prEN ISO 20770-4

Drilling and foundation equipment - Safety - Part 4: Diaphragm walling equipment (ISO/DIS 20770-4:2025)

See attached draft

Geräte für Bohr- und Gründungsarbeiten - Sicherheit - Teil 5: Geräte für Schlitzwandarbeiten (ISO/DIS 20770-4:2025)

Dieses Dokument behandelt zusammen mit Teil 1 alle signifikanten Gefährdungen für Geräte für Schlitzwandarbeiten, wenn sie bestimmungsgemäß und unter den Bedingungen der Fehlanwendung, die vernünftigerweise vom Hersteller vorhersehbar sind und mit der gesamten Lebensdauer der Maschine in Verbindung stehen, verwendet werden (siehe Anhang B).
Die Anforderungen in diesem Teil gelten zusätzlich zu den in ISO 20770–1:____ gestellten Anforderungen.
Das vorliegende Dokument wiederholt nicht die Anforderungen von ISO 20770–1:____, sondern ergänzt oder ersetzt die Anforderungen für die Anwendung von Geräten für Schlitzwandarbeiten.

Machines de forage et de fondation - Sécurité - Partie 4: Machines pour parois moulées (ISO/DIS 20770-4:2025)

Oprema za vrtanje in temeljenje - Varnost - 4. del: Oprema za izdelavo membranskih sten (ISO/DIS 20770-4:2025)

General Information

• Status: Not Published
• Publication Date: 13-Sep-2026
• ICS: 53.100 - Earth-moving machinery
• Technical Committee: CEN/TC 151 - Construction equipment and building material machines - Safety
• Drafting Committee: CEN/TC 151/WG 3 - Drilling equipment - Safety
• Current Stage: 4060 - Closure of enquiry - Enquiry
• Start Date: 08-May-2025
• Due Date: 15-Feb-2025
• Completion Date: 08-May-2025
• Directive: 2006/42/EC - Directive 2006/42/EC of the European Parliament and of the Council of 17 May 2006 on machinery, and amending Directive 95/16/EC (recast)
• Directive: 2023/1230 - Regulation (EU) 2023/1230 of the European Parliament and of the Council of 14 June 2023 on machinery and repealing Directive 2006/42/EC of the European Parliament and of the Council and Council Directive 73/361/EEC (Text with EEA relevance)
• Mandate: M/396 - Mandate to CEN and Cenelec for standardisation in the field of machinery
• Mandate: M/605 - COMMISSION IMPLEMENTING DECISION of 20.1.2025 on a standardisation request to the European Committee for Standardization and to the European Committee for Electrotechnical Standardization as regards machinery and related products in support of Regulation (EU) 2023/1230 of the European Parliament and of the Council
• Ref Project: oSIST prEN ISO 20770-4:2025 - Drilling and foundation equipment - Safety - Part 4: Diaphragm walling equipment (ISO/DIS 20770-4:2025)

Relations

• Revises: EN 16228-5:2014+A1:2021 - Drilling and foundation equipment - Safety - Part 5: Diaphragm walling equipment
• Effective Date: 04-Oct-2023

Overview

prEN ISO 20770-4 (ISO/DIS 20770-4:2025) - "Drilling and foundation equipment - Safety - Part 4: Diaphragm walling equipment" is a draft CEN/ISO safety standard that specifies safety requirements and risk-reduction measures for diaphragm walling equipment throughout the machine life cycle. Issued as a draft international standard (ISO/DIS) and prepared by ISO/TC 195/SC 3 (secretariat AFNOR), it complements the common requirements in ISO 20770‑1 and addresses hazards specific to diaphragm wall rigs, cutters and grabs used to form diaphragm (moulded) walls on construction sites.

