Metallic industrial piping - Part 3: Design and calculation

1.1 The purpose of EN 13480 is to define the requirements for design, manufacture, installation, testing and inspection of industrial piping systems and supports, including safety systems, made of metallic materials (but initially restricted to steel) with a view to ensure safe operation.
1.2 EN 13480 is applicable to metallic piping above ground, ducted or buried, independent of pressure.

Metallische industrielle Rohrleitungen - Teil 3: Konstruktion und Berechnung

Tuyauteries industrielles métalliques - Partie 3 : Conception et calcul

No scope available

Kovinski industrijski cevovodi - 3. del: Konstruiranje in izračun - Dopolnilo A3

General Information

Status
Published
Publication Date
18-Aug-2020
Withdrawal Date
27-Feb-2021
Current Stage
6060 - Definitive text made available (DAV) - Publishing
Start Date
19-Aug-2020
Due Date
16-Oct-2020
Completion Date
19-Aug-2020

Relations

Buy Standard

Amendment
EN 13480-3:2018/A3:2020
English language
32 pages
sale 10% off
Preview
sale 10% off
Preview
e-Library read for
1 day
Draft
EN 13480-3:2018/oprA3:2019
English language
30 pages
sale 10% off
Preview
sale 10% off
Preview
e-Library read for
1 day

Standards Content (Sample)

SLOVENSKI STANDARD
SIST EN 13480-3:2018/A3:2020
01-oktober-2020
Kovinski industrijski cevovodi - 3. del: Konstruiranje in izračun - Dopolnilo A3
Metallic industrial piping - Part 3: Design and calculation
Metallische industrielle Rohrleitungen - Teil 3: Konstruktion und Berechnung
Tuyauteries industrielles métalliques - Partie 3 : Conception et calcul
Ta slovenski standard je istoveten z: EN 13480-3:2017/A3:2020
ICS:
23.040.10 Železne in jeklene cevi Iron and steel pipes
77.140.75 Jeklene cevi in cevni profili Steel pipes and tubes for
za posebne namene specific use
SIST EN 13480-3:2018/A3:2020 en,fr,de
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

---------------------- Page: 1 ----------------------
SIST EN 13480-3:2018/A3:2020

---------------------- Page: 2 ----------------------
SIST EN 13480-3:2018/A3:2020


EN 13480-3:2017/A3
EUROPEAN STANDARD

NORME EUROPÉENNE

August 2020
EUROPÄISCHE NORM
ICS 23.040.01
English Version

Metallic industrial piping - Part 3: Design and calculation
Tuyauteries industrielles métalliques - Partie 3 : Metallische industrielle Rohrleitungen - Teil 3:
Conception et calcul Konstruktion und Berechnung
This amendment A3 modifies the European Standard EN 13480-3:2017; it was approved by CEN on 12 July 2020.

CEN members are bound to comply with the CEN/CENELEC Internal Regulations which stipulate the conditions for inclusion of
this amendment into the relevant national standard without any alteration. Up-to-date lists and bibliographical references
concerning such national standards may be obtained on application to the CEN-CENELEC Management Centre or to any CEN
member.

This amendment exists in three official versions (English, French, German). A version in any other language made by translation
under the responsibility of a CEN member into its own language and notified to the CEN-CENELEC Management Centre has the
same status as the official versions.

CEN members are the national standards bodies of Austria, Belgium, Bulgaria, Croatia, Cyprus, Czech Republic, Denmark, Estonia,
Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway,
Poland, Portugal, Republic of North Macedonia, Romania, Serbia, Slovakia, Slovenia, Spain, Sweden, Switzerland, Turkey and
United Kingdom.





EUROPEAN COMMITTEE FOR STANDARDIZATION
COMITÉ EUROPÉEN DE NORMALISATION

EUROPÄISCHES KOMITEE FÜR NORMUNG

CEN-CENELEC Management Centre: Rue de la Science 23, B-1040 Brussels
© 2020 CEN All rights of exploitation in any form and by any means reserved Ref. No. EN 13480-3:2017/A3:2020 E
worldwide for CEN national Members.

---------------------- Page: 3 ----------------------
SIST EN 13480-3:2018/A3:2020
EN 13480-3:2017/A3:2020 (E)
Contents Page
European foreword . 3
1 Modification to Clause 2, Normative references . 4
2 Modification to 5.2.4, Steel castings . 4
3 Modification to Annex A, Dynamic effect . 4
4 Modification to Clause G.3, Physical properties of steels . 27
5 Introduction of a new Clause G.4, Material properties of carbon steel at elevated
temperatures . 27
6 Introduction of a new Annex R, Surveillance of components operating in the creep
range . 28
7 Modification to Bibliography . 32

2

---------------------- Page: 4 ----------------------
SIST EN 13480-3:2018/A3:2020
EN 13480-3:2017/A3:2020 (E)
European foreword
This document (EN 13480-3:2017/A3:2020) has been prepared by Technical Committee CEN/TC 267
“Industrial piping and pipelines”, the secretariat of which is held by AFNOR.
This European Standard shall be given the status of a national standard, either by publication of an
identical text or by endorsement, at the latest by February 2021, and conflicting national standards shall
be withdrawn at the latest by February 2021.
Attention is drawn to the possibility that some of the elements of this document may be the subject of
patent rights. CEN shall not be held responsible for identifying any or all such patent rights.
This document has been prepared under a standardization request given to CEN by the European
Commission and the European Free Trade Association, and supports essential requirements of
EU Directive(s).
For relationship with EU Directive(s), see informative Annex ZA, which is an integral part of this
EN 13480-3:2017.
This document includes the text of the amendment itself. The amended/corrected pages of
EN 13480-3:2017 will be published as Issue 4 of the European Standard.
According to the CEN-CENELEC Internal Regulations, the national standards organisations of the
following countries are bound to implement this European Standard: Austria, Belgium, Bulgaria, Croatia,
Cyprus, Czech Republic, Denmark, Estonia, Finland, France, Germany, Greece, Hungary, Iceland, Ireland,
Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Republic of North
Macedonia, Romania, Serbia, Slovakia, Slovenia, Spain, Sweden, Switzerland, Turkey and the United
Kingdom.
3

---------------------- Page: 5 ----------------------
SIST EN 13480-3:2018/A3:2020
EN 13480-3:2017/A3:2020 (E)
1 Modification to Clause 2, "Normative references"
Add the following normative reference:
“EN 12516-2:2014, Industrial valves — Shell design strength — Part 2: Calculation method for steel valve
shells”.
2 Modification to 5.2.4, "Steel castings"
Clause 5.2.4 shall read as follows:
“5.2.4 Steel castings
For steel castings, allowable stresses are specified in EN 12516-2:2014.”
3 Modification to Annex A, "Dynamic effect"
Replace the existing Annex A with the following:
4

