Estimation of Welding CostByK.R.Prasanna VenkatesanWE0663

Sayings If you cant measure it, you cant manage it Peter Drucker.If you are not measuring it you are not managing it - corollary

Types of CompaniesLarge Scale.Design first, Cost Next.Small Scale.Cost First, Design Next.

EstimatingIt is the process of determining the probable cost of a Product / Process (Welding) before the manufacturing.

Estimation is the Process done by a Technical Person and not by Accountant.

Both Over Estimation and Under Estimation is Dangerous.

CostsDirect Cost.Material Cost.Labour Cost.Expenses. Indirect Cost.Over heads.Admin. Expense.Selling and Distribution.Profit, Discount.

Ladder of Cost.Direct Expense, Material, Labour CostFactoryPrime CostAdmin.Work CostSales and DistributionProdn. CostProfitTotalOrUltimate costDiscountSelling PriceMarket Price

Material CostIt is the cost of Materials required for a Process (Welding)Example: Direct: Filler, Flux, Gas, etc.Indirect: Cotton wastes, Coolant, etc.

Labour CostIt is the cost spent to the workers who are directly or indirectly involved in Manufacturing.Examples:Direct: Operators, WeldersIndirect: Watchman, Supervisor

ExpensesAll other expenditure other than Material and Labour cost is called Expenses.Examples:Direct: Power consumption, Welding M/C. cost.Indirect or overhead cost: Depreciation.

Welding Cost ParametersJoint Design TypeWeld SizeWeld TypeWelding ProcessElectrode Deposition EfficiencyOthers (Safety)

Thinking of Welders

If a little is Good, a lot size is Better, and too big is Just Right.

But this leads to failure of Weld, and increase in cost, which is not preferred.

Butt WeldFillet Weld

Factors of Welding CostTime for joint preparation. Time to prepare the material for welding (blasting, removal of oils, etc.). Time for assembly. Time to preheat the joint (when required). Time for tack-up. Time for positioning. Time for welding. Time to remove slag (when applicable). Time to remove spatter. Time for inspection.

Factors of Welding Cost

Time for changing electrodes. Time to move the welder from one location to another. Time to change welding machine settings. Time spent by personnel for personal purposes. Time to repair or re-work defective welds. Costs associated with any required stress relief. Cost of electrodes. Cost of shielding materials. Cost of electric power. Cost of fuel gas for pre-heat (when required).

The Operating Factor The ratio of hours spent welding to total hours worked is called the operating factor.

Basic Cost FormulaWelding Costs = (L&O) + (Consumables Costs)

Gas Welding & Cutting Cost Direct Material cost = base material cost + Consumables Cost (Filler, O2 & C2H2)Direct Labour cost = Preparation or pre welding cost + welding cost + Post welding cost.Direct expense = Cost of fixture and auxiliaries.Over heads.

Three Basic Approaches Cost per unit. Cost per length. Cost per weight. The application will determine which approach is most appropriate.

Cost Per Unit This method suits for pieces that move through a workstation.

For SMAW Cost/unit = (L&O/unit) + (filler metal and shielding material cost/unit)L&O/unit = (welding-related time/unit) x (L&O rate)

Cost Per Unit - Contd.For Wire Fed processes: Filler metal cost/unit = (wire feed speed) x (welding time) x (weight of electrode/mm) x (electrode cost/kg) Filler metal cost (SMAW) = [{(electrode melt off rate) x (welding time) x (weight of electrode/mm)}/(% of electrode used)] Shielding gas cost/piece = (flow rate) x (welding time) x (gas cost/m 3 )SAW flux cost/piece = (wt. of flux used) x (cost of flux/kg.)

Cost Per Length This method is appropriate for estimating the cost of long welds Formula:Cost/length = (L&O cost/length) + (filler metal and shielding cost/length) L&O cost/length = (L&O rate)/(travel speed) x (operating factor) Filler metal cost/length (wire fed processes) = {(wire feed speed) x (wt. of electrode/(m or mm).) x (cost of electrode/Kg.)}/(travel speed)

Cost Per Length - Contd.Filler metal cost/length (SMAW) = (melt off rate) x (wt. of electrode/length) x (cost of electrode/Kg.)/(travel speed)(% of electrode used) Shielding gas cost/length = (gas flow rate) x (gas cost/m3 )/(travel speed) Shielding cost/length (flux) = (wt. of weld metal/length) x (ratio of flux to weld metal) x (cost of flux/Kg.)

Cost per weightIt is best used in applications in which significant volumes of weld metal must be deposited, such as multi pass applications. Hard facing and overlay welding are ideal applications.

FormulaCost/Kg. = (L&O cost/Kg.) + (filler metal and shielding cost/Kg.) L&O Cost/Kg. = (L&O rate)/{(deposition rate) x (operating factor)} Filler metal cost/Kg. (any process) = (cost of filler metal/Kg.)/(electrode efficiency) Shielding cost/Kg. (gas) = (shielding gas flow rate) x (cost of shielding gas/m3 ) /(deposition rate)Shielding cost/Kg. (flux) = (cost of flux/Kg.) x (ratio of flux to filler metal)

Thumb RuleIn case of on site welding process, if it is difficult to estimate the weldment weight. for such case, the Universal Thumb Rule is weldment weight is 2% of total structures weight.

Power Cost.V x A t 1 1 1000 60 rxxxxcWhere V Voltage in volts A Current in amps t Welding time in min Efficiency of the welding machine, (0.6 Transformer & 0.25 Generator) r Operating factor C Rate of Electricity per kWhr in rupees

Theoretical Vs ActualTooling time.Fit upsFixture non alignment because of spatter depositionFiller may change, So quality. may changeSkill varies from men to men.

So we should use Digital communication technology for monitoring the welding and whether the std. are followed or not.

Theoretical Vs ActualIf we increase the size of fillet weld, the area of Fillet will be Doubled, And the cost will increase. And not only that, it leads to Stress.

Weld Area Vs. CostNote: Labour Cost is 80% of Total Cost (Based on Typical Modern Welding rates and Efficiency)

TipsSelect the cost calculation method that most directly measures the important cost variables for the specific application.

When evaluating the effect on overhead costs, ask: Will the changes in the welding operations affect the company throughout?

Carefully evaluate the impact of the proposed change on the operating factor. Some changes will decrease this variable, others will increase it.

Make sure the data used for cost computations reflect reality.

Some Data

Steps to Reduce Welding CostAnalyze the delivery of consumable and accessories to welding point.Analyze whether material handling is effective.Look for ways to correct over welding.Enhance current welding process and procedures.Optimize joint preparation.Eliminate any extra welds from design.Look for items that can be welded rather than cast.Look for ways to eliminate costly record keepingExamine safety concerns

An ExampleIf we consider a boiler drum, there are linear and circumferential welds.

That can be done by all kind of welding processes.

So here we are going to see some sample calculations.

Given DataLength 3mDiameter 1.2mThickness 15mmBoth side welding.Rate of weld 2m/hr(outside), 2.5m/hr (inside)Length of electrode required 1.5m/m of weld.

Given DataCost of electrode 2.75/mPower consumption 4kwhr/m of weldPower charge -45 paise / kwhrLabour Charge Rs. 9/hrOver heads 90% of prime costDiscarded Electrode 6%Fatigue and setting up time 5% of weld time.

CalculationsLength of weld:= 2 x x D + (2 x L) = 13.54mTotal electrode length = 1.5 x 13.54 = 20.31mElectrode Discarded = 6% = 1.22m.Total electrode wanted = 1.22 + 20.31 = 21.53mCost of electrode = Rs.59.21

CalculationsLabour CostLength of inside weld = 3m. Time = 1.5hrLength of outside weld = 10.54m.Time = 4.216 hr.Net time = 5.716 hr.Total time = net + (Fatigue) = 6 hr.Cost = Rs. 54.

CalculationsPower Consumption = 4 x 13.54 = 54.16 kwhr.Cost = 0.45 x 54.16 = Rs. 24.37Prime cost = 59.21 + 54 + 24.37 = Rs. 137.58Over Heads = Rs. 123.82 (90%)Total Cost = 137.58+123.882 = Rs. 261.40

In other process the process may vary. But the procedure is same

ConclusionSimplified calculations make this task easier Can find Alternate means of manufacturingCompany with economy and new technology can and will compete Successfully

ReferencesProcess Planning and Cost Estimation V. Jayakumar.Welding Principles and Applications Larry JeffusDesign and planning manual for cost effective welding AWS.www.weldingdesign.com - www.weldingdesign.com/323/Issue/Article/False/10864/ http://www.weldingdesign.com/323/Issue/Article/False/10760/Issue