---

4.5 Design documentation

• .5.1 General

Any pipe installation shall be made on basis of design documentation that is sufficiently detailed to ensure execution of the project presupposed quality.

If the installation is changed during execution the design documentation shall be changed accordingly.

General design documentation in all project classes shall comprise:

1. general operational data,

2. data related to the pipeline,

3. specifications for quality control.

• .5.2 Operational data

Operational data:

1. design life, design pressure and design temperature,

2. number of operating temperature and pressure cycles and their duration occurring during the life of the pipelines (estimated pipeline operating pattern over its life).

Application rule:

The relevant values for both summer and winter conditions as well as the expected number of full cycles should be specified.

• .5.3 Data related to the pipeline

Data on pipeline location, materials and special provisions.

a) Data on the pipeline route

Drawings must contain all information required for a safe and reliable design, such as:

1. map of the planned route,

2. the longitudinal profile,

3. the location of the pipeline with respect to other structures, including intersecting or parallel pipelines or cables, buildings and other obstacles,

4. locations of horizontal and vertical bends, tees and reducers, casings, fixpoints, concrete ducts, etc.,

5. information on civil engineering works and special constructions.

Application rule:

Above data may be presented in the form of:

• a geographical map with, where applicable, an indication of the area covered by the individual route maps,

• route maps or similar drawings,

• detail maps and drawings standard structures, indicating the route map(s) to which they apply and providing all information needed for assessment of the design and installation.

The following drawings can be required:

• drawings of pipeline elements, fixed points, casings, etc.,

• isometric calculation drawings for special structures,

• distances between the pipeline and buildings (survey distance) and project class, on a separate list or route map,

• drawings of sheet-piling structures (pile driving plan).

2. Data related to pipeline dimensions:

1. outside diameters and tolerances,

2. nominal wall thickness and tolerances,

3. relevant data on fittings, including bend radii or other information relating to the pipeline element (reducers, tees, etc.),

4. corrosion allowances if applied,

5. data on abutting structures and supports which affect the distribution of forces acting on the medium­carrying pipeline.

2. Material data:

1. material specifications and certificates.

2. Installation data.

Information may be required on the following aspects, among others:

1. any pre-stressing applied to the pipeline, and the point at which and methods by which this pre-stressing is applied,

2. small angular deviations and permitted elastic bending radii applied to the pipeline, both permanent and temporary,

3. test pressure,

4. installation temperature.

2. As built drawings:

1. registration of location.

Application rule:

An installation plan should include the items a) to d).

4.5.4 Specifications for quality control

Application rule:

A plan for quality control should be elaborated for each project.

Quality control can e g. be divided into five stages:

• procurement,

• design,

• installation and approval,

• setting into operation,

• operation phase.

Quality control should be ensured for each stage covering the following domains:

• management and organisation of the quality control,

• management and organisation of the inspection.

It is recommended to

• compare the draft project with the specified objectives and the conditions of the intended operation,

• check the design,

• check the preinsulated components,

• check each stage of the execution, paying special attention to the construction details,

• require the inspections, tests and certificates specified in the quality control plan for applied materials prior to setting into operation.

During each stage of execution the supplier, the manufacturer and the owner should keep the complete documentation updated:

• description of materials,

• quality control plan,

• design report,

• report on setting into operation,

maintenance records,

inspection certificates for the materials, works certificates, welding, tests, etc., as specified in the quality control plan, report on transfer to the user.

5 Components and materials

Preinsulated bonded pipe systems for district heating having a pipe assembly of steel service pipe, polyurethane thermal insulation and an outer casing of high density polyethylene shall as a minimum comply with the basic material requirements in EN 253, EN 448, EN 488 and EN 489.

All materials significant to the proper functioning of the system shall possess stable properties during the service life of the system, considering the temperatures and other actions to which the materials will be exposed. Fatigue, creep and ageing shall be considered in this context.

When designing the system the properties of the components shall be calculated in values, which are valid throughout the entire service life of the system.

Application rule:

Properties, which are not directly influencing the service life of the system such as thermal conductivity, should be calculated with weighted average values.

To the extent to which preinsulated pipes, fittings and joints, not covered by the aforementioned standards, are used for the circulation of district heating water the necessary requirements for material properties, strength and durability shall be substantiated on basis of relevant European Standards, or it shall be otherwise documented that properties and system design comply with the functional requirements of this standard throughout the service life of the system.

Non standardized components shall fulfill the requirements for standardized components whenever applicable.

Steel pipe components under the scope of this standard are:

1. straight pipe,

2. bends,

3. tees and branch connections,

4. reducers and extensions,

5. other steel components like wall penetrations and single action compensators.

The technical delivery condition of the service pipe shall be in accordance with Table 5 with diameter tolerances according to EN 253.

Table 5 — Technical delivery conditions for service pipes

Application rule:

EN 253 specifies stricter tolerances on diameter than specified in the above mentioned steel standards.