---------------------- Page: 6 ----------------------
SIST EN 13480-3:2018/A3:2020
EN 13480-3:2017/A3:2020 (E)
Annex A
(informative)

Dynamic effect
A.1 General
A.1.1 Introduction
In addition to the static conditions and cyclic pressure and temperature loadings covered by 4.2, piping
may be subjected to a variety of dynamic loadings. Dynamic events should be considered in the design of
the piping. However, unless otherwise specified, such consideration may not require detailed analysis.
The effects of significant dynamic loads should be added to the sustained stresses in the design of the
piping. Continuous dynamic loads should be considered in a fatigue analysis.
Analysis methods are proposed in A.2.
However vibration may be more difficult to predict and recommendations for installations are also
provided in a design guidelines A.1.2.
A vibration risk assessment may be performed, based on the combined knowledge of vibration sources
and the dynamic properties of the piping system (A.2.7).
The piping system dynamic properties may also be used to judge the dynamic quality of the layout, to
locate vibration measures and damages.
A.1.2 Vibration design guidelines
A.1.2.1 General
The following guideline may be used to get a reduction in the number of pipework circuits that exceed
vibratory acceptance criteria.
Three aspects are faced to optimize the vibrational behaviour of the piping system:
— the definition of the operation of circuits;
— the recommendation for pumps, valves, and orifice plates;
— the installation of piping and their supports.
A.1.2.2 Operation of the circuit
A.1.2.2.1 Functional analysis
To minimize the potential crack initiation on small bore pipe connections to large pipes or valves, it is
essential to conduct a complete functional analysis of the system. This should include, in particular, the
periodic testing and condition monitoring during operation and the ambient environment in extreme
conditions. This procedure applies even if the operating times in some configurations are low (of the
order of a few minutes per cycle).
The adequacy of the equipment and the installation for every operational modification should be
assessed.
5

---------------------- Page: 7 ----------------------
SIST EN 13480-3:2018/A3:2020
EN 13480-3:2017/A3:2020 (E)
A.1.2.2.2 Partial flow or overflow operation
The operation of pumps with partial flow or overflow leads to significant flow fluctuations. Partial flow
or overflow refers to an operation of the pumps outside of the field of maximum efficiency (areas 1 and
2 of Figure A.1.1.1-1), in theory close to the nominal value (point 8 of Figure A.1.1.1-1), and leading to a
high fluid excitation source (curve 6 of Figure A.1.1.1-1) compared with the nominal value.

Key
X flowrate 4 basic vibration limit
Y1 head 5 best efficiency point, flowrate
Y2 vibration 6 typical vibration vs. flowrate curve showing
maximum  allowable vibration
1 allowable operating region of flow
7 head-flowrate curve
2 preferred operating region of flow
8 best efficiency point, head and flowrate
3 maximum allowable vibration limit at flow
limits
Figure A.1.1.1-1 — Relationship between flow and vibration
The operation of pumps with partial flow or overflow should be avoided. The periodic testing should be
positioned where possible in the operating conditions that are least damaging from a vibratory stand
point. When these configurations cannot be achieved, the operating times should be limited.
Pump by-passes (feedback of the discharge to the vacuum or to the tank) fitted with ahead loss unit may
be implemented, but should ensure that regulation of the flow during discharge remains close to the
nominal value. In this case, particular care should be taken to ensure that the vibratory design of these
by-pass lines comply with the rules for valves and installation.
6

---------------------- Page: 8 ----------------------
SIST EN 13480-3:2018/A3:2020
EN 13480-3:2017/A3:2020 (E)
Size the zero flow rate lines used in the context of the pump periodic testing to be on an operating level
close to the nominal value in accordance with the periodic testing rules.
The pump should have a flow rate above 70 % and below 110 % of the nominal flow rate of the pump.
If the equipment is known, the partial flow rate may possibly be defined by the manufacturer.
A.1.2.2.3 Cavitation
Cavitation is known to lead to excessive vibrations in the pipework circuits (cavitation of orifice plates,
cavitation of butterfly valves and vacuum orifice plates under vacuum conditions).
It is important to note that in cavitation conditions, the operating conditions cannot be ranked. The
experience feedback from vacuum conditions or from the operation of plants, does indeed show that
changes in vibratory levels are not correlated with the increase or decrease in cavitation indexes from
the literature
Cavitation should be prevented or at least limited. This rule is generally complied with through the choice
of equipment (A.1.2.3). However, it is absolutely necessary for the operation managers to provide the
consultants with the worst case head losses and flow rates. To this end, it should take into account all the
operating configurations (normal, disturbed, occasional, accidental, periodic testing) in accordance with
A.1.2.2.1.
The Installation Rules for water hammer recommendations concerning the cavitation should be applied.
A.1.2.2.4 Connected small bore pipes
The reduction in the number of connected small bore pipes leads directly to the reduction of the risk of
cracking by vibratory fatigue, thus the number of functional connected small bore pipes should be
minimized.
Slope reversals should be reduced so as to minimize the number of connected small bore pipes for drains
and vents.
A.1.2.2.5 Flow velocity
The following flow velocity values are recommended.
For liquids:
— Normal velocity < 3 m/s
— Exceptional velocity or pressure greater than 50 bar < 5 m/s
For air and gases:
— Flow velocity < 40 m/s
For steam as function of specific volume:
3
— 0,02 m /kg: 35 – 45 m/s
3
— 0,05 m /kg: 40 – 50 m/s
3
— 0,1 m /kg: 45 – 55 m/s
3
— 0,2 m /kg: 50 – 60 m/s
7

