• Home
  • » Plant
    • » Plant & Equipment

Plant and Equipment

The decision to hire or to own plant and equipment distinguishes a Contractor’s commitment to the long-term development of a knowledge based workforce. The decision of an individual within that organisation to educate themselves with a detailed spectrum of technical knowledge distinguishes that individual’s commitment to their own ultimate competence.

 

In Ward and Burke Construction Ltd. the decision to own all of our own construction plant and equipment is based on the normal economic factors, technical practicalities, scientific necessities and most of all on human and social considerations. Caterpillar say in their Handbook that “A well trained operator, working under suitable conditions, utilizing a modern, properly-equipped machine provides a machine-operator team capable of giving maximum production”. Providing equipment is a financial consideration, facilitating, producing and motivating well trained operators and constructors is part of our long term commitment to skill development. For our construction engineers and managers to understand and utilise these skills in their projects an equal commitment will be required. Here is an introduction to why knowledge of plant and equipment is important to all constructors within our organisation.

 

Excavators | Operators | Excavator Capacities | Deep Excavation | Pumping
Trench Support | Rock Breaking | No Dig | Tarmac Reinstatement | Transport | Heavy Lifting | Servicing
Training | Conclusion

 

Excavators

We have concentrated our plant fleet around reputable manufacturers.  CAT, Kobelco & JCB are world leaders in the provision of excavators. The interface of our work with the Public requires Zero-Swing multi-attachment handling excavators. The resultant range within our fleet of 75 excavators can be seen in the following table, some of the pertinent statistics are tabulated to help the Site Agents select the appropriate machine.

Back to top

 

Operators

The skill level and concentration required from plant operators while working in the public domain is extremely high. Not unlike sportsmen, natural talent is a great advantage to them but consistency, reliability and an interest in the final product are the essential ingredients. While the possession of a Safe Pass safety awareness card and a CSCS Plant Operators ticket are the minimum legal requirements to operate equipment it is the willingness and experience of the operator within the system of work which is critical to efficiency. Effective methods of work require Safe Equipment + Safe People + Safe Site. Training for operators and mechanics is underway and we expect to rationalise alot of the operators’ experience into some useful theories which will be an essential guide to our future standard practices.

Back to top

 

Excavator Capacities

Sample List only:

Back to top

 

Deep Excavations

Most engineering projects entail excavations into water bearing soils. These soils can vary unexpectedly and it is in the management of these variations that experienced plant and equipment operators and engineers distinguish themselves. Powers in 1992 stated “the successful practitioner in de-watering will be a man who understands the theory and respects it, but who refuses to let the theory overrule his judgement” Success for such temporary works practitioners is based on having a sound knowledge of plant capability and application and also having that plant available to them. We take the view that once the opportunity to deepen our judgement or knowledge of engineering arises, the experience must be harnessed and held within our organisation so it may be reproduced as standard procedure in the future. This requires a commitment to purchasing and managing the appropriate plant.

Back to top

 

Pumping

A detailed knowledge of pumping equipment for dewatering excavations is essential. Understanding the limits of diesel engine driven dry prime and wet prime vacuum pumps can impact greatly on ones ability to dewater a trench, cofferdam, and caisson or open excavation. Vacuum pumps rely on and are limited by atmospheric pressure to force water from an excavation up into their low pressure suction chambers. The pumps ability to maintain the vacuum during priming is a function of the rate of air evacuation from the suction chamber and hoses and the quality of their seal from the atmosphere. Aska Sykes operate a vane pump which has a typical air handling capacity of 40cfm while Godwin use a compressor and venturi to induce 4cfm for the same purpose. The maintenance requirement for each pump is also different so it is essential to employ the correct pump for the correct application. Submersible pumps whether they be driven by an electric motor from a generator or a hydraulic motor from a power pack are capable of lifting water from much greater depths than the typical 6-8m of the vacuum type. Recently we excavated 1200m3 of silt and sand using an electric submersible as part of sinking a cofferdam 12m deep. The electric submersibles proved extremely reliable under difficult conditions as the inflowing water liquidised the soil. Subsequent Pipe laying at shallower depths used the high air handling Sykes pump with header pipe and self jetting reusable wellpoints to lower the water table suitable for conventional excavation methods. The installation of the wellpoints requires a high-head high-volume delivery pump. We have the option to use the HL125 Godwin capable of delivering 200m3/hr at 10bar where there is a local supply of water or the Garda pump mounted on the Major water tanker where water needs to be drawn to the work site. The hydraulic submersible is robust and an essential item when working in areas subject to flammable gasses such as digester tanks in sewerage treatment works. It is intrinsically safe due to the hydraulic drive motor on the pump, and the flexibility to locate the power pack remote to the pump by extending the hydraulic hoses. Our fleet of over 50 pumps gives us the necessary flexibility to respond to the variability of the ground in which we work. 

