Excavator Operation Techniques

Excavator Operating Techniques

Chapter Introduction

This chapter covers all excavator operating techniques as assessed on the Red Seal exam. You will find the fundamental principles, safety procedures, production calculations, and applicable Canadian regulatory requirements. Each section has been designed to correspond directly to the tasks and sub-tasks of the National Occupational Analysis (NOA) for the heavy equipment operator (excavator) trade.

Fundamental Operating Principles

Machine Stability

The stability of an excavator depends on three factors: the centre of gravity, the reach, and the ground reaction. The centre of gravity shifts constantly depending on the boom angle, bucket position, and load being lifted. The golden rule: the combined centre of gravity (machine + load) must always remain within the support polygon formed by the tracks and outriggers (if equipped).

The rated lifting capacity of an excavator is determined according to ISO 10567 (Earth-moving machinery – Hydraulic excavators – Lift capacity). This standard requires that the lifting capacity be reduced to 75% of the tipping load or 87% of the hydraulic capacity, whichever is lower. These percentages are mandatory safety values.

The Stability Triangle

For a track-mounted excavator, the stability triangle is formed by the two front contact points and the rear contact point of the opposite track. When you are performing grading work with the bucket oriented to the side, the stability triangle narrows considerably. Never perform lifting or lateral pushing with the boom perpendicular to the track axis at full reach.

Ground Pressure

Ground pressure (in kPa) is calculated as follows:

Ground pressure = Total machine weight (N) ÷ Track contact area (m²)

Example: a 25,000 kg excavator (245,250 N) with tracks measuring 3.0 m × 0.6 m each (total area = 2 × 1.8 m² = 3.6 m²) exerts a pressure of:

245,250 N ÷ 3.6 m² = 68,125 Pa = 68.1 kPa

This value must be compared to the bearing capacity of the soil (table below) to determine whether load-spreading mats (cribbing, steel plates) are required.

Soil Type	Approximate Bearing Capacity (kPa)
Sound rock	600 – 2,000
Compacted gravel	300 – 600
Dense sand	200 – 400
Firm clay	150 – 300
Soft clay	50 – 100
Peat / organic soil	0 – 30

Excavating Techniques

Bulk Excavation

Bulk excavation involves digging from a higher level to a lower level, with the bucket filling through a pulling motion toward the machine. This technique is the most efficient because it uses the machine's weight to penetrate the material. The bucket attack angle should be approximately 30° to 45° relative to horizontal. An angle that is too steep (greater than 60°) increases penetration resistance and causes premature wear on the teeth.

Trench Excavation

For a trench, the recommended procedure is as follows:

25.Position the machine parallel to the trench axis, with tracks at a minimum distance of 0.6 m from the edge (or according to the requirements of the Construction Safety Code – RSST, Section 3.15.2, which requires a distance of at least 1 metre if the soil is loose).

26.Dig in successive passes of 0.3 to 0.5 m in depth, starting from the side farthest from the machine.

27.Maintain the trench bottom at the required depth using the automatic grading system (if available) or by checking with a laser level.

28.Place spoil at a minimum distance of 0.6 m from the trench edge (RSST, Section 3.15.3) to prevent any collapse.

Calculating Excavated Volume

The volume of a trench with vertical walls is calculated:

V = L × W × D

Where:

V = volume (m³)

L = length (m)

W = width (m)

D = depth (m)

For a sloped trench (with side slopes), the volume is expressed:

V = L × [(W₁ + W₂) ÷ 2] × D

Where W₁ and W₂ are the widths at the bottom and at the surface.

Swell factor: the volume of spoil in place (banked) increases after excavation. For clay soil, the swell is approximately 30%; for rocky soil, 50% to 60%; for dry sand, 10% to 15%. The swelled volume is calculated:

V_swelled = V_in_place × (1 + swell rate)

Optimal Digging Depth

The optimal digging depth (sweet spot) is between 40% and 60% of the machine's maximum digging depth. At this depth, cycle time is minimal and breakout force is maximal. Digging at full depth increases cycle time by 20% to 30% and reduces hourly production.