---------------------- Page: 9 ----------------------
SIST EN 13480-3:2018/A3:2020
EN 13480-3:2017/A3:2020 (E)
A.1.2.3 Equipment
A.1.2.3.1 Pumps and compressors
The cracking of connected small bore pipes may be due to excessive vibrations of such components. The
damage from these vibrations is amplified when they coincide with the vibratory modes of the piping.
The vibratory design rules of pumping/compression systems, should be taken into account, in particular
the non-concurrence of frequency between the pump/compressor peaks and the vibratory modes of
pump/compressor-header assemblies.
The excitation frequencies, resulting from pump speed and number of blades (for centrifugal pumps),
should be checked for their effect on the piping system by determining the natural frequencies or by
means of harmonic excitation.
Piston pumps and compressors cause strong pressure pulses inducing high vibrations. The experience
feedback shows that post installation, it is very difficult to limit the vibrations of headers and connected
small bore pipes induced by this type of component.
In general, the use of piston pumps/compressors should be avoided.
However, if strong functional requirements impose the use of this type of component, validated pulsation
dampers or acoustical filters should be proposed by the manufacturer.
In general, adding head losses in a circuit is equivalent to increasing the level of vibratory sources,
reducing efficiency and therefore increasing operating cost.
The use of orifice plates in order to adjust the pump characteristics for the pipework circuit head losses
is not recommended. However, for some pipework circuits, the opening of valves may be limited in order
to prevent the operation of pumps outside their normal range.
Furthermore, the impeller diameter reduction automatically leads to a reduction in pump performance
and an increase in the corresponding hydro acoustic source.
It is recommended to avoid where possible the use of oversized pumps leading to the pointless addition
of head losses in the pipework circuit.
The characteristics of pumps (flow rate, pressure) should be specified based on a functional analysis of
the system.
The specifications of pump characteristics (flow rate, pressure) should be estimated as accurately as
possible based on the characteristics of the pipework circuit and operating conditions.
A.1.2.3.2 Valves
Experience shows that cavitation in control valves, in particular butterfly valves leads to high vibratory
levels in the pipework circuits. The switch to cavitation conditions leads to a sudden increase of these
levels.
Cavitation should be prevented on control valves, especially for butterfly valves.
For other valves, excluding control valves, there is no indication of cavitation leading to high levels of
vibration. It is nevertheless preferable to limit the risk of cavitation on the other types of valves.
The limitation of cavitation and associated criteria are the responsibility of valve Manufacturers, in
accordance with the application of current standards.
A.1.2.3.3 Orifice Plates
Single hole orifice plates present risks of air ‘whistling’ at a higher frequency, between vortex release at
the orifice and an acoustic cavity of the piping. Outside of a possible acoustic discomfort, this air
‘whistling’ can present a fairly high energy vibratory source that may lead to damage.
8

---------------------- Page: 10 ----------------------
SIST EN 13480-3:2018/A3:2020
EN 13480-3:2017/A3:2020 (E)
The frequency of vortex release is characterized by the Strouhal number:
f t

S =
r
V
Where:
S depends on the studied geometry and remains in the region of 0,2 for a mono-hole orifice
r
plate of ratio t/D < 1,
hole
f is the frequency of vortices,
t is the thickness of the diaphragm
V is the flow velocity in the orifice.
D is the elementary diameter of the orifice plate hole(s)
hole
For a plate with N holes:
2
π D Nft
hole
S =
r
4Q
Where:
Q is the flowrate
The example of system single and multi-hole orifice plates with identical head loss coefficients shows that
3
the increase in the number of holes has little impact on the frequency of vortex release at Q = 30 m /s
with S = 0,2
r
— Orifice plate single-hole N = 1, D = 22,3 mm f = 304 Hz;
hole
— Orifice plate multi-holes N = 47, D = 3 mm, f = 358 Hz.
hole
However, the multi-hole orifice plate does not make any air ’whistling’. This observation can be explained
by the ratio t/D > > 1 which leads to S > > 0,2.
hole r
The multi-hole plates also enable the level of turbulence to be reduced by reducing the scale of vortices
and decorrelating them.
However, the use of multi-hole plates only enables a moderate reduction of cavitation and its vibratory
effects.
Orifice plates such as single-hole plates should be prohibited except for flow rate measurement orifice
plates. It is recommended to implement multi-hole plates, maximizing the number of holes with a
minimum diameter of a few millimetres, but not so small that flow is blocked by particles in the flow.
Purging and filters can be applied to avoid this.
Many single-stage orifice plates in plants are cavitating. The multistage technology is widely used in
plants and the sizing methods of valve Manufacturers have been validated.
The use of orifice plates with several plates in series enables head losses to be distributed while
maintaining pressures downstream of every plate sufficiently high not to cause cavitation. The critical
plate is generally the last as it should withstand a low headloss and its critical Tullis number is the lowest.
The flow rate orifice plates generally have low head losses which explains why cavitation experience
feedback from this type of component is reduced or even non-existent. The sizing should still be checked
if they do not cavitate. If they cavitate, two solutions exist. Either reduce their head loss, or increase their
9

---------------------- Page: 11 ----------------------
SIST EN 13480-3:2018/A3:2020
EN 13480-3:2017/A3:2020 (E)
downstream pressure (p2) by moving them in the pipework circuit. Furthermore, the validity of the flow
rate measurement taken at the terminals of a cavitating orifice plate can be questioned.
It is recommended to size the orifice plates taking account of the risk of cavitation Implement multi-stage
multi-hole orifice plates to prevent this risk, except for flow rate measurement orifice plates.
For flow rate measurement orifice plates, reduce their head loss coefficient and place them if possible in
a zone of the pipework circuit where the pressures are the highest.
For flow rate measurement orifice plates (single hole), the Thoma number σ – defined as follows, should
be greater than or equal to 5.
By stating:
p is upstream pressure
1
p is downstream pressure
2
Δp is p – p
2 1
p is liquid steam pressure at the service temperature
v
For the worst case conditions, the Thoma number should comply with:
pp−
2 v
σ ≥ 5
∆p
For multi-hole orifice plates, the sizing rules established and validated by valve Manufacturers should be
applied. If the worst case operating conditions do not enable the use of multi-hole single stage plates, the
implementation of multi-hole multi-stage orifice plates should be considered.
A.1.2.4 Layout
A.1.2.4.1 Main piping (headers)
From experience and the seismic requirements, concentrated masses (e.g. valves, pulsation dampers)
should be as close as possible to supports.
High power pumps induce much energy, it is recommended for pipework circuits with pumping systems
that have a power (Q x TDH) greater than 500 kW, to perform a vibratory design review in order to limit
the risks of excessive vibrations before start-up.
3
— Q is flowrate (m /s)
— TDH is Total Dynamic Head (kPa)
It is recommended to limit the 'vibratory bridges' between pipe lines supports. If this is not possible, the
rigidity of the common supports should be increased.
It is recommended to have supports positioned a maximum of three bends upstream or downstream of a
potential vibration source (e.g. a partial flow pump). The supports referred to here are those without
clearance.
The downstream turbulence of a valve or orifice plate may propagate itself downstream in the piping.
This rule enables the direct excitation of the pipework circuit by the turbulence to be limited.
Independent of vibratory problems, it is recommended to ensure that the straight lengths upstream and
downstream of pressure dropping features are adequate.
10
=