Key topics and technical requirements

The standard focuses on practical safety controls and verification for diaphragm walling equipment, including:

• Scope and risk coverage - hazards during intended use and reasonably foreseeable misuse (see Annex B for significant hazards).
• Strength and stability (Section 4.2) - structural stability of the rig and loads from diaphragm wall cutting tools.
• Winches, pulleys and hoisting systems (Section 4.3) - safe design and operation for rope‑suspended cutters and grabs.
• Control systems (Section 4.4) - operator controls, free‑fall triggering, winch control when changing ropes and cutter operation.
• Moving parts, maintenance and recovery (Sections 4.5–4.6) - protection of personnel during operation, stuck-tool recovery and maintenance instructions.
• Hose and cable handling (4.7), holding brakes (4.8), and compatibility/inclination of carrier machines (4.9–4.10) - requirements when cutters are mounted on excavators, cranes or other carriers.
• Operating positions and noise (4.11–4.12) - operator safety, noise test code (Annex A) and information for use, including operator’s and maintenance manuals (Clause 6).
• Verification and conformity (Clause 5) - tests and checks to confirm safety requirements are met.
• Regulatory correlation - informative annexes mapping the standard to Directive 2006/42/EC and Regulation EU 2023/1230 (Annex ZA/ZB).

Practical applications and users

This standard is intended for:

• Manufacturers and OEMs of diaphragm walling rigs, diaphragm wall cutters and grabs;
• Design and safety engineers specifying equipment stability, hoisting and control systems;
• Site managers, contractors and plant operators ensuring safe operation, maintenance and recovery procedures;
• Notified bodies and certification/inspection organizations assessing conformity with machine safety and EU machinery requirements;
• Component suppliers (winches, brakes, hose/cable systems) who must ensure compatibility with carrier machines.

Applied in design reviews, risk assessments, operator and maintenance manuals, commissioning checks and site safety planning, prEN ISO 20770-4 helps reduce accidents linked to diaphragm wall construction.

Related standards

• ISO 20770‑1 (Common requirements)
• ISO 20770‑3 (Foundation equipment)
• ISO 11886 (Drilling/foundation machine specifications)
• EN 474‑5, EN 474‑12 (earth‑moving machinery)
• EN 13000 (mobile cranes)
• ISO 12100, ISO 6395/6396 (safety and noise testing)

Note: prEN ISO 20770‑4 is a draft circulated for comment (ISO/DIS) and may be revised before final publication.

Standards Content (Sample)

SLOVENSKI STANDARD
01-april-2025
Oprema za vrtanje in temeljenje - Varnost - 4. del: Oprema za izdelavo
membranskih sten (ISO/DIS 20770-4:2025)
Drilling and foundation equipment - Safety - Part 4: Diaphragm walling equipment
(ISO/DIS 20770-4:2025)
Geräte für Bohr- und Gründungsarbeiten - Sicherheit - Teil 5: Geräte für
Schlitzwandarbeiten (ISO/DIS 20770-4:2025)
Machines de forage et de fondation - Sécurité - Partie 4: Machines pour parois moulées
(ISO/DIS 20770-4:2025)
Ta slovenski standard je istoveten z: prEN ISO 20770-4
ICS:
53.100 Stroji za zemeljska dela Earth-moving machinery
93.020 Zemeljska dela. Izkopavanja. Earthworks. Excavations.
Gradnja temeljev. Dela pod Foundation construction.
zemljo Underground works
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

DRAFT
International
Standard
ISO/DIS 20770-4
ISO/TC 195/SC 3
Drilling and foundation
Secretariat: AFNOR
equipment — Safety —
Voting begins on:
Part 4:
2025-02-13
Diaphragm walling equipment
Voting terminates on:
2025-05-08
Machines de forage et de fondation — Sécurité —
Partie 4: Machines pour parois moulées
ICS: 53.100
THIS DOCUMENT IS A DRAFT CIRCULATED
FOR COMMENTS AND APPROVAL. IT
IS THEREFORE SUBJECT TO CHANGE
AND MAY NOT BE REFERRED TO AS AN
INTERNATIONAL STANDARD UNTIL
PUBLISHED AS SUCH.
This document is circulated as received from the committee secretariat.
IN ADDITION TO THEIR EVALUATION AS
BEING ACCEPTABLE FOR INDUSTRIAL,
TECHNOLOGICAL, COMMERCIAL AND
USER PURPOSES, DRAFT INTERNATIONAL
STANDARDS MAY ON OCCASION HAVE TO
ISO/CEN PARALLEL PROCESSING
BE CONSIDERED IN THE LIGHT OF THEIR
POTENTIAL TO BECOME STANDARDS TO
WHICH REFERENCE MAY BE MADE IN
NATIONAL REGULATIONS.
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.
Reference number
ISO/DIS 20770-4:2025(en)
DRAFT
ISO/DIS 20770-4:2025(en)
International
Standard
ISO/DIS 20770-4
ISO/TC 195/SC 3
Drilling and foundation
Secretariat: AFNOR
equipment — Safety —
Voting begins on:
Part 4:
Diaphragm walling equipment
Voting terminates on:
Machines de forage et de fondation — Sécurité —
Partie 4: Machines pour parois moulées
ICS: 53.100
THIS DOCUMENT IS A DRAFT CIRCULATED
FOR COMMENTS AND APPROVAL. IT
IS THEREFORE SUBJECT TO CHANGE
AND MAY NOT BE REFERRED TO AS AN
INTERNATIONAL STANDARD UNTIL
PUBLISHED AS SUCH.
This document is circulated as received from the committee secretariat.
IN ADDITION TO THEIR EVALUATION AS
BEING ACCEPTABLE FOR INDUSTRIAL,
© ISO 2025
TECHNOLOGICAL, COMMERCIAL AND
USER PURPOSES, DRAFT INTERNATIONAL
All rights reserved. Unless otherwise specified, or required in the context of its implementation, no part of this publication may
STANDARDS MAY ON OCCASION HAVE TO
ISO/CEN PARALLEL PROCESSING
be reproduced or utilized otherwise in any form or by any means, electronic or mechanical, including photocopying, or posting on
BE CONSIDERED IN THE LIGHT OF THEIR
the internet or an intranet, without prior written permission. Permission can be requested from either ISO at the address below
POTENTIAL TO BECOME STANDARDS TO
WHICH REFERENCE MAY BE MADE IN
or ISO’s member body in the country of the requester.
NATIONAL REGULATIONS.
ISO copyright office
RECIPIENTS OF THIS DRAFT ARE INVITED
CP 401 • Ch. de Blandonnet 8
TO SUBMIT, WITH THEIR COMMENTS,
CH-1214 Vernier, Geneva
NOTIFICATION OF ANY RELEVANT PATENT
Phone: [phone]
RIGHTS OF WHICH THEY ARE AWARE AND TO
PROVIDE SUPPORTING DOCUMENTATION.
Email: [e-mail]
Website: www.iso.org
Published in Switzerland Reference number
ISO/DIS 20770-4:2025(en)
ii
ISO/DIS 20770-4:2025(en)
Contents Page
Foreword .iv
Introduction .v
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Safety requirements and/or protective/risk reduction measures . 3
4.1 General .3
4.2 Requirements for strength and stability .3
4.2.1 General .3
4.2.2 Loads from diaphragm wall cutting tools .3
4.2.3 Stability of diaphragm walling rig .3
4.3 Winches and pulleys .4
4.4 Control devices .5
4.4.1 General .5
4.4.2 Control of the diaphragm walling rig equipped with cutter .5
4.4.3 Control of winches for suspending grabs or cutters when changing ropes .5
4.4.4 Free-fall operation .5
4.5 Moving parts involved in the process .7
4.6 Maintenance of diaphragm wall cutters .7
4.7 Hose and cable handling systems .7
4.8 Holding brake .7
4.9 Compatibility of the carrier machine .7
4.10 Inclination of the carrier .8
4.11 Operating position(s) .8
4.12 Noise .8
5 Verification of the safety requirements and/or protective/risk reduction measures . 8
6 Information for use .10
6.1 Operator’s manual .10
6.1.1 General .10
6.1.2 Specific instructions on the diaphragm wall cutting tools put on the market
separately .10
6.2 Maintenance instructions .10
Annex A (normative) Noise test code .12
Annex B (informative) List of additional significant hazards .13
Annex ZA (informative) Relationship between this European Standard and the essential
requirements of Directive 2006/42/EC aimed to be covered . 14
Annex ZB (informative) Relationship between this European Standard and the essential
requirements of Regulation EU 2023/1230 aimed to be covered . 19
Bibliography .25

