THE MAGAZINE FOR THE DRAINAGE, WATER & WASTEWATER INDUSTRIES
SPECIAL FEATURES
coefficient of thermal expansion of cast iron is low (at 0.0105mm/m/K), which is similar to that of concrete. Its thermal stability means there is very little differential movement in pipe systems, so expansion joints are not generally needed, saving on both space and cost. By comparison HDPE systems often require multiple expansion joints to be installed, which may require additional space and supporting brackets to attach the system to the structure.
Another benefit of cast iron is that it remains serviceable over long periods of time. Harmer SML pipes and fittings incorporate a two-part epoxy coating on its internal surface and an anti-corrosive primer on the exterior, to ensure an installation will require minimal maintenance during its lifetime. Its durability is what makes cast iron the ideal material for inaccessible and difficult to reach areas and for below-ground drainage, where its ability to resist chemical attack, degradation and ground movement are hugely beneficial.
Above ground, the excellent acoustic properties of Harmer SML means that additional sound protection is not normally required to protect against noise breakout
from fluids flowing in the pipework. This is important in all buildings and particularly so in high quality residential schemes, hospitals and high rise commercial. In addition, sound transmission through the structure is also ensure pipework is not in direct contact with the structure. In comparison, HDPE systems often require specialist acoustic pipework and/or additional sound insulation, which can add to both material and labour costs.
While there are many technical, ecological and financial reasons to consider cast iron drainage, by far the most compelling reason is the material's superior performance in a fire. Cast iron is non- combustible, making it ideal for installation where drainage pipework has to penetrate a wall or floor in fire compartment. Cast Iron has the added benefit of requiring simple, low-cost fire-stopping in the annular space between the pipe and structure. In comparison, PVCu and HDPE pipework will require more expensive, high performing intumescent fire collars to be fitted to prevent fire breaching the compartment wall or floor when the plastic pipework inevitably melts.
It is reassuring to know that Harmer SML soil & waste and rainwater drainage
systems have been rigorously tested and proven to achieve the highest possible fire rating under BS EN 13501 - the European standard for the fire classification of construction products. The complete system is compliance tested, including the pipe connections with their elastomer gasket couplings as well as associated fittings and coatings.
The complete system has a Euroclass rating of A2-s1, d0. Its A2 classification means that Harmer SML is non-combustible; the S1 classification means that it has the lowest possible level for smoke emissions; while the d0 designation means the system does not produce flaming droplets. Cast iron's d0 flaming droplet classification is significant, cast Iron as a material unpainted is A1. In a fire, plastic pipework does melt, and the melted droplets can fall to initiate new fires.
Finally, in addition to its fire performance benefits, the environmental benefits of cast iron are increasingly being appreciated. Because it is extremely durable any installation will have a longer lifespan than an equivalent installation in plastic. And, at the end of its (very long) life, cast iron is 100% recyclable which is good for the planet.
The loo taboo: new study explores uptake of controversial technologies
Researchers have provided an important insight into the cultural taboo surrounding an innovative ‘green’ technology that enables users to transform their domestic toilet waste into biogas.
The team at the University of Stirling believe that their findings – part of a larger study – will help decision-makers understand and overcome the barriers preventing uptake of new technologies designed to reduce impact on the natural environment.
One pioneering process enables home toilets to be connected to an anaerobic digester – airless units in which bacteria breaks down organic matter – which converts the waste into biogas for use as a clean cooking fuel, and fertiliser to improve soils. However, despite its efficiency, recycling human waste in this way is uncommon because most cultures consider it unsavoury.
FOLLOW US
Multidisciplinary researchers from Stirling conducted in-depth interviews in Nepal, where uptake of toilet-linked anaerobic digesters (TLAD) is high, to understand how people overcame their cultural aversion. Those who adopted TLAD improved their home sanitation, indoor air quality and use of resources, the study found.
Natalie Boyd Williams, a PhD researcher in the division of Biological and Environmental Sciences, said: “I believe we have all the technology and the means to solve the world’s problems, but whether we are using it or not often depends on social factors.
“Particularly in the West, decision-makers often make assumptions about what people will or won’t accept – meaning that they don’t properly explore how certain technologies can be adopted. There has been community resistance to wind farms and biogas plants, for example, which has
Natalie Boyd Williams
been dismissed and overlooked by developers, when engagement with these communities can in fact lead to acceptance.
“We wanted to challenge the assumption by exploring how an initially unacceptable technology – in this case, toilet-linked anaerobic digesters in Nepal – can become widely adopted. This is understood in Nepal but less so outside it.”
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