The types of cranes used underground will depend on the lifting operation and the size of the workspace, but their usage tends to be limited because of the restricted space available, cluttered work area, sometimes explosive atmosphere, and linear nature of the workspace.

Indeed, there are, says Dr Donald Lamont, director at Hyperbaric & Tunnel Safety, few machines used underground purely as cranes: “You are working in a confined space that can be 3, 4, or 5m in diameter, roughly rectangular, so a crane is really not much good because you can’t get the jib up, and you need a certain amount of space below the hook between the load and the end of the jib.

“Any lifting underground tends to be done more by hydraulic means: by jacking, sliding, or using an escalator as a crane because that’s already down there.”

Besides, he adds, tunnels and mines tend to be long linear worksites which is not conducive to crane operation.

Cranes are rarely used on a typical tunnel building operation because the work will normally be carried out by a tunnel boring machine (TBM), says Lamont. He says the segments that line a tunnel wall tend to arrive either by train or by rubber-tyred vehicle: “There are between five and ten or so segments in a ring and segments can weigh anything from 5–100t depending on the size of the tunnel. The segments are lifted off the vehicle onto the segment path or magazine.

“The segment path is the area of the machine where they are taken forward. The magazine is where they are laid out in order and they are sent to the erector, a ring erector that can extend radially. It picks the segment up from the invert, rotates into position and pushes the segment out radially into the position it has to be for the lining.”

The erector is used as lifting machine, but it is fixed in the TBM. It can rotate and move radially, and picks tunnel segments up on a vacuum pad.

However, says Shannon O'Keeffe, tunnel agent for Costain on the Tideway East project, the choice of lifting equipment is more extensive in sprayed concrete lining tunnels: “Here, you can find mobile and truck-mounted cranes as well as forklift trucks used for lifting. Tunnel boring machines (TBMs) generally have bespoke cranes built into them, including segment cranes, davit arms, erector cranes, pipe fittings, rail lifters, etc.”

Cranes used in underground applications do, though, require modification, as O’Keeffe explains: “Underground lifting carries the same risks as general duties, with the obvious additional consideration of confined/ restricted space. This often necessitates the use of limiters.”

Tom Pawson, chief engineer at Costain Group, explains: “Due to the confined nature of a tunnel, more use of limiters such as virtual walls/ceilings is more commonplace than it would be outside a tunnel environment. Virtual walls/ceilings [to mitigate surrounding fixed hazards] can be provided as pretty much standard now. They can be aftermarket fitted if required, using systems such as Prolec.”

The PME500 instrument from James Fisher Prolec, for example, combines height, rated capacity indicator, and slew limiting technology to maximise protection using ‘virtual walls’.

James Fisher Prolec has more than 30 years’ experience supplying machines to boost productivity and safety systems. These include height limitation technology, machine guidance solutions, on-board weighing systems and rail safety equipment.

In the UK, cranes and component systems like Prolec need to comply with LOLER, the Lifting Operations and Lifting Equipment Regulations, and BS7121, the standard for safe use of cranes; other markets around the world have similar requirements. But, once you head underground, additional standards should also be considered. In the UK, one such is BS6164, Health and safety in tunnelling in the construction industry. Sections of the standard apply to cranes (and other equipment) used underground, and detail steps that may need to be taken to ensure surface equipment is safe for underground use.

Determining factors for the use of cranes below ground include the atmosphere—this is why electric cranes are generally favoured, because they don’t emit the toxic exhaust fumes produced by diesel engines—as well as the risk of entrapment and/or inability to escape load exclusion zones.

Electric power for cranes used underground typically comes from mains power. But what about battery-powered cranes? Says O’Keeffe: “I haven’t come across battery-powered mobile cranes as such before in the UK or Australia [in tunnel applications], but there are a number on the market and the popularity is increasing.

“Batteries can be lithium ion, but… there is a risk of fire which needs to be fully managed and mitigated to ALARP (as low as reasonably practicable). We use these batteries in our underground railway systems to power our locomotive units, so we always undertake charging of such in a segregated location.

