ISO/TR 11071-2:1996

ISO/TR 11071-2: 1996(E)
Page
CONTENTS
1 Scope and field of application . 1
Terminology . 2
Basis for lift safety standards development . 4
Approach to design safety for hydraulic components . 10
...................... 25
5 Driving machines and jacks (plungers and cylinders)
........................................ 34
6 Valves, piping, and fittings
.
7 Ropesandchains .
.47
8 Capacity and loading .
.......................................... .53
9 Spaces and clearances
................... 55
10 Protection against free-fall, excessive speed and creeping
.59
11 Electrical devices .
Annexes
A Tabulations 63
...................................................
Al Spaces and clearances . .64
A2 Electrical devices .68
..........................................
B References .80
..................................................
C .81
CEN/TClO/WGl/N99 .
0 IS0 1996
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Unless otherwise specified, no part of this publication may be
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photocopying and microfilm, without permission in writing from the publisher.
International Organization for Standardization
Case Postale 56 l CH-1211 Geneve 20 l Switzerland
Printed in Switzerland
ii
0 IS0 ISO/TRll071=2:1996(E)
Foreword
IS0 (the International Organization for Standardization) is a worldwide federation of national
standards bodies (IS0 member bodies). The work of preparing International Standards is
normally carried out through IS0 technical committees. Each member body interested in a
subject for which a technical committee has been established has the right to be represented on
that committee. International organizations, governmental and non-governmental, in liaison
with ISO, also take part in the work. IS0 collaborates closely with the International
Electrotechnical Commission (IEC) on all matters of electrotechnical standardization.
The main task of technical committees is to prepare International Standards, but in exceptional
circumstances a technical committee may propose the publication of a Technical Report of one
of the following types:
the required support cannot be obtained for the publication of an
type 1, when
International Standard, despite repeated efforts;
type 2, when the subject is still under technical development or where for any other
reason there is the future but not immediate possibility of an agreement on an
International Standard;
type 3, when a technical committee has collected data of a different kind from that
which is normally published as an International Standard (“state of the art”, for
example).
Technical Reports of types 1 and 2 are subject to review within three years of publication, to
decide whether they can be transformed into International Standards. Technical Reports of
type 3 do not necessarily have to be reviewed until the data they provide are considered to be
no longer valid or useful.
ISO/TR 11071-2, which is a Technical Report of type 3, was prepared by Technical Com.m-We
ISO/TC 178, Lijk, escalators, passenger conveyors.
ISOA’R 11071 consists of the following parts, under the general title Comparison of worldwide
1ijZ safety standards:
Part 1: Electric lij?s (elevators)
Part 2: Hydraulic lifts (elevators)
Annexes A to C form an integral part of this part of ISO/TR 1107 1.
. . .
0 IS0
ISO/TR 11071=2:1996(E)
Introduction
At the 1981 plenary meeting of ISO/TC 178, work was started on a comparison of CEN
standard EN 81/l with the American, Canadian, and USSR lift safety codes. In 1983, Working
Group 4 was officially formed to carry out the task of preparing a cross reference between the
relevant sections of these standards and to analyze the differences on selected subjects. The
goal at that time was to prepare a technical report which would provide reference information
to assist national committees when reviewing and revising individual standards which may
initiate a gradual convergence of the technical requirements. In 1984, the study was expanded
to include the CMEA safety standard. That report, ISO/TR 11071-1, Comparison of worldwide
lzj? safety standark Part I Electric lijts (elevators), was published 1990-12-01.
In 1989, the charge to WG 4 was expanded to include hydraulic lifts. Since there was no
standard for hydraulic lifts in the Russian Federation, and the Council for Mutual Economics
Assistance (CMEA) standard was being phased out of use, this Part 2 of the comparison is
generally limited to the ASME, CEN, and CSA standards. The Japan Elevator Association was
invited to add their standards to this comparison, however, no response to this request was
received.
This report is intended to aid standards writers in developing their safety requirements, and to
help standard users understand the basis for the requirements as they are applied throughout the
world
This report is not intended to replace existing safety standards. Conclusions are arrived at in
some cases, but only where there is unanimity amongst the various experts. In other cases, the
reasons for the divergent views are expressed.
This report must be read in conjunction with the various safety standards, as it was often
necessary to summarize the requirements for the sake of clarifying the comparisons. Further,
the information contained in this report does not necessarily represent the opinions of the
standards writing organizations responsible for the development of the safety standards which
are being compared, and they should be consulted regarding interpretations of their
requirements (see Annex B).
iv
IS0 11071-2: 1996(E)
TECHNICAL REPORT @ IS0
Comparison of worldwide lift safety standards -
Part 2:
Hydraulic lifts (elevators)
1 Scope and field of application
This Technical Report consists of a comparison of
the requirements of selected topics as covered by
the following worldwide safety standards (excluding
regional or national deviations):
a) CEN -- European Standard EN81: Part 2, Lifts
and Service Lifts @Zdition 1987 - as presented
in BS5655:Part 2: 1988 (excluding national
Appendix)]
b) ASME -- ASME A17.1 Safety Code for
Elevators and Escalators (Edition 1993)
c) CSA -- CSA Standard CAN-B44 Safety Code
for Elevators (Edition 1994)
This Technical Report applies to hydraulic lifts
only, both of the direct and indirect acting type.
