NES 781 Process and Procedure Requirements for the Protection of Sea - Water Systems Using Sodium...

Ministry of Defence Defence Standard 02-781 (NES 781)

Issue 1 Publication Date 01 April 2000

Incorporating NES 781 Category 3

Issue 3 Publication Date September 1990

Process And Procedure RequirementsFor The Protection Of

Sea-Water Systems UsingSodium Dimethyldithiocarbamate

DStan

DStan is now the publishing authority for all Maritime Standards (formerly NESs). Any reference to any other publishing authority throughout this standard should be ignored. Any queries regarding this or any other Defence Standard should be referred to the DStan Helpdesk as detailed at the back of this document.

AMENDMENT RECORD

Amd No Date Text Affected Signature and Date

REVISION NOTE

This standard is raised to Issue 1 to update its content.

HISTORICAL RECORD

This standard supersedes the following:

Naval Engineering Standard (NES) 781 Issue 3 dated September 1990.

Ministry of Defence

Naval Engineering Standard

NES 781 Issue 3 (Reformatted) September 1990

PROCESS AND PROCEDURE REQUIREMENTSFOR THE PROTECTION OF SEA−WATER SYSTEMSUSING SODIUM DIMETHYLDITHIOCARBAMATE

This NES Supersedes

NES 781 ISSUE 2

Record of Amendments

AMDT INSERTED BY DATE

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2

3

4

5

6

7

8

9

10

i

NAVAL ENGINEERING STANDARD 781

ISSUE 3 (REFORMATTED)

PROCESS AND PROCEDURE REQUIREMENTS

FOR THE PROTECTION OF SEA−WATER SYSTEMS

USING SODIUM DIMETHYLDITHIOCARBAMATE

The issue and use of this Standard

is authorized for use in MOD contracts

by MOD(PE) Sea Systems and

the Naval Support Command

ECROWN COPYRIGHT

Published by:

Director of Naval ArchitectureProcurement Executive, Ministry of DefenceFoxhill, Bath BA1 5AB

NES 781Issue 3 (Reformatted)

iii

SCOPE

1. This NES covers the process and procedure to be used to prevent excessive corrosion of shipssea water system and heat exchangers due to use of sulphide polluted sea-water duringconstruction.


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v

FOREWORD

Sponsorship

1. ThisNaval Engineering Standard (NES) is sponsored by theProcurement Executive, Ministryof Defence, Chief Naval Architect (CNA), Section NA 132.

2. It is to be applied as required by any Ministry of Defence contract for the protection of seawater systems using sodium dimethyldithiocarbamate.

3. If it is found to be technically unsuitable for any particular requirement the Sponsor is to beinformed in writing of the circumstances, with a copy to the Chief Naval Architect SectionNA 145.

4. Any user of this NES either within MoD or in industry may propose an amendment to it.Proposals for amendments which are:

a. not directly applicable to a particular contract are to be made to the Sponsor of theNES;

b. directly applicable to a particular contract are to be dealt with using existing proceduresor as specified in the contract.

5. No alteration is to be made to this NES except by the issue of a formal amendment.

6. Unless otherwise stated, reference in this NES to approval, approved, authorised or similarterms, means by the Ministry of Defence.

7. Any significant amendments that may be made to this NES at a later date will be indicatedby a vertical sideline. Deletions will be indicated by 000 appearing at the end of the lineinterval.

8. This NES had been reissued because of amendments to the text and the update of Sea Systemsnomenclature.

Conditions of Release

General

9. This Naval Engineering Standard (NES) has been prepared for the use of the Crown and ofits contractors in the execution of contracts for the Crown. The Crown hereby excludes allliability (other than liability for death or personal injury) whatsoever and howsoever arising(including but without limitation, negligence on the part of the Crown, its servants or agents)for any loss or damage however caused where the NES is used for any other purpose.

10. This document is Crown Copyright and the information herein may be subject to Crown orthird party rights. It is not to be released, reproduced or published without written permissionof the MOD.

11. The Crown reserves the right to amend or modify the contents of this NES without consultingor informing any holder.

MOD Tender or Contract Process

12. ThisNES is the property of the Crown and unless otherwise authorized in writing by theMODmust be returned on completion of the contract, or submission of the tender, in connectionwith which it is issued.


vi

13. When this NES is used in connection with aMOD tender or contract, the user is to ensure thathe is in possession of the appropriate version of each document, including related documents,relevant to each particular tender or contract. Enquiries in this connection may be made ofthe local MOD(PE) Quality Assurance Representative or the Authority named in the tenderor contract.

14. When NES are incorporated into MOD contracts, users are responsible for their correctapplication and for complying with contracts and any other statutory requirements.Compliance with an NES does not of itself confer immunity from legal obligations.

Related Documents

15. In the tender and procurement processes the related documents listed in each section andAnnex A can be obtained as follows:

a. British Standards British Standards Institution,389 Chiswick High Road,London W4 4AL

b. Defence Standards Directorate of Standardization and Safety Policy,Stan 1, Kentigern House, 65 Brown Street,Glasgow G2 8EX

c. Naval Engineering Standards CSE3a, CSE Llangennech, Llanelli,Dyfed SA14 8YP

d. Other documents Tender or Contract Sponsor to advise.

Note: Tender or Contract Sponsor can advise in cases of difficulty.

16. All applications to Ministry Establishments for related documents are to quote the relevantMOD Invitation to Tender or Contract Number and date, together with the sponsoringDirectorate and the Tender or Contract Sponsor.

17. Prime Contractors are responsible for supplying their subcontractors with relevantdocumentation, including specifications, standards and drawings.

Health and Safety

Warning

18. ThisNESmay call for the use of processes, substances and/or procedures thatmay be injuriousto health if adequate precautions are not taken. It refers only to technical suitability and inno way absolves either the supplier or the user from statutory obligations relating to healthand safety at any stage of manufacture or use. Where attention is drawn to hazards, thosequoted may not necessarily be exhaustive.


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CONTENTSPage No

TITLE PAGE i. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

SCOPE iii. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

FOREWORD v. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Sponsorship v. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Conditions of Release v. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

General v. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .MOD Tender or Contract Process v. . . . . . . . . . . . . . . . . . . . . . . . . .

Related Documents vi. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Health and Safety vi. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Warning vi. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

CONTENTS vii. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

SECTION 1. METHOD 1.1. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

SECTION 2. EQUIPMENT REQUIRED 2.1. . . . . . . . . . . . . . . . . . . .FIGURE 2.1 DIAGRAMMATIC ARRANGEMENTOF DOSING RIG 2.2. . . . . . . . . . . . . . . . . . . . . . . . . . . .

SECTION 3. PROCEDURE 3.1. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

SECTION 4. REQUIREMENT FOR REDOSING WITH SDD 4.1. .

ANNEX A. RELATED DOCUMENTS A.1. . . . . . . . . . . . . . . . . . . .

ANNEX B. DEFINITIONS AND ABBREVIATIONS B.1. . . . . . . .

ALPHABETICAL INDEX


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1.1

1. METHOD

a. The process consists of admitting a 0.05% by volume solution of sodiumdimethyldithiocarbamate (SDD) in fresh water before any river or pollutedwater is admitted to the system. It forms a chelate film on the surface of thesystem and so protects the metal surface from the corrosive effects of sulphidepollution in estuarine river waters. Retreatment at intervals is required.

b. Sulphide pollution in river estuary waters causes a brittle sulphide layer to formon the sea-water piping and components. This brittle layer can cause stresscorrosion cracking of certain copper alloys such as brasses.


1.2


2.1

2. EQUIPMENT REQUIRED

a. A rig is required to introduce the inhibitor into the Surface Ships sea-watersystem. The basic requirements of the rig are as shown diagrammatically inFIGURE 2.1. It is then recommended that pipework of the rig be 91/10cupro-nickel and if possible the components should also be made of copper alloy,as steel components will be corroded.

b. The rig comprises:

(1) One Fresh Water flow meter ‘A’ to operate in the region of 50−500 litresper minute (or constant flow valve).

(2) One air pump to deliver approximately 2.4 bar at shut valve condition (orexisting air line).

(3) One inhibitor flow meter ‘B’ operating in the region of 0.5− 1.5 litres perminute.

(4) One tank of 120 litres capacity (approximately) fitted with air relief valve,air supply point and facilities for filling with inhibitor. The tank is to havea working pressure of 2.4 bar.

(5) Pipework and valves to approximate sizes shown.

c. The following are also required (see BR 3925, Chapter 12):

(1) Corrosion Meter, built by Waverley Electronics Ltd.

(2) Sensing probes for heat exchangers. Material of probes to be matched tomaterial of system under test; for surface ships usually 90/10cupro-nickel.

NE

S781

Issue3

(Reform

atted)

2.2

FIGURE2.1

DIAGRAMMATIC

AR

RA

NG

EM

EN

TO

FD

OSIN

GR

IG


3.1

3. PROCEDURE

a. The plant is to be erected adjacent to the sea-water service upper deck hydrantor any other suitable point which will allow the whole of the system to beflooded.

b. Introduce SDD at 40% solution into the tank.

c. Dilute the SDD with fresh water to give a final 10% solution by volume.

d. Connect the plant to the shore water main and to the deck hydrant or othersuitable point.

e. Flush the systemwith shore water for at least 15minutes. Overboard dischargesfrom the system are to be closed until pressure is on the system to avoid reverseflow. Ensure that all systems have been vented.

f. Open air pressure to the inhibitor tank and set flow to the required rate to givea 0.05% solution of SDD and fresh water.

g. After flows have settled, check for the presence of SDD at each heat exchangerby taking a sample of the circulating water in a test tube and adding a few dropsof test indicator, if SDD is present a dense brown discoloration will form. Thetest indicator is to be prepared by dissolving about 10g of cupric chloride indistilled water, adding a few drops of dilute ammonia (5M) solution andmakingup to one litre in a clean container.

h. Take off 100ml of circulating water for laboratory analysis.

i. When all heat exchangers have SDD indication, close discharge valves, shutdown plant and allow to stand for at least 24 hours before admitting river water.There is no risk of corrosion due to leaving the ships system for prolongedperiods filled with SDD treated water unless there are ferrous metals in thesystem.


3.2


4.1

4. REQUIREMENT FOR REDOSING WITH SDD

a. The requirement for redosing the sea-water system is to be checked by dailyreadings of corrosion rates determined on test probes in each heat exchangerwater box.

b. After dosing with SDD, corrosion rate readings should be less than 1.0μA/mVfor a 90/10 cupro-nickel system and when this rises to 1.5μA/mV, the systemrequires redosing with a 0.02% solution of SDD using the procedure in Section3.

c. Corrosion rate readings should be less than 0.5μA/mV for a 70/30 cupro-nickelsystem and when this rises to 1.0μA/mV, the system requires redosing with a0.02% solution of SDD.

d. A description of the corrosion meter and the sensing probes together withoperating data is given in BR 3925, Chapter 12.


4.2


A.1 ANNEX A.

ANNEX A.

RELATED DOCUMENTS

A.1 Reference is made to:

Referredto inClause

BR 3925 Aids to Maintenance—Non-destructive Methods andEquipment

2.c., 4.d.


A.2ANNEX A.


B.1 ANNEX B.

ANNEX B.

DEFINITIONS AND ABBREVIATIONS

B.1 There are no Definitions and Abbreviations for this NES.


B.2ANNEX B.


INDEXINDEX.1

ALPHABETICAL INDEX

AAir pump, 2.1

Analysis, 3.1

BBrittle Sulphide, 1.1

CCorrosion meter, 2.1, 4.1

Corrosion rates, 4.1

Cracking, 1.1

FFlow meter (FM), 2.1

Flow meter (Inhibitor), 2.1

PPipework and valves, 2.1

Pollution sulphide, 1.1

Protection, 1.1

RRedosing, 4.1

Retreatment, 1.1

Rig, 2.1

SSensing probes, 2.1

Stress corrosion, 1.1

TTank, 2.1

Tests, 3.1

VVolume of solution, 1.1, 3.1


INDEX INDEX.2

Inside Rear Cover

© Crown Copyright 2000

Copying Only as Agreed with DStan

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File Reference

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Contract Requirements

When Defence Standards are incorporated into contracts users are responsible for their correctapplication and for complying with contractual and statutory requirements. Compliance witha Defence Standard does not in itself confer immunity from legal obligations.

Revision of Defence Standards

Defence Standards are revised as necessary by up issue or amendment. It is important thatusers of Defence Standards should ascertain that they are in possession of the latest issue oramendment. Information on all Defence Standards is contained in Def Stan 00-00 Standardsfor Defence Part 3 , Index of Standards for Defence Procurement Section 4 ‘Index of DefenceStandards and Defence Specifications’ published annually and supplemented regularly byStandards in Defence News (SID News). Any person who, when making use of a DefenceStandard encounters an inaccuracy or ambiguity is requested to notify the Directorate ofStandardization (DStan) without delay in order that the matter may be investigated andappropriate action taken.

NES 781 Process and Procedure Requirements for the Protection of Sea - Water Systems Using Sodium...

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