“Use of acid-based batteries is covered extensively in BS6164 for this reason.”

Although he says it is better if the lifting uses no power or electric plant, diesel is sometimes used to power cranes operating in larger workspaces such as underground caverns (ticket offices or large tunnel intersections). Says O’Keeffe: “In the case of diesel, most lifting plant needs to be new or near new, with Euro 4 or better ratings along with fitting of scrubbers.”

The risk of fire is a critical safety consideration when working underground, so fire suppression systems are also a must.

Minis for mines

B&B Plant is the sole importer and distributor of mini spider cranes in South Africa. The company says Unic mini spider cranes are ideal for work underground in mines because of their comprehensive safety features and ability to access restricted areas.

The only replacement parts are the rubberised tracks which, in a typical mining application, might need changing once a year (and less so in other operations such as in manufacturing plants).

The company has upwards of ten cranes working in mines throughout Southern Africa, and more than 60 units sold to date. Bob Fogg, owner of B&B Cranes, is confident that the Unic mini spider cranes his business represents have a bright future in underground applications.

Last year, the company brought in the URW1006, a 10t mini spider crane. Fogg says there is no other mini crane of this size mounted on crawlers in the country. Not only can the URW1006 reach confined spaces, but it can pick and carry its load.

Adjustments to B&B Cranes’ machines include a fire suppression system to prevent and/or extinguish the spread of fire and minimise the possibility of reflash. Typically, the system automatically detects a fire, although it can also be operated manually.

Fogg adds: “If it’s a coal mine, they want the fire suppression system plus two handheld 9kg fire extinguishers…If the engine or hydraulic pump catches fire, then the fire suppression comes into play and floods the crane with foam.”

Reflective tape is also a requirement in mines, Fogg says: “It’s usually fairly dark working underground, so we have amber reflective tape which we put on the sides of the crane, white tape on the front and red on the back.”

If another vehicle is passing a crane that is parked up with no lights on, then its headlights will pick up the reflective tape. Fogg adds: “The Unic cranes don’t have a cab, so some of the mines want two strips of green on the back behind the seat where the operator sits, and on the side where he climbs onto the machine.”

Because of the poor light conditions, extra lights are also required. Fogg again: “We work a lot in diamond mines where they are installing new conveyors quite high into the roof of the shaft where it is very dark. We put extra lights on the top of the boom plus two spotlights on the back for reversing and one on the front.”

Other requirements include a lock-out switch whereby the operator can turn a switch mounted on the bottom of the seat to isolate cables to the battery. Once it is locked out, a padlock is typically fitted to ensure nobody else can use the crane.

An emergency stop comes as standard on the mini crane, but a mine requires two emergency stops, one at the front and another at the back.

Phil Cooley, a consultant with B&B Cranes, adds: “Our cranes are typically three-cylinder diesels, but we also bring them in with diesel and an electric power pack on the back, so they are actually a hybrid. The power pack takes a threephase plug. Then the crane runs on an entirely separate motor and hydraulics. Some mines work at 380W and others at 550W, so we have to fit the appropriate power pack to fit their specific need.”

A lot of mines have a caged goods and equipment lift. Some, Fogg says, carry up to 35t so “most of the time we simply put the crane in a cage, and it is offloaded at the bottom of the shaft.”

If the mine has no goods and equipment lift, says Cooley: “Sometimes, to get the cranes underground we have to take all the liquid out of them, remove the outriggers and place bow shackles (a bow shackle is able to be loaded at an angle).

“We lift the back of the crane up and put the nose down and drop it down the hole, say 1,000m to the shaft. Down there they will have a forklift which pulls the crane flat onto its rubber tracks. Then we lower the legs down separately, to be reinstalled in the mine.”

Adapted to fit

A few years ago, Boliden, a Swedish metal company with its own mines and smelters, asked Manitex Valla (through its UK dealer, Hird) to supply an electric-powered carry deck crane to work in the Boliden- Tara zinc mine in Ireland.

The crane needed to be as compact and manoeuvrable as possible because of the confined space in which it would work

The crane Valla supplied was a modified 1725-36SD with ‘global control’, which allows the user to define special features including virtual wall and increased systemoperator awareness. Tele-diagnosis is planned as a future expansion.