It should be noted that in addition to the above
listed standards, lifts must conform to the
requirements of other standards (for example,
standards covering mechanical, structural, and
electrical equipment; building codes, and
environmental regulations). Some of the standards
will be referred to in this Technical Report.

0 IS0
ISO/TRll071-2:1996(E)
CSA Standard. This is not necessarily applicable to
2 Terminology
CEN, as the electric and hydraulic lifts are covered
by two separate standards.
2.1 Lifts and elevators
2.2.3 Terminology in this report
2.1.1
The CEN term lift corresponds to the ASME and
In this report, the CEN terminology will be used,
CSA term elevator. These terms are used inter-
with the ASME and CSA terms in brackets if
changeably in this report.
different.
2.1.2
For the purposes of this report, unless otherwise
Table 2.2
specified, the term passenger Zzj2 and freight lift
Hydraulic Terminology
correspond to the following terms used in other
standards:
ColumnA Column B cohlmn c Column D
Descrfption Agreed upon
CEN ASME & CSA
Term used Correspond to terms used in the
Current points: ASME
in following standards*
& CSA
this report
proposed
CEN ASME & CSA
changes
-
Passenger
Lift, except Passenger elevator & Direct acting Direct plunger Direct acting
hydraulic elevator hydraulic
lift lift
non-commercial freight elevator
elevator
vehicle lift permitted to carry
passengers
Indirect acting Roped hydraulic - No change
lift Elevator
Freight lift Non-commercial Freight elevator
-
Machine Hydraulic
mP*
vehicle lift with
motor, machine
instructed users**
valves
*See the definitions in the applicable Stand&k
Driving machine Cylinder and Hydraulic jack
Jack
**fiti term is used only to enable comparisons to be made
ram
It does not indicate recognition of the
later in this report.
Plunger or piston - Plunger(ram)
Ram
term ‘Ifreight l$” by CEN.
or piston
Head/bottom Cylinder end No change
Base
2.2 Hydraulic terminology
(Includes plunger
cap
end cap as well)
2.2.1 Difference
VaPves:
There are some notable differences in the standards
respecting hydraulic lift terminology as shown in
-
Non-return Check No change
the Table 2.2, Column A and B.
-
Pressure relief Pump relief No change
2.2.2 Agreed-upon points, re: hydraulic
-
Direction Control No change
terminology
-
No change
Rupture ASMESafety
CSA-Rupture
The differences should be eliminated or minimized
through recently proposed changes to ASME and
CSA Standards, as shown in Table 2.2, Column D.
2.3 Working pressure vs full load pressure
ASME uses working pressure (WP), which is
If approved by ASME and CSA Committees, the
defined as the pressure at the cylinder when lifting
proposed changes would eliminate major differences
the car and its rated load at rated speed, or with
between CEN and North American Standards.
class C2 loading, when levelling up with maximum
speed.
Column C gives the description of the equipment
that a term (listed in Column A, B, or D) embraces.
fill load pressure (FLP) as the static
CEN defines
pressure exerted at the piping directly connected to
In addition to “hydraulic machine”, ASME and
the jack, the car with the rated load being at rest at
CSA propose to introduce the term “hydraulic
the highest landing level.
driving machines” which may be “direct or roped
hydraulic driving machines”. The terms are needed
CEN clause 12, Note 1, recognizes that friction
to differentiate between “electric” and “hydraulic”
losses as a result of fluid flow are on the order of
driving machines all covered in one ASME and one
0 IS0
15%; thus a factor of 1,15 is included in their factor
of safety determination.
Thus, ASME WP = 1,15 x (CEN FLP)
The CSA definition of working pressure (WP)
corresponds to that in ASME.
2.4 Other terms
Additional terminology, where there is a difference
between the CEN and the ASME and CSA
standards, is shown in Table 2.4:
Table 2.4
CEN ASME & CSA
Truck zone operation
Docking operation
Electric safety device Electrical protective device
Fastenings
Fixings
Hoistway door (ASME)
Landing door
Landing door (CSA)
Main power supply
Mains
Reeving ratio Roping ratio
Instantaneous safety Type A safeties (instantaneous
safeties)
IFa
Progressive safety gear Type B safeties
(progressive safeties)
Pulley Sheave
Safety gear Safeties
Hoistway
Well
2.5 Abbreviations
The following abbreviations are used in this report:
FOS = Factor of safety or safety factor
YP = Yield point
WP = Working pressure
= Ultimate tensile strength
UTS
FLP = Full load pressure
Note: See also list of abbreviations in items 4.1.2.

0 IS0
ISO/TR 11071=2:1996(E)
Human behaviour and endurance; and
3 Basis for lift safety standards b)
development (basic assumptions)
Acceptable level of safety and safety margins.
d
3.1 Historical background
3.2.2 Where the probability of an occurrence is
considered highly unlikely, it is considered as not
3.1.1 All lift safety standards assume certain things
happening.
as being true, without proving them as such, and
stipulate safety rules that are based on these
3.2.3 Where an occurrence proves that an
assumptions.
assumption is false, it does not necessarily prove
that all other assumptions are false.
