01lecture03a Cost Calculations Slides

7/30/2019 01lecture03a Cost Calculations Slides

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Cost Calculations

Cost Calculations

Cost estimates for bidding on welding work in projects

Setting rates for incentive Programs

Comparing Welded construction to alternatives Comparing competing welding processes

Cost of Weldment vs Cost of a Weld


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Cost of Welding

($/ft) Cost incurred to make a weld

(includes joint prep, consumables,labor, overhead, pre- & post-weld

treatment, etc.)

Used to compare cost advantages

of weld vs. Other manufacturingprocesses

Used to decide on the most cost

effective joint design or most cost

effective welding process to use

Used as a basis for investment innew automated equipment

Cost of Weldment

($/piece) Cost incurred to make

entire structure (includes all of aboveplus summation of all the weldments

and raw material costs)

Used to bid on a welding job

Cost Calculations


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Cost Calculations The Basis - Welding Procedure Specification (WPS)

This is the starting point for cost estimating.

Procedure should include:

Joint details Welding process

Type of filler

Type of gas/fluxes

Welding current

Position (operator factor)

Travel speed

Post weld treatment


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Cost Calculations Main Factors

INDIVIDUAL PARTS OF ESTIMATE

(Look at each item individually)

1. Cost of Joint Prep

2. Cost of Materials (Consumables)

3. Cost of Materials (Flux & Shielding)

4. Labor Costs

5. Power Costs

6. Post Weld Costs

7. Overhead Costs


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Cost Calculations

1. Cost of Joint Preparation

Machined Joints - (most expensive)

Flame or Plasma Cut Joints Square Butt w/o Surface Prep - (least expensive)

A) Do cost analysis on several joint designs to minimize joint prep cost:

Note:If a non-prequalified joint is used, you may incur the added cost

of procedure qualification.

B) Trade off reduced costs to prepare joint with amount of weld metal to

fill joint.

Example: A submerged arc joint can be flame cut (inexpensive) but

may require a lot of weld metal to fill the joint (expensive).s

DIVIDUAL PART OF ESTIMATE(Look at each item individually)

Cost of Joint PrepCost of Materials (Consumables)

Cost of Materials (Flux & Shielding)Labor Costs

Power CostsPost Weld Costs

Overhead Costs


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Cost Calculations

2. COST OF MATERIALS (CONSUMABLES)

Procedurea) Calculate the theoretical weight of weld metal required to fill the weld

joint

b) Calculate the weight of filler actually consumed (spatter etc. included)

1. Estimating Losses2. Automated Method

c) Calculate the electrode costs





Overhead Costs


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Cost Calculations


a) Theoretical weight of weld metal

Cross Section Area of Joint - Use geometry or refer to tables forstandard joint configurations





Overhead Costs


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Cost Calculations


a) Theoretical weight of weld metal (contd)

Weight of Deposit (lb) = CSA (in2) x Density (Kg/in3) x Length (in)

Or Weight of Deposit (lb/in) = CSA (in2) x Density (lb/in3)

Th Wt of deposit (lb/ft) = CSA (in2) x density (lbs/in3) x 12 (in/ft)

Th Wt of deposit (lbs) = Wt Weld (lb/ft) x Total ft of weld (ft)

Reinforcement

Add 10% for single groove welds

Add 20% for double groove welds Add 10% for fillet welds





Overhead Costs

a) Calculate the theoretical weight of weld metalrequired to fill the weld joint

b) Calculate the weight of filler actually consumed(spatter etc. included)1) Estimating Losses

2) Automated Methodc) Calculate the electrode costs


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Overhead Costs

2. Electrode Filler Metal YieldCovered Electrode

SMAW 14 manual = 55-65% yield

SMAW 18 manual = 60-70% yield

SMAW 28 automatic = 65-75% yield Solid Bare Electrode For

Submerged arc = 95-100% yield Electroslag = 95-100% yield

GMAW = 90-95% yield

Cold Wire = 100Tubular-flux Cored Electrodes For

Flux Cored Arc Welding = 80-85% yield Cold Wire = 100%

1. Electrode Losses(SUM)Stub Losses

14 with 2 stub = 14% loss



Coating or Slag Losses

Thinner coating E6010 = 10%loss

Heavy coating E7024 = 50% loss

Spatter Losses

Depends on technique, usually= 5-15% loss

Calculate the theoretical weight of weld metalrequired to fill the weld joint

Calculate the weight of filler actually consumed(spatter etc. included)1) Estimating Losses

2) Automated MethodCalculate the electrode costs

Cost Calculations

2. COST OF MATERIALS (CONSUMABLES)b) Estimating Losses


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Overhead Costs




Cost Calculations

2. COST OF MATERIALS (CONSUMABLES)b) Wt of filler required

Wt of filler Required (lbs) = Th wt of deposit (lbs) / (1- total electrode loss)

Wt of filler Required (lbs) = Th wt of deposit (lbs) / {filler metal yield (%) }

Wt of filler Required (lbs/hr) = Wire feed speed (in/min) x 60 .

