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Contractors World International

Even before Network Rail introduced the new standards,

the popularity of GRP enclosures was quickly gaining

momentum. Metal had always been the traditional, go-

to solution because of its inherently robust nature, but

as competition within the industry increased, many

newcomers to the market were noticing that the incum-

bent favourite had several disadvantages that they could

improve upon.

While metal enclosures are undoubtedly strong, an

essential quality in a trackside enclosure, they are prone

to denting when subjected to forceful impact. Once the

metal is dented its protective coating will be damaged,

which will allow for corrosion to occur, quickly compro-

mising the integrity of the connection within. Of course,

if the connection becomes compromised, then the con-

ductivity of the metal makes the enclosure itself a health

and safety risk.

A good quality GRP enclosure, by contrast, will have

a tensile strength that, while not equal to, is still com-

parable to its metal counterpart, yet it will not dent and

is not at risk of corrosion should the paintwork on the

surface get damaged.

In addition, the material does not conduct electricity,

meaning there is no risk of electrocution should anyone

come into accidental contact with the enclosure.

When most engineers are asked to specify the tough-

est enclosure possible they naturally turn to metals like

stainless steel. This is a force of habit brought on by

traditional misconceptions, and usually answered with-

out the real-world considerations of cost and


While metal enclosures may offer the highest

strength, when it comes to all round toughness, it’s easy

to make a case for GRP.

Spelsberg UK

Competence in Gravel Extraction

Modern duty cycle crawler cranes

from Liebherr are being used by

Kiesabbau Wiedemann for various

tasks in the sand and gravel extrac-

tion industry.

The south German company has

strengthened its position with four

further machines, namely three HS

8070 HD and one HS 895 HD. Two

of the duty cycle crawler cranes in

Kiesabbau Wiedemann’s fleet

proved their efficiency during the

last year as part of an infrastructure

project in Hungary.

The task of the duty cycle crawl-

er cranes was the extraction of grav-

el material for the development of

the Hungarian motorways. Despite

the relatively large volume of the

extraction, Kiesabbau Wiedemann

decided against a larger machine and opted for two HS

8070 HD instead, thus considering the difficult soil


Thanks to the performance of the two 70-tonne

Liebherr duty cycle crawler cranes, the ground pressure

could be kept as low as possible while lifting the dragline


Approximately 16,000 Tonnes of

Gravel per Day

For about one year, the duty cycle crawler crane worked

twenty-four hours, seven days a week in order to meet

the requirements for gravel.

Each machine was equipped with a 23 m long boom

as well as a dragline bucket with a filling capacity of 3

m³. Every day about 16,000 tonnes of sand and gravel

were extracted from depths of down to 12 metres. That

means a turnover of approximately 330 tonnes per hour

and machine.

Thus, in the course of the year, it was possible to

meet the customer’s expectations and achieve approx-

imately 5.5 million tonnes of material as required.

Kiesabbau Wiedemann provided a well-experienced

team of six operators for the task. They worked in shifts

and achieved low cycle times of under one minute.

Liebherr-Werk Nenzing GmbH

Contractors World International Vol 7 No 4