CD 534 – Keeping up with the standards
Two crucial standard updates the industry may have missed
Critical industry standards have recently been updated at a time where many have had their attention dominated by COVID-19. Our Technical Manager Barry Turner, former chairman of the BSi BS EN 124 Standard committee, shares an overview of both BS 7903: 2020 and CD 534, providing a simple way to get up to speed on these recent and crucial changes.
In the UK, BS 7903 has just been updated to the 2020 version, which supersedes the 1997 version. It gives guidance for the selection and installation of manhole tops and gully tops conforming to BS EN 124: 2015 used in conjunction with other components and materials in highway applications. It expands on EN 124, with particular reference to UK practice, and is an important normative reference contained in many UK standards, regulations and specifications, including CD 534.
BS 7903 advises its users to consider the desirability of obtaining third-party certification of conformity with BS EN 124. It goes into much more detail than EN 124 on the importance of installation materials and their compatibility and interaction with the frame. Regarding classification and place of installation, it also highlights the need to consider pre-service loads such as construction site traffic. Also to be taken into account are dynamic forces from traffic leading to seating wear and frame bearing pressure.
In February 2020, DMRB/CD 534 was introduced as a Highways England Technical Regulation.
The Design Manual for Roads and Bridges (DMRB) has recently been updated by Highways England (HE). For more than ten years, HA 104/09 (an ‘advice note’ within the DMRB) has been a key document for chamber tops and gully tops setting out procedures and denoting materials which Highway Authorities believe provide the best possible performance for installations in trunk roads and motorways.
This crucial HA 104/09 advice note has now been replaced by CD 534, a new Technical Regulation posted and referenced on the European Commission Technical Regulation Information System (TRIS) website. Both documents were produced by the HE in association with Transport Scotland, the Welsh Government and Northern Ireland’s Department of Infrastructure, and contain HE’s requirements for road chamber top and gully top installations on motorway and all-purpose trunk roads.
Whereas HA104/09 was ostensibly a stand-alone document, CD 534 contains ‘normative references’ (a document to which reference is made in the standard in such a way as to make it indispensable for the application of the standard) and must be read in conjunction with these as they contain some of the important requirements for chamber tops and gully tops that were previously explicit in HA104/09. Linked with CD534 is Series 500 of Volume 1 of Highways England’s Manual of Contract Documents for Highway Works (MCHW).
Third Party Certification to BS EN 124 continues to be required
A key example is that of third-party certification of products. In clause 3.5 of HA 104/09, there is a requirement that chamber tops and gully tops be certified by one of the accepted UKAS certification bodies (e.g. BSI Kitemarked) to BS EN 124. There is no such clear requirement in CD 534. However, detailed study of the regulation and its cross references reveals that under its clause 1.6 the HE requirements contained in GG 101 shall be followed. G101 is the introduction to the DMRB and states ‘the requirements and advice given in DMRB documents are provided on the basis that the works are constructed in accordance with the MCHW’. Appendix B of the MCHW concerns ‘product certification schemes’ and it is here we find the requirement for a third-party certification scheme for BS EN 124.
Areas of difference between HA104/09 and CD 534
There are several areas where CD 534 differs from HA104/09 and some of these are summarised in the table below.
|HA 104/09 Requirement||CD 534||Comment|
|3rd party certification||Not explicit but captured in the linked appendix B of the normative reference MCHW||BS7903 highlights consideration of Third-Party Certification. Also recommended by CEN Technical Committee TC165;|
|Chamber top frame bearing pressure to be ≤ 2.1N/mm2||Not present explicitly||BS 7903 refers to this requirement and HE’s Series 500 of the MCHW specifies bedding mortar strength properties which assume a maximum bearing pressure of 2.1N/mm2|
|Frames weighing more than 15kg must have provisions to allow balanced lifting||Not present explicitly||BS 7903 recommends this requirement (6.19)|
|Bedding mortar compressive (30N/mm2) and tensile strength (5N/mm2)||Not present explicitly but captured in 507.24 of the normative reference MCHW||BS 7903 expands on the importance of mortar specification under 5.5|
|Packing materials must be compatible with the mortar||Not present||BS 7903 expands on the importance of the compatibility of packing materials under 5.5|
|Chamber top PSRV of >45 or >60 depending on the site risk||All Group 4 chamber tops to have a PSRV 60||Sensible to have PSRV tests carried out and confirmed by a UKAS accredited laboratory|
|Consider E600 chamber tops in certain circumstances||E600 chamber tops must be used where the AADT LGV >1500 in each direction||Introduces the requirement for E600 chamber tops in many roads|
|Not specifically contained in HA104/09, but referred to in Highway England Interim Advice Note: 196/17 and/or 197/17||The installation of chamber tops shall be avoided in motorways and all-purpose trunk roads carriageways||This requirement is to be applied where possible, but in the predominant instances of existing chamber top installations, CD534 makes allowance for their use in the carriageway. This clause falls within the remit of scheme designers, contractors, etc., rather than chamber top suppliers or manufacturers|