---------------------- Page: 12 ----------------------
SIST EN 13480-3:2018/A3:2020
EN 13480-3:2017/A3:2020 (E)
To limit vibration problems, a minimum distance of 5 DN (nominal diameter), recommended 7 DN, should
be maintained between the isolated head loss component and the first downstream bend or change in
direction.
A.2 Analysis by calculation
A.2.1 General
The main different methods for the calculation of the effect of dynamic events, are:
a) simplified static equivalent;
b) quasi-static equivalent;
c) modal response spectra analysis;
d) force time history.
Experience has shown that for properly supported piping, the use of simplified methods generally leads
to acceptable engineering solutions for the prevention of damage during dynamic events. Where complex
analysis is to be undertaken, care should be exercised in the selection of suitable programs and consistent
data for the derivation of forces and allowable loads.
Piping and piping components may also be verified by subjecting full or part scale models to a vibratory
regime comparable to the expected dynamic loading.
A.2.2 Seismic events
A.2.2.1 General
Seismic events produce vibratory ground movements which are transmitted through the building
structure to piping and other equipment. The structure and equipment respond by undergoing
accelerations and displacements whose magnitude varies with their stiffness and natural resonance
frequencies.
The analysis of the interaction of the building structure with the seismic driving forces is not within the
scope of piping design and the associated response will normally be supplied by the purchaser or site
owner, following earthquake assessment and structural analysis of the proposed building.
An analysis of the piping should be carried out to show the maximum forces and moments generated
within the piping as a result of the structures response to the predicted earthquake; combining those
forces whose direction makes them additive to the static loads. However, care should be taken regarding
the displacements as both plus and minus movements may be needed for layout and supporting detail
design.
The type of calculation determines the form and extent of seismic data to be made available to the piping
designer.
A.2.2.2 Simplified static equivalent analysis
This method ignores the variation in the structure's response at different frequencies and damping rates,
and calculates the displacements and forces in the piping using a single equivalent static accelerating
force for each principal direction of seismic movements. This acceleration is based upon the maximum
value arising from the earthquake. It may be presented to the designer as a ground base response
spectrum, or calculated for each level within the building structure, or given as a single set of responses
which are considered to envelope the different responses applicable to the piping.
11

---------------------- Page: 13 ----------------------
SIST EN 13480-3:2018/A3:2020
EN 13480-3:2017/A3:2020 (E)
Where no building related accelerations are available, the designer should use the peak ground
acceleration as the maximum acceleration ai.
The static equivalent acceleration, acqi, for direction i is calculated as follows:
a = k a  (A.2.1-1)
cqi i i
Where:
ai is the maximum acceleration defined for the level in direction i;
ki is a factor;
ki = 1 where the natural frequencies of the piping can be shown not to coincide within 10 %
of the peak vibration frequencies in the response spectrum of the structure;
ki = 1,5 where no check on the coincidence of piping and building vibration characteristics
has been undertaken.
A.2.2.3 Quasi-static equivalent analysis
This calculation applies a single static acceleration for each of the directions of the ground vibration
equivalent to the highest acceleration in the building response spectrum which can excite the piping. For
this method, the significant natural frequencies of the piping should be calculated.
The quasi-static equivalent acceleration aqe i for direction i is calculated as follows:
a = ka (A.2.1-2)
qe i i fi
Where:
afi is the maximum acceleration in the ground or level vibration spectrum at frequencies
greater than or equal to the first own frequency of the piping;
is a factor related to the contributions of multiple own frequencies for the shape of the
k
i
piping system.
The factor k should be determined from Table A.2.1–1. Lower values of the factor may be used where
i
their admissibility is demonstrated.
Table A.2.1–1 — Values of k
i
Model

k
i
Multi supported linear beam with equal span lengths 1,0
Cantilever beam 1,0
Single beam supported at both ends (maximum forces are to be applied at every 1,0
cross section)
Single plane systems, e.g. frames, girder systems, single plane piping 1,2
3 dimensional systems with complex shapes 1,5
For rigid piping (i.e. where the lowest own frequency of the system is higher than or equal to the cut-off
frequency of the ground vibration spectrum) the value of k may be taken as 1,0.
i
12

---------------------- Page: 14 ----------------------
SIST EN 13480-3:2018/A3:2020
EN 13480-3:2017/A3:2020 (E)
For the determination of support reactions, the value of k may be taken as 1,0 irrespective of which
i
model is used from Table A.2.1-1.
A.2.2.4 Modal response spectra analysis
A.2.2.4.1 General
For modal response spectra analysis, the piping designer requires a building response spectrum for each
level/location within the structure, or a spectrum which can be considered to envelope the responses
within the structure. This modal response spectrum is derived from the maximum accelerations
generated by the earthquake at differing frequencies over an appropriate period of time, and their
interaction with the building structure. Vibration analysis of the piping should be carried out to
determine the displacements, moments, and forces for the imposed accelerations at each significant
frequency in the modal spectrum.
A.2.2.4.2 Modal combination
The total response of the piping (displacements, moments, forces) for each direction should be
obtained by combining each peak modal response using a suitable superposition method:
Absolute sum superposition (ABS):
n
RR=± (A.2.1-3)
i ji

j=1
Square root of the sum of the squares (SRSS):
n
2
RR=± (A.2.1-3)
i ∑ ji
j=1
Complete quadratic combination (CQC):
nn
R =± RRρ
i ∑∑ ji jk ki
jk1 1
where:
2 32/
81ζ + rr
( )
ρ = ,
ij
2
2
2 2
1−+r 4ζ rr1+
( )
)
(
ω
j
ζ
r= , : Damping (A.2.1-4)
ω
i
Maximum value superposition (MAX):
n
R =±max R (A.2.1-5)
i j=1 ji
Where:
13
==

---------------------- Page: 15 ----------------------
SIST EN 13480-3:2018/A3:2020
EN 13480-3:2017/A3:2020 (E)
is the total response in the principal direction i;
R
i
is the peak response due to mode j in the principal direction i;
R
ji
n is the number of significant modes.
Absolute combination can always be used but may be over-conservative in many situations. If the
response components can be considered statistically non-correlated the SRSS method can be used. For
situations with many close modes (with similar frequency) the CQC method is most suitable. The MAX
superposition should only be used in cases where simultaneous action of the components is very
improbable and interactions can be neglected.
A.2.2.4.3 Missing-Mass
In order to take into account the residual mass, not participating in the mode shapes calculated up to a
given frequency limit during the analysis, the remaining mass should be accelerated using a static
acceleration corresponding to the maximum value of the response spectrum above the frequency limit
(highest calculated eigenfrequency). This result is called “residual mode” and should be combined with
the modal response using a suitable superposition method (typically SRSS).
A.2.2.4.4 Building Contributions
If the piping system is attached to different buildings which perform independent movements during a
seismic event, the contribution of each building and each direction should be calculated separately. These
building contributions should be combined with the modal response using a suitable superposition
method (typically SRSS).
A.2.2.4.5 Spatial combination
The three spatial directions should be combined with the modal response using a suitable superposition
method.
For most piping systems the combination of piping responses
...

