01lecture03a Cost Calculations Slides
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Transcript of 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
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)
a) Theoretical weight of weld metal
Cross Section Area of Joint - Use geometry or refer to tables forstandard joint configurations
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)
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
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
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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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
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
18 with 2 stub = 11% loss
28 with 2 stub = 7% 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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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
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) 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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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
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
Electrode Cost ($/ft) = Th wt of deposit (lbs/ft) x Electrode Price ($/lb)Filler metal yield (%)
2. COST OF MATERIALS (CONSUMABLES)
c) Calculating the Electrode Cost
Electrode Cost ($/ft) = Wt of filler required (lbs)x Electrode Price ($/lb)
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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
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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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
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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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
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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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
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 ($/kWh) x volts x amps x Wt Weld metal deposit (lb/ft)}
1000 x dep rate (lb/hr) x OpFact (%) x Pow Source Eff (%)}
Cost Calculations
5. Power Costs
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DIVIDUAL PART OF ESTIMATE(Look at each item individually)
Cost of Joint PrepCost of Materials (Consumables)
Cost of Materials (Flux & Shielding)Labor Costs
Power CostsPost Weld Costs
Overhead Costs
POST WELD COSTS
Final Machining
Grinding/Polishing
Heat Treating
Shot BlastingStraightening
Inspection
OVERHEAD COSTS Salaries: executives, supervisors, inspectors maintenance
people, janitor, etc. (those costs which can not charge
directly to weldment costs)
Rent / Depreciation of plant
Taxes
Maintenance supplies and costs Utilities (not charged to weldment) i.e. light, plant heat,
etc.
Employee benefits
Insurance
Overhead cost ($/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