3.1.2 No standard, however, clearly spells out the
assumptions used. The CEN committee analyzed
3.2.4 The assumptions should be subject to
its standard and summarized in the document
periodic review by standards writing organizations
CEN/TClO/WGl N99 (see Annex C) the
to ensure their continuing validity -- considering
assumptions that, in the opinion of the committee,
accident statistics, as well as such things as changes
were used in the CEN standard.
in technologies, public expectations (e.g. product
liability), and human behaviour.
3.1.3 The CEN assumptions were compared with
assumptions implicitly built into other safety
3.3 Assumption l-safe operation assured to
standards. It has been indicated that:
125% of rated load
a) Some assumptions apparently used in the CEN
Safe operation of lifts is assured for loads ranging
standard were not listed in the document
from 0 to 100% of the rated load. In addition, in
referred to in CEN/TClO/WGl N99;
the caSe of passenger Zijts (see 2.1.2), safe operation
is also assured for an overload of 25%; however, it
b) Some assumptions used in other standards
is not necessary to be able to raise this overload nor
differ from those in CEN/TClO/WGl N99.
to achieve normal operation (rated load
performance).
3.1.4 Using CENITClONVGl N99 as a model, the
following list of assumptions (see 3.3 through 3.9 in
3.3.1 Rationale for Assumption 1
this report) has been developed, which could be
used as a basis for future work on safety standards.
3.3.1.1 All safety standards limit the car area in
relation to its rated capacity (load and/or number of
The CEN assumptions 5 (related to car speed) and
persons) in order to minimize the probability of
7 (related to restrictors) as listed in Annex C have
inadvertent overloading. However, it is recognized
not been considered for adoption in this report,
that the possibility of an overloading of up to 25%
since they are deemed to be design parameters.
still exists on passenger Zijts. To eliminate any
hazard for passengers, safe operation must be
Further, CEN assumption 2 is adopted in this report
assured, but not necessarily normal operation.
as assumption 1 and CEN assumption 6 as
assumption 3(c) in order to be consistent with
3.3.1.2 In the case of freight Zi$ts, no overloading is
Part 1 of this report.
anticipated. It is assumed that designated attendants
and freight handlers will adhere to instructions
In summary, CEN assumptions 1, 3, 4, 8, 9, and 10
posted in cars and will not overload them.
correspond to assumptions 1, 2, 3, 4, 5, and 6 in
this report. Assumption 7 is not covered in the
3.3.2 Assumptio 1 as applied in current
CEN document.
standards
3.2 General
3.3.2.1 Currently CEN does not specifically require
a 25% overload safety margin; however, the design
3.2.1 Listed in 3.3 through 3.9 (except as noted)
requirements provide for that level of safety.
are those things specific to lifts that are assumed as
true, although not yet proven or demonstrated as
ASME (Rules 301.10 and 207.8) and CSA (Clauses
such, including:
4.17.1 and 3.9.8) specifically require that safety be
assured on passenger Zifls in the case of 25%
a) Functioning and reliability of lift components;
overload.
0 IS0 ISO/T.R11071-2:1996(E)
3.3.2.2 With exceptions given in 3.3.2.5, the ratio suspension means and supporting structure is at
of the rated load to the car platform area for least 3 times higher than that of the traction driving
passenger lifts is equal (+5%) in all standards for systems, when friction between the suspension
the range of 320 to 4000 kg, and in that respect, ropes and the grooves of the%drive sheave is taken
universality of the assumption #I is achieved. into account. Consequently, the safety risk of
unintended car movement downwards due to the
However, the assumed average weight of a overloading on hydraulic lifts is significantly lower
than on electric traction lifts.
passenger differs: 75kg (CEN), 72,5kg (CSA),
while in ASME it is not specified (prior to
A17.la-1985, the assumed weight for purposes of Furthermore, assuming that the car weight is equal
computing the maximum number of passengers to the rated load, in that case an overload of x% on
the electric traction lift would correspond to only
which could be safely transported in an emergency
was 68 kg). x/2% overload for the hydraulic system.
3.3.2.3 Furthermore, the rated load to car platform For car areas up to 5 m2, the required rated load in
table “1. 1A” for a hydraulic lift may be 1,6 times
area ratio is different for freight Zijts.
less than the rated load of an electric lift. Note that
CEN (non-commercial vehicle 1.6 is an ISO-standard number R5. This is
with instructed users) 200kg/m2 important in view of the rated loads according to
IS0 4190-1, e.g. a bed lift with 5 m2 available car
ASMEKSA (general freight area requires 2500 kg rated load in the case of an
Class A) 244/240 kg/m2 electric lift’ and 1600 kg in the case of a hydraulic
(motor vehicle Class B) 146/145 kg/m2 lift. For car areas bigger than 5 m2 there is no
(industrial truck Class C) 244/240 kg/m2 mathematical background.
3.3.2.4 The CEN standard contains two tables See Table 3.3.2.5 for an abbreviated comparison of
showing the ratio between the rated load and the the CEN Tables.
maximum available car area (for passenger lifts>.
The CEN table “1.1” corresponding to the
requirements for electric lifts is based on the
rationale explained in 3.3.1.1 and was taken into
consideration when formulating the statement in
3.3.2.2.