SLOVENSKI STANDARD
SIST EN 13480-3:2018/oprA3:2019
01-april-2019
.RYLQVNLLQGXVWULMVNLFHYRYRGLGHO.RQVWUXLUDQMHLQL]UDþXQ'RSROQLOR$
Metallic industrial piping - Part 3: Design and calculation
Metallische industrielle Rohrleitungen - Teil 3: Konstruktion und Berechnung
Tuyauteries industrielles métalliques - Partie 3 : Conception et calcul
Ta slovenski standard je istoveten z: EN 13480-3:2017/prA3
ICS:
23.040.10 Železne in jeklene cevi Iron and steel pipes
77.140.75 Jeklene cevi in cevni profili Steel pipes and tubes for
za posebne namene specific use
SIST EN 13480-3:2018/oprA3:2019 en,fr,de
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

---------------------- Page: 1 ----------------------

SIST EN 13480-3:2018/oprA3:2019

---------------------- Page: 2 ----------------------

SIST EN 13480-3:2018/oprA3:2019


DRAFT
EUROPEAN STANDARD
EN 13480-3:2017
NORME EUROPÉENNE

EUROPÄISCHE NORM
prA3
March 2019
ICS 23.040.01
English Version

Metallic industrial piping - Part 3: Design and calculation
Tuyauteries industrielles métalliques - Partie 3 : Metallische industrielle Rohrleitungen - Teil 3:
Conception et calcul Konstruktion und Berechnung
This draft amendment is submitted to CEN members for enquiry. It has been drawn up by the Technical Committee CEN/TC 267.

This draft amendment A3, if approved, will modify the European Standard EN 13480-3:2017. If this draft becomes an
amendment, CEN members are bound to comply with the CEN/CENELEC Internal Regulations which stipulate the conditions for
inclusion of this amendment into the relevant national standard without any alteration.

This draft amendment was established by CEN in three official versions (English, French, German). A version in any other
language made by translation under the responsibility of a CEN member into its own language and notified to the CEN-CENELEC
Management Centre has the same status as the official versions.

CEN members are the national standards bodies of Austria, Belgium, Bulgaria, Croatia, Cyprus, Czech Republic, Denmark, Estonia,
Finland, Former Yugoslav Republic of Macedonia, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania,
Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Romania, Serbia, Slovakia, Slovenia, Spain, Sweden, Switzerland,
Turkey and United Kingdom.

Recipients of this draft are invited to submit, with their comments, notification of any relevant patent rights of which they are
aware and to provide supporting documentation.

Warning : This document is not a European Standard. It is distributed for review and comments. It is subject to change without
notice and shall not be referred to as a European Standard.


EUROPEAN COMMITTEE FOR STANDARDIZATION
COMITÉ EUROPÉEN DE NORMALISATION

EUROPÄISCHES KOMITEE FÜR NORMUNG

CEN-CENELEC Management Centre: Rue de la Science 23, B-1040 Brussels
© 2019 CEN All rights of exploitation in any form and by any means reserved Ref. No. EN 13480-3:2017/prA3:2019 E
worldwide for CEN national Members.

---------------------- Page: 3 ----------------------

SIST EN 13480-3:2018/oprA3:2019
EN 13480-3:2017/prA3:2019 (E)
Contents Page
European foreword . 3
1 Modification to Clause 2, Normative references . 4
2 Modification to 5.2.4, Steel castings . 4
3 Modification to 13.11.4, Determination of component sizes. 4
4 Modification to Annex A, Dynamic analysis . 4
5 Modification to subclause G.3, Physical properties of steels . 26
6 Introduction of a new subclause G.4, Material properties of carbon steel at elevated
temperatures . 26
7 Introduction of a new Annex R, Surveillance of components operating in the creep
range . 27
8 Modification to Bibliography . 30

2

---------------------- Page: 4 ----------------------

SIST EN 13480-3:2018/oprA3:2019
EN 13480-3:2017/prA3:2019 (E)
European foreword
This document (EN 13480-3:2017/prA3:2019) has been prepared by Technical Committee CEN/TC 267
“Industrial piping and pipelines”, the secretariat of which is held by AFNOR.
This document is currently submitted to the CEN Enquiry.
This document has been prepared under a standardization request given to CEN by the European
Commission and the European Free Trade Association, and supports essential requirements of
EU Directive(s).
For relationship with EU Directive(s), see informative Annex ZA, which is an integral part of this
document.
This document includes the text of the amendment itself. The amended/corrected pages of
EN 13480-3:2017 will be published as Issue 2 of the European Standard.

3

---------------------- Page: 5 ----------------------

SIST EN 13480-3:2018/oprA3:2019
EN 13480-3:2017/prA3:2019 (E)
1 Modification to Clause 2, Normative references
Add the following normative reference:
“EN 12516-2:2014, Industrial valves — Shell design strength — Part 2: Calculation method for steel valve
shells”.
2 Modification to 5.2.4, Steel castings
Sub-clause 5.2.4 shall read as follows:
“5.2.4 Steel castings
For steel castings, allowable stresses are specified in EN 12516-2:2014.”
3 Modification to 13.11.4, Determination of component sizes
rd
In 13.11.4.1, the 3 sentence shall read as follows:
“For further guidance, see Annexes G.4, I, J, K, L and M.”.
4 Modification to Annex A, Dynamic analysis
Replace the existing Annex A with the following: “
Annex A
(informative)
Dynamic effect
A.1 General
In addition to the static conditions and cyclic pressure and temperature loadings covered by 4.2, piping
may be subjected to a variety of dynamic loadings. Dynamic events should be considered in the design of
the piping. However, unless otherwise specified, such consideration may not require detailed analysis.
The effects of significant dynamic loads should be added to the sustained stresses in the design of the
piping. Continuous dynamic loads should be considered in a fatigue analysis.
Analysis methods are proposed in A.2.
However vibration may be more difficult to predict and recommendations for installations are also
provided in a design guidelines A.1.1.
A vibration risk assessment may be performed, based on the combined knowledge of vibration sources
and the dynamic properties of the piping system (A.2.6).
The piping system dynamic properties may also be used to judge the dynamic quality of the layout, to
locate vibration measures and damages.
A.1.1 Vibration design guidelines
The following guideline may be used to get a reduction in the number of pipework circuits that exceed
vibratory acceptance criteria.
Three aspects are faced to optimize the vibrational behaviour of the piping system:
— the definition of the operation of circuits;
— the recommendation for pumps, valves, and orifice plates;
— the installation of piping and their supports.
4

