of bolts and pins;
§ operation of the emergency protection system;
§ reactor power change;
§ shutdown;
§ hydraulic tests;
§ actuation of safety valves;
§ abnormal operation;
§ transition from natural circulation to forced circulation.
4.1.6. At the checking calculation it is necessary to use the physical and mechanical characteristics of the basic metal specified in national standards, standards of organizations or in TS on materials of the corresponding assortment.
4.1.7. During the checking calculation of the deposited or clad walls, the stresses in the wall and deposit welding are considered with due regard to temperature stresses caused by the difference in the coefficients of linear expansion of the base metal and deposit welding.
4.1.8. The need to take into account residual stresses (welding, surfacing, installation, etc.) in specific sections of the checking calculation shall be established in the relevant regulatory documents.
4.2. Stress Calculation Procedure
4.2.1. For the structural element under consideration of equipment and pipeline, on the basis of analysis of operating conditions, manufacturing and installation, a possible sequence of alternation in time of operating modes and loading, including test conditions, NO and AO, must be established.
4.2.2. On the basis of the adopted sequence of operating modes and loading, calculations in the elastic formulation should determine the values of the main stresses without taking into account the concentration and temperature effects. For the initial and final moments of time, the values of the main stresses must be zero.
4.2.3. According to the adopted sequence of modes of operation and loading, it is necessary to determine the stress state of the element taking into account the temperature effects and stress concentration and to plot the graphs of variation of reduced conventional elastic stresses over time.
4.2.4. Requirements to plotting of the above graphs, use of theoretical and effective coefficients of concentration of stresses, as well as to formation of categories of the reduced stresses for check of various criteria of durability and allocation of cycles of variation of conventional elastic reduced stresses shall be established in the documents of organizations which are engaged in design and manufacture of the equipment and pipelines approved by Federal Service for Nuclear Supervision.
4.3. Calculation for static strength
4.3.1. In calculating the static strength, it is necessary to take into account the design loads specified in paragraph 4.1.4, in addition to vibration and impact loads, as well as all the operational modes listed in paragraph 4.1.5.
4.3.2. The static strength assurance conditions must limit the stresses causing:
§ viscous or brittle destruction;
§ plastic friction throughout the cross section of the structural element;
§ crushing the surface of the structural element;
§ shear;
§ deformation.
4.3.3. The strength conditions shall be set by limiting the level of relevant categories of stresses relative to the values of RTр0,2 or [σ].
4.3.4. The total stress level within the group of categories of stresses causing uniform plastic deformation in the cross section of the structural element under the action of mechanical ;loads must be no more than:
§ [σ] at NO;
§ 1.2 [σ] at AO.
4.3.5. The total level of stresses included in the group of stress categories that cause a plastic hinge in the cross section of the structural element (except for bolts and pins) under mechanical loads must be no more than:
§ 1.3 [σ] at NO.
§ 1.6 [σ] at AO.
4.3.6. The specific dependencies used to test the static strength of different groups of stress categories are established in the relevant regulatory documents.
4.4. Calculation for stability
4.4.1. The stability calculation shall be performed in relation to the static loading of structural elements of equipment and pipelines. For impact loading, refer to section 4.7.
4.4.2. The stability check should be performed for elements of vessels (shells, convex bottoms) with joint or separate action of external pressure exceeding the internal, and compressive forces.
4.4.3. Under the strength conditions, the permissible values of external pressure and compressive forces should be determined.
4.4.4. Methods of strength calculation and strength conditions are set in the relevant regulatory documents.
4.5. Calculation for cyclic strength
4.5.1. The determination of the permissible number of cycles by given stress amplitudes or permissible stress amplitudes for a given number of cycles should be carried out:
1) according to design fatigue curves, which characterize, within the limits of their application, the dependence between the permissible amplitudes of conventional elastic stresses and the permissible numbers of cycles;
2) according to the equations relating permissible amplitudes of conventional elastic stresses and permissible numbers of cycles.
4.5.2. In the calculation it is necessary to take into account the influence on the cyclic strength of the material characteristics (including those of welded joints), the asymmetry of the cycle of conventional elastic reduced stresses (including those caused by the action of residual stresses), temperature, neutron fluence, the impact of the coolant.
When calculating parts made of titanium alloys, the influence of creep effects should be taken into account.
4.5.3. The strength condition in the presence of different cyclic loads should be determined by the accumulation of fatigue damage up to the permissible value.
4.5.4. In cases where low-frequency cyclic stresses associated with starting-up, shutdown, power change, actuation of emergency protection, or other modes, are accompanied by the imposition of high-frequency stresses, such as those caused by vibration, temperature pulsation when mixing coolant flows with different temperatures, the cyclic strength is calculated with due regard to high-frequency loading.
4.5.5. The evaluation of cyclic strength on the basis of fatigue curves obtained experimentally for the considered loading conditions and the state of the metal of the structure, or the results of tests of prototypes or their models designed and manufactured in accordance with the requirements for standard structures, shall be allowed.
4.5.6. Methods of calculation of cyclic strength, as well as calculated and experimental determination of fatigue curves, shall be established in the documents of the organizations which are engaged in design and manufacture of equipment and pipelines approved by Federal Service for Nuclear Supervision.
4.6. Calculation for resistance to brittle fracture
4.6.1. The calculation for brittle fracture resistance should be carried out for all modes of NO, AO and hydraulic tests.