3.3.2.5 The CEN table “1. 1A” is based on the
rationale that where there is a low probability of the
car being overloaded with persons, the available
area of a hydraulic lift may be increased up to
therein specified maximum, provided that additional
safety measures are taken to ensure the safe
interruption in the lift operation. Such measures
include:
A pressure switch to prevent a start for a
normal journey when the pressure exceeds the
full load pressure by more than 20%;
The design of the car, car sling, car-ram
b)
connection, suspension means, car safety gear,
rupture valve, clamping or paw1 device, guide
rails, and buffers must be based on a load
resulting from table ” 1.1”;
The design pressure of the jack and the piping
d
shall not be exceeded by more than 1,4.
Starting point for CEN’s Table “1. 1A” was the
comparison of safety factors of driving systems on
electric traction lifts versus hydraulic lifts. On
hydraulic lifts the safety factor for the car

0 IS0
ISO/TR 11071-2: 1996(E)
TABLE 3.3.2.5
Increase in Car Area
Rated Load Maximum Car Area
CEN Table l.lA ‘WA” over “1.1”
CEN Table 1.1
%
m2 m2
kg
1,17 1,68 44
2,~ 2,96 48
1200 2,80 4,08
1600 3,56
5,04 42
over 1600, add N/A 0,40/100 kg
N/A
2000 4,20
6,64 58
2500 5,~
8,84 73
over 2500, add 0,16/100 kg
0,4/100 kg 250
3.3.2.6 Lift components that are normally designed Section 1 I. 1.3 deals in particular with discrepancies
in assumptions implied in requirements for design
to withstand, without permanent damage, overloads
greater than 25% (such as ropes, guides, sheaves, of electric safety devices.
buffers, disconnect switches) are not considered in
failure of mechanical
this comparison. 3.5 Assumption 3 -
devices
Note: CEN Assumption 2 (see Annex C} is not a
a) With the exception of items listed below, a
new assumption, but rather one of the methods as
mechanical device built and maintained
to how Assumption 1 is applied in the CEN
standard. according to good practice and the requirements
of a standard comprising safety rules for lifts is
- failure of electric safety assumed not to deteriorate to the point of
3.4 Assumption 2
devices creating hazards before the failure is detected.
(Note: National practices and safety rules may
The possibility of a failure of an electric safety be diflerent, such as safety factors. See sections
4.1.3 and 4.2.1 of this report.)
device complying with the requirement(s) of a lift
safety standard is not taken into consideration.
b) The possibility of the following mechanical
Since national safety rules for lifts may be based on failures shall be taken into consideration:
different assumptions (some are listed below),
universality of Assumption 2 may be questioned. 1) rupture of car suspension means.
3.4.1 Rationale for Assumption 2 2)
rupture and slackening of any connecting
means such as safety related auxiliary
Reliability and safety performance of lift ropes, chains and belts where the safety of
components designated as electric safety devices is normal lift operation or the operation of a
assured if designed in accordance with rules safety related standby component is
contained in a given lift safety standard. However, dependent on such connections.
the design rules may be based on different
assumptions. 3) small leakage in the hydraulic system (jack
included)
3.4.2 Assumption 2 as applied in current
standards c) The possibility of a car or counterweight
striking a buffer at a speed higher than the
Most methods of assuring performance reliability of buffer’s rating is not taken into consideration.
electric safety devices are similar in present
standards. There are, however, differences and
d) The possibility of a simultaneous failure of a
inconsistencies, as detailed in section 11.
mechanical device listed above and another

0 IS0
ISO/TRl1071-2:1996(E)
mechanicaI device provided to ensure safe operation terminal stopping devices, but they do not anticipate
failure of an overspeed governor rope. Only CEN
of a lift, should the first failure occur, is not taken
into consideration. (9.10.2.10.3) assumes the possibility of governor
rope failure.
NOTES:
The Working Group could not agree upon 3.5.2.3 All standards have adopted the assumption
1)
adopting the CEN Assumption 4.3 (see Annex that the possibility of a car or counterweight
striking buffers at a speed higher than the buffer’s
C) requiring that “the possibility of rupture in
rating is not taken into consideration.
the hydraulic system (jack excluded) shall be
taken into consideration. ”
3.5.2.4 All standards have adopted the assumption
Presently, this assumption is implemented only that the possibility of a simultaneous failure of a
2)
mechanical device mentioned in Assumption 3 and
in CEN by requiring a rupture valve or similar
another mechanical device provided to ensure safe
devices, while CSA assumes the rupture of
operation of a lift, should the first failure occur, is
flexible hoses only and, in that case only, the
rupture valve is required. In ASME, the not taken into consideration.
rupture valve (safety valve) is only required in
3.5.2.5 All standards require an anti-creep system
seismic risk zones 2 or greater.
based on assumption 3.5(b)(3).