Back to top

 

Trench Support

Temporary works are typically used to support the ground while the permanent materials are installed.
Their successful deployment requires an understanding of ground conditions as well as the method of construction of the permanent works. The intended duration of ground support can vary from minutes as in the case of a dragbox for pipelaying or months for a sheetpiled cofferdam for a concrete structure. Other times there is a requirement for sheetpiling for the pipe and the concrete structure is open cut. Our experience is that a well placed excavator can perform most functions when operated by a suitably experienced operator. The Movax side grip piling hammer is operated off the quick hitch and hydraulics of the SK330 Kobelco excavator. It has the capability to drive and pull steel sheet piles up to 16m long and has managed to drive steel bearing pile up to 58m deep for bridge pier foundations. This equipment is highly versatile and mobile when working under restricted conditions. More specialised crane mounted piling hammers such as the PVE 2330 Vibro-hammer has greater pulling capacity but needs a large crane to handle its considerable 8t suspended weight and 40t of line pull. This hammer has the capacity to start vibrating above the natural frequency of the pile thus avoiding undesirable ground vibrations. For driving piles into clay an impact hammer is more suitable a BSP SL30 has the capacity to impart 30KJ of energy into the pile thus encouraging it to penetrate the most resistant ground. We operate 5 piling hammers and over 1000 sheet piles and associated steel frames to facilitate the planned and unexpected requirements of ground support. Trench Boxes, Drag Boxes, Manhole Boxes and Plate boxes are all essential as part of the standard trench support system.  Our fleet of over 120 units allow us great flexibility in dealing with the varying depths and soil types associated with trench work.

Back to top

 

Rock Breaking

The removal of rock from confined trenches, shafts and tunnels is a demanding job for equipment. Standard rock-breakers such as those constructed by Sandvic or Krupp are highly designed for their environment. They are high maintenance and require skilled operators and service mechanics to keep in operation. The output of these devices can be enhanced by creating artificial discontinuities in rock mass using Pyrotechnic Gas Blasting or pre drilling the rock. We have an excavator mounted ‘down the hole’ drilling rig which will bore the hardest 400MPa granite at 300mm/min. We use this unit where conventional high explosives are unsuitable and standard rock-breaking un-economical. Our fleet of 30 rock-breakers cover the excavator range from mini to 50t. Keeping trench sides vertical through rock mass is impossible using rock breakers. Where the rock mass characteristics are suitable in terms of fracture spacing and compressive strength the Vermeer T758 offset Rock Trencher is a commanding machine. It has the capacity to remove up to 2m deep by 300mm to 750mm wide trenches at a rate of up to 2m per minute. Carbide tips spaced on a rotating chain develop a fracture pressure capable of removing the rock and the machines conveyor belts will load the material directly into a truck all within a 2.5m wide corridor. This process should not be confused with the grinding actions of diamond tipped equipment.

Back to top

 

No Dig

As described throughout this article and as delays at roadworks will testify there is an inordinate effort involved in installing what seems to be a relatively small pipe as part of utility works. Often the volume excavated, transported, disposed of, replaced, blasted, crushed, imported, double handled, compacted and reinstated in a typical trench can be of the order of a factor of 50 times the final product! Tunnelling technology has improved over time and now the removal of the mixture of hard rock, soft silts and loose gravels within a tunnel bore is possible and much more efficient.

 

Soil Conditions
Soil conditioning is an essential part of this the ‘no-dig’ system, bentonite or cement based slurries and/or polymer/foam additives can be mixed and delivered to the soil often in advance of the tunnel drive. This is achieved using the Colcrete CX4/10 colloidal grout mixer/pump unit which will deliver up to 3000l/hr at 12bar through the 12X HDD rig. Horizontal columns of treated ground can be formed with pin-point accuracy such that permeability and strength can be modified in advance of larger product tunnels. The sinking of the launch and reception shafts whether sheetpiled, bolted segmental or insitu-formed caissons is also a critical part of this tunnelling process. Precast sections up to 3.2m id can be installed using our excavator mounted or roped clamshells with minimum disruption. Larger diameter shafts are catered for using the flexible radius steel shutters or precast sections stitched together. Underwater excavation is often technically essential for these shafts so the hydraulic gradient in the ground water can be controlled. Circular shafts obviously require less reinforcement due to their inherent compressive stress state and are more flexible for drive direction.

 

Soil Mechanics
With all of the above systems a detailed knowledge of geotechnical engineering and soil conditioning is necessary. To this end John Grennan one of our tunnel Engineers is well into his 2 year Masters Research programme at MIT in Boston. John is investigating the characteristics of Irish Silt especially those encountered in our Tunnelling works in Skibbereen. Brien Curran has started a similar Masters programme in NUIG on the ‘Bore-ability of Rock in Microtunnels’. This aggressive approach to developing a calibrated knowledge of Irish soil conditions is essential to the efficient deployment of the correct equipment. This initiative is in keeping with the sentiments of Samuel Johnson who said in 1758 that ‘Vulgar and inactive minds confound familiarity with knowledge and conceive themselves informed of the whole nature of things when they are shown their form or told their use; but the speculatist , who is not content with superficial views, harasses himself with fruitless curiosity, and still as he inquires more, he perceives only that he knows less’

Back to top

 

Tarmac Reinstatement

A consistent finish to trench reinstatement work is traditionally difficult to achieve. This relates to the difficulty in preparing the 804 to a consistent depth below the existing often variable road surface. Conventional methods of preparing this surface are by back-hoe or mini excavator or by hand which is unsatisfactory. Our method involves the use of a road planer. Firstly the trench is compacted up level with the existing road surface using the excavator mounted compactor plate this ensures complete compaction with no local soft spots as a result of over dig. The surplus material is struck level with the road producing a level running surface for the planer. The Wirtgen D500 or D600 milling machines can then remove the required depth (typically 50mm) consistently over the trench surface which will produce a plane parallel to the existing road surface. This then allows the tarmac to be laid and rolled producing a smooth running surface. Our mini pavers the Vogele Super 600, Super 800 and Super 1203 can handle paving widths from 0.6m to 4m which makes them extremely versatile and nimble in restricted working areas. The Bomag 90 and 120 smooth drum rollers discharge water to the drum when rolling thus ensuring no pick up from the tar and some cooling of the surface thus allowing early opening to traffic.

Back to top

 

Transport

To deploy this equipment to the particular works location nationwide requires a specialist transport fleet. Our Scania double-drive tractor units up to 620hp provide the appropriate pulling power for our Nooteboom 5 and 6 axel low loaders. The hydraulic all-steer system in the trailer means the trailer follows the tractor unit without cutting the corners making the tightest sites accessible. Pay loads over 100t are possible on these rigs at the appropriate speeds. The 10m long bed on these semi-trailers give the flexibility to move either pre-cast concrete chambers or excavators’ thus maximising productive time on the road. Site based transport of equipment and material is complicated by the variable nature of running conditions in fields and roadways. The John Deere 6920 series of agricultural tractors can tow a 21t tri axel low loader trailer at 50km/h on the road. Its air and hydraulic systems ensure full breaking and suspension control over the trailer. It can still produce the appropriate traction for field work and can also tow a 16t dump trailer; operate a road sweeper and load and un-load materials using its front in loader. Wet field conditions may require the Morooka tracked dumper or Bogmizer. Its low ground pressure allows the distribution of pipeline materials in the worst quagmire. Small site dumpers are essential utility machines. The 6t Thwaites swivel dumper allows a pipe trench to be filled from the side as the dumper travels parallel to the trench affording the driver the best visibility of his work. Where trench backfill stone can’t be stored local to the works area the 20t stoning cart pulled by the John Deere tractor can discharge fully via an adjustable conveyor in 3 minutes. This unit is ideal for reinstatement behind the rock trencher when on full production. 8 wheel Lorries by Scania are ideal for taking muck away from trenching operations. Their bodies are also to tar specification therefore insulated with roll over covers and chutes to suit the tarmac reinstatement demands of the job.