Grading Techniques

Fine Grading

Fine grading requires perfect mastery of the controls. The basic technique consists of:

48.Positioning the boom at an angle of 45° to 60° relative to horizontal.

49.Using the arm as the primary grading component, keeping the boom nearly fixed.

50.Angling the bucket to the natural angle of repose of the material to avoid scraping or pushing the material.

51.Working by pulling toward the machine for finishing passes, which allows for better visual control.

Grading with a Tilt Bucket

The tilt bucket allows for lateral rotation of ±45° and fore-and-aft tilting. This option reduces the need to reposition the machine. Grading accuracy with a tilt bucket is in the range of ±10 mm with an experienced operator, compared to ±25 mm with a standard bucket.

Using Laser and GPS

The laser grading system (receiver on the boom or bucket) allows for automatic depth control. The GPS (Global Positioning System) with RTK (Real-Time Kinematic) correction offers accuracy of ±20 mm horizontal and ±30 mm vertical. These systems do not replace the operator's judgment: they must be calibrated daily and checked against known control points.

Loading Techniques

Truck Loading

The loading cycle consists of four phases: digging, swinging, dumping, returning. The optimal cycle time is 20 to 30 seconds for a competent operator. Hourly production is calculated:

Production (m³/h) = (Bucket capacity (m³) × Fill factor × 3,600 s/h) ÷ Cycle time (s)

Example: 1.5 m³ bucket, fill factor of 0.90, cycle time of 25 s:

(1.5 × 0.90 × 3,600) ÷ 25 = 194.4 m³/h (swelled volume)

To convert to bank volume: 194.4 ÷ (1 + swell rate). For clay soil (30% swell): 194.4 ÷ 1.30 = 149.5 m³/h bank measure.

Number of Buckets per Truck

Number of buckets = Truck box capacity (m³) ÷ Bucket capacity (m³)

Round up to the next whole number. A 15 m³ truck with a 1.5 m³ bucket requires 10 buckets. Loading time is 10 × 25 s = 250 s = 4 min 10 s.

Truck Positioning

The truck must be positioned so that the swing angle of the superstructure is minimal (ideally 90° or less). Each 30° increase in swing angle adds approximately 3 to 5 seconds to the cycle time. The truck must be placed on stable ground, at a safe distance from the edge of the excavation.

Demolition Techniques

Demolition by Pushing

Demolition by pushing is performed by applying horizontal force with the bucket or a demolition attachment (ripper). The available pushing force is limited by the track traction force and the machine's stability. Never push a wall taller than 3 metres without having verified the stability of the structure and the machine's capacity.

Demolition by Pulling

Pulling is more effective than pushing because it uses the arm's breakout force, which is generally greater than the track traction force. The technique consists of:

75.Attacking the structure at the highest possible point.

76.Pulling toward the machine while maintaining the arm at an angle of 30° to 45°.

77.Letting gravity do the work: the structure collapses under its own weight.

Demolition Safety Rules

According to the Construction Safety Code (RSST, Chapter S-2.1, r. 4) , demolition operations must comply with:

Section 3.9.1: verification of the absence of hazardous materials (asbestos, etc.) before work begins.

Section 3.9.2: disconnection of supply lines (electricity, gas, water) before demolition.

Section 3.9.3: protection of workers from falling materials.

The minimum distance between the machine and the structure being demolished must be at least the height of the structure + 2 metres.

Working on Slopes

Operating Limits on Slopes

An excavator can work on slopes up to a maximum inclination of 30° (58%) when climbing and 25° (47%) when descending, according to the manufacturer. These values are given for a machine with an empty bucket and the boom in the low position. The presence of a load significantly changes these limits.