iii
ISO/DIS 20770-4:2025(en)
Foreword
ISO (the International Organization for Standardization) is a worldwide federation of national standards
bodies (ISO member bodies). The work of preparing International Standards is normally carried out through
ISO 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. ISO collaborates closely
with the International Electrotechnical Commission (IEC) on all matters of electrotechnical standardization.
The procedures used to develop this document and those intended for its further maintenance are described
in the ISO/IEC Directives, Part 1. In particular, the different approval criteria needed for the different types
of ISO documents should be noted. This document was drafted in accordance with the editorial rules of the
ISO/IEC Directives, Part 2 (see www.iso.org/directives).
ISO draws attention to the possibility that the implementation of this document may involve the use of (a)
patent(s). ISO takes no position concerning the evidence, validity or applicability of any claimed patent
rights in respect thereof. As of the date of publication of this document, ISO [had/had not] received notice of
(a) patent(s) which may be required to implement this document. However, implementers are cautioned that
this may not represent the latest information, which may be obtained from the patent database available at
www.iso.org/patents. ISO shall not be held responsible for identifying any or all such patent rights.
Any trade name used in this document is information given for the convenience of users and does not
constitute an endorsement.
For an explanation of the voluntary nature of standards, the meaning of ISO specific terms and expressions
related to conformity assessment, as well as information about ISO's adherence to the World Trade
Organization (WTO) principles in the Technical Barriers to Trade (TBT), see www.iso.org/iso/foreword.html.
This document was prepared by Technical Committee ISO/TC 195, Building construction machinery and
equipment, Subcommittee SC 3, Drilling and foundation machinery and equipment.
A list of all parts in the ISO 20770 series can be found on the ISO website.
Any feedback or questions on this document should be directed to the user’s national standards body. A
complete listing of these bodies can be found at www.iso.org/members.html.

iv
ISO/DIS 20770-4:2025(en)
Introduction
This document is a type C standard as stated in ISO 12100:2010.
The machinery concerned and the extent to which hazards are covered are indicated in the scope of this
standard.
When requirements of this type C standard are different from those which are stated in type A or B standards,
the requirements of this type C standard take precedence over the requirements of the other standards, for
drilling and foundation equipment that have been designed and built according to the requirements of this
type C standard.
v
DRAFT International Standard ISO/DIS 20770-4:2025(en)
Drilling and foundation equipment — Safety —
Part 4:
Diaphragm walling equipment
1 Scope
This document, together with part 1, deals with all significant hazards for diaphragm walling equipment
when they are used as intended and under the conditions of misuse which are reasonably foreseeable by the
manufacturer associated with the whole life time of the machine (see Annex B).
The requirements of this part are complementary to the common requirements formulated in ISO 20770–1:____.
This document does not repeat the requirements from ISO 20770–1:____, but adds or replaces the
requirements for application for diaphragm walling equipment.
2 Normative references
The following documents are referred to in the text in such a way that some or all of their content constitutes
requirements of this document. For dated references, only the edition cited applies. For undated references,
the latest edition of the referenced document (including any amendments) applies.
EN 474-5:2022, Earth-moving machinery — Safety — Part 5: Requirements for hydraulic excavators
EN 474-12:2022, Earth-moving machinery — Safety — Part 12: Requirements for cable excavators
EN 13000:2010+A1:2014, Cranes — Mobile cranes
ISO 6395:2008, Earth-moving machinery — Determination of sound power level — Dynamic test conditions
ISO 6396:2008, Earth-moving machinery — Determination of emission sound pressure level at operator's
position — Dynamic test conditions
1)
ISO 11886, ____, , Drilling and foundation machinery — Soil or soil and rock mixture drilling and foundation
machines — Commercial specifications
ISO 12100:2010, Safety of machinery — General principles for design — Risk assessment and risk reduction
2)
ISO 20770-1, ____, , Drilling and foundation equipment — Safety — Part 1: Common requirements
3)
ISO 20770-3, ____, , Drilling and foundation equipment — Safety — Part 3: Foundation equipment
3 Terms and definitions
For the purposes of this document, the terms and definitions given in ISO 12100:2010, ISO 11886:____ and
the following apply.
1) At the stage of preparation : ISO/DIS 11886:2023
2) Currently at stage CD
3) Currently at stage CD
ISO/DIS 20770-4:2025(en)
ISO and IEC maintain terminology databases for use in standardization at the following addresses:
— ISO Online browsing platform: available at https:// www .iso .org/ obp
— IEC Electropedia: available at https:// www .electropedia .org/
3.1
diaphragm wall
structural retaining wall or cut-off wall, both of which can be impermeable and constructed in-situ in the
ground as a series of contiguous panels
Note 1 to entry: Panels are typically narrow but deep and are cut between surface guide walls and can depend on a
slurry or mud suspension for temporary ground support. Structural walls are typically of reinforced concrete with
the concrete placed from the bottom of the panel upwards to displace the slurry or mud suspension.
Note 2 to entry: There are other diaphragm wall techniques, for example continuous trenchers; these techniques use
machines and cutting tools such as digging chain or wheel disc, which are covered by EN 474–10:2022.
3.2
diaphragm walling rig
carrier machine equipped with cutting tool to cut panels for diaphragm walls (3.1)
Note 1 to entry: The diaphragm walling rig is either:
— a complete machine satisfying this document, or
— a carrier machine able to withstand dynamic loads as specified in 4.2 with interchangeable equipment in the form
of diaphragm wall cutting tools, which can be provided by different suppliers or manufacturers.
Note 2 to entry: The carrier machine is, e.g.:
— foundation equipment as defined in ISO 20770–3:____; or
— a crane as defined in EN 13000:2010+A1:2014; or
— a cable excavator as defined in EN 474–12:2022; or
— a hydraulic excavator as defined in EN 474–5:2022.
3.3
diaphragm wall cutting tool
tool for cutting panels for diaphragm walls
Note 1 to entry: Diaphragm wall cutting tools can either be:
— diaphragm wall grab (as defined in ISO 11886:____, 3.4.4.1);
— diaphragm wall cutter (as defined in ISO 11886:____, 3.4.4.3).
Note 2 to entry: Diaphragm wall cutting tools can be rope suspended and guided by frames or kelly bars.
3.4
recovery
extraction of a diaphragm wall cutting tool
Note 1 to entry: For example, grab or cutter when it is stuck in the panel.
3.5
triggering of free-fall
action (manual or automatic) that causes the starting of the free-fall

ISO/DIS 20770-4:2025(en)
4 Safety requirements and/or protective/risk reduction measures
4.1 General
Diaphragm walling equipment shall comply with the requirements of ISO 20770-1:____ except as modified or
replaced by the requirements of this part of the standard.
For the compatibility between the diaphragm walling equipment and the carrier machine, see 4.9.
4.2 Requirements for strength and stability
4.2.1 General
ISO 20770-1:____, 4.2 applies with the following additions:
4.2.2 Loads from diaphragm wall cutting tools
When calculating stability in accordance with ISO 20770-1:____ the following shall be taken into account:
— weight of the diaphragm wall cutting tools (including any hose and cable handling system and their
mounts);
— weight of the excavated material, slurry or suspension materials and any material adhering to the tool;
— loads applied to the tools during tool extraction;
— all loads induced by rope suspended components are acting at the point where the rope is leaving the
upper pulley.
4.2.3 Stability of diaphragm walling rig
4.2.3.1 General
Diaphragm walling equipment can have diaphragm wall cutting tools either rope suspended or guided by
frames or kelly bars rigidly connected to the carrier machine.
In both cases a general method for calculating stability shall be used, see 4.2.3.2 below.
For rope suspended cutting tools, a simplified method for calculating stability may be used, see 4.2.3.3
below which differs from ISO 20770-1:____, 4.2.3.
The simplified method ensures the equipment is stable only when the working platform is horizontal.
Therefore it cannot be used when working on slopes and travelling.
4.2.3.2 General method for calculating stability
The required stability angle as mentioned in ISO 20770-1:____, 4.2.3.5 shall be as stated in Table 2 below:
Table 1 — Required stability angle, dynamic influences included
Stability class NC Stability class SC
(normal conditions) (special conditions)
Travelling 8 degrees 5 degrees + β (see c) below)
a
Operating and tramming 5 degrees 2,5 degrees + β (see c) below)
Recovery 3,5 degrees 1 degree + β (see c) below)
a
A static stability angle of 5 degrees + β (see c) below) calculated without dynamic accelerations and wind loads is also
required.
NC and SC are the stability classes (see explanations below).