Length of wire per weight (in/lb)


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Overhead Costs




Cost Calculations

Electrode Cost ($/ft) = Th wt of deposit (lbs/ft) x Electrode Price ($/lb)Filler metal yield (%)


c) Calculating the Electrode Cost

Electrode Cost ($/ft) = Wt of filler required (lbs)x Electrode Price ($/lb)


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Overhead Costs

Calculation of Flux Costs

Flux Cost ($/ft)=Flux price ($/lb) x Weld Metal Deposit (lb/ft) x Flux ratio

Where, Flux Ratio = Wt of Flux (lb)Wt of Wire (lb)

Sub Arc = 1-1.5 (approx. 1 lb flux/ 1 lb wire)Electroslag = 0.05-0.10

Calculation of Shielding gas and Backing gas Costs

Gas Cost ($/ft) = {gas price ($/ft3) x flow rate (ft3/hr)}

Travel (ipm) x 1/12(ft/in) x 60(min/hr)

Gas Cost ($) = Weld Gas Cost ($/ft) * feet of weldOr

Gas Cost ($) = {Gas price ($/ft3) x flow rate (ft3/hr) x weld time (min)}

60 (min/hr)

Guide tubes Studs / Ferrules Spot-weld electrode

Cost Calculations

3. COST OF MATERIALS (FLUX & SHIELDING GASES)

Calculation of Miscellaneous Costs


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Overhead Costs

Operator Factor: percent of time that a

welder is actually making a useful weld. Semi-automatic and automatic plants have higher operator

factors Field welding / construction work with small welds in

scattered locations have low operator factor Welding in the flat position has higher operator factor than

horizontal, vertical, overhead:1. Faster travel speed

2. Fewer defects / fewer repairs Use of fixtures, positioners, and handling equipment

increases operator factor Slag chipping, electrode changes, moving from joint to joint

all reduce operator factor

Cost Calculations

4. LABOUR COST(single greatest factor in total cost of weldment)

Labor Cost ($/ft) = Welder pay rate ($/hr) .

Travel Speed (in/min) x Operator Factor (%) x 5


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Overhead Costs

Cost Calculations

4. LABOUR COST(single greatest factor in total cost of weldment)

Deposition Rate (lb/hr) = melt of rate (in/min) x 60 x Filler Metal yield (%)

Length of electrode wire per weight (in/lb)

Labor Cost ($/ft) = Welder pay rate ($/hr) x Weight of weld metal deposit .

Deposition Rate (lb/hr) x Operator Factor (%)


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Overhead Costs

Energy charge

Fuel adjustment charge

Taxes Demand charge (time of day)

Power factor penalty

Power Source Efficiency (%)

See machine performance curves (see attached)

Local Power Rate ($/kWh) includes:

Power Cost ($/ft)= local power rate ($/kWh) x volts x amps x Wt Weld metal deposit (lb/ft)}

1000 x dep rate (lb/hr) x OpFact (%) x Pow Source Eff (%)}

Cost Calculations

5. Power Costs


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Overhead Costs

POST WELD COSTS

Final Machining

Grinding/Polishing

Heat Treating

Shot BlastingStraightening

Inspection

OVERHEAD COSTS Salaries: executives, supervisors, inspectors maintenance

people, janitor, etc. (those costs which can not charge

directly to weldment costs)

Rent / Depreciation of plant

Taxes

Maintenance supplies and costs Utilities (not charged to weldment) i.e. light, plant heat,

etc.

Employee benefits

Insurance

Overhead cost ($/ft) = Overhead rate ($/hr) x Wt Weld (lb/ft)

dep rate (lb/hr) x OpFact (%)

6 & 7. Post Weld and Overhead Costs

Overhead cost ($/ft) = Overhead rate ($/hr) ,

travel speed (in/min) x OpFact (%) x 5


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Welding Cost - Per Foot Analysis

Cost of Joint Prep ($/ft)

Cost of Weld Metal

Flux Cost

Gas Cost

Misc. guide tubes etc.Labor Cost ($/ft)

Power Costs

Overhead Costs

TOTAL

Welding Cost - Per Piece Analysis

Base Material Cost ($/pc)

Cost of Joint Prep

Cost of Weld Metal

Flux Cost

Gas CostMisc. guide tubes etc.

Labor Cost ($/pc)

Power Cost

Post Weld CostsOverhead Costs ($/pc)

TOTAL

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01lecture03a Cost Calculations Slides