Slope Working Technique

To work on a slope, the machine must be positioned perpendicular to the slope (tracks running up and down the slope) or parallel (tracks perpendicular to the slope), depending on the task. The parallel position offers better lateral stability but reduces reach. The perpendicular position allows for better depth control but increases the risk of lateral tipping.

Rule of thumb: on a slope greater than 15° (27%), the machine must be stabilized with wedges or outriggers before any lifting operation.

Calculating Slope

Percentage slope is calculated:

Slope (%) = (Elevation change (m) ÷ Horizontal distance (m)) × 100

A 10% slope corresponds to an angle of 5.7° (arctan 0.10). Conversion table:

Slope (%)	Angle (°)	Ratio (H:V)
5	2.9	20:1
10	5.7	10:1
15	8.5	6.7:1
20	11.3	5:1
25	14.0	4:1
30	16.7	3.3:1
33	18.3	3:1
50	26.6	2:1
100	45.0	1:1

Working Near Infrastructure

Minimum Distances from Power Lines

According to the Canadian Electrical Code, Part I (CE Code), the minimum distances between a machine and an energized power line are:

Line Voltage (kV)	Minimum Distance (m)
0 – 750 V	3.0
750 V – 75 kV	4.5
75 kV – 250 kV	6.0
250 kV – 550 kV	8.0
Above 550 kV	10.0

These distances apply to any part of the machine (boom, bucket, cable, load). No work may be performed within these zones unless the line owner has taken measures to de-energize or protect the line.

Gas Pipelines

The CSA B149.1 standard (Natural gas and propane installation code) requires that excavations near gas pipelines be performed manually (by hand) within a zone of 0.6 metres on either side of the pipeline, unless written authorization is obtained from the owner. The operator must know the exact location of pipelines before starting any work.

Water and Sewer Mains

The CSA B182 standard (Plastic piping systems for water mains and sewers) recommends a minimum distance of 1.0 metre between mechanical equipment and the pipeline. Any excavation within 1.0 metre must be performed manually or with light hand-controlled equipment.

Operational Safety Procedures

Pre-Operational Inspection

The daily inspection must cover, according to CSA Z150 (Safety code on mobile cranes, applicable by analogy) and manufacturer recommendations:

110.Fluid levels: hydraulic oil, fuel, coolant, engine oil.

111.Hydraulic hoses and fittings: check for leaks, cuts, and abrasion wear.

112.Tracks: tension, wear on links, pins, and bushings.

113.Bucket: wear on teeth, adapters, cracks in the structure.

114.Swing system: excessive play, abnormal noise.

115.Safety devices: backup alarm, fire extinguisher, first aid kit.

Safe Start-Up Procedure

117.Perform a complete visual inspection.

118.Enter the cab using the three-point contact method.

119.Fasten the seatbelt.

120.Verify that all controls are in the neutral position.

121.Sound the horn before starting.

122.Start the engine and allow it to warm up to operating temperature (generally 5 minutes or until the coolant temperature reaches 60 °C).

123.Check the operation of all controls without a load before beginning work.

On-Site Communication

Standardized communication signals (per CSA Z460 – Lockout, or the hand signals from the Construction Safety Code) must be known by all operators:

Signal	Meaning
Closed fist	Stop
Arm horizontal, palm down	Lower
Arm horizontal, palm up	Raise
Arm extended, index finger pointing	Direction
Both hands on head	Emergency stop

Production and Efficiency Calculations

Bucket Fill Factor

The fill factor depends on the type of material:

Material	Fill Factor
Dry sand	0.80 – 0.90
Wet sand	0.90 – 1.00
Gravel	0.85 – 0.95
Hard clay	0.80 – 0.90
Wet clay	1.00 – 1.10
Crushed rock	0.70 – 0.80
Topsoil	0.90 – 1.00

Job Efficiency

Job efficiency is the ratio of effective production time to total working time. Typical values:

Excellent: 50 minutes per hour (83%)

Good: 45 minutes per hour (75%)

Average: 40 minutes per hour (67%)

Poor: 35 minutes per hour (58%)

Actual Hourly Production

Actual production (m³/h) = Theoretical production × Efficiency

Example: theoretical production of 194.4 m³/h, efficiency of 75%:

194.4 × 0.75 = 145.8 m³/h (swelled volume)

Production Cost

The production cost per cubic metre is calculated:

Cost ($/m³) = Total hourly machine cost ($/h) ÷ Actual production (m³/h)

The total hourly cost includes: depreciation, fuel, maintenance, labour, and insurance. For a 25-tonne excavator, the total hourly cost is typically $120 to $180/h in Canada.