The CEN rupture valve protects only in the
3)
3.6 Assumption 4 - imprudent act by users
case of rupture of piping, not the cylinder. The
A user may in certain cases make one imprudent
USA’S experience indicates that most problems
act, intentionally made to circumvent the safety
arise from the rupture of cylinders rather than
function of a lift component without using special
piping.
tools. However, it is assumed that:
Refer to section 10 and table 10.1.2 in this
4)
place
two imprudent acts by users will not take
Report for detailed comparison of requirements
simultaneously; and
for free fall and excessive speed protection.
an imprudent user’s act and the failure of the
3.5.1 Rationale for Assumption 3 b)
backup component designed to prevent the
safety hazard resulting from such imprudent
3.5.1.1 Although recent accident records do not
acts will not take place simultaneously (e.g. a
support the assumption in 3.5(b)(l), most safety
user manipulating an interlock and a safety
standards (including those studied in the preparation
circuit failure).
of this report) still assume that the risk of
suspension means failure, in particular wire ropes
Assumption 4 as applied in current
3.6.1
and chains, exists.
standards
3.5.1.2 With the assumption in 3.5 (b)(2) it is
All three standards are based on this assumption.
recognized that the listed components could
deteriorate to the point of creating a direct or
3.7 Assumption 5 - neutralization of safety
potential hazard (by making a safety related standby
devices during servicing
component inoperative) before the deterioration is
detected.
If a safety device, inaccessible to users, is
deliberately neutralized in the course of servicing
3.5.2 Assumption 3 as applied in current
standards work, the safe operation of the lift is no longer
assured,
3.5.2.1 CEN (9.5.1) clearly assumes failure of
3.7.1 Rationale for Assumption 5
suspension means, while ASME (301.8) and CSA
If a mechanic, while servicing a lift, neutralizes or
(4.16.1) rules imply that safety gear must be able to
circumvents a safety device (e.g. bypassing door
stop, or at least slow down, a free falling car.
interlocks using a jumper cable or readjusting
overspeed governor) safe lift operation cannot be
3.5.2.2 Standards differ significantly in regard to
assured.
the rupture or slackening of connecting means.
Only CEN seems to be consistent in adopting this
While it is assumed that lifts wilI be designed to
assumption. Some standards are inconsistent, e.g.
ASME [209.2d(2)] and CSA (3.11.2.4~) anticipate facilitate ease of servicing work and that service
failure of tapes, chains or ropes operating normal mechanics will be equipped with adequate
ISO/TR 11071=2:1996(E) 0 IS0
Rationale for Assumption 6
instructions, tools and expertise to safely service 3.8.1
It is assumed that a person leaning against a vertical
lifts, it is recognized that “fail-safe” service work
surface will exert these forces at that surface. It is
can never be assured solely by the design of a lift.
ftier assumed that more than one person can
3.7.2 Assumption 5 as applied in existing exert this force on a surface simultaneously. Only
standards by relating a force to the width of a surface on
which it can be exerted, can a realistic design
3.7.2.1 All three standards are based on this requirement be obtained.
assumption.
Assumption 6 as applied in current
3.8.2
standards
3.7.2.2 The standards, however, differ in
requirements for the “tools” that must be provided
by the design of a lift in order to facilitate ease and From Table 3.8.2 it is obvious that forces assumed
safety of servicing work. All standards require stop in the standards are different.
switches on the car roof, in the hoistway pit and
3.9 Assumption 7 - retardation
pulley room, and also means for inspection
operation from the car top. The standards differ in
the following: A person is capable of withstanding an average
vertical retardation of lg (9,81 m/s ) and higher
a) CEN(7.7.3.2) requires “emergency unlocking transient retardations.
device “to be provided for every landing door,
while ASME (111.9 & 111.10) and CSA (2.12.9 & 3.9.1 Rationale for assumption 7
2.12.10) require such a device only on two landings The retardation which can be withstood without
and permit it on all other landings. injury varies from person to person. Historically,
the values used in the standards (see table 3.9.2)
b) Only CSA (3.12.1.4) requires “bypass switches” have not been shown to be unsafe for a vast
to be provided in the machine room, which would majority of people.
bypass interlocks or car-door-contact, disconnect
Note: See 3.9.3 regarding retardation limits on
normal operation and enable car-top-inspection
emergency car stops.
operation, in order to facilitate the mechanic’s
servicing of faulty interlocks or car-door contacts. 3.9.2 Assumption 7 as applied in current
standards
c) Only CEN (5.9) requires lighting of the
hoistway.
Table 3.9.2 gives a comparison of requirements
based on the assumed safe retardation rates. Major
38 . Assumption ii- horizontal forces exerted differences are noted in relation to rupture valves,
by a person
plunger stops, and emergency speed limits.
One person can exert either of the following
No standard limits retardation in the case of
horizontal forces at a surface perpendicular to the stops initiated by an electrical safety device.
plane at which the person stands:
3.9.3 Agreed-upon points
a) static force - 300 N
All Standards should consider retardation limits on
b) force resulting from impact - 1000 N emergency stops initiated by an electrical safety
device, albeit based on bio-mechanical studies.
Static forces of short time duration may be exerted
by the simultaneous deliberate acts of several
people located immediately adjacent to each other at
every 300 mm interval along the width of a surface.

0 IS0 ISO/TR 11071=2:1996(E)
TABLE 3.8.2
ASSUMPTION 6 AS APPLIED IN CURRENT STANDARDS
ASME CSA
Assumptions CEN
1.0 Static force
1.1 Landing doors 300 N (7.2.3) 5004 N [llO.lle(7)]
2500 N (2.11.10.4.7)
1.2 Car enclosure 300 N (8.3.2.1)
334 N (204.1~) 330 N (3.6.1.3)
2.0 Impact No spec. 5004 N (llO.llh)
5000 N (2.11.10.5)
3.0 Force distribution No spec. No spec.
No spec.
