Clay offer longer-term pipe products: Edward Naylor

Clay Technology magazine
7 Jun 2019

Naylor CEO Edward Naylor talk about issues in the clay sector.

What are the challenges facing clay pipe manufacturers and what is Naylor doing to address them?

One major issue for the UK clay industry is encouraging long-term thinking. A clay pipe system will outlive an equivalently installed plastic pipe system – unlike plastic pipes which suffer a reduction in ring stiffness over time, clay pipes retain their initial strength. In many overseas markets, product life costing is paramount but the UK appears to have an unhealthy focus on short-term cost, which tends to favour plastics. In addition, installers like plastic pipes as they tend to be longer and lighter. They can literally be ‘chucked in a trench’ so to speak, although this seems a poor basis for deciding on the material for one of our most important infrastructures.

What clay pipe developments are you currently working on?

Naylor has continued to grow its clay business as a result of the development of specialist systems which have drawn on the natural advantages of clay. These include Denlok jacking pipes – a very strong clay pipe for trenchless installation – it can be pushed through the ground without digging a trench. We also developed Thermachem, a high-performance pipe for handling very hot or aggressive effluents.

Can you tell me about advances made in the material strength and performance of your clay products?

Clay pipe production has evolved to meet the requirements of each generation. Recent decades have seen the evolution of the easy to install, push-fit ‘sleeve’ system. Most recently, water jetting – a common deblocking technique – has emerged as a challenge to sewer systems. Independent research identified that most jetting contractors carried equipment capable of jetting at pressures considerably in excess of 2,600psi, and indeed, a significant proportion of blockages required pressures in excess of 2,600psi to clear them. This was an issue for the plastic pipe industry, with most flexible pipe systems only being able to withstand jetting pressures up to 2,600psi.

Testing of clay pipes identified that they had an unrivalled ability to withstand high-pressure jetting, and UK clay pipe manufacturers responded to the water industry’s challenge by introducing a guarantee against high-pressure water jetting up to 7,500psi.

Clay pipes for drainage systems have long been claimed to be more sustainable than plastic alternatives. With the many developments in plastic materials, is this still the case?

The sustainability credentials of the clay pipe do not just hinge on the energy requirements of the production process, although independent studies have consistently confirmed that the total energy required to produce a clay drainage system compares very favourably with systems produced from all alternative materials, including PVCu, concrete and cast iron. They also draw on the material itself as well as the durability of the product.

Firstly, the material. In contrast to, say, PVCu – the production of which results in harmful byproducts – clay is a natural material in abundant supply. The UK clay pipe manufacturers draw on local quarries and have an excellent record in the restoration of spent clay pits. Minimal waste is produced in clay pipe production, raw clay scrap is returned for reuse while fired scrap is ground up and fed back into the mix in the form of grog – an essential element of the mix that improves dimensional accuracy and performance and speeds up drying and firing, hence reducing energy consumption.

Secondly, durability. Clay pipes have unrivalled durability, which has been proven over periods of hundreds and even thousands of years in service. Clay pipes have excellent heat and chemical resistance and excellent resistance to abrasion and pipe cleaning operations. Indeed, for design purposes, clay pipes can be assumed to have an infinite life.

What do you do to maximise energy efficiency and resource usage of fired clay?

Clay pipe production has evolved significantly over recent decades and the industry has introduced fast firing or roller kiln techniques, that allow the manufacture of pipes and fittings in as little as three hours. In comparison, the firing processes of previous generations – beehive, tunnel and intermittent kilns – have been measured in days, if not weeks. Process improvements have also significantly reduced the amount of scrap being produced in the various clay pipe factories.

What options are there for extending their life?

Clay pipes form a strong and permanent structure. They are easy to connect into, repair or replace, and end-of-life clay pipes can be broken up and returned to the earth. However, relining is a cost-effective way of repairing a pipeline that has been disturbed or damaged, and trenchless techniques such as pipe bursting allow existing clay pipelines to be upsized.