Products, training and operational support services for professional work at height and rescue
Question:
There is a ‘rule of thumb’ that in the tower climbing industry it is recommended that
climbers do not work at wind speeds greater than 20 knots (23 mph) at the working
height. Does this include gusting?
Answer:
In short, ‘No’. 20 knots (23 mph) is considered to be a mean wind speed. Gusting will be
higher.
Climbing shall not be undertaken when the environmental conditions are such as they would
impose unreasonable risk on the personnel involved. This will depend upon the operation
being undertaken, the height to be climbed and the experience of the individual members of
the climbing team. As an example, suitable wind conditions for the installation of a large
diameter lightweight dish will be far lower than for simple access to inspect an existing
antenna from a fixed platform. The final decision must be made on a case by case basis by
the site supervisor.
Climbing capability is likely to depend upon experience. Some companies operate a regime
where climbers are classified as ‘occasional’, ‘basic’ and ‘skilled’. The greater the climbing
competency the greater the maximum wind speed that can be worked in, as well as the range
of operations that can be undertaken.
Definitive guidance on an acceptable wind speed when working at height is scarce. A
number of sources have been reviewed (see Postscript, below) for some relevant and useful
guidance, viz.:
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Winds in excess of 23mph (Force 5) will affect a person’s balance.
Twice the wind speed means four times the pressure.
Weather forecasts should be taken to be mean wind speeds unless gust speeds are
explicitly mentioned.
When comparing speeds quoted in forecasts use the ‘rule of thumb’ that: 10 m/s = 20
knots = 23 mph.
It is gusts that matter, if only a mean speed is known use the approximation: gust speed
1
= 2.0 x mean speed .
Even for a steady wind, conditions will be windier higher off the ground and will not be
the same throughout a large site.
Surrounding obstructions can provide locally sheltered regions, and wind can be
funnelled by sloping ground or surrounding obstructions.
2
Wind speed, inclement conditions and working height will affect available working times .
The table refers to the Beaufort Wind Force Scale is based on a 10-minute mean wind
speeds in knots measured at 10 m above ground (ant not at the surface which, at 2 m,
may be only 50-70% of these figures).
The Met Office website is www.metoffice.gov.uk/.
The ‘Beaufort scale’ is an empirical measure that relates wind speed to observed
conditions at sea or on land. Its full name is the ‘Beaufort wind force scale’, although it is
a measure of wind speed and not of force in the scientific sense.
This may be used as a safe general guide for all heights up to 35m
See BS 8437: 2005 + A1: 2012, Table I1
The heightec Group Ltd, Lake District Business Park, Mint Bridge Road, Kendal, Cumbria, LA9 6NH, UK
Tel:
Fax:
+44 (0) 1539 728866
+44 (0) 1539 728833
Email: [email protected]
Web: heightec.com
Training division: heightec - The National Access and Rescue Centre – Aberdeen, Birmingham, Kendal, Leeds, London
Company no.03435385
Registered in England and Wales
VAT No. 698 1128 04
Products, training and operational support services for professional work at height and rescue
Postscript:
Advice on ‘wind speed’ has been included in a number of documents:
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Health and Safety Executive (HSE): Website
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Lifting Operations and Lifting Equipment Regulations 1998 (LOLER) - Safe use of
lifting equipment, Approved Code of Practice and guidance, HSE, L113 (First edition,
published 1998)
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Health and Safety Executive - Health and safety in roof work (HSG33)
heightec - Foundation for Work at Height (v5)
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Advisory Committee for Roofsafety (ACR) - Best Practice Guide, ACR (CP) 002: 2012
BS 8437: 2005 + A1: 2012, Code of practice for selection, use and maintenance of
personal fall protection systems and equipment for use in the workplace
BS 7985: 2013, Code of practice for the use of rope access methods for industrial
purposes – Recommendations and guidance supplementary to BS ISO 22846
BS 7121-1:2006, Code of practice for safe use of cranes – Part 1: General
British Constructional Steelwork Association (BCSA) - Guide to steel erection in windy
conditions
Prefabricated Access Suppliers’ and Manufacturers Association (PASMA) - Operator’s
code of practice. 9th Edition, 2003
Ministry of Defence - MoD Health & Safety Handbook - JSP 375 Vol. 3 Chapter 7 –
Working at Height on Restricted High Places
Defence Estates - Safety Rules & Procedures 07, Working at Height - Masts, Towers &
Fixed Accessways, SRP 07 - MOD Safety Rules and Procedures for Working at Height
on Masts, Towers and Fixed Accessways
© The heightec Group Ltd
August 2014
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http://www.hse.gov.uk/construction/faq-height.htm
http://www.hse.gov.uk/pubns/priced/l113.pdf
http://www.hse.gov.uk/pubns/priced/hsg33.pdf
Guidance Note for safe working on fragile roofs or roofs with fragile elements (Second
edition) - Covering the designing, planning and carrying out of inspection, maintenance,
repair and refurbishment work (www.roofworkadvice.info).
The heightec Group Ltd, Lake District Business Park, Mint Bridge Road, Kendal, Cumbria, LA9 6NH, UK
Tel:
Fax:
+44 (0) 1539 728866
+44 (0) 1539 728833
Email: [email protected]
Web: heightec.com
Training division: heightec - The National Access and Rescue Centre – Aberdeen, Birmingham, Kendal, Leeds, London
Company no.03435385
Registered in England and Wales
VAT No. 698 1128 04