ISO/DIS 20770-4:2025(en)
Use of stability class NC is recommended.
The manufacturer may use stability class SC provided that all of the following conditions are fulfilled:
a) The ground shall support the machine and can reliably withstand the supporting forces, without
significant unintended displacements or taking into account their affect on stability (support by, e.g.
timber plates, steel plates and/or improved ground surface may be required). This shall also be shown
in the case, if supports (those not causing rigid body movement) become unloaded and thus cause
maximum forces at other supports.
b) Masses of relevant parts of the machine shall be evaluated by weighing with an accuracy of ±2,5 %.
c) When using tipping line 1 as defined in ISO 20770-1:____, Figure 1 the required tipping angle shall be
increased by β.
d) Hoist speed is not greater than 10 m/min.
e) No free-fall winch mode is used.
f) Freely suspended loads are secured when travelling and tramming, in order to avoid swinging.
4.2.3.3 Simplified method for calculating stability
The calculation of stability shall be done in the most unfavourable position of track orientation and at the
maximum operating radius on the horizontal platform.
The sum of all overturning moments shall not exceed 75 % of the sum of all stabilizing moments, where the
stabilizing and tipping moments include:
— the base machine alone, its tipping moment is given by the load chart for the actual boom configuration.
The safety percentage given by the manufacturer has to be converted to 100 % in order to get of limit
tipping moment;
— additional equipment permanently mounted to the carrier machine, e.g. power pack, guiding system,
hose reels, special boom head, walkways, etc. Moments are calculated with the load at the distance of the
tipping line.
When using a rope suspended grab:
— the moment induced by the weight of the rope suspended part multiplied by 1,25 (excavating tool, with
clamshells full of soil of specific weight = 20 kN/m ).
When using a rope suspended cutter:
— moment induced by the weight of the cutter with full hydraulic hoses;
— moment induced by the weight of mud hose. Depending on the configuration of mud circuit (suspended
on the boom or hose reel at the back of the machine) the mud weight can create tipping or stabilizing
moments. So the stability has to be calculated with full and/or empty mud hose;
— minimum specific weight of mud = 12,5 kN/m .
4.3 Winches and pulleys
ISO 20770-1:____, 4.8.2 and 4.8.3 apply with following additions and/or modifications:
For working ropes used to lift cutting tools only, the minimum factor of safety (minimum breaking load,
guaranteed by the manufacturer, in relation to the maximum static load on the rope caused by the winch
line pull in the first layer) shall be 2,5.
Diameters of sheaves and drums used to lift the excavation tools only shall meet the following minimum
requirements:
ISO/DIS 20770-4:2025(en)
winch drum pitch: 16,0 d
sheave pitch: 16,0 d
compensation pulley: 14,0 d
where d is the diameter of the rope.
4.4 Control devices
4.4.1 General
ISO 20770-1:____, 4.16 applies with the additions of 4.4.2 and 4.4.3:
4.4.2 Control of the diaphragm walling rig equipped with cutter
During operation, the diaphragm wall cutter shall be controlled from the diaphragm walling rig operator’s
position.
Diaphragm walling rigs shall be designed and equipped with a remote control or control station adjacent or
close to each winch for providing slow rotation speed and to give the operator/maintenance staff clear view
of a cutter during maintenance tasks and assembly/dismantling.
Freefall mode shall be prevented on the winches of the diaphragm walling rigs fitted with diaphragm wall
cutter (e.g. by a key-operated control).
4.4.3 Control of winches for suspending grabs or cutters when changing ropes
There shall be a remote control or control station adjacent or close to each winch with a full view to the winch.
The mode for changing ropes shall be activated by a lockable mode selector.
In this mode, the maximum rotation speed shall be limited to 2 rpm.
It shall not be possible to operate more than one winch at the same time. This control shall be of hold-to-run type.
From the control station for this mode, it shall be possible to have a view to the winch and the person guiding
the rope for handling and communication.
Controls (for use in this mode) shall either be located close to the winches involved and allow full visibility of
the winches or on a remote device that will allow only operation of the winches. Enabling of a remote control
shall be done at the operator station and can be combined with the mode selector function.
It shall not be possible for the normal winch controls at the operator station to operate the winches whilst
the mode for changing ropes is activated.
4.4.4 Free-fall operation
4.4.4.1 General
Diaphragm walling equipment designed for free-fall operation shall comply with 4.4.4.2 to 4.4.4.5.
4.4.4.2 Common requirements for free-fall operation
The free-fall system shall be designed that an uncontrolled run-up or run-off of the rope is avoided, e.g. by a
rope guide.
There shall be a specific lockable selector (e.g. could be integrated in the mode selector) to enable/disable
the free-fall operation.
ISO/DIS 20770-4:2025(en)
There may be one selector for all winches or one selector per winch.
The design of the free-fall system may provide different types of operation (automatic/manual) as well
as different types of deactivation (automatic/manual) and triggering (automatic/manual) as described in
4.4.4.3 to 4.4.4.5.
These different types shall be selected either by a separate control or by the lockable free-fall operation
selector.
The selected type shall be indicated at the operator´s station.
4.4.4.3 Free-fall brake
The winch shall be fitted with a free-fall brake.
The use of the main winch disconnecting system shall only be possible when the free-fall function is
activated.
The free-fall brake shall be designed that the deceleration of a dynamic load shall be possible.
A proportional actuation of the free-fall brake shall be possible.
4.4.4.4 Manual free-fall operation
4.4.4.4.1 General
Manual free-fall operation shall only be possible for following conditions:
— free-fall operation is selected;
— free-fall function is activated.
4.4.4.4.2 Activation/deactivation of free-fall function
Activation of free-fall function shall only be possible by actuation of two independent controls simultaneously
(e.g. pedals and additional control). In accordance with ISO 20770-1:____, 4.8.2, both controls shall be of the
hold-to-run type.
There shall be no lowering at activating/deactivating the free-fall function.
The free-fall function can be with an automatic deactivation (see 4.4.4.4.3) or manual deactivation (see
4.4.4.4.4).
Triggering after activation of the free-fall function shall be done by a separate control (e.g. by releasing the
pedals).
4.4.4.4.3 Automatic deactivation of free-fall function
Free-fall function is deactivated automatically for following conditions:
— hoist winch stands still;
and
— moving the control for winch to lifting or lowering position.
4.4.4.4.4 Manual deactivation of free-fall function
Free-fall function has to be deactivated manually by operator.

