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Last updateThu, 09 May 2024 2pm

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Clark-Drain launch new cover for utility, highways and public sectors

Clark-Drain launches new version of its D400 High Max series – designed with Water Companies, Local Authorities and Highways Contractors in mind. The manhole cover will satisfy the heavily trafficked needs of UK road networks. 

As road traffic intensifies and weather conditions become more changeable the ‘best-fit’ specification and installation of access covers to specific industry requirements has a role to play in supporting ‘whole life costs’ and health and safety needs. 

Fash Shahidi, Clark-Drain’s Key Account Manager at Clark-Drain comments:

“Choosing covers which help to prolong surface wear and skid resistance life is an important consideration for organisations interested in ‘value improvement’ based around total cost of installation and whole life costs, particularly in the Water, Highways and Environmental sectors.”

Premature failure in the bedding material is often cited as the main factor contributing to poor performance of installations.

Fash continues:

“Product design plays a massive role in extending product life. With High Max it was important to incorporate an understanding of dynamic loads. Finite Element Analysis and 3D modelling was used in the design of High Max to evaluate how these were dispersed under heavy load stresses to minimise the impact on the bedding. A tread pattern with 25% more density than the minimum requirement specified in EN 124 and 40% greater tread height than rival manhole covers all contribute.”

Through the years significant improvements in frame and cover design have generally been integrated into the Nation’s roads - The Highways Agency’s guidance HA 104/09 for example has driven improvement. Fash adds:

“What is needed is a new way of delivering the best possible performance for the installation. We have engineered High Max to meet these needs by providing exceptionally good durability, safety and flexibility in use. ”

With road traffic increasing almost 25% in the last 15 years despite government attempts to get people to drive less and with vehicles becoming bigger and heavier,‘Total Cost of installation’ was one issue Clark-Drain was particularly keen on tackling. 

“Durability is an increasingly important factor in delivering value, so we have deliberately designed High Max as our heaviest duty D400 manhole cover to address this,”Fash notes. “Heavy duty design, coupled with unique features that encourage longevity, such as ‘Inboard’ cover supports reduce the risk of cover collapse under extreme loads. High Max is also quiet in use with non-rock three point suspension using oversized cover corners to direct the loading stresses for best-case frame and bedding interaction and to minimise surface noise. The shape of the flange has also been optimised to increase the area where loads are concentrated, whilst a flared frame design transfers dynamic loads around the corners to minimise the stresses on the bedding and extend the life of the installation.”

With increasing incidence of flooding, High Max also delivers additional levels of safety with accessories to help curb the impact of increment weather. Fash adds:

“Ingress of surface water into a sewer network can add to problems of surging during increased flows in the drainage system. The low leak sealing plate slows down/prevents the ingress of surface water off the road. For heavier rainfalls and subsequent flood conditions manhole covers are often forced out of the ground, creating a hazard. High Max features a bolt in steel sealing plate designed to overcome back pressure experienced in sewer shafts  up to 0.5 bar (equivalent to pressure of 5 metres head of water). 


To offer multiple applications with one frame design Clark-Drain has developed High Max to accommodate five accessory options (bolt-in sealing plate, low leak plate, safety grid, Glass Reinforced Plastic (GRP) sealing plates and prison grills). The bolt-in plate option is factory fitted whilst the others are either factory fitted, or retrofitted. Fash states:

“This is another value-based design element we considered. It avoids having to buy separate products which can be costly to meet differing safety and security needs of a wide variety of project types.The multiple insert design also enables stockists to keep one product instead of separate products to minimise yard space” 

Manual handling

Manual handling is also a key design consideration. Health and safety is supported by High Max as the product has a double triangular design with four keyholes enabling a two person lift. The problem of disengagement is also reduced with non-slip safety key holes compatible with long handle lifting keys and other mechanical lifting devices. 


Manufactured from ductile iron and Kitemark certified to BS EN 124 the High Max series exceeds the required 400kN loading for D400 class and includes design featureswhich make it a valuable low maintenance option:

  • Clear opening sizes include CD 901H KMD (600mm x 600mm x 100mm), CD 901AH KMD (600mm x 600mm x 150mm), CD 902H KMD (675mm x 675mm x 100mm) and CD 902AH KMD (675mm x 675mm x 150mm)
  • Non rock three point suspension
  • Recessed locators in cover provide bolt locking option
  • Non slip safety key holes compatible with long handle lifting keys and other mechanical lifting devices supports safe manual handling
  • For existing, older installations that need replacement covers the 600x600mm clear opening High Max products incorporate a frame design to accommodate imperial 24’’x24’’ pit sizes
  • Vented grouting pockets on flange improves bond to mortar and lateral stability of manhole cover in service
  • Solid flange meets the minimum 75mm width conforming to BS 7903
  • Range accessories to enhance, protect and increase safety include - Drop in ductile iron low leak plate; Bolt-down steel sealing plate; GRP sealing plate; Safety Grids; Security grills for prisons.