Back to top

 

Heavy Lifting

Insitu reinforced concrete structures such as reservoirs and municipal water and sewerage treatment works require a high standard surface finish. In order to meet these fair faced finishes and still retain the flexibility and efficiency of panelled formwork we have invested in the Belgian manufactured Construx steel faced panels. These panels are 30% heavier than their timber faced counterparts and as a result need substantial cranes to handle gang shutters. We operate 60t, 70t, 100t and 140t crawler cranes with  60t and 80t mobiles for short duration works. A lorry mounted 72m.t Palfinger crane allows self contained lifting and shifting. The development of our off-site pre-casting facility has warranted our recent investment in a Liebherr 140t crawler. It can load a 70t chamber while still handling shuttering, steel moulds and wet concrete in the yard. Excavators are often used in a lifting capacity. All boom and dipper rams are fitted with check valves which protect against the sudden collapse of the arm due to a hydraulic hose bursting. Certified lifting points are identified on each machine. Appropriate lifting chains, slings and shackles are carried in each van. They are routinely tested every 6 months and inspected with every use for any damage.

Back to top

 

Servicing

In order to achieve economical levels of utilisation effective maintenance is essential. Depot facilities, central workshops and highly trained and experienced staff are required. Planned preventive maintenance through routine servicing and known wear component replacement is essential. Planned corrective maintenance can be undertaken efficiently on site by well equipped mobile fitters. Accurate pre-inspection of plant for such maintenance is essential. A well documented asset history record card compiling the information from repair job cards and the hours worked allows rational comparisons to be made with budgeted costs. These comparisons are used to guide maintenance procedures and ultimately the decision to replace or sell the item of plant. We operate a 3 pronged maintenance service. Field fitters work with site based constructors and operators to keep plant operational they carry the basic stock of components and use their ingenuity to the full. Independently service fitters work through scheduled servicing working their way through over 2000 such events per year. They use lap-top computers to down load the fault history from machines and recalibrate engine and hydraulic functions regularly. Finally workshop facilities are available in our home yard in Creggs, Co Galway where complete overhaul of units is possible. A dedicated management team is beginning to take shape which will allow all of these procedures bear fruit.

Back to top

 

Training

Dixon in 1966 said that “To make a correct decision is to choose the one alternative from those available which best balances or optimises the total value, considering all the various factors”. Experience and technical knowledge are required to make decisions, training in a formal procedure to gain experience and knowledge. There are many people involved in the construction process in need of this training and we have instigated a programme which will expose all of our employees to some form of training annually. Engineering staff need to understand the capabilities of plant and equipment in order to design safe and efficient methods of work. Their course is a 3 hour site based module given by our Plant Director who is also a civil engineer. Mechanical, hydraulic and functional features are discussed and the relevant technical information shared. Mechanical fitters need at least 1 to 2 days with each manufacturer in order to update and develop their knowledge of plant technology. Apprentice fitters are moved around the company in order to broaden their exposure of plant in order to help them use their college based time to maximum effect. Drivers and plant operators often rely on their own curiosity to investigate the workings of a new item of plant which is an unacceptably random means of introducing such equipment. An in-house technical instructor will now be available to induct these end users in the finer operational details. Management similarly require 1 day’s appreciation of the changing demands of new technology and to share critical information with the dealer and manufacturer. This training programme while still in its infancy has been a revelation to all concerned and is sure to pay dividend through increased uptime on plant and cultural improvements in plant operation.

 

Conclusion

In observing all of the above basic points our conclusion is that while technical information is openly available to construction engineers from manufacturers and text books and working knowledge is common amongst the plant operators and plant hire company owners there is a communications void between these parties through which little information is exchanged. This is very unsatisfactory when an efficient and safe system of work is required. Training and field experience is ad-hoc and variable for young entrants to the construction industry. Management and workers are informed separately of their duties and often develop an incomplete view of their role in the construction process. With a directly employed workforce and an ownership policy for plant and equipment there is the beginning of an integration learning process for all of our construction personnel. Not unlike the horse and the water the appropriate conditions are required for effective learning. We endeavour to deliver these conditions. Our continued success will rely heavily on our commitment to facilitate our employees in this regard.

 

Back to top