Common Pitfalls to Avoid

148.Confusing swelled volume and bank volume: the swell factor must always be applied when calculating truck loading.

149.Forgetting the efficiency factor: theoretical production is never achieved under real conditions.

150.Using the rated lifting capacity as an absolute value: ISO 10567 requires reductions of 75%/87% depending on configuration.

151.Neglecting ground pressure: a 25-tonne machine on soft clay soil (50 kPa) will sink if the ground pressure exceeds the bearing capacity.

152.Working too close to power lines: the Canadian Electrical Code, Part I distances are absolute minimums, not recommendations.

153.Always digging at full depth: the optimal depth is 40% to 60% of maximum depth.

154.Ignoring the swing angle: each additional 30° of swing angle increases cycle time by 3 to 5 seconds.

155.Not checking track tension: a track that is too loose can derail; one that is too tight reduces component lifespan.

156.Forgetting the three-point contact when mounting or dismounting the machine.

157.Working on slopes without calculating stability: the maximum slope of 30° is an absolute limit, not a comfort limit.

Summary

Excavator stability depends on the centre of gravity, reach, and ground reaction. The combined centre of gravity must always remain within the support polygon.

Rated lifting capacity is reduced to 75% of the tipping load or 87% of the hydraulic capacity (ISO 10567).

Ground pressure (kPa) = weight (N) ÷ contact area (m²). Compare with the soil bearing capacity.

Bulk excavation is the most efficient technique; the optimal bucket attack angle is 30° to 45°.

The optimal digging depth is 40% to 60% of maximum depth.

Excavated volume is calculated as V = L × W × D; apply the swell factor for swelled volume.

Hourly production = (bucket capacity × fill factor × 3,600) ÷ cycle time, multiplied by efficiency.

Minimum distances from power lines are defined by the Canadian Electrical Code, Part I: 3 m for low voltages, up to 10 m for very high voltages.

CSA B149.1 requires manual excavation within 0.6 m of gas pipelines.

Pre-operational inspection, standardized signal communication, and adherence to start-up procedures are mandatory.

Review Questions (Self-Assessment)

172.What is the actual lifting capacity of an excavator with a tipping load of 12,000 kg and a hydraulic capacity of 14,000 kg?

Answer: 12,000 × 0.75 = 9,000 kg (the lower value between 75% of tipping load and 87% of hydraulic capacity = 14,000 × 0.87 = 12,180 kg; therefore, 9,000 kg is used).

174.A 30,000 kg excavator has tracks measuring 3.5 m × 0.7 m. What is its ground pressure?

Answer: Weight = 30,000 × 9.81 = 294,300 N; area = 2 × (3.5 × 0.7) = 4.9 m²; pressure = 294,300 ÷ 4.9 = 60,061 Pa = 60.1 kPa.

176.A 20 m³ truck must be loaded with a 2.0 m³ bucket. How many buckets are required?

Answer: 20 ÷ 2.0 = 10 buckets.

178.What is the minimum distance for an excavator from a 120 kV power line?

Answer: 6.0 metres (Canadian Electrical Code, Part I).

180.Clay soil has a swell of 30%. What swelled volume will a 100 m³ bank excavation produce?

Answer: 100 × 1.30 = 130 m³ swelled.

This chapter prepares you for exam questions on operating techniques. Mastery of calculations, standards, and safety procedures is essential for passing the Red Seal exam and for practising the trade safely.