Nowadays, requests for drilling in restricted and narrow spaces are frequent and not only in Europe. Activities such as retrofitting existing structures, installing micropiles in old buildings, rock anchors, soil nails and grout injections in low headroom locations are part of the foundation business. Also, geothermal drilling is required in small spots, usually private buildings or single houses.
To perform such works, drilling rigs of reduced size and weight, that can be easily transported, put in place quickly and drill with good performance are required.
A solution is a rig with a separate power pack that’s connected through hydraulic hoses. The smaller rig can be driven inside houses, buildings, gardens and low headroom spaces, and the power pack can be set outside or in a different space nearby. Normally these units are operated by radio remote control, so the driller can be placed in a good spot for checking the borehole and rotary, avoiding dust, hidden corners or other obstacles from the view.
Another application of these small rigs is drilling in small pits or holes, where the only possibility to reach the lower floor is to lift the machine using a crane. In these cases, it is extremely helpful to have a rig with reduced weight and dimensions, so positioning will be easier.
One of the models that are frequently used for these applications is the Fraste MITO 4 CS micropile drilling rig. This drilling rig is composed by a base machine with a mast and rotary head, and a separate power pack. The remote power pack can be diesel or electric driven. The main technical specifications of the MITO 4 CS drilling rig are:
- Engine: 90 kilowatts (kW) (120 horsepower) Tier V – Stage 4F
- Optional electric power pack
- Modular mast
- Rotary stroke: 900 mm/1,400 mm/2,200 mm (2.9 ft/4.6 ft/7.2 ft)
- Crowd system: by gear motor
- Pull-up force: 5,000 dekanewtons (daN) (11,240 pounds [lb])
- Pull-down force: 5,000 daN (11,240 lb)
- Rotary head torque: up to 1,180 daN metres (8,700 foot-pounds)
- Full radio remote controlled
- Expandable crawler carrier for a greater stability: 780–1,200 mm (30.7–47.2 in)
- Total weight: 4,300 kilograms (kg) main rig, plus 2,100 kg power pack (9,500 lb, plus 4,600 lb)
- Clamps and breakers: diameter 40–250 mm (1.57–9.84 in)
- Hydraulic winch: 1,000 daN (2,240 lb)
One of the interesting features of this rig is the possibility to enter buildings using standard doors. The rig’s minimum width is 780 mm (30.7 in). Many customers appreciate this point. The modular mast is another interesting characteristic with a minimum rotary stroke of 900 mm (2.9 ft) and a maximum of 2,200 mm (7.2 ft) for rods up to two metres (m) (6.5 ft). Radio control is standard, helping the driller to be in the best spot for viewing and safety.
The expandable undercarriage allows the rig to have extremely good stability during drilling operation and to go through narrow spaces as well.
Instead of the standard rotaries, it is possible to mount hydraulic drifters from different manufacturers. This permits the rig to work with self-drilling hollow bars or on any other work where percussion and rotation is needed. It is also possible to have the line lubricator mounted on-board, with the option to be quickly detached from the rig in very narrow spaces.
In case of an exceptionally wide borehole, it is possible to install bigger clamps and breakers, with diameters up to 415 mm.
Other options
The machine can be powered by an electric motor with 45 kW power, maintaining overall performance. The rig will be connected to the local electric network or by a separate battery. A hydraulic hose rewinder can be mounted on top of the power pack. This feature allows the driller to quickly rewind and unwind all the hoses that connect the power pack to the drilling rig.
The power pack can be mounted on the undercarriage. The standard configuration of the rig is with the power pack mounted on rubber wheels, but it can be installed on its own undercarriage to be trammed independently from the drilling rig.
An electric/hydraulic small power pack can be installed on the drilling unit to power only the undercarriage. This allows the independent tramming of the drilling base without connecting to the standard power pack.
A range of mud pumps can be installed on the back of the rig to have it ready to drill. The MITO 4 CS is also used in drilling for geothermal energy. In fact, the demand of geothermal loops in private buildings requires the use of small rigs for drilling in narrow spaces. These shallow depth boreholes are used for heating and cooling facilities using heat pumps.
Normally, in this type of project, preparation happens in the garden or yard of private properties, where the drilling rig is then set up. It is important to leave as little evidence of the work as possible, ensuring not to damage slabs and lawns more than it is necessary. It is also possible to protect the ground with special plastic layers/mattresses before the machine enters the site.
The duration of these works is variable, depending on the number of boreholes required and on the depths. The MITO 4 CS has worked on projects with depth up to 150 m (490 ft) and diameters of 140–150 mm (5.5–5.9 in).
Once drilling is completed and the equipment is removed, it is important to restore the site as close as possible to initial conditions. The MITO 4 CS has proven to be very efficient and reliable, including for geothermal loop activity.