Construction MachineryAssociated costs and basic concepts

Need for machinery

• Reducing costs

• Doing the heavy lifting

• Reducing duration of work

Advent of Modern machines

• Simple machines have combined overtime to form more complex machines

• Developments of internal combustion and compression ignition engines has replaced humans as source of power for machines

• Developments in materials such as rubber, nylon, steel etc. have made mobile machines of today possible.

Parts of construction machines

• Platform

• Power pack

• Power train

• Equipment or tool

Types of machinery

• Earthwork – Dozers, loaders, scrapers

• Lifting – cranes, gantry, lifter

• Transportation – dump truck, pumps

• Concrete equipment – mixers, batching plant, compactors, spreaders, vibrators

Choice of machinery

• Quality of work required

• Schedule

• Material to be handled

• Site conditions

• Budget

• Capacity of work

• Aim of machine

Categories of equipment

• Small tools and consumables: drill bits, blades etc.

• Shared equipment - fairly expensive equipment used throughout construction process

• Task specific equipment – costly equipment used in specific stages of construction

Equipment Selection - considerations

• Optimal production and within time and budget constraints

• Sufficient power and capacity

• Costs: Ownership, operating, labour, replacement, salvage

• Site conditions

• Working surface and material to be handled

• Volume and nature of work

• Labor availability

• Relations with manufacturers

• Client demands

Cost Components of production unit

• 1 production unit cost includes:• Ownership costs

• Operational costs

• Overheads

• Profit

Overhead

• These are costs associated with running a machinery maintenance and storage facility and the associated workforce;• Wages of mechanics and supervisory personnel

• Clerical and records support

• Rental or amortization of the maintenance facility

• Expressed as a percentage of the total operation hours logged by the entire fleet of equipment.

Ownership costs

• The cost of owning a machine whether its in operation or remains idle.

• Components of ownership:• Initial capital cost – cost of transporting machine to construction site

and set up cost• Depreciation – decline in value of machine with passage of time due to

general economic decline, obsolescence or deterioration Related concept of Salvage value – cash inflow from machine having some value

at the time of disposal• Interest cost – capital invested in a machine annually (converted to

hourly cost)• Insurance – insurance theft, fire damage, accident • Taxes – cost of licenses and property tax• Storage – cost of rent and maintenance, guards

Depreciation methods

• Straight line : (I-S or D)/Y

• Sum of digits: (year number/sum of year numbers)(D) cost highest in 1st year

• Declining balance: Rate of depreciation * I (constant every year)

Investment

• Annual amount of capital invested in a machine. Equals to Average value x interest rate.

Operating costs

• Tire repair and replacement costs = 1.15 xcost of a set of tires

expected tire life in(h)

• Fuel cost = time factor x efficiency x average fuel consumption per hpx hp x cost per gal

• Lubricants = or 10% of fuel cost

• Repairs (opposite of depreciation)

Equipment life

• Physical life: Machine reaches a stage where it can no longer reliably produce. Must be abandoned or scrapped.

• Economic life: It is the time taken for the machine to produce maximum operating profit.

• Profit life: The time period during which the machine operates at a profit.

Factors affecting productivity

• Haul unit horsepower

• Haul road rolling resistance

• Haul road grades

• Haul unit loaded and empty weight

• Haul unit transmission characteristics

• Haul unit loading time

• Haul unit travel time

• Haul unit delay time

• Altitude of the project site

Rolling resistance is resistance offered to movement

of materials on a plain surface; often expressed in

pounds per ton of materials.

The coefficient of traction can be defined as the factor by

which the total weight on the drive wheels or tracks should be

multiplied to determine the maximum possible tractive force

between the wheels or tracks and the surface just before

slipping will occur.

Usable force = Coefficient of traction X Weight on powered

running gear

• Time to load a mover for load shifting will determine no of loads that can be transferred. Longer loading time lesser will be productivity.

• Te is cycle time for loader

• Ch is capacity of a hauler

• Ce loading rate/capacity of loder