Five main modifications were requested by Boliden.

First, it needed a shortened boom, to increase its ability to travel in reduced/cramped spaced.

Secondly, it featured automatic Lincoln lubrication systems. Because of the aggressive working environment in the mine, the customer needed the pins to be lubricated every few working hours. Since there was a hydraulic slewing collector on the turret with a limited number of hydraulic lines, it was decided to have two independent, automatic lubrication systems: one for the lower structure (axles, pins) and the other for the upper structure (pins).

Thirdly, the crane was fitted with an ANSUL-Tyco fire suppressing system. A mine is a high-risk environment, so Valla added fire suppression to the crane. While not included on this crane, the company can also adapt cranes for AtEx environments.

Fourthly, a Perkins 854F-E34TA Stage IV diesel engine was installed in the crane which complies with non-road mobile machinery (NRMM) rules in force in 2016. One complication occurred because of the presence of a urea system and post treatment system that took up a lot of space on the crane. That engine was CAN network linked to the global control system so that its status/functioning was fully integrated on the crane’s single human interface machine (HMI).

Finally, Boliden was keen to develop a well-trained team of its own people to operate the crane and fix small issue that might arise on the equipment so it asked Manitex Valla to provide training.

Cristian Falceri, product development and operations manager at Manitex Valla, explained: “After delivering the crane in November 2016, the customer began to consider how to increase the workload performed of the crane. This led to a request for a quotation to modify the upper structure to make it even more compact.”

Modification took place at Manitex Valla’s facility in Italy in November 2019 and the updated crane was delivered at the beginning of January 2020. The upper structure of a 1725-22 crane was mounted on the 1725-36SD.

A new three-position tilting head design was fitted. To save overhead space, the customer wanted a head that was able to tilt forward 45° and 90° in addition to the vertical position. Finally, radio remote was installed to allow upper structure control from a position other than the cabin.

Falceri concluded: “We learned valuable lessons from this project. The most important was that it is crucial that information related to special applications must be documented and shared directly between the end user and manufacturer because each actor in the loop might introduce ‘noise’ or bias especially if there is a lack of past track records.”

Underground London

UK crawler crane hire company NRC Plant’s smallest ‘zero’ tail swing mini crane – the Hitachi ZX75UST – has been busy working in a confined space 30m below the streets of East London at the BBMV (Balfour Beatty, Morgan Sindall, and VINCI Construction joint venture) Crossrail Site in Whitechapel, London.

This telescopic crawler has as maximum lifting capacity of 4,900kg and a rated total load x working radius of 4.9 tons x 2.1m. Operational within minutes of being lowered to its work area, the ZX75UST was able to extend and retract when working in the restricted head heights of the tunnel.

Dave Rees, Operations Manager at NRC Plant, said: “We didn’t supply specific ‘underground’ cranes; just conventional telescopic crawler cranes with additional safety features because ventilation was so good down in the tunnels. The safety features included fire suppression systems to prevent the spread of fire and spark arrestors. To mitigate a potential build-up of exhaust fumes and other gases, the spark arrestors prevent the emission of flammable debris entering the engine.

“There were also additional light packages added – high intensity work lights – fitted on the front of the cranes to improve visibility.”

Valla has also seen its minicranes used on tunnelling projects in London. The company recently had one its cranes lowered 20m down a shaft to support construction of the latest extension of the London Underground. The Manitex Valla 250E electric pick and carry crane, the latest addition to Redhill, UK-based crane hire specialist Hird’s small crane fleet, is being used to carry and install precast concrete sections in the new Battersea station on the Northern Line.

The pick and carry crane, with a maximum lifting capacity of 25t, is being used to carry and install reinforced concrete panels which have been lowered into the shaft by a tower crane.

The two-mile Northern Line extension, being built by a joint venture of Ferrovial Agroman and Laing O’Rourke, with a budget of £500m, with two new stations at Battersea and Nine Elms will then terminate at Clapham Junction.