Here is the structured content for a Technical Calculation and Estimator’s Manhour Manual , designed to be formatted into a PDF. This content includes methodology, formulas, tables, and a framework for estimating manhours across disciplines (Civil, Mechanical, Electrical, Instrumentation).
Title Page TECHNICAL CALCULATION AND ESTIMATOR’S MANHOUR MANUAL For Project Estimation, Budgeting, and Resource Allocation Version: 2.0 Effective Date: [Date] Prepared By: [Your Company/Name] Classification: Internal Use / Confidential
Table of Contents
Introduction & Purpose Fundamental Estimation Formulas Manhour Factor Tables (by Discipline) Productivity Adjustment Factors (Weather, Shift, Location) Step-by-Step Technical Calculation Workflows Sample Estimation Sheets (Templates) Contingency & Risk Loading Glossary Here is the structured content for a Technical
1. Introduction & Purpose This manual provides standardized manhour estimation methods for engineering, procurement, and construction (EPC) projects. It bridges the gap between technical quantities (m³ concrete, tons of steel, linear feet of cable) and required labor effort. Key definitions:
Manhour (Mh): One person working for one hour. Productivity Factor (Pf): Expected output per manhour (e.g., 0.5 m³ concrete/Mh). Crew Mix: Ratio of skilled to unskilled labor (e.g., 1:2).
2. Fundamental Estimation Formulas Use these core formulas for all calculations: 2.1 Basic Manhour Calculation [ \text{Manhours} = \frac{\text{Quantity of Work}}{\text{Productivity Rate (units/Mh)}} ] 2.2 Weighted Crew Manhours [ \text{Crew Mh} = \text{Base Mh} \times (1 + \text{Skill Ratio Factor}) ] 2.3 Adjusted Manhours (with productivity modifiers) [ \text{Adjusted Mh} = \text{Base Mh} \times \prod_{i=1}^{n} \text{Adjustment Factor}_i ] Where factors include: elevation, temperature, access difficulty, overtime. Productivity Factor (Pf): Expected output per manhour (e
3. Manhour Factor Tables (Sample Data) Table 3.1: Civil Works – Concrete & Rebar | Activity | Unit | Productivity (Units/Mh) | Manhour per Unit | Crew (Skilled:Unskilled) | | :--- | :--- | :--- | :--- | :--- | | Formwork (ordinary) | m² | 0.8 | 1.25 | 1:2 | | Rebar placement | ton | 0.35 | 2.85 | 2:3 | | Concrete pouring (pump) | m³ | 1.2 | 0.83 | 1:3 | | Finishing (screed/trowel) | m² | 1.5 | 0.67 | 1:1 | Table 3.2: Piping – Welding & Assembly | Pipe Size (NPS) | Schedule | Welding Type | Minutes per weld | Manhours per weld (incl. fit-up) | | :--- | :--- | :--- | :--- | :--- | | 2" | 40 | SMAW | 45 | 0.75 | | 6" | 80 | GTAW root + SMAW | 120 | 2.0 | | 12" | Std | SMAW | 210 | 3.5 | | 24" | 40 | Automatic | 300 | 5.0 | Table 3.3: Electrical – Cable Pulling & Termination | Cable Type | Size (AWG/kcmil) | Manhour per 100 ft (tray) | Termination manhour per end | | :--- | :--- | :--- | :--- | | THHN | #12 | 0.6 | 0.2 | | MC Cable | #2 | 1.2 | 0.5 | | Armored (3C) | 350 kcmil | 2.8 | 1.5 | | Instrumentation | #18 pair | 1.0 | 0.8 (shielded) | Table 3.4: Equipment Setting (Mechanical) | Equipment | Weight (kg) | Manhours (incl. rigging, leveling, bolting) | | :--- | :--- | :--- | | Small pump | <100 | 4.0 | | Centrifugal blower | 500 | 16.0 | | Compressor (skid) | 2000 | 40.0 | | Cooling tower cell | 5000 | 80.0 |
4. Productivity Adjustment Factors Apply these multipliers to base manhours based on conditions. Table 4.1: Environmental Modifiers | Condition | Factor | Range | | :--- | :--- | :--- | | Temperature > 32°C | 1.15 – 1.25 | +15-25% manhours | | Rain (intermittent) | 1.10 | +10% | | High altitude (>2000m) | 1.20 | +20% | | Night work (no bonus) | 1.30 | +30% | | Confined space | 1.40 – 1.60 | +40-60% | Table 4.2: Learning Curve Effect (for repetitive tasks) | Units produced | Cumulative manhour multiplier | | :--- | :--- | | 1 – 10 | 1.00 | | 11 – 50 | 0.90 | | 51 – 200 | 0.80 | | >200 | 0.75 |
5. Step-by-Step Technical Calculation Workflows 5.1 Estimating Manhours for Piping Installation Input: 500 meters of 6" Schedule 80 carbon steel pipe, 80 butt-welds, field erected. Step 1: Base welder manhours (Table 3.2) 80 welds × 2.0 Mh/weld = 160 Mh Step 2: Add fitter & helper (1 fitter : 1 welder) 160 Mh (welder) + 160 Mh (fitter) = 320 Mh Step 3: Add handling, alignment, hydrotest (20% of welding) 320 × 0.20 = 64 Mh Subtotal: 384 Mh Step 4: Apply environmental factor (outdoor, hot climate: 1.20) 384 × 1.20 = 460.8 Mh Step 5: Apply crew mix (skilled:unskilled = 2:1) → no change if already accounted. Final Manhour Estimate: 461 Mh 5.2 Calculating Concrete Foundation Manhours Input: 50 m³ concrete, 4 tons rebar, 100 m² formwork. Step 1: Rebar = 4 tons × 2.85 Mh/ton = 11.4 Mh Step 2: Formwork = 100 m² × 1.25 Mh/m² = 125 Mh Step 3: Pouring = 50 m³ × 0.83 Mh/m³ = 41.5 Mh Total Base Mh: 177.9 Mh Step 4: Add supervision (10% of skilled labor) = 17.8 Mh Total: 195.7 Mh Conceptual → 13
6. Sample Estimation Sheets (Templates) Template 6.1 – Manhour Summary by Discipline | WBS Code | Description | Quantity | Unit | Productivity | Base Mh | Adj Factor | Final Mh | | :--- | :--- | :--- | :--- | :--- | :--- | :--- | :--- | | C-101 | Concrete pour | 120 | m³ | 1.2 | 100 | 1.15 | 115 | | M-205 | Pump setting | 3 | ea | 4.0 Mh/ea | 12 | 1.00 | 12 | | E-310 | Cable pull 500ft | 500 | ft | 0.012 Mh/ft | 6 | 1.20 | 7.2 | | Total | | | | | | | 134.2 | Template 6.2 – Daily Crew Resource Plan | Date | Activity | Skilled (#) | Unskilled (#) | Total Mh/day | Duration (days) | | :--- | :--- | :--- | :--- | :--- | :--- | | Day 1-3 | Rebar | 4 | 6 | 80 | 3 | | Day 4-5 | Formwork | 3 | 6 | 72 | 2 | | Day 6 | Pour concrete | 2 | 6 | 64 | 1 |
7. Contingency & Risk Loading Add the following manhour contingency based on project phase: | Project definition | Contingency (% of total Mh) | | :--- | :--- | | Conceptual estimate | +30% to +50% | | Budget authorization | +20% to +30% | | Detailed estimate (IFB) | +10% to +15% | | Control estimate (post-award) | +5% to +10% | Example: Base Mh = 10,000, Conceptual → 13,000 – 15,000 Mh.
