Lecture 3- Excavation equipment Flashcards
What is the main use of excavators?
To place materials from point A to point B
What is struck capacity?
The actual volume enclosed by the bucket with no allowance for the bucket teeth
What is heaped capacity/volume?
Loose condition. The max volume in the bucket without spillage is based on the material’s angle response.
What is a hydraulic excavator (hoes) mainly used for?
Photo is available at slide #6
Trenching work and other trenching functions. Laying pipe bedding, trenching functions, pulling trench shields, and backfilling (mainly ground level)
What is the excavator production formula?
Production (Loose material/h) = B x C x E x S x V (BCEE x Sushiville (S&V))
B = Bucket fill factor
C = Cycles/h
E = Job efficiency
S = Swing depth factor
V = Heaped bucket volume (comes from the manufacturer)
Criteria for selecting the proper excavator:
1) Max digging depth
2) Working radius (digging reach)
3) Dumping height
What not to do with the bucket?
Use it as a sledge in attempting to fracture rock
What can sufficiently loose rocks?
Light blasting, ripping or power hammer.
In shovels, digging action is a combination of what forces?
Crowding force (stick cylinder) and breakout force (bucket cylinder)
True or false: Shovels are the most efficient when digging below track level.
False. Shovels have limited ability to dig below track level but are most efficient when digging above track level.
True or False: Shovels form its own roadway as it advances
True
Compare the advantages and disadvantages of bottom dump bucket and front dump bucket in shovels
Bottom - More Versatile, greater reach & dump clearance. Less spillage but it is heavier than front dump buckets, which results in lower bucket capacity
Front - Less maintance, slight production disadvantage and less costly (maybe)
What are the two major factors to control shovel production? Job management
1) Swing angle - ideally it should be kept to a minimum
2) Lost time during the production cycle: Haul trucks must be positioned to minimize the time lost as entering and exiting the loading position
Explain what dragline is used for:
- A versatile machine to dig from above the machine level to significant depth in soft to medium-hard material
- Due to a lack of lateral control, the bucket may bounce or move sideways and spillage may occur
True or false: Skilled operators should use bigger haul units in dragline compared to a shovel with a similar size
Facts
Dragline: True or false.
Max production is obtained with a maximum swing angle
False
Max production is obtained with a MINIMUM swing angle.
Dragline: What is the most efficient digging area?
15 degrees forward and back of the vertical line thought the boom point
Dragline: What are the advantages of
using light bucket?
It will increase the allowable bucket size and reduce cycle time
Dragline: What is the most efficient digging area?
15 degrees forward and back of the vertical line through the boom point
What is the dragline production formula
Ideal output (table) x Swing depth (2 tables) x Efficiency
(ESO-efficiency, swing, output)
* Don’t forget to convert to LCY using the load factor
Add the purpose of each tool (hydraulic excavators from the book)
page 7 in the slides. or at 1:50 in the video
True or false: Using the back bucket to loosen up material will cause harm to the bucket and shorten its lifespan
True
Explain what approach is best suitable for (frontal & parallel)
Frontal - Best for hard materials (mining operation)
Parallel - Good for limited spaces (highways)
Draglines: Explain why dragline could have more spillage than a shovel
Due to a lack of lateral control, the bucket may bounce or move sideways during hard digging, which will create more spillage
What are the two types of crane families
- Mobile cranes - machine of use in NA
- Tower crane - Became more popular since the 2000’s even for mid rise construction
When the tower cranes the machine of choice
- Site conditions are restrictive
- Lift height and reach are great
- There is no need for mobility
- Noise limits are imposed (Very quiet)
Explain what a top-slewing (fixed tower) is
Fits what construction.? Piles length?
partly stabilized at its base (by ballasts) and assembled from modular lattice-type sections. Can reach great heights, and fits mid-rise construction.
Pillings cannot be over 70 ft.
Explain what a Bottom-slewing (slewing tower) is
with foldable or telescopic tubular mast, both the tower and jib assembly rotate to the base chassis. Ideal for low buildings. Can often be towed between job sites.
Cranes: Bottom vs top-slewing.
1) How long does the setup of each take
2) Which one requires assistance?
3) Which one is mobile, and which one if fixed?
1) Bottom slewing can be built single-handedly, taking up to a few hours while top-slewing takes 1-7 days.
2) Only top-slewing requires assistance
3) Bottom slewing is mobile, top-slewing is fixed (usually)
What are the most important factors to be considered when selecting a tower crane?
- Operating radius (reach)
- Lifting capacity
- Lifting speed
What is the main disadvantage of setting a crane on rails?
Advantages?
Dis: Space. Takes 13-27 ft and always requires this area to be empty/clean.
Adv: More economical option than dismantling and reassembly.
What are the properties of a travelling tower crane?
Max grade is not usually more than 1%
Max height for top-slewing: 230ft, bottom slewing 100ft.
Speed: 65 to 100ft./min
What are the advantages and disadvantages of using the elevator shaft for a crane setup?
1) No pre-strengthening is required
2) No temporary sharing
3) No openings are left
Dis:
1) Bring delay in elevator assembly
2) May limit the choice of forming system for the shaft
How is a crane disassembled at the end of the construction?
- Mobile Cranes, if the height is reachable.
- Derrick (a lifting Device temporarily installed on the finished rooftop)
- The use of a Helicopter
What applied to the computed weight?
5% working margin
Generally, what type is applied for the radius of below 90 ft and over 90 ft?
Usually, below a radius of 90 ft we use a four-part line, above 90 ft we use the two-part line.
What factors must be considered for safe rigging?
1) weight
2) Center of graivty
3) Stresses
4) Motion of the load
What are the 4 safety categories for crane operation?
1) Human factor - The competence and experience of the operator, slinger (rigger), signaler, & lift director
2) Project factor - Presence of powerlines, site congestion, crane’s oversailing, inside cab conditions
3) Environmental factors - Winds, severe temperature, visibility difficulties
4) Safety mgmt. factor: Site level safety, maintenance mgmt. of the cranes & lifting accessories
Based on what parameters the lifting capacity is provided for a hydraulic excavator?
- Distance - from the center of gravity of the load to the axis of rotation
- Height of the bucket lift point above the bottom of the tracks