TABLE 3.9.2
ASSUMPTION 7 AS APPLIED IN CURRENT STANDARDS
CSA
Assumption CEN ASME
Maximum Average
Retardation*
@Progressive Safety Gear 1 g (9.8.4) 1 g (205.8b) 1 g (3.7.9.2)
N/A
l Progressive Clamping 1 g (9.9.4) N/A
Device
l Oil Buffers 1 g (3.3.5.2) 1 g (3.3.5.2)
1 g (10.4.3.2)
*Rupture valve 1 g (12.5.5.1) No spec. No spec.
@Plunger stops 1 g (12.2.3) No spec. No spec.
1 g (4.21.2.2.b)
@Emergency speed limit No spec. 1 g [305.2b(2)]
No. spec. No spec.
@Emergency car stops No spec.
Maximum retardation
Gafety gear No spec. No spec. No spec.
l Buffers > 2,5 g (201.4b) > 2,5 g (3.3.5.2)
> 295 g
(ift = Duration) (10.4.3.2) tI0,04s t 2 0,04 s
t *Maximum average retardation levels exceeding 1 g can occur with a lightly
loaded lifi during safety or buffer application.
Note: 1 g = 9,81 m/s2
ISO/TR 11071=2:1996(E)
Radius of gyration
4 Approach to design safety for
z
Acceleration of gravity
&n
hydraulic components
(dimensionless) Cm
Reeving (roping) ratio
Mass of empty car
kg p3
Rated load in car
kg Q
4.1 Historical Background
Mass of ram Pr
kg
Mass of ram head equipment kg Prh
4.1.1 Philosophical differences
Design load on ram N
F,
This section concentrates on differences between the F
Actual load on ram N
mm4
Second moment of ram area
CEN and ASME requirements for the &sign of J”
hydraulic components. Reference to the CSA
*If two entries, then the first applies to CEN, the second to ASME.
standard is made where it differs from ASME.
4.1.3 Factor of Safety Comparison
a) Differences in both design philosophy and design
formulae lead to different cylinders and rams,
CSA Clause 4.19.1.1.1, and ASME Rules 3022a and
valves, pipes, and fittings when designed to CEN
303.3a require that:
and ASME standards. Philosophical differences
are as follows:
For tensile, compressive bending and torsional
1)
1) ASMF uses the ultimate tensile strength
loading, the plunger, cylinder and connecting
subject to a minimum percentage elongation
couplings shall have a factor of safety not less
of the material as a design criterion.
than 5 based on ultimate tensile strength (UTS).
2) CEN uses the 0,2% proof stress yield point
as the design criterion. Percentage
For pressure calculations of the components
2)
elongation is not considered.
that are subject to fluid pressure, including the
3) The working pressure is differently defined
plunger, connecting coupling, control valves,
in ASME and CEN.
cylinder, and rigid piping shall have a factor of
4) The factors of safety used are also different.
safety (FOS) not less than that calculated from:
b) The differences are demonstrated by examples as
F = 5,04 + 2,7
(4
E -2,8
illustrated by the following comparisons:
1) Thickness of cylinder walls of single stage
jacks (4.1.4);
where
2) Thickness of flat cylinder base/head (4.15);
F = Minimum FOS based on 0,2% proof stress yield
3) Thickness of semi-elliptical cylinder
point. The minimum allowable F shall be 3.
head/cambered base (4.1.6);
E = Percentage Elongation in 50 mm gauge length as
4) Thickness of ram wall for buckling (4.1.7).
per ASTM Standard E8, expressed as a whole
number (eg, 20% = 20 and 5% = 5). The
4.1.2 Nomenclature
minimum allowable E shall be 5.
The following nomenclature is used in the two
The allowable stress to be used for pressure
different standards:
calculations, according to ASME (130.2.5b), shall be
determined as follows:
units* CEN ASME
Item
s I Y.P.
kPa -
Working pressure
P
(W
MPa
Full load pressure F
P
Inside diameter of cylinder d
Di
Diameter of flat head d
where
Inside diameter of skirt D
Di
= Allowable stress @Pa).
Outside dia. of cylinder, pipe D D S
Wall thickness, cylinder e t
Y.P. = Yield point based on 0,2% proof yield stress
cyl
Wall thickness, flat bottom t
e1
point.
Wall thickness, semi-elliptical t
e,
F = FOS per formula (A).
Additional wall thickness C
e,
Design or allowable stress S
Y.P. CEN (12.2.1 .l .l) requires that rams and cylinders be
0.2% proof stress
RPo.2
Tensile strength
R, designed with a FOS of 3,91 (2,3 x 1,7), based on the
E
Modulus of elasticity
0,2% proof stress (YP) and the full bad pressure
Cross-sectional area of plunger mm2/m2 An A
(FL0
Slenderness ratio (dimensionless) L
mm
Maximum unsupported ram 1 L
length
For calculations of tensile, compressive, bending and
torsional loads the following relationship between
ASME and CEN requirements can be established:
qez=0,2% proof stress
0 IS0
ISOfI’R 11071-2: 1996(E)
ASME WP = 1,15 (CEN FLP) e,=l,O mm
ASME FOS = 5 (ASME Working Stress)
CEN FOS = 3,91 (CEN working stress at FLP) It was noted that e0 may be 0,5 in some cases;
however it was agreed to leave it at 1,0 for the sake
or
= 3,4(ASME working stress at WP) of simplicity.
