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DNV GL AS
RULES FOR CLASSIFICATION
Ships
Edition January 2018
Part 4 Systems and components
Chapter 7 Pressure equipment
FOREWORD
DNV GL rules for classification contain procedural and technical requirements related to obtaining
and retaining a class certificate. The rules represent all requirements adopted by the Society as
basis for classification.
© DNV GL AS January 2018
Any comments may be sent by e-mail to [email protected]
If any person suffers loss or damage which is proved to have been caused by any negligent act or omission of DNV GL, then DNV GL shall
pay compensation to such person for his proved direct loss or damage. However, the compensation shall not exceed an amount equal to ten
times the fee charged for the service in question, provided that the maximum compensation shall never exceed USD 2 million.
In this provision "DNV GL" shall mean DNV GL AS, its direct and indirect owners as well as all its affiliates, subsidiaries, directors, officers,
employees, agents and any other acting on behalf of DNV GL.
Part 4 Chapter 7 Changes - current
Rules for classification: Ships — DNVGL-RU-SHIP Pt.4 Ch.7. Edition January 2018 Page 3
Pressure equipment
DNV GL AS
CHANGES – CURRENT
This document supersedes the January 2017 edition of DNVGL-RU-SHIP Pt.4 Ch.7.
Changes in this document are highlighted in red colour. However, if the changes involve a whole chapter,
section or sub-section, normally only the title will be in red colour.
Changes January 2018, entering into force 1 July 2018.
Topic Reference Description
Harmonisation of hydraulic
pressure test requirements for
valves / equipment of boilers
Sec.7 [4.6.7] Procedure for the testing of equipment, valves and fittings with
design temperature above 120°C specified.
Sec.4 [6.4.1]Inconsistent thickness
requirements for nozzles and
branches Sec.4 [6.4.2]
Sec.4 [6.4.1] separated in Sec.4 [6.4.1] for general wall
thickness and Sec.4 [6.4.2] for taking additional loads into
account.
Inconsistency of minimum wall
thickness requirements
Sec.4 [2.6.1] and
[2.6.2]
—Sec.4 [2.6.1]: minimum thickness of shells and dished ends
completed by requirements for stainless steel and non-
ferrous materials. Requirements for type C independent
tanks and process pressure vessels according to IGC added.
— Sec.4 [2.6.2]: deleted.
Reinforcing plates for supports Sec.4 [2.3.2] Loads for installation and support that shall considered for the
design of the pressure equipment.
Requirements for material
testing
Sec.1 [3.2.2] Guidance note added for material certification of parts directly
welded to pressurised parts of the pressure equipment.
UT Testing for plates Sec.7 [4.1.4] Ultrasonic testing for flat plates loaded by residual welding
stress specified.
Sec.1 [1.1.2] Expression "including mountings" deleted for pressure vessels,
because it is covered by the scope of Ch.6. Term "mountings"
modified to "equipment, valves and fittings" and added also to
thermal oil heaters.
Sec.1 Table 8 Table created for certification requirements for equipment,
valves and fittings.
Sec.3 [3.2.2] Requirement for drenching system restored.
Sec.4 [2.5.2] Calculation of the nominal design stress for austenitic stainless
steels modified from specified minimum lower yield stress at
design material temperature to 1.0% proof stress at design
material temperature.
Sec.4 [3.5.2] Expression "open feed water system" modified to system
"without adequate feed water treatment and degassing".
Sec.4 [4.1.1] Explanation for 's' modified to "minimum plate thickness after
forming" and "calculated thickness" modified to "minimum plate
thickness after forming" in the text.
Other changes
Sec.4 [4.1.4] Explanation for 's' modified to "minimum plate thickness after
forming".
Part 4 Chapter 7 Changes - current
Rules for classification: Ships — DNVGL-RU-SHIP Pt.4 Ch.7. Edition January 2018 Page 4
Pressure equipment
DNV GL AS
Topic Reference Description
Sec.4 [4.2.4] Last sentence in Sec.4 [4.2.2] deleted and new para added
regarding the thickness of the cylindrical parts of dished ends.
Sec.4 [6.6.1] Use of the calculation of openings extended to stayed and
unstayed flat plates.
Sec.4 [7] Heading made more generic to cover the calculations of fired
and unfired cylindrical shells under external pressure.
Sec.5 [1.1.3] Term "mounting" modified to "equipment, valves and fittings".
Sec.5 [2.1] Location for the installation of safety valves at steam boilers
added.
Sec.6 Table 2 For "salinity high" and "oil content high" "shut-down of feed
water pump" has been modified to 'interruption of feed water
supply' and monitoring is only necessary if contamination with
salt or oil is possible.
Sec.7 [4.4.3] Procedure for WPT of circumferential welding seams specified.
App.A [2] Number, type and location of inspection openings made
mandatory.
Editorial corrections
In addition to the above stated changes, editorial corrections may have been made.
Part 4 Chapter 7 Contents
Rules for classification: Ships — DNVGL-RU-SHIP Pt.4 Ch.7. Edition January 2018 Page 5
Pressure equipment
DNV GL AS
CONTENTS
Changes – current.................................................................................................. 3
Section 1 General requirements............................................................................10
1 Classification......................................................................................10
1.1 Application..................................................................................... 10
1.2 Cross-references............................................................................. 10
2 Definitions..........................................................................................11
2.1 Terms............................................................................................ 11
2.2 Specifications................................................................................. 11
2.3 Symbols.........................................................................................13
2.4 Units............................................................................................. 17
2.5 Pressure equipment classes............................................................. 17
3 Documentation...................................................................................19
3.1 Documentation requirements............................................................19
3.2 Certification requirements................................................................ 21
4 Accumulators for hydraulic systems.................................................. 25
4.1 Design........................................................................................... 25
4.2 Fabrication..................................................................................... 26
4.3 Certification....................................................................................26
5 Gas cylinders for fixed fire extinguishing systems.............................26
5.1 General..........................................................................................26
5.2 Design........................................................................................... 26
5.3 Fabrication..................................................................................... 26
5.4 Certification....................................................................................26
6 Operating instructions and signboards.............................................. 27
6.1 General..........................................................................................27
Section 2 Materials................................................................................................28
1 Material requirements........................................................................28
1.1 General..........................................................................................28
1.2 Boilers and pressure vessels............................................................ 28
1.3 Thermal-oil heaters......................................................................... 29
Section 3 Arrangement..........................................................................................30
1 General.............................................................................................. 30
1.1 Access and inspection openings........................................................ 30
1.2 Draining and venting.......................................................................30
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