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A short class with Sarah and her students. The other ways are under More.
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Today, we're discussing the operation of a double acting steam hammer. Can anyone tell me what a double acting hammer is?
It's a hammer powered by air or steam, used for driving piles.
Exactly! So, how does it operate? It has two cylinders—one for the upward stroke and one for downward. Let's explore how air is supplied to each cylinder.
Air goes into the lower cylinder to push the hammer up?
Correct! And what happens to the air in the upper cylinder during this process?
It gets expelled through the exhaust.
Great job! Remember the acronym 'ACT'—Air into Cylinder upward, Cylinder exhaust. This will help you recall the sequence!
And then for the downward stroke, air goes into the upper cylinder!
Right! So the cycles alternate, allowing for effective pile driving. Let's summarize: the hammer uses compressed air or steam and operates efficiently in lighter soils.
Let's move on to blow energy. Can anyone tell me how much of the blow energy is derived from steam?
90%! It’s really high.
Yes! This is why we can have lighter hammers. Why do you think we wouldn't want a heavier hammer?
A heavy hammer might damage the pile or cause inefficiencies?
Precisely! The design allows for a compact hammer which is efficient for normal soil conditions. Remember 'LIGHT'—Lighter design for Impact in good conditