Manhole frame regulation – the technique has come of age
Up until 25 years ago, technical knowledge in Germany was such that installing manhole frames, or regulating frames which have dropped, slipped or tilted, meant bedding them on a layer of concrete. This manual technique was very expensive; and the 3-day curing time for the mortar was extremely inconvenient. It regularly led to diversions or bottlenecks which impeded traffic flow.
The need for manhole frame regulation has always been due to chemical processes (road salt), and the steadily increasing volume of traffic, especially of heavy goods vehicles.

The basic essential: high quality dry mortar

The impetus for innovations in the area of manhole frame regulation was the escalating cost of conventional frame-lifting which relied on expensive but error-prone manual labour. Another reason was the inexorable increase in traffic which exacerbated the problem of hold-ups caused by roadworks. The challenge was two-fold: to reduce costs by improving and rationalising techniques, while at the same time minimising disruption to traffic flow.
The development of dry mortars then quickly pointed the way to numerous applications for modified cementitious materials in sewage installations and pipework.
The German firm of ERGELIT GmbH marketed ERGELIT superfix grout as early as 1981. This mortar guaranteed easy handling, and could be used in a wide variety of fluctuations in temperature and atmospheric humidity. Great strides were thus made in reducing possible failures. Furthermore this product provided the necessary bond between the manhole frame and the top of the shaft. The ease of application and the small amount of labour required meant significant savings. A fast setting time also led to reduced costs. Whereas conventional frame regulation methods allowed traffic to flow after 24 hours at the earliest, this grout meant traffic was free to flow after just 1 hour. In addition, this mortar’s resistance to frost and road-salt was an important factor in the development of new techniques for frame regulation.
The new type of regulation has been continuously improved. To support both clients and suppliers, HERMES Technologie brought out a quality assurance handbook in 2000, and offers contracting firms an extended product guarantee, once they have gained HERMES Technologie certification.
Machinery and equipment

The frame regulation market has access to a range of ideal products, now that grouts have been developed and become more and more sophisticated and specialised over the years. In the course of time, the process was further rationalised with the development of specialised machinery and equipment.

Formwork

The new grout, which achieved the desired bond thanks to their high flow-rate, could not be applied using conventional shuttering. Special types of tubular collar were developed for directing the grout into the repair joint between the lower edge of the raised frame and the top of the shaft. It is customary nowadays to use ribbed plugs for round sewer shafts.
Formers were also produced in various materials (rubber, lead) for inserting in lateral connections and for rectangular shafts.
Frame lifters
Naturally, even 25 years ago manhole frames were not just loosened and raised with a pneumatic hammer and a pick-axe. But it was with the development of the shaft renovation process that the development of frame lifting apparatus was able to make crucial progress. Mechanical frame lifters with a lifting capacity of over 20 metric tons are also in use, as are hydraulic lifters, both manually operated and motorised, with hoisting capacities of up to 50 metric tons and with different diameters.
Shaft debris collectors

While the frame is being raised or while the gap to be filled under the frame is being prepared, loose material or old pieces of grouting can quickly be caught on grouting sheets. These collectors are very easy to install underneath the area of repair (one man operation), and they prevent material falling down into the shaft. As far as this operation is concerned, the tedious and dangerous practice of climbing down shafts is a thing of the past.
Height adjusters
Frames which have subsided are raised to approximately the original level by means of a manhole frame lifting apparatus. There are various aids to determining the exact level. A tried and tested solution is the three-point frame-lifter equipped with three 35cm arms and an adjustment range of –5mm to +55mm. Levelling is quicker and more precise. In the case of both new build and frame replacement, this apparatus means one can avoid the incorrect and inaccurate practice of packing stones - or even worse, wooden wedges - under the frame. The height adjuster allows the injection of high early strength grout into the whole of the gap between the frame and the top of the shaft, in one smooth operation.
Manhole cover lifters

Lifting and shifting sewer shaft covers in situ with inadequate tools such as pick-axes or crowbars present direct and indirect dangers (injury to feet and legs, injuries to the back). The development of the Titan-ALU manhole cover lifter has removed such dangers. This universal lever, made of titanium-aluminium with an extremely high bending strength, is extremely adaptable and can cope with freeing, lifting and swinging both round and rectangular covers.





Another technique for lifting manhole covers and transporting them short distances is provided by the Universal manhole cover lifter UDH-60. The UDH-60, with its operator-controlled automatic claws, is mounted on a two-wheeled axle. This makes it easy to roll the cover away from the immediate repair area. Further developments, such as the all-purpose cover lifter DH 18 for particularly heavy manhole covers, complete the range of shaft renovation tools.
Manhole top cutting machines

Manhole frame cutting machines were developed for cutting out manhole tops in asphalt or concrete, cleanly and economically. They are particularly useful for raising flanged frames, especially where a new carrier layer is being laid. Cutters such as the petrol-powered DS 1400 are designed for shafts with a diameter of 60 to 140cm, and have a variable cutting depth of up to 15cm. These machines are easily transported around the site, and are particularly appropriate for larger scale operations.

In 2005, a new method for cutting very precise circular holes arrived on the specialist market in the form of the RKS 20T. This very light, user-friendly machine is equipped with an electric motor. It produces circular cuts of from 80 to 150cm Ø. Depending on which motor is fitted (1300 watt / 2500 watt), the RKS 20T’s concave blade has a cutting depth in asphalt of between 25mm and 40mm. The clean cut thus produced neatly separates the repair area from the surrounding asphalt. This clean-cut edge is vital when it comes to inserting bitumen tape. The hydraulically powered Stehr milling cutter achieves a similar result. It is connected as an attachment to a wheeled trolley.

Edge work: materials

The full ‘manhole frame regulation’ process requires a range of further materials. We should mention here VBT damping rings, commonly known as ‘anti-rattle rings’. A noteworthy new development in this area has been ‘anti-rattle filler’. This malleable compound of two environmentally neutral synthetic components is inserted into the manhole cover support or into the frame itself in the form of a bead of self-hardening paste, as a damping layer. This compound is a versatile, high quality alternative to sound-damping, and is quite unaffected by the diameter or size of the manhole frame. Special materials also exist for repairing crumbling or cracked edges around the frame. For this work -depending on the extent of the loss of surface material – there are bituminous tape, masking tape and shaft sealing strips. Supplementary products MSK liquid asphalt or MSK “cold” Rephalt have proved themselves in the repair of damage to asphalt edges. In their physical properties they are in every way equal to the surrounding hot asphalt.
The future

Manhole frame regulation is a safety concern for highways authorities, and is thus an on-going source of business for road repairers. Firms constantly offer innovations, but these are not always taken up, because of the financial pressure which has arisen from the undeniably tight budgets of highways authorities. Even more striking, since it has an effect on the general economy, is a certain quite unjustifiable tendency observable in the public sector, to award contracts only to the lowest tender. The quality of innovative yet proven processes which give a more cost-effective repair in the long run, is usually ignored. Suppliers frequently try to respond with prices that don’t cover their costs. Sometimes they try to bring in new, but not better, processes. Tried and tested processes and high quality ‘know how’ which have been developed over a long period suddenly become unattractive thanks to a dubious tendering system, and could lose out to the competition – perhaps even disappear from the market altogether.

It is not just in this segment of the market that the situation outlined here puts a brake on inventiveness. It is a common problem, because this search for cheapness, which is economically unjustifiable, is spreading across the whole of the demand side. It distorts competition, blocks technological advance, and leads to a supply-side decline and consequent loss of jobs.