---------------------- Page: 6 ----------------------

SIST EN 13480-3:2018/oprA3:2019
EN 13480-3:2017/prA3:2019 (E)
A.1.1.1 Operation of the circuit
A.1.1.1.1 functional analysis
To avoid cracks apparition on connections of small pipe on big pipe or valve, it is essential to conduct a
complete functional analysis of the system. This should include, in particular, the periodic testing and
condition monitoring during operation and the ambient environment in extreme conditions. This
procedure applies even if the operating times in some configurations are low (of the order of a few
minutes per cycle).
The adequacy of the equipment and the installation for every operation modification is recommended to
be analysed.
A.1.1.1.2 Partial flow or overflow operation
The operation of pumps with partial flow or overflow leads to significant flow fluctuations. Partial flow
or overflow refers to an operation of the pumps outside of the field of maximum efficiency (areas 1 and
2 of Figure A.1.1.1-1), in theory close to the nominal value (point 8 of Figure A.1.1.1-1), and leading to a
high fluid excitation source (curve 6 of Figure A.1.1.1-1) compared with the nominal value.
5

---------------------- Page: 7 ----------------------

SIST EN 13480-3:2018/oprA3:2019
EN 13480-3:2017/prA3:2019 (E)

Key
X flowrate
Y1 head
Y2 vibration
1 allowable operating region of flow
2 preferred operating region of flow
3 maximum allowable vibration limit at flow limit
4 basic vibration limit
5 best efficiency point, flowrate
6 typical vibration vs. flowrate curve showing maximum allowable vibration
7 head-flowrate curve
8 best efficiency point, head and flowrate
Figure A.1.1.1-1 — Relationship between flow and vibration
The operation of pumps with partial flow or overflow should be avoided. The periodic testing should be
positioned where possible in the operating conditions that are least damaging from a vibratory stand
point. When these configurations cannot be achieved, the operating times should be limited.
Pump by-passes (feedback of the discharge to the vacuum or to the tank) fitted with ahead loss unit may
be implemented, but should ensure that regulation of the flow during discharge remains close to the
nominal value. In this case, particular care should be taken to ensure that the vibratory design of these
by-pass lines comply with the rules for valves and installation.
6

---------------------- Page: 8 ----------------------

SIST EN 13480-3:2018/oprA3:2019
EN 13480-3:2017/prA3:2019 (E)
— Size the zero flow rate lines used in the context of the pump periodic testing to be on an operating level
close to the nominal value in accordance with the periodic testing rules.
The pump should have a flow rate so that:
0,7 Q < Q < 1,1 Q
n n
If the equipment is known, the partial flow rate may possibly be defined by the manufacturer.
A.1.1.1.3 Cavitation
Cavitation is known to lead to excessive vibrations in the pipework circuits (cavitation of orifice plates,
cavitation of butterfly valves and vacuum orifice plates under vacuum conditions).
It is important to note that in cavitation conditions, the operating conditions cannot be ranked. The
experience feedback from vacuum conditions or from the operation of plants, does indeed show that
changes in vibratory levels are not correlated with the increase or decrease in cavitation indexes from
the literature.
Cavitation should be prevented or at least limited. This rule is generally complied with through the choice
of equipment (A.1.1.2). However, it is absolutely necessary for the operation managers to provide the
consultants with the worst case head losses and flow rates. To this end, it should take into account all the
operating configurations (normal, disturbed, occasional, accidental, periodic testing) in accordance with
A.1.1.1.1.
The Installation Rules for water hammer recommendations concerning the cavitation should be applied.
A.1.1.1.4 Connected small bore pipes
The reduction in the number of connected small bore pipes leads directly to the reduction of the risk of
cracking by vibratory fatigue, thus the number of functional connected small bore pipes should be
minimized.
Slope reversals should be reduced so as to minimize the number of connected small bore pipes for drains
and vents.
A.1.1.1.5 Flow velocity
The following flow velocity values are recommended.
For liquids:
— Normal velocity < 3 m/s;
— Exceptional velocity or pressure greater than 50 bar < 5 m/s.
For air and gases:
— Flow velocity < 40 m/s.
For steam as function of specific volume:
3
— 0,02 m /kg: 35 – 45 m/s;
3
— 0,05 m /kg: 40 – 50 m/s;
3
— 0,1 m /kg: 45 – 55 m/s;
3
— 0,2 m /kg: 50 – 60 m/s.
7

---------------------- Page: 9 ----------------------

SIST EN 13480-3:2018/oprA3:2019
EN 13480-3:2017/prA3:2019 (E)
A.1.1.2 Equipment
A.1.1.2.1 Pumps and compressors
The cracking of connected small bore pipes may be due to excessive vibrations of such components. The
damage from these vibrations is amplified when they coincide with the vibratory modes of the piping.
The vibratory design rules of pumping/compression systems, should be taken into account, in particular
the non-concurrence of frequency between the pump/compressor peaks and the vibratory modes of
pump/compressor-header assemblies.
Piston pumps and compressors cause strong pressure pulses inducing high vibrations. The experience
feedback shows that post installation, it is very difficult to limit the vibrations of headers and connected
small bore pipes induced by this type of component.
In general, the use of piston pumps/compressors should be avoided.
However, if strong functional requirements impose the use of this type of component, validated pulsation
dampers or acoustical filters should be proposed by the manufacturer.
In general, adding head losses in a circuit is equivalent to increasing the level of vibratory sources,
reducing efficiency and therefore increasing operating cost.
The use of orifice plates in order to adjust the pump characteristics for the pipework circuit head losses
is not recommended. However, for some pipework circuits, the opening of valves may be limited in order
to prevent the operation of pumps outside their normal range.
Furthermore, the impeller diameter reduction automatically leads to a reduction in pump performance
and an increase in the corresponding hydro acoustic source it is recommended to avoid where possible
the use of oversized pumps leading to the pointless addition of head losses in the pipework circuit. The
characteristics of pumps (flow rate, pressure) should be specified based on a functional analysis of the
system.
The specifications of pump characteristics (flow rate, pressure) should be estimated as accurately as
possible based on the characteristics of the pipework circuit and operating conditions.
A.1.1.2.2 Valves
The experience shows that cavitation in control valves, in particular butterfly valves leads to high
vibratory levels in the pipework circuits. The switch to cavitation conditions leads to a sudden increase
of these levels.
Cavitation should be prohibited on control valves, especially for butterfly valves.
For other valves, excluding control valves, there is no indication of cavitation leading to high levels of
vibration. It is preferable to limit the risk of cavitation on the other types of valves.
The limitation of cavitation and associated criteria are the responsibility of valve Manufacturers, in
accordance with the application of current standards.
A.1.1.2.3 Orifice plates
The single hole orifice plates present risks of air ‘whistling’ at a higher frequency, between vortex release
at the orifice and an acoustic cavity of the piping. Outside of a possible acoustic discomfort, this air
‘whistling’ can present a fairly high energy vibratory source that may lead to damage.
The frequency of vortex release is characterized by the Strouhal number:
ft
S =
r
V
where
8

