Today’s drainage specifier is faced with a range of material choices, yet drainage may be well down the pecking order when compared to other more visible material issues.
Getting this decision wrong however can compromise the success of the whole project. Effluents or ground conditions can pose challenges to the drainage material and these are coupled with a certain degree of client pressure – a need to avoid pollution incidents and the accompanying attention of the Environment Agency and the media:
• Contaminated ground or chemical processes or discharges may threaten pipe or joint integrity.
• Sterilisation procedures such as super-steam or hot discharges from hospital laundries for example may melt conventional plastic piping and pose thermal shock risks to rigid pipe systems.
• Aggressive cleaning fluids in dairies, breweries or food plants may be beyond the capabilities of conventional drainage products.
In addition, the specifier may have to anticipate future changes in the use of buildings and incorporate a degree of future proofing. This is particularly relevant to drainage installed below the main floor slab within chemical and process plants where future repair or amendment would be prohibitively expensive.
So where does the specifier look when wanting a pipe material to meet these challenges? There are a number of special materials available to meet abnormally hot or aggressive effluents:
• Stainless steel tends to be used above ground – for drainage channels. It is able to withstand fluctuations in discharge temperatures, and can deal with constant high temperature discharges. But stainless steel is not a panacea: it is prone to acid attack, particularly in the case of chloride salts and is very expensive for underground applications.
• Ductile Iron has good strength characteristics and also performs well at temperature, although again, is prone to acid attack.
• Plastic drainage pipes are light and flexible, but have differing performances in the face of heat and aggressive chemicals dependent on the type of plastic used. As an example, neither PVC nor Polyethylene is suitable for temperatures above 60°C. There are also limitations at colder temperatures, uPVC is not suitable below freezing and Polyethylene is not recommended below -40°C.
• Other specialist pipe materials are available including glass pipes for chemical processes, although these tend to be very expensive and have long lead times.
An increasingly popular option is Naylor Hathernware – a high performance range of ceramic pipes suited to aggressive operating environments such as where effluents are corrosive, sudden temperature changes arise or where chemical spillages or attacks occur. The High Temperature range (HT) in particular is a product, which not only withstands chemically aggressive discharges but can also withstand thermal shock and so can handle the very hot effluent discharges associated with many process and food manufacturing applications. Hathernware ceramic pipework has a much lower thermal expansion than any of the above materials and its coefficient is half that of steel and ductile, and 10% of uPVC. Hathernware pipework systems can withstand up to 99.6% of all chemicals and the product has resistance to thermal shock at temperature changes of up to 120°C.
All Hathernware pipework is manufactured to comply with the stringent requirements of BS EN295-1. As Hathernware has such high crushing strengths, it can often be laid on the natural trimmed trench bottom as a dug material can be used for the backfill, all resulting in significant savings in granular bedding material.
The specifier who gives ground and effluent issues full consideration will avoid pipes vulnerable to corrosion or failure and ensure that project quality is not compromised.
Edward Naylor is Chief Executive at Naylor Drainage.
