Barhale Construction was undertaking a Thames Water Hoddesdon transfer project based in Hertfordshire, England, and decided to use Naylor’s Denlok range of jacking pipes. This project, which involved a major sewage transfer scheme situated close to a trunk road, included thirteen crossings beneath roads, rivers and railways, which Barhale were to install using Iseki microtunnelling machines.

 

However Barhale faced a problem – the largest diameter Denlok pipe which Naylor produced at the time had 600 mm inside diameter which was too small to accommodate the 600 mm flanged ductile iron pipes which had to be inserted within the jacked pipes at the crossings. Alternative materials were either far more expensive or were not preferred for technical reasons.

 

Naylor therefore decided to develop a 700 mm Denlok pipe especially for this application. A combination of close teamwork with Barhale and fast track design and development work by Naylor resulted in delivery of the new size on time to meet Barhale’s construction timetable. The success of both the product and the Naylor/Barhale collaboration was featured as a case study in the Constructing Excellence Publication ‘Building Success: Lessons from Suppliers and Manufacturers Who Got It Right’.

 

Whilst Naylor’s early development work concentrated on smaller diameter products, starting with 150 mm inside diameter (id) it quickly became apparent that there was a demand for a larger diameter jacking pipe and therefore Naylor extended the range to 700 mm id, with pipe lengths being available up to 2 m long.

 

Within the UK market, the company’s clay drainage products are most prominent in sewerage work – most notably infrastructure work (roads and sewers on housing schemes) and civil engineering projects. Whilst plastic drainage has gained something of a foothold in building drainage, clay continues to be a preferred material where greater longevity or environmental considerations are important. The strength, durability – an expected 100+ year life – and lack of vulnerability to rodent attack and maintenance procedures (rodding, jetting) results in widespread specifications for housing association and public sector work such as schools and hospitals. A plastic pipe by contrast, has much less inherent strength and a high dependency on good bedding and site practice. Plastic progressively weakens in service and, according to Naylor, will have lost 60%-80% of its initial strength after 50 years.

 

In addition to manufacturing traditional clay drainage such as densleeve (plain ended) and denseal (socketed) pipes, the company has developed two clay ranges, Denlok jacking pipes, as used in the Hertfordshire transfer project, and Hathernware chemical drainage for aggressive environments.

 

Whilst jacking pipes are made out of other materials such as concrete and glass reinforced plastic, clay as a material readily lends itself to trenchless installation. Naylor says clay drainage is strong and durable and popular with those parties where environmental considerations are paramount.

 

Naylor’s Hathernware drainage range comprises ceramic pipes suited to aggressive operating environments, such as badly contaminated ground, 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 can withstand chemically aggressive discharges and thermal shock and so can manage the very hot effluent discharges associated with many process and food manufacturing applications in dairies and breweries, as well as hospital laundries and chemical plants.

 

The company’s Hathernware range was relied on during the recent construction of a new textile production plant in Skhirat, Morocco for clothing manufacturer Fruit of the Loom. As part of the factory construction process, drainage systems were installed beneath the factory floor to handle wastewater effluents produced during the various manufacturing and finishing processes – most critically beneath the dye plant, where effluent is both high in temperature (100oC+) and chemically active with a variety of different chemicals depending on the dyeing processes being undertaken. These severe and adverse operating conditions necessitated specialist wastewater piping; given the anticipated chemical composition of the effluent. As a result of this need all of the Hathernware HT pipes, joints and bends were connected using band-seal chemical couplings.

 

The HT system consists of plain-end pipes and fittings, made from a specially formulated clay body, which allows them to withstand the thermal shock of a sudden temperature change of up to 120oC. Joints are affected using either HT polypropylene couplings or flexible Band-Seal couplings; special band-seal chemical couplings are available incorporating a heat-shrunk PTFE liner, which are appropriate where scheme conditions anticipate aggressive discharges as well as high temperatures.

 

Within the chemical and process industries, the product also allows a degree of ‘future-proofing’, enabling the designer to incorporate a worst-case scenario or anticipate future changes in building use or process. This is particularly relevant to drainage installed below the main floor slab where future repair or amendment would be prohibitively expensive.

The new larger diameter jacking pipes used on the Hertfordshire sewage transfer project, have enabled Naylor to increase its exporting activities. Denlok has now been used on every continent; overall some 300 kilometres have been supplied and installed worldwide, with South East Asia proving to be a particularly fruitful area for Denlok. United Engineers Sdn Bhd of Bandar Seri Begawan, Brunei, recently ordered Denlok as part of its bulk clay pipe supply to the Kiulap project.

 

Naylor has also developed a parallel system, Revit, which is used in trenchless size-for-size replacement or for upsizing old sewers with new clayware pipes. Naylor’s Revit system is designed for installation from existing manholes, using short length clay pipes with flexible joints. These are jacked in behind a hydraulic burster unit, which breaks out the old pipe.

Whilst the company is committed to clay drainage for foul sewerage applications, Naylor plans to develop plastic pipe systems for less sensitive applications. The company will soon launch a DN100-600 twin wall surface water drainage system, designed for highway drainage and agricultural usage. Naylor are also looking closely at rainwater management as an area of potential growth.

 

At the recent Manufacturing Excellence Awards, organised by the Institution of Mechanical Engineers, Naylor Drainage won the Best Small to Medium Engineering award. The judges acknowledged the company’s “strategic direction, investment in process and product plus boundless enthusiasm” as the reason for this decision. •