B) deleted text

All steel pipes and components used for manufacturing of pipe assemblies under the scope of this standard shall as a minimum be delivered to the manufacturer with a ‘Type 3.T certificate according to EN 10204.

The manufacturer shall keep documentation of the certificates. The certificate shall on request be passed on to the customer.

Values for the yield strength at design temperature shall be derived from the specified minimum yield strength or 0,2 %-proof stress at elevated temperature given by the relevant material standards. These specified minimum values guaranteed for the delivery condition can be used for design purposes, unless heat treatment is known leading to lower values. In such cases the values to be used shall be agreed upon by the parties involved.

However, for the calculation of the yield strength of steel grade P 235 GH, at the design temperature range 50 °С < T< 140 °С, the following formula shall be used:

R_e= 227 - 0,28 (T-50) N/mm²

Up to design temperatures of 50 °С, the value of R_e at 20 °С shall be used in the calculation.

In case steel pipe or pipe components are delivered without the required certificate according to 6.2.2 the specified minimum yield strength shall be divided by an extra safety factor ^п,_уіеМ= 1,2. (This factor is to be multiplied by the partial factor for yielding of base material, according to 6.4.2.)

Application rule:

Tests performed by the steel pipe manufacturer at elevated temperatures to determine the yield strength values for a specific material delivery may lead to acceptance of a higher yield strength value at elevated temperatures compared with the values specified in the relevant standard.

Up to design temperatures of 50 °С, the value of R_e at 20 °С shall be used in the calculation.

For the calculation of the yield strength of steel grades P 235 TR-1and P 235 TR-2, at the design temperature range 50 C < Ts 140 C, the following formula shall be used:

R_e= 227 - 0,28 (T-50) (N/mm²)

In other cases, where the material standards for unalloyed and low alloy steels show no specified value for the yield strength at elevated temperatures, the following formula shall be used:

720 -T ₂

^RpM = ^R” 1755“ (N/mm²) for 50 C < T.

Application rule:

The following formulas should be used for non alloy or low alloy steel with temperatures up to 140 C:

£■ = [21,4- — j-10⁴

E

(N/mm²) О

) I 175J

B) a = | 11,4 + — |-10“⁶ (1/K)®1

I 129J

For simple design and temperatures up to 100 °С the value of the product E a may be valued equal to 2,52 N/mm²/K.

The use of mitred bends made from straight pipe sections for the service pipe is normally not allowed.

Bends and tees shall normally be made of steel with the same (or higher) specified minimum yield strength than the adjacent straight pipes.

When installing a bend or a tee in a pipe system, the nominal wall thickness of the bend or tee at the welding ends shall normally not be less than the nominal wall thickness of the adjacent straight pipes.

Only set-on branches shall be used. The use of branches welded into the run pipe is not permitted.

^x I

Figure 4 — Set-on branch

Tees may be reinforced by increasing the wall thickness of the run pipe and/or the branch pipe or by compensating plates to withstand the internal pressure, bending moments and axial compressive forces according to the requirements of Annexes A and C.

Application rule:

For extruded tees for project class C the nominal design stress should be generally reduced to 90 % of <7_d given in 5.2.3.

Reinforcement of tees by compensating plates in project class C is limited to a diameter ratio of d_ob/d_or< 0,8 where d_ob and d_or are the outer diameters of the branch and the run pipe respectively.

Reducer material shall have the same or higher yield strength as the adjacent straight pipes.

Annex A specifies additional requirements for non standardised components.

Application rule:

As an alternative to ISO 3419 an equivalent European or national standard may be used. See 3.1.5 of EN 448:2009.

Other components like wall penetrations E) deleted text О shall be considered as non-standardised components for which the conditions of 5.1.2 apply.

The thermal insulation shall comply with the requirements of EN 253.

Application rule:

Characteristic values for PUR foam:

Elasticity modulus: E_PUr = 6,5 MPa (long term at 140°C)

E_pur= 10,0 MPa (at 23°C)

Concerning insulation thickness, see Annex D.

The PE casing and welding of PE casing shall comply with the requirements of EN 253, EN 448 and EN 489.

Materials selected for use in expansion cushions shall provide the required flexibility, be chemically stable and possess the required strength, during the entire service life of the pipe system at the design range of temperatures.

The thickness of the cushion shall be selected so that the surface temperature at the PE casing pipe is not exceeding 50 °С.

Elasticity modulus as a function of the percentage of compression (secant modulus) shall be specified by the manufacturer based on tests.

Application rule:

Expansion cushions should be closed cell and of a type preventing the progressive compaction caused by sand backfill of the soil cavity occurring after pipe displacement.

When load-deformation curves made up from uni-axial tests are used it should be observed that the cushions in practice will be approximately twice as rigid due to Poisson’s ratio.

Preinsulated valves shall comply with EN 488.

The applied materials and the fabrication methods shall be such that the design conditions can be fulfilled throughout the entire service life.

Valves and accessories shall be dimensioned to withstand operational conditions and external actions in accordance with the relevant chapters and annexes of this standard. Special attention shall be paid to ensure that high axial compressive forces in restrained pipelines parts can be taken up.