ISO/DIS 20770-4:2025(en)
Triggering of free-fall after lifting or lowering can be done by the following options:
— automatic (triggering of free-fall will start automatically when returning the control for lifting or
lowering to neutral position);
NOTE 1 In this case, the holding brake (see 4.9) will not be activated automatically after returning the control for
lifting or lowering to neutral position.
or
— manual (triggering of free-fall will start by actuation by the operator after returning the control for
lifting or lowering to neutral position).
NOTE 2 Triggering of free-fall will start by actuation by the operator e.g. by releasing the brake pedal.
4.4.4.5 Automatic free-fall operation
When a diaphragm walling equipment is fitted with an automatic cycle mode, including free-fall operation
(e.g. chiselling operations), the activation of the automatic cycle mode shall be possible only after selecting
free-fall operation mode.
The diaphragm walling equipment shall be equipped with a system to control the automatic cycle mode.
The control system shall not stop the cycle during the free-fall.
After stop of the automatic cycle or loss of energy, restarting of the automatic operation shall only be possible
by an intentional action by the operator.
4.5 Moving parts involved in the process
ISO 20770-1:____, 4.23.2 does not apply.
NOTE It is not practicable to guard the rotating parts of cutters and the clamshells of grabs.
4.6 Maintenance of diaphragm wall cutters
It shall be possible to secure the wheels of diaphragm wall cutters to prevent them moving unintentionally
during transportation or maintenance.
4.7 Hose and cable handling systems
A purpose built diaphragm walling rig shall be fitted with a hose and cable handling system.
NOTE Hoses include hydraulic hoses for the diaphragm wall excavation tools and any slurry/mud hoses. Cables
include; electrical and control cables for the diaphragm wall excavation tools.
4.8 Holding brake
The winch of diaphragm walling equipment shall be fitted with a brake, which actuates immediately after
releasing operational controls (e.g. levers or pedals) or in case of loss of energy.
The holding brake for hoisting and luffing systems operated by winches shall be able to exert a restraining
torque at least 33 % greater than the maximum torque transmitted from the rope drum to the brake under
working or erection conditions, whichever is greater.
4.9 Compatibility of the carrier machine
When the carrier machine of diaphragm wall equipment is a:
— cable excavator it shall also comply
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