4.6.2. Areas shall be subject to analysis, in which one can expect the highest values of the stress intensity factors K1 for the calculated defect, or the minimum values of fracture toughness К1С, or the smallest ratio K1C/K1.
4.6.3. When calculating the elements made of titanium alloys, it is necessary to take into account the viscous nature of their destruction, and to use RTp0.2 the value of the critical opening of the alloy crack as the strength characteristics.
4.6.4. The choice of design defect, design characteristics of fracture toughness, critical brittleness temperature, values of residual stresses and the subsequent strength analysis should be carried out in accordance with the provisions of the documents approved by the Federal Service for Nuclear Supervision of organizations involved in the design and manufacture of equipment and pipelines.
4.6.5. It is allowed not to carry out brittle fracture resistance calculation for components of structure that are not exposed to radiation (or exposed at temperatures of 523623 К up to the fluence of no more than 1022 neutrons/m2 at the neutron energy E ≥ 0.5 MeV) in the following cases:
1) materials of the components of structure (including welded joints) have a yield limit at a temperature of 293 K less than 300 MPa, and the wall thickness of the component of structure is not more than 25 mm;
2) materials of the components of structure (including welded joints) have a yield limit at a temperature of 293 K less than 600 MPa, and the wall thickness of the component of structure is not more than 16 mm;
3) the wall thickness of the structural component under consideration meets the following condition:
| mm |
at КT1С in MPa
and RTp0.2 in MPa (the values of the both characteristics should be taken at the lowest operating temperature and the state corresponding to the end of operation).
4.7. Calculation for shock resistance
4.7.1. The basis for the calculation of shock resistance is the requirement of reliable operation of equipment and pipelines of SGP under the impact of shock loads specified in paragraph 4.1.4. Specific parameters of impact loads are determined by the design of the SGP and (or) the technical assignment for the strength calculation.
4.7.2. The check of shock resistance should be performed for allowable stresses and allowable displacements.
4.7.3. At determination of allowable stresses, one should take into account:
§ effect of strain rate and design temperature on the dynamic yield limit,
§ admissibility of limited plastic deformation in the most loaded areas of the element under short-term external imaction;
§ the materials being particularly prone to brittle fracture
4.7.4. The allowable displacement should be established from the conditions of impossibility of collisions of the designed equipment and pipelines with adjacent ones or with vessel structures, or unacceptable damage.
4.7.5. The calculation should be performed for the NO modes.
4.7.6. In the calculation, the stresses from operating loads should only be added to dynamic ones, when they exceed the latter by more than 10% (otherwise they may be ignored).
4.7.7. The determination of allowable stresses, displacements and the subsequent analysis of the strength of equipment and pipelines should be carried out in accordance with the relevant regulatory documents.
4.8. Calculation for vibration strength
4.8.1. Th assessment of the vibration strength of equipment and pipelines should be made for vibration loads caused by the rotation of the propeller shaft of the vessel, as well as other sources of forced vibrations, if any.
4.8.2. The basic requirements of vibration resistance should ensure the absence of resonance with vibration loads acting on the equipment and pipelines in the frequency range corresponding to the one designed.
4.8.3. In cases where it is not possible to ensure the absence of resonance, it is allowed not to comply with the requirements of paragraph 4.8.2 subject to the mandatory confirmation of vibration resistance by experiment or calculation, as well as based on the results of the analysis of vibrations recorded in the process of commissioning and (or) on the installation being operated.
4.8.4. The calculation of vibration resistance of equipment and pipelines should be carried out according to the methods given in the relevant regulatory documents.
4.8.5. The general requirements to experimental assessment of vibration strength are specified in section 5.
4.8.6. The estimated assessment of vibration strength is recommended to be carried out with taking into account the requirements of paragraph 4.5.4.
5. EXPERIMENTAL ASSESSMENT OF VIBRATION STABILITY AND VIBRATION STRENGTH
5.1. Tests for the detection of the resonances should be held in cases stipulated in paragraph 4.8.3 to identify the vibration frequencies of the equipment and pipelines in accordance with the frequency range for the strength calculation stipulated in the design and (or) the technical assignment.
5.2. Vibration stability tests should be carried out to verify the ability of the equipment and pipelines to perform their functions and maintain their parameters during the impact of vibration within the limits specified by the design and (or) the technical assignment for the performance of the strength calculation.
5.3. Vibration strength tests should be carried out to verify the ability of the equipment and pipelines to withstand the destructive effects of vibration, to perform their functions and maintain their parameters after the impact of vibration within the designed limits.
5.4. Test methods according to items 5.1 - 5.3, including requirements to preparation of the equipment for tests, the procedure of performance of tests and assessment of their results, are established in the relevant regulatory documents.
6. TESTING MODEL SAMPLES AND ELEMENTS OF FULL-SIZE STRUCTURES FOR CYCLIC STRENGTH
6.1. The cyclic strength characteristics established in the tests should be used:
§ for substantiation of the cyclic strength of structural elements of equipment and pipelines with the determination of safety factors based on the amplitudes of conventional elastic stresses and the number of cycles;
§ for determination of the effective concentration coefficients at cyclic loads.
6.2. Requirements for the design, materials, manufacturing technology, control of prototypes and elements of full-scale structures for testing, as well as to the conditions, procedure of tests and methods for determining the effective stress concentration coefficients are set in the relevant regulatory documents.