Therefore: For a valid comparison, the two formulae should be
written as close, as possible in the same form, using
common parameters.
UTS > 5 ASME working stress
YP 2 3,4 ASME working stress
(0,2% proof stress = YP) As the full load pressure (p) in Equation (2) is in fact
the static pressure of the system (PJ, and, based on
Section 2.3 in this report, the working pressure (p) in
Nominal equality of ASME and CEN requirements
Equation (1) may be written as p = 1,15(P,),
would occur if:
consequently Equation (1) may be rewritten as
follows:
lJTS 5 = 147
YP=3,4 ’
P l d
1,15 s
in the
However, the formulae employed are different = .
t --
the comparison is more complex 2 s
two codes, so
P l d
For comparisons of stresses due to pressure it is
a
t = 0,575 - s
(1 )
necessary to determine the FOS from the formula (A)
S
and the allowable stress from formula (B).
Examples of the differences between CEN and
Recognizing that D = d + 2ecyl, Equation (2) may be
ASME/CSA are presented in the following sections
rearranged in terms of the inside diameter as follows:
4.1.4 through 4.1.7
1,96P8 . d + eJ$, 2
e 2 a
Note: For further observations and suggestions (2 >
cyl
R po2 - 3,91P -
regarding the factor of safety, refer to Section 4.2.1 s
and 4.2.4.
In order to establish difference in the cylinder wall
4.1.4 Cylinder wall thickness of single stage jacks thickness when calculated per ASME versus CEN
formula, the following is assumed:
According to ASME (1302.2), the cylinder wall
thickness of a single stage jack is calculated with the a) the cylinder is made of material having
following formula:
Y.P. = R@)J = 187,5 MPa, and
E = 14,8
Pd
t=-
(1)
2s
b) the static pressure of the system is P, = 3 MPa
From formula (A) F = 3,125, and from formula
where
(B) S = 60 MPa.
d = inside diameter
= working pressure
P
The wall thickness is calculated in formulae (la) and
S = working (or allowable) stress
(2a) and plotted against cylinder inner diameter in
= minimum wall thickness
t
Figure 4.1.4.
From CEN Clause 12 Note 1 .l:
The graphs show that for a practical range of cylinder
2,3 9 1,7 D + e
e 2 diameters the wall thickness required by CEN is
(2)
.
R P-T 0
d
always greater than that by ASME.
M-2
4.1.5 Thickness of flat cylinder base/head
where
e = wall thickness
Cyl
ASME Rule 1302.3a requires that the wall thickness
= full load pressure
P
of a flat unreinforced head be designed according to
D = outside diameter
the formula:
0 IS0
ISO/TR 11071=2:1996(E)
t=d &
(3)
$
For p = 1,15 Ps,
t = 0,536 d
(W
CEN Clause 12, Note 1.2.1, for flat base with
relieving groove, gives the following formula for the
cylinder base thickness:
” +e
e, 2 0,791D. -
1 0
R
PO.2
where Di = inner diameter of the cylinder.
Using the same material and assuming the same static
pressure as in section 4.1.4, Equations (3a) and (4a)
may be plotted on a common axis, as shown in
Figure 4.1 S.
It is evident that for cylinder inner diameters greater
than about 60 mm, the ASME requires a greater wall
thickness than the CEN.
This result is perhaps reasonable in that the stress
relieving groove would help to reduce stress
concentrations in the CEN case.
0 IS0
ISO/TR 11071-2: 1996(E)
0 50
100 150 200 250
Cylinder Inner Diameter (mm)
Working Pressure - - 3 MPa, Yield Point = 187,5 MPa
Figure 4.1.4
Variation of Required Wall Thickness with Cylinder Diameter
-c
-2 20
.E
z
g 15
.LI
G
5 10
.5 5
.d
;
150 200 250
0 50 100
Cylinder Inner Diameter (mm)
Working Pressure = 3 MPa, Yield Point = 187,5 MPa
Figure 4.1.5
Variation of Required Thickness of Flat Cylinder Base/Head with Cylinder Inside Diameter
ISO/TR 11071=2:1996(E) 0 IS0
4.1.6 Thickness of Semi-Ellipsoidal Cylinder 4.1.7 Thickness of Ram Wall for Buckling
Head/Cambered Base
Both the CEN and the ASME standards recognize the
elastic stability of rams as a limitation on elevator
The case of dished seamless ellipsoidal heads is dealt
load. Guidelines are provided to determine the safe
with in ASME Rule 1302.3~.
strokes for given loading, geometry, and end
CEN Clause 12, Notes 1.2.2, covers the case of conditions. The approach to calculation in both
standards is essentially on the lines of the
cambered bases. The cambered shape approximates
an ellipsoidal form. conventional Euler analysis, with a factor of safety
For
built into the formulae for long slender rams.
The ASME requirement for the wall thickness is shorter, stockier rams, the limitation of compressive
strength of the ram is recognized in the formulae.
given by the following formula:
The design of rams not subject to eccentric loading is
5PD covered by ASME Rule 1302.la.
t=-
6s
The relationships between the total load (VV), the ram
cross sectional area (A), the ram unsupported length
where D = inside diameter of the skirt.
(L), and the radius of gyration (R) are expressed as
two separate equations, one for a slenderness ratio of
For p = 1,15 P,
L/R < 120, the other for L/R > 120.
PD
For L/R c 120 the following formula applies:
t = 0,958 S
s
W
= 9,773 l lo7 - 3,344 l l@(L /R)2
(7)
The wall thickness in CEN is given by the following
A
formula:
For L/R > 120, this relationship becomes:
e > 293 l VP D
(6)
2-
R l -z +eo
PO.2
W 6,552 l 1O1’
(8)
A=
(L lRj2
where D = outside diameter.
CEN Clause 12, Note 2, gives the following formulae
for the calculation of rams against buckling (for
nomenclature, refer to 4.1.2):
Substituting @i + 2e2) for D and simplifying the
following relationship results in:
For hn < 100:
l,955pD, + Rpo2
e, 2
R
- 3,91p
PO.2
F4Rm -(R/210) f&J]
(9)
where
where D
= inside diameter
i
F, =
1,4g,EC,(P,+Q)+0,64P~+P~~
Using the same material and assuming the same static
i.e.: Fs = 1,4F
pressure as in Section 4.1.4, the head wall thickness,
calculated with formulae (5a) and (6a), may be
plotted as shown in Figure 4.1.6.
F > g,[C,(P,+Q)+0,64P,+P,,l
For values of the inside diameter in excess of 75 mm,
the wall thickness required by ASME exceeds that
required by CEN. This result may in part be due to
geometrical differences between the two
configurations, but is consistent with the findings in
section 4.1.5.
ISO/TR 11071-2: 1996(E)
0 IS0
Therefore from (9) + (lOa):
For hn 2 100:
n2 l E l J,
Fs =
(11)
2 l L2
Therefore:
7t2’E*J
F.
(W
A--
2,8 l L2 0;
n
n
Equation (lla) may be further simplified to resemble
.
($1
F 7,28 x 1O1’
A=
(L lRj2
n
(1W
Note: F/A, is the equivalent of W/A, or F=W and
A=%.
For purposes of illustration, the combination of
Equation (7) and (8) is compared to the combination
of Equations (9a) and (llb), for a steel having
ultimate tensile strength of k = 331 MPa.
This direct comparison of CEN and ASME is shown
on Figure 4.1.7.
It is noteworthy that both the CEN and the ASME
plots show smooth curves of similar shape. The L/R
ratio of 120 for ASME and 100 for CEN defines the
point of inflection in each curve. For higher values
of L/R, the ASME and CEN curves are very close,
the ASME curve giving more conservative values of
load by about 11%. The differential between the two
is independent of material strength. For lower values
of L/R (i.e. L/R c loo), the differential between the
ASME and CEN increases as the L/R ratio decreases.
This reflects the particular value chosen for the
material strength. Thus, a lower material strength
would bring the curves closer together. The ASME
curve assumes a fixed material strength; hence, the
constant coefficients in Equation (7).
0 IS0
ISO/TR 11071-2: 1996(E)
50 100 150 200
Cylinder Inner Diameter (mm)
= 187,5 MPa
Working Pressure - - 3 MPa, Yield Point
Figure 4.1.6
Variation of Elliptical Bottom Thickness with Cylinder Inside Diameter
W=Total Load
L=Free Length of Ram
A=Cross Sectional Area of Ram
R=Radius of Gyration of Ram
.
s
.
g 60
.
m
. I
a
I
- 0 . 2; 4; 60 8; 100 Ii0 140 40 40 2oa
UTS=331 MPa
Figure 4.1.7
Comparison of Buckling Criteria
0 IS0 ISO/TR 11071-2: 1996(E)
4.1.11 Capacity of pressure relief valve
4.1.8 Buckling of Rams - Special Cases
The pressure relief valve has to be adjusted to limit
4.1.8.1 Plungers with varying cross sectional area,
the pressure to the following:
according to ASME Rule 1302.la(4), must be
designed with factors of safety of not less than 3
ASME (303.4b(l)): 150% WP
based on accepted elastic stability analysis. CEN
does not specifically address this issue.
CEN (12.5.3): 140% FLP, or
170% FLP in the systems with
4.1.8.2 ASME Rule 1302.lb deals with the specific
high internal losses
situation of rams subject to bending as a result of
eccentric loading in addition to buckling loads. This
Considering the relationship WPLFLP established in
situation is not covered by CEN, as clause 12.2.2.1
Section 2.3, one can find that ASME requires higher
requires a flexible connection between the car and the
capacity of the relief valve, or:
ram. (See also 5.1.1 and 5.2.1 of this report.)
4.1.9 Wall thickness of rigid pipes
150% l 1915 = 1234
ASME .
140%
-cm=
According to ASME (1302.4) and CSA (4.19.3.2) the
minimum wall thickness of rigid pipes is cakulated
on the basis of allowable stress (see formula (B)),
However, for the systems with “high internal losses”
using same formula (la) as for cylinders, except that
the requirements in both standards are approximately
the following wall thickness must be adde
...