Preinsulated valves for buried installation shall be designed in such a way that they require a minimum of maintenance.

Any preinsulated component shall be fully welded.

Valves and accessories shall be clearly and durably marked allowing identification of manufacturer, pressure class (if applicable), design temperature, etc.

The manufacturer shall keep documentation that the components have been designed according to this standard.

Application rule:

Each prefabricated component which is a part of a district heating pipe system should by labelling be furnished with a declaration stating the conditions the component has been designed and manufactured for.

The declaration shall specify following design data:

1. material and grade,

2. max. operating pressure,

3. max. axial stress for straight pipe parts or maximum axial force,

4. max. bending moment (for valves, one time compensators),

5. installation method:

1. conventional installation methods ( e.g. pre-heating, single action compensators),

2. cold installation.

6 Actions and limit states

Design and calculation must be performed in such a way that sufficient documentation is provided that the pipe system will be able to withstand all relevant actions and fulfil the safety and functional requirements during its entire service life.

Application rule:

For a given pipeline system the design and calculation procedure, as presented in Figure 5, can be followed. It includes the following steps:

1. Assessment of design data.

2. Classification of actions.

3. Sub-division of the pipeline, along the proposed route into sections for stress analysis.

4. Determination of project class and options for simplified analysis.

5. Selection of the combinations of actions to be considered.

6. Limit state design (and the safety factors to be applied).

7. Determination of cross sectional forces and displacements due to the action combinations calculated.

8. Calculation of the stresses (and/or strains).

9. Selection of assessment criteria (limit states and associated limit values).

10. Checking of the calculated stresses, strains and deformations with the limit values.

The depth of analysis for each of these steps depends on:

— complexity of the pipe system in the section considered,

• physical pipe parameters,

project class

.

In project classes A and В design and installation can be performed on the basis of generalised documentation, provided it is in compliance with the requirements of this standard and fulfil the prerequisites (pressure, temperature, traffic actions, etc.) corresponding to local conditions.

Application rule:

Generalised documentation can be e g. company standards or manufacturers’ manuals, provided that the company or manufacturer keeps documentation that the company standards or manufacturers manuals are in compliance with this standard.

Proven construction details can be installed on the basis of available experience provided that the new construction is not subject to more severe actions.

Application rule:

Fatigue life should always be checked, by estimation of the equivalent number of full temperature cycles, for the pipe system considered, see C.5.2. The number of cycles must be lower than the number of full temperature cycles presupposed in the generalised documentation (minimum values, see Table 9).

Actions shall be determined in such a way that the calculation models used provide sufficient documentation that the installation complies with given functional requirements.

Application rule:

The characteristic value of a stochastic variable action is in principle defined as the action value which, at a probability of 95 %, will not be exceeded.

Selfweight may, in most cases, be calculated on the basis of the nominal dimensions and mean unit masses.

For the assessment of actions and possible combinations, installation phase and operating phase and any foreseen modification in the use of the current installation and areas shall be taken into consideration.

Application rule:

The installation phase includes transport, handling, welding, laying, backfilling, testing, commissioning (note that actions arising during the installation phase may persist during the operating phase, e g. pre-stressing).

The operating phase includes the situation after completion of installation, whether the pipeline is in service or not.

Design actions are obtained by multiplying (or dividing) the characteristic values by partial safety factors, y₃.

The actions and partial safety factors that shall be taken into account in the design are presented in Table 6.

Actions can be divided into:

1. force-controlled actions and

displacement-controlled actions.

Table 6 — Classification of actions and partial safety coefficients

FORCE-CONTROLLED ACTIONS	PARTIAL SAFETY FACTORS /a
PRESSURE operating pressure pressure surges. Note 1 external pressure internal vacuum. Note 2 test pressure	1,2 1,2 1,05 1,2 1,0
PERMANENT ACTIONS Selfweight pipe assembly water accessories (valves, etc.) buoyancy neutral/passive soil pressure settlements. Note 3	1,0 1,0 1,0 1,2 1,0-1,5**) 1,2
VARIABLE ACTIONS — traffic — wind — snow	1,0-1,5**)
DISPLACEMENT-CONTROLLED ACTIONS
TEMPERATURE VARIATIONS — variations during operation — start-up/shut-down cycles — lateral soil reactions — soil/pipe friction	1,0
PERMANENT ACTIONS pre-stressing thermal, electrical, mechanical settlements. Note 4 differential settlements deformations during installation	1,0 1,5 1,0 1,2 1,0
NOTE 1 Application rule: Steps in design and operation should be taken to reduce the risk of harmfull pressure surges. In project class C the possibility and consequences of pressure surges should be analysed. NOTE 2 The design pressure for vacuum > -1 bar. NOTE 3 If it is not acceptable that the pipe follows soil settlement the weight of soil should be treated as a force-controlled action. NOTE 4 Depending on the standard used for actions.

Скачать бесплатно