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How Can Cover Specification Go Wrong (and What’s the Damage When It Does)?

Recently, we wrote about how we at Clark-Drain are working with NBS Source to give you and your construction partners open access to a comprehensive online library of data and information about our products, to help make the product specification process quicker, easier, more accurate, and more cost-effective for whole life use.

One critical area these resources provide information on is the technical specifications that determine a product’s suitability for use in specific environments – so, load-bearing capability, dimensions, drainage capacity, and resistance to damaging substances, to name a few.

In this piece, we explore what can happen when specification goes wrong in regard to load class, and explain what a product that can perform looks like in comparison.

Poor specification = money down the drain

Let’s focus on covers and their load-bearing capabilities, as getting this specification wrong can be a major issue, with destructive and costly consequences – and potentially, a legal liability of negligence for the installer if the incorrect load rating is deemed to have created a dangerous situation.

Incorrect load specification means the cover and frame can often end up being damaged by the weight of vehicles (see images below).

Image 1 – damaged cover and frame

In more serious cases, the cover may even fail completely, leaving a deep cavity that can damage vehicles and present a health and safety hazard, (see image 2 below).

Image 2 – failed cover

All this adds up to dangers, liabilities, and costs. Had the specification incorporated the correct loading class in the photos above, the issues wouldn’t have happened.

But what constitutes the correct loading class?

Taking the strain: how load classes work

Load classes for covers range from A15 (pedestrian and cyclist use only) to F900 (particularly high wheel loads such as airports), with various gradations in between, each described in terms of the environments that load class is typically appropriate for.

So, for heavy traffic areas (bus depots, car parks, petrol stations, municipal maintenance facilities, fleet fuelling sites), the correct class for the wheel loads that are likely to be encountered is D400 – which means the cover can withstand weights of up to 40 tonnes.

Even in nominally lighter-traffic areas, where traffic weight and volume may possibly increase periodically or over time, or where there is doubt about the accuracy of these designations, you should err on the side of caution and specify the load class above the one originally envisaged.

Load rating isn’t the only measure of a cover’s performance, resilience, or suitability for the job, and it’s important to consider all factors.

D400 done the Clark-Drain way

“Grounded in expertise” is our slogan, and our D400 recessed ductile iron cover illustrates that commitment to a tee, as it offers benefits no other supplier’s products can match.

Engineered for heavily trafficked, paved, and tarmac areas, it is designed to cope with frequent, heavy-duty, slow-moving wheel loads with greater stability, flexibility, and durability than traditional steel equivalents, and actually exceeds the 40-tonne load requirement.

The design concentrates the load transfer in the optimum areas of the frame flanges, delivering great strength whilst minimising the strain on the bedding.

Increased corner areas, compared to traditional designs, provide excellent seating for stable installation, and the recessed tray permits the use of a range of infill materials, including tarmac, paving, and concrete.

As ever, we go further to deliver better. The use of ductile iron, for example, means the cover can be installed into a roadway, whereas the use of steel covers is not permitted.

Also, ductile iron doesn’t rust or corrode when trafficked, which means not only that the cover and its frame are more durable, will last for longer, and provide better return on investment, they will also not seize or fuse, and so will continue to open with ease, inspectable, and maintainable throughout their lifespan.

And in line with our commitment to sustainability and environmental responsibility, the cover is fully recyclable at end of life.

Specification that goes a step further

In short, whilst the wrong specification can fail the job in hand, the right choice of product for the specification required can deliver benefits above and beyond – something we at Clark-Drain have been doing consistently for our customers since 1963.

For more information on our D400 recessed ductile iron cover, get in touch today.


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