---------------------- Page: 10 ----------------------

SIST EN 13480-3:2018/oprA3:2019
EN 13480-3:2017/prA3:2019 (E)
S depends on the studied geometry and remains in the region of 0,2 for a mono-hole orifice plate
r
of ratio t/D < 1;
hole
f is the frequency of vortices;
t is the thickness of the diaphragm;
V is the flow velocity in the orifice;
D is the elementary diameter of the orifice plate hole(s).
hole
For a plate with N holes:
2
π D Nft
hole
S =
r
4Q
where
Q is the flowrate.
The example of system single and multi-hole orifice plates with identical head loss coefficients shows that
3
the increase in the number of holes has little impact on the frequency of vortex release at Q = 30 m /s
with S = 0,2
r
— Orifice plate single-hole N = 1, D = 22,3 mm, f = 304 Hz;
hole
— Orifice plate multi-holes N = 47, D = 3 mm, f = 358 Hz.
hole
However, the multi-hole orifice plate does not make any air ’whistling’. This observation can be explained
by the ratio t/D > > 1 which leads to S > > 0,2.
hole r
The multi-hole plates also enable the level of turbulence to be reduced by reducing the scale of vortices
and decorrelating them.
However, the use of multi-hole plates only enables a moderate reduction of cavitation and its vibratory
effects.
Orifice plates such as single-hole plates should be prohibited except for flow rate measurement orifice
plates. It is recommended to implement multi-hole plates, maximizing the number of holes with a
minimum diameter of a few millimetres, but not so small that flow is blocked by particles in the flow.
Purging and filters can be applied to avoid this.
Many single-stage orifice plates in plants are cavitating. The multistage technology is widely used in
plants and the sizing methods of valve Manufacturers have been validated.
The use of orifice plates with several plates in series enables head losses to be distributed while
maintaining pressures downstream of every plate sufficiently high not to cause cavitation. The critical
plate is generally the last as it should withstand a low headloss and its critical Tullis number is the lowest.
The flow rate orifice plates generally have low head losses which explains why cavitation experience
feedback from this type of component is reduced or even non-existent. The sizing should still be checked
if they do not cavitate. If they cavitate, two solutions exist. Either reduce their head loss, or increase their
downstream pressure (p ) by moving them in the pipework circuit. Furthermore, the validity of the flow
2
rate measurement taken at the terminals of a cavitating orifice plate can be questioned.
It is recommended to size the orifice plates taking account of the risk of cavitation Implement multi-stage
multi-hole orifice plates to prevent this risk, except for flow rate measurement orifice plates.
9

---------------------- Page: 11 ----------------------

SIST EN 13480-3:2018/oprA3:2019
EN 13480-3:2017/prA3:2019 (E)
For flow rate measurement orifice plates, reduce their head loss coefficient and place them if possible in
a zone of the pipework circuit where the pressures are the highest.
For flow rate measurement orifice plates (single hole), the Thoma number σ – defined as follows, should
be greater than or equal to 5.
By stating:
p is upstream pressure
1
p is downstream pressure
2
Δp is p – p
2 1
p is liquid steam pressure at the service temperature
v
For the worst case conditions, the Thoma number should comply with:
pp−
2 v
σ ≥ 5
∆p
For multi-hole orifice plates, the sizing rules established and validated by valve Manufacturers should be
applied. If the worst case operating conditions do not enable the use of multi-hole single stage plates, the
implementation of multi-hole multi-stage orifice plates should be considered.
A.1.1.3 Layout
A.1.1.3.1 Main piping (headers)
From experience and the seismic requirements, concentrated masses (e.g. valves, pulsation dampers)
should be as close as possible to supports.
High power pumps induce much energy, it is recommended for pipework circuits with pumping systems
that have a power (Q x TDH) greater than 500 kW, to perform a vibratory design review in order to limit
the risks of excessive vibrations before start-up.
3
— Q is flowrate (m /s);
— TDH is Total Dynamic Head (kPa).
It is recommended to limit the 'vibratory bridges' between pipe lines supports. If this is not possible, the
rigidity of the common support.
It is recommended to have supports positioned a maximum of three bends upstream or downstream of a
potential vibration source (e.g. a partial flow pump). The supports referred to here are those without
clearance.
The downstream turbulence of a valve or orifice plate may propagate itself downstream in the piping.
This rule enables the direct excitation of the pipework circuit by the turbulence to be limited.
Independent of vibratory problems, it is recommended to comply with straight lengths upstream and
pressure dropping units downstream.
To maintain a minimum distance between the isolated head loss component and the first bend or the first
change of direction downstream, recommended distance is of 7 NPS (nominal diameter and not less than
5 NPS) is favourable to limit vibratory problem.
A.2 Analysis by calculation
The main different methods for the calculation of the effect of dynamic events, are:
a) simplified static equivalent;
b) quasi-static equivalent;
10
=

---------------------- Page: 12 ----------------------

SIST EN 13480-3:2018/oprA3:2019
EN 13480-3:2017/prA3:2019 (E)
c) modal response spectra analysis;
d) force time history.
Experience has shown that for properly supported piping, the use of simplified methods generally leads
to acceptable engineering solutions for the prevention of damage during dynamic events. Where complex
analysis is to be undertaken, care should be exercised in the selection of suitable programs and consistent
data for the derivation of forces and allowable loads.
Piping and piping components may also be verified by subjecting full or part scale models to a vibratory
regime comparable to the expected dynamic loading.
A.2.1 Seismic events
A.2.1.1 General
Seismic events produce vibratory ground movements which are transmitted through the building
structure to piping and other equipment. The structure and equipment respond by undergoing
accelerations and displacements whose magnitude varies with their stiffness and natural resonance
frequencies.
The analysis of the interaction of the building structure with the seismic driving forces is not within the
scope of piping design and the associated response will normally be supplied by the purchaser or site
owner, following earthquake assessment and structural analysis of the proposed building.
An analysis of the piping should be carried out to show the maximum forces and moments generated
within the piping as a result of the structures response to the predicted earthquake; combining those
forces whose direction makes them additive to the static loads. However, care should be taken regarding
the displacements as both plus and minus movements may be needed for layout and supporting detail
design.
The type of calculation determines the form and extent of seismic data to be made available to the piping
designer.
A.2.1.2 Simplified static equivalent analysis
This method ignores the variation in the structure's response at different frequencies and damping rates,
and calculates the displacements and forces in the piping using a single equivalent static accelerating
force for each principal direction of seismic movements. This acceleration is based upon the maximum
value arising from the earthquake. It may be presented to the designer as a ground base response
spectrum, or calculated for each level within the building structure, or given as a single set of responses
which are considered to envelope the different responses applicable to the piping.
Where no building related accelerations are available, the designer should use the peak ground
acceleration as the maximum acceleration a .
i
The static equivalent acceleration, a , for direction i is calculated as follows:
cqi
a = k a (A.2.1-1)
cqi i i
where
a is the maximum acceleration defined for the level in direction i;
i
k is a factor;
i
k = 1 where the natural frequencies of the piping can be shown not to coincide within 10 % of the
i
peak vibration frequencies in the response spectrum of the structure;
11

---------------------- Page: 13 ----------------------

SIST EN 13480-3:2018/oprA3:2019
EN 13480-3:2017/prA3:2019 (E)
k = 1,5 where no check on the coincidence of piping and building vibration characteristics has been
i
undertaken.
A.2.1.3 Quasi-static equivalent analysis
This calculation applies a single static acceleration for each of the directions of the ground vibration
equivalent to the highest acceleration in the building response spectrum which can excite the piping. For
this method, the significant natural frequencies of the piping should be calculated.
The quasi-static equivalent acceleration a for direction i is calculated as follows:
qe i
a = ka (A.2.1-2)
qe i i fi
where
a is the maximum acceleration in the ground or level vibration spectrum at frequencies greater
fi
than or equal to the first own frequency of the piping;
k  is a factor related to the contributions of multiple own frequencies for the shape of the piping
i
system.
The factor k should be determined from Table A.2.1-1. Lower values of the factor may be used where
i
their admissibility is demonstrated.
Table A.2.1–1 — Values of k
i
Model
k
i
Multi supported linear beam with equal span lengths 1,0
Cantilever beam 1,0
Single beam supported at both ends (maximum forces are to be applied at every 1,0
cross section)
Single plane systems, e.g. frames, girder systems, single plane piping 1,2
3 dimensional systems with complex shapes 1,5

For rigid piping (i.e. where the lowest own frequency of the system is higher than or equal to the cut-off
frequency of the ground vibration spectrum) the value of k may be taken as 1,0.
i
For the determination of support reactions, the value of k may be taken as 1,0 irrespective of which
i
model is used from Table A.2.1-1.
A.2.1.4 Modal response spectra analysis
For modal response spectra analysis, the piping designer requires a building response spectrum for each
level/location within the structure, or a spectrum which can be considered to envelope the responses
within the structure. This modal response spectrum is derived from the maximum accelerations
generated by the earthquake at differing frequencies over an appropriate period of time, and their
interaction with the building structure. Vibration analysis of the piping should be carried out to
determine the displacements, moments, and forces for the imposed accelerations at each significant
frequency in the modal spectrum.
12

---------------------- Page: 14 ----------------------

SIST EN 13480-3:2018/oprA3:2019
EN 13480-3:2017/prA3:2019 (E)
A.2.1.4.1 Modal combination
The total response of the piping (displacements, moments, forces) for each direction should be
obtained by combining each peak modal response using a suitable superposition method:
Absolute sum superposition (ABS):
n
RR=± (A.2.1-3)
i ji

j=1
Square root of the sum of the squares (SRSS):
n
2
RR=± (A.2.1-3)
i ji

j=1
Complete quadratic combination (CQC):
2 32/
nn
ω
81ζ + rr
( )
j
R =± RRρ whereρ = , r= , ζ : Damping  (A.2.1-4)
i ji jk ki ij
∑∑
2
2 ω
2 2 i
jk1 1
1−+r 4ζ rr1+
( )
( )
Maximum value superposition (MAX):
n
R =±max R (A.2.1-5)
i j=1 ji
where
R is the total response in the principal direction i;
i
R is the peak response due to mode j in the principal direction i;
ji
n is the number of significant modes.
Absolute combination can always be used but may be over-conservative in many situations. If the
response components can be considered statistically non-correlated the SRSS method can be used. For
situations with many close modes (with similar frequency) the CQC method is most suitable. The MAX
superposition should only be used in cases where simultaneous action of the components is very
improbable and interactions can be neglected.
A.2.1.4.2 Missing-mass
In order to take into account the residual mass, not participating in the mode shapes calculated up to a
given frequency limit during the analysis, the remaining mass should be accelerated using a static
acceleration corresponding to the maximum value of the response spectrum above the frequency limit
(highest calculated eigenfrequency). This result is called “residual mode” and should be combined with
the modal response using a suitable superposition method (typically SRSS).
A.2.1.4.3 Building contributions
If the piping system is attached to different buildings which perform independent movements during a
seismic event, the contribution of each building and each direction should be calculated separately. These
building contributions should be combined with the modal response using a suitable superposition
method (typically SRSS).
13
==

---------------------- Page: 15 ----------------------

SIST EN 13480-3:2018/oprA3:2019
EN 13480-3:2017/prA3:2019 (E)
A.2.1.4.3 Spatial combination
The three spatial directions should be combined with the modal response using a suitable superposition
method.
For most piping systems the combination of piping responses from the three principal directions can be
based on the following assumptions:
— the piping responses to different building modal peaks do not occur at the same time;
— peak responses do not occur simultaneously in the three principal directions.
Consequently the maximum response of the system may be calculated by applying the MAX or SRSS
method to the three orthogonal directional maxima.
A.2.1.5 Force time history analysis
Where seismic displacements of the supporting structure are know
...

Questions, Comments and Discussion

Ask us and Technical Secretary will try to provide an answer. You can facilitate discussion about the standard in here.