CPD PROGRAMME
Professional development
The CIBSE Journal CPD Programme
Members of the Chartered Institution of Building Services Engineers (CIBSE) and other professional bodies are required to maintain their professional competence throughout their careers.
Continuing professional development (CPD) means the systematic maintenance, improvement and broadening of your knowledge and skills, and is therefore a long-term commitment to enhancing your competence. CPD is a requirement of both CIBSE and the Register of the Engineering Council (UK).
CIBSE Journal is pleased to offer this module in its CPD programme. The programme is free and can be used by any reader. This module will help you to meet CIBSE’s requirement for CPD. It will equally assist members of other institutions, who should record CPD activities in accordance with their institution’s guidance.
Simply study the module and complete the questionnaire on the final page, following the instructions for its submission. Modules will be available online at
www.cibsejournal.com/cpd while the information they contain remains current.
You can also complete the questionnaire online, and receive your results by return email.
This module considers the application of CSST in the UK market Corrugated stainless steel tube for use in domestic, commercial
and industrial applications
Corrugated stainless steel tube (CSST) was first developed around 40 years ago in Japan, where gas piping must be able to withstand movement caused by earth tremors. Now used all over the world, its share of UK and European markets is growing steadily. CSST is manufactured from austenitic stainless steel strip, which is corrugated during the manufacturing process to give it semi-rigid properties, while also maintaining its strength and resistance to impact. This CPD article will relate specifically to the application of CSST in the UK market; local codes and standards will differ around the world. CSST is mainly used between the outlet of
the gas meter – or second stage regulator for liquid petroleum gas (LPG ) – and the inlet to fixed appliances, as an alternative to rigid pipe materials such as steel and copper. It can be used in domestic, commercial and industrial applications. CSST in the UK market will be manufactured to BS 7838:1996 Specification for corrugated stainless steel semi-rigid pipe and associated fittings for low-pressure gas pipework of up to DN 50 and/or BS EN 15266:2007 Stainless steel pliable corrugated tubing kits in buildings for gas with an operating pressure up to 0.5 bar. Both standards result in assured products,
but CSST manufactured to BS 7838 may be used in a broader range of situations, such as being routed externally and being buried directly in the ground or screed without additional corrosion protection.
www.cibsejournal.com The outer jacket of a BS 7838 product is
typically thicker (minimum 0.5 mm) than that of a BS EN 15266 product (which has no minimum specification). The outer jacket of a BS 7838 product is also manufactured and tested to be resistant to the effects of ozone, ultraviolet light and higher temperature ranges. If a product manufactured to BS EN 15266 is to
be used externally or in harsher environments, additional corrosion and mechanical protection needs to be applied, as would be required for rigid steel and some copper applications. Both standards cover first, second and third family gases. First family gas – Manufactured gases such as coal gas, used in the UK until conversion to natural gas was undertaken between 1967 and 1977. Second family gas – Natural gas, which is predominantly used in the UK and supplied from the national gas network. Third family gas – Liquefied petroleum gas (LPG), which includes propane and butane (usually supplied in bulk vessels or cylinders).
Manufacture and supply of CSST CSST is available in diameters ranging
from DN 12 to DN 50 (nominal diameter 12 mm to 50 mm), making it suitable for most domestic, commercial and many industrial gas installations. Products manufactured to BS 7838 will be certified to a maximum operating pressure
of 0.075 bar, whereas BS EN 15266 allows pressures up to 0.5 bar. As the majority of natural gas installations downstream of the gas meter will rarely be higher than 21 mbar (0.021 bar), and for LPG installations, 37 mbar (0.037 bar)
after the second stage regulator for propane and 28 mbar (0.028 bar) for butane, both standards stipulate operating pressures significantly higher than would be typically encountered. Where higher pressures are required – for example, for industrial processes – the CSST manufacturer should be consulted, as higher operating pressures may be permissible. CSST is manufactured from stainless
steel strip that, when manufactured to BS 7838, falls into the ‘300 series’ classification of
stainless steel. Products manufactured to BS EN 15266 will comply with the requirements of BS EN 10028-7 Flat products made of steels for pressure purposes. Stainless steels, and may have classifications such as 1.4306 and 1.4404, indicating the properties of the steel, including maximum carbon content and minimum nickel content. During manufacture, the stainless steel strip
is rolled into a tube, with a single longitudinal butt weld along the seam. The smooth tube is then annularly corrugated so it becomes semi-rigid and can be bent and formed by hand. Some manufacturers of CSST anneal (or soften) the stainless steel during the manufacturing process, which can result in the product being less resistant to mechanical damage.
September 2013 CIBSE Journal 61
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