HSEHealth & Safety

Executive

Noise and vibration

OFFSHORE TECHNOLOGY REPORT

2001/068

HSEHealth & Safety

Executive

Noise and vibration

Edited under the HSE Technical Support Agreement by BOMEL LtdLedger House

Forest Green RoadFifield

MaidenheadBerkshire SL6 2NR

HSE BOOKS

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© Crown copyright 2002Applications for reproduction should be made in writing to:Copyright Unit, Her Majesty’s Stationery Office,St Clements House, 2-16 Colegate, Norwich NR3 1BQ

First published 2002

ISBN 0 7176 2522 2

All rights reserved. No part of this publication may bereproduced, stored in a retrieval system, or transmittedin any form or by any means (electronic, mechanical,photocopying, recording or otherwise) without the priorwritten permission of the copyright owner.

This report is made available by the Health and SafetyExecutive as part of a series of reports of work which hasbeen supported by funds provided by the Executive.Neither the Executive, nor the contractors concernedassume any liability for the reports nor do theynecessarily reflect the views or policy of the Executive.

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CONTENTS Page No FOREWORD v 1 INTRODUCTION AND SCOPE 1 2 MINIMISING NOISE AND VIBRATION 3 2.1 Equipment Selection 3 2.2 Noise Control Measures 3 2.3 Vibration Control Measures 4 2.4 Fog Horns 4 3 NOISE 5 3.1 Terminology 5 3.2 Application of Criteria 5 3.3 Maximum Permissible Noise Levels (Overriding Limits) 5 3.4 General Work Area Nose Limits 5 3.5 Specific Work Area Noise Limits 5 3.6 Sleeping / Recreation Area Noise Limits 6 3.7 Relaxation of Noise Limits in the General Work Area 6 4 VIBRATION 9 4.1 Terminology 9 4.2 Relevant Surfaces for Application of Criteria 9 4.3 Vibration Limits for Human Exposure 9 4.4 Relaxation of Vibration Limits 13 5 REFERENCES 15

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FOREWORD

This document provides technical information previously contained in the Fourth Edition of the Health and Safety Executive’s ‘Offshore Installations: Guidance on Design, Construction and Certification’ (1990 edition plus amendments)(1). The ‘Guidance’ was originally published in support of the certification regime under SI289, the Offshore Installations (Construction and Survey) Regulations 1974(2). However, SI289 was revoked by the Offshore Installations (Design and Construction, etc) Regulations, 1996, which also introduced the verification provisions into the Offshore Installations (Safety Case) Regulations, 1992. The ‘Guidance’ was formally withdrawn in its entirety on 30 June 1998 (see HSE OSD Operations Notice 27(3)).

The withdrawal of the ‘Guidance’ was not a reflection of the soundness (or otherwise) of the technical information it contained; some sections (or part of sections) of the ‘Guidance’ are currently referred to by the offshore industry. For this reason, after consultation with industry, relevant sections are now published as separate documents in the HSE Offshore Technology (OT) Report series.

It should be noted that the technical content of the ‘Guidance’ has not been updated as part of the re-formatting for OTO publication, although prescriptive requirements and reference to the former regulatory regime have been removed. The user of this document must therefore assess the appropriateness and currency of the technical information for any specific application. Additionally, the user should be aware that published sections may cease to be applicable in time and should check with Operations Notice 27, which can be viewed at http://www.hse.gov.uk/hid/osd/notices/on_index.htm, for their current status.

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1. INTRODUCTION AND SCOPE This Offshore Technology (OT) Report provides technical information on the way in which noise and vibration, as affecting human exposure, should be taken into account in the design and construction of Offshore Installations. It details suggested maximum levels for all areas of the Installation and provides basic information that may be followed when designing and laying out an Installation to minimise potential noise and vibration problems. It is based on guidance previously contained in Section 52 of the Fourth Edition of the Health and Safety Executive’s ‘Offshore Installations: Guidance on Design, Construction and Certification’(1) which was withdrawn in 1998. As discussed in the Foreword, whilst the text has been re-formatted for Offshore Technology publication, the technical content has not been updated. The appropriateness and currency of the information contained in this document must therefore be assessed by the user for any specific application. This document does not attempt to provide a comprehensive design guide since each Installation will clearly present particular problems, depending upon its size and function. It is important that consideration of noise and vibration should form an integral part of the platform design from the inception of the project, when, for instance, major changes in platform layout can be made, to reduce potential problems. Where necessary, specialist advice should be obtained. For acoustic design purposes all calculations should be performed in the eight octave bands centred between 63 Hz and 8kHz (see BS 2475(4)). The noise rating curve (ISO 1996(5, 6, 7) and Kosten and Van Os(8)), numerically 5dB less than the dBA criterion, may be used as an approximate limit for the frequency spectrum of the noise. The overriding requirement, however, is that the dBA level would need to be met. The octave band values of the appropriate noise rating curves are given in Table 1 below.

Table 1 Noise rating numbers and corresponding octave band sound pressure levels approximating to dBA noise criteria

Octave band centre frequency (Hz) Noise Criteria

dBA

Design Noise rating

63 125 250 500 1k 2k 4k 8k

90 88 70 60 55 50 45

NR 85 NR 83 NR 65 NR 55 NR 50 NR 45 NR 40

103 101 87 79 75 71 67

96 94 70 70 66 61 57

91 89 72 63 59 54 49

88 86 68 58 54 49 44

85 83 65 55 50 45 40

83 81 63 52 47 42 37

81 79 61 50 45 40 35

80 78 59 49 44 38 33

Note: Where alternative dBA noise criteria are specified the appropriate NR values should be selected

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2. MINIMISING NOISE AND VIBRATION Consideration should be given to limiting noise levels throughout the Installation in order to:

a) Minimise the risk of hearing damage to personnel in work areas.

b) Ensure that warning signals are audible.

c) Allow adequate speech, telephone and radio communication.

d) Maintain working efficiency.

e) Provide an acceptable sleep and recreation environment in accommodation areas.

In a similar manner consideration should be given to limiting vibration levels in order to:

a) Prevent a health hazard to personnel.

b) Maintain prof iciency of personnel in performing designated tasks.

c) Provide an acceptable sleep and recreation environment in accommodation areas.

2.1 EQUIPMENT SELECTION The need for noise and vibration control should be taken into account when deciding which of different production methods or processes are to be used. Noise limits for individual items or machinery would need to be included as part of the general equipment specification issued to vendors. These individual limits would need to be set taking into account the location of all equipment in a particular area and its acoustic environment such that, in total, the relevant area noise criteria will be achieved. Sound absorptive materials do not necessarily affect the sound output of equipment and may become ineffective. It is preferable to specify low noise equipment though, if noise levels are still too high, reduction by absorptive materials is likely to be acceptable. All vendors would need to supply documentary evidence of the noise levels expected to be created by their equipment. Noise tests may conveniently be included as part of the normal mechanical acceptance testing of equipment. In a similar manner vendors would need to supply all available vibration test data for their equipment, together with mounting and foundation details. 2.2 NOISE CONTROL MEASURES Noise control equipment should be designed to cause minimum interference with routine inspection and maintenance of equipment. Suitable access doors and observation windows should be provided and where necessary the control equipment should be easily removable.

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It is suggested that personal hearing protection should not be proposed as a substitute for effective noise control. Personal hearing protection should only be considered for use where engineering methods of noise control have been shown not to be reasonably practicable. 2.3 VIBRATION CONTROL MEASURES The selection of suitable isolators, where fitted, would need to take into account structural design loads and environmental conditions. 2.4 FOG HORNS Consideration should be given to the choice and location of fog horns in order to minimise potential annoyance to personnel within accommodation areas.

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3. NOISE 3.1 TERMINOLOGY Interpretation of the terminology used in this section should be in accordance with BS 4727 Part 3(9) Group 08. All noise limits in this section are quoted as 'A' weighted sound pressure levels (dBA) with the exception of the overriding limits given in Sections 3.3, 3.4, 3.5 and 3.6 of this document. In all cases the reference sound pressure is 2 x 10-5 N/m2. 3.2 APPLICATION OF CRITERIA Consideration should be given to meeting the noise criteria in full at any spatial location within a designated area to which personnel may have access, except for work areas and other areas housing noisy equipment where, for design purposes, the criteria would need to generally apply at a minimum distance of 1 metre from operational equipment. If personnel are normally required to work closer than a distance of 1 metre to equipment then it is suggested that the noise criteria should also apply at these locations. 3.3 MAXIMUM PERMISSIBLE NOISE LEVELS (OVERRIDING LIMITS) Notwithstanding the criteria for the designated areas, it is suggested that under no operation design condition should the unprotected ear be exposed to sound pressure levels exceeding 135 dBA (linear). 3.4 GENERAL WORK AREA NOISE LIMITS All areas, other than those stated in Sections 3.5 and 3.6, would need to meet the general work area noise level limit of 88 dBA for a 12-hour working day. This limit is based on hearing damage risk considerations and is derived from the requirements of the HSE Code of Practice(10). If shift lengths are less than 12 hours then the noise limit of 90 dBA will be applicable for an eight-hour shift. These limits generally apply for broad band noise. Where a noise exhibits dominant tonal characteristics, then it may be desirable to suppress such characteristics (Hawkins & Stevens(11)). 3.5 SPECIFIC WORK AREA NOISE LIMITS Where reliable speech, telephone or radio communication is required, or demanding mental tasks must be performed, then the noise limits for these areas would need to be considerably less than the limit for general work areas. Suggested noise limits for particular work areas such as control rooms etc. are given in Table 2. Any tonal characteristic would need to be suppressed so as not to give rise to annoyance. These limits refer to background noise, including ventilation and external noise sources, but not to manually controlled operations involving inherently noisy equipment, e.g. drilling, mixing etc. for which general work area noise limits are applicable. This does not include the radio/communications room in which noisy office equipment, e.g. telex machines, would either not be installed or would be suitably quietened.

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Table 2 Recommended noise limits for specific work areas of Offshore Installations

Specific work areas of Offshore Installations

Noise limit, dBA

Workshops General stores Kitchens Control rooms Offices Laboratories Radio / Communications rooms

70 70 60 55 55 55 45

3.6 SLEEPING/RECREATION AREA NOISE LIMITS Noise limits are suggested in Table 3 for those areas of living accommodation on Offshore Installations where satisfactory recreation, rest and sleeping conditions are required. Any tonal characteristics would need to be suppressed so as not to give rise to annoyance. It is suggested that the limits presented should be regarded as maximum acceptable noise levels for these areas. Where lower levels can be relatively easily obta ined (e.g. by ventilation silencing) then it is desirable that noise control measures should be implemented.

Table 3 Recommended noise limits for sleeping / recreation areas of living accommodation on Offshore Installations

Specific work areas of Offshore Installations

Noise limit, dBA

Washing facilities Changing rooms Toilets Dining rooms Recreation rooms Theatre / meeting rooms Television rooms Sleeping areas Medical rooms Quiet rooms

60 60 60 55 50 45 45 45 45 45

3.7 RELAXATION OF NOISE LIMITS IN THE GENERAL WORK AREA Consideration should be given to taking all reasonably practicable means to comply with the suggested noise levels. If the limit cannot be achieved in certain areas then these would need to be treated as ‘restricted’ and appropriate warning notices posted. Personnel entering these areas should generally be obliged to wear suitable ear protectors unless their daily unprotected noise exposure can be shown to be within the provisions of Reference 10.

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Examples of restricted areas could be as follows:

• Normal operational conditions - within noise control enclosures large enough to admit service personnel.

• Intermittent operation conditions - on the helideck when a helicopter is present.

• Design emergency conditions - near emergency safety relief valves.

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4. VIBRATION The vibration limits suggested in this section are derived from the acceptability of exposure of human beings to vibration (BS 6841(12)). 4.1 TERMINOLOGY Interpretation of the terminology used in these proposals should be in accordance with ISO 2041(13). 4.2 RELEVANT SURFACES FOR APPLICATION OF CRITERIA The suggested vibration limits should be met on surfaces designated as normal access for standing and sitting. 4.3 VIBRATION LIMITS FOR HUMAN EXPOSURE 4.3.1 Exposure time The vibration limits provided for general work areas are based on a 12-hour working day. It is suggested that these limits should be taken as the design values for Offshore Installations. In certain circumstances some relaxation of the general work area vibration limits may be considered acceptable. 4.3.2 Frequency range The suggested criteria cover the frequency range 1-80 Hz and are not intended to be extrapolated beyond these limits. 4.3.3 Direction of vibration Criteria are expected for both vertical and horizontal linear motion and apply separately to the resolved components of the vibration in these directions. Direction, az, corresponds with the foot to head axis of the human body (see BS 6841(12)). 4.3.4 Non-sinusoidal, random or broad band vibration It is suggested that such vibration should be analysed using narrow band filters with a bandwidth not exceeding one-third octave (BS 2475(14)). The limits are then appropriate to the centre frequency of that band. In cases where the crest factor (ratio of peak to rms) is greater than 3, the suggested limits would need to be regarded as tentative. In certain circumstances vibration components at more than one frequency, occurring simultaneously, may interact and a weighted rms summation of the interacting components may be necessary (BS 6841(12)).

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4.3.5 Criteria The suggested vibration limits are divided into five different categories (Table 4, below) ranging from ‘recommended’ vibration limits in living accommodation (category V) to ‘prohibited’ vibration levels (greater than category I). Tables and figures showing vibration limits are given below. Vibration limits in this section are given as rms acceleration levels in m/sec2. The suggested vibration limits for human exposure in the vertical and horizontal axes respectively are shown in Figures 1 and 2.

Table 4 Description of vibration limit categories for Offshore Installations

Category Description I

II

III

IV

V

Restricted area (less than 4 minutes exposure) vibration limits. Short exposure to levels about these limits may create a health hazard and cause difficulty in walking. These high levels of vibration usually cause such alarm and discomfort that action is immediately and intuitively taken by persons subjected to the vibration. Vibration levels above these limits should be treated as prohibited. Just acceptable locally to equipment, although vibration limits for machinery may be more restrictive than these levels. Annoyance and discomfort may be experienced. Recommended design vibration limits for all general work areas. Vibration levels are easily detectable but not uncomfortable. Recommended design vibration limits for office, control rooms and similar areas. Recommended design vibration limits for sleeping, recreation and similar areas in living accommodation. These vibration levels are just detectable.

Table 5 Restricted exposure periods to high vibration levels

at / aI Allowable exposure time 1.00 0.92 0.76 0.59 0.42 0.29 0.18 0.11 0.08

1-4 minutes 8 minutes

15 minutes 30 minutes

1 hour 2 hours 4 hours 8 hours

12 hours

Note: t is the allowable exposure time for vibration level at aI is the restricted area vibration limit (category I) for 1-4 minutes' exposure.

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Figure 1 Vibration limits for Offshore Installations: ‘Horizontal’ axes (ax,ay)

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Figure 2 Vibration limits for Offshore Installations: ‘Vertical’ axis (az)

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4.4 RELAXATION OF VIBRAT ION LIMITS All reasonably practicable means should be taken in the design of Offshore Installations to achieve vibration levels in general work areas equal to or less than the limits given in category III. Higher levels than those given in category II may, however, be tolerated for shorter exposure periods than 12 hours without a serious hazard to health, although some fatigue and decreased working proficiency may occur. The maximum allowable exposure period for levels of vibration greater than those given in category II may be calculated from Table 5. Note that the existence of these higher levels is not recommended and every effort should be made to limit the levels to those given in category III. Where exposure occurs to varying levels of high vibration over the period of the working day, then an equivalent exposure ratio may be calculated in accordance with the method given in BS 6841(12) with reference to the maximum levels given in category I. If the equivalent exposure ratio exceeds unity then it is suggested the exposure should be classified as ‘prohibited’. No relaxation of vibration limits is suggested for categories IV and V.

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5. REFERENCES 1. Department of Energy. Offshore Insta llations: Guidance on Design, Construction and

Certification, 4 th Edition. HMSO, Consolidated Edition, 1993 (plus Amendment No. 3, 1995). [Withdrawn 1998 by Operations Notice 27].

2. SI 1974 / 289 – The Offshore Installations (Construction and Survey) Regulations 1974,

HMSO, 1974. [Revoked and has been replaced by SI 1996 / 913 – The Offshore Installations and Wells (Design and Construction etc.) Regulations, 1996 – ISBN: 0 110 54451 X].

3. Health and Safety Executive. Status of Technical Guidance on Design, Construction and

Certification. Operations Notice 27. Revised and Reissued, August 1998. 4. British Standards Institution. BS 2475 – Octave and One Third Octave Band Pass Filters.

[Superseded and replaced by BS EN 61260 – Electroacoustics – Octave Band and Fractional Octave Band Filters. 1996.]

5. International Organisation for Standardisation. ISO 1996 – Acoustics – Description and

Measurement of Environmental Noise. Part 1 – Basic Quantities and Procedures, 1982. 6. International Organisation for Standardisation. ISO 1996 – Acoustics – Description and

Measurement of Environmental Noise. Part 2 – Acquisition of Data Pertinent to Land Use, 1987.

7. International Organisation for Standardisation. ISO 1996 – Acoustics – Description and

Measurement of Environmental Noise. Part 3 – Application to Noise Limits, 1987. 8. Kosten and Van Os. Community Reaction Criteria for External Noises. National Physical

Laboratory Symposium No. 12. HMSO, 1962. 9. British Standards Institution. BS 4727 – Glossary of Electrotechnical, Power,

Telecommunications, Electronics, Lighting and Colour Terms. Part 3 – Terms Particular to Telecommunications and Electronics.

10. Health and Safety Executive. Code of Practice for Reducing the Exposure of Employed Persons

to Noise. HMSO. 1972. [This has been superseded by SI 1989 / 1790 – The Noise at Work Regulations. HMSO. 1989. Plus associated guidance – Guidance on the Noise at Work Regulations. L108. HSE. 1998.]

11. Hawkins and Stevens. Masking of Pure Tones and Speech by White Noise. Journal of the

Acoustic Society of America. 1950. 12. British Standards Institution. BS 6841 – Guide to Measurement and Evaluation of Human

Exposure to Whole Body Mechanical Vibration and Repeated Shock. 1987.

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13. International Organisation for Standardisation. ISO 2041 – Vibration and Shock – Vocabulary. 1990. [This is identical to BS 3015 – Glossary of Terms Relating to Mechanical Vibration and Shock. 1991.]

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Printed and published by the Health and Safety ExecutiveC0.50 07/02

OTO 2001/068

£10.00 9 780717 625222

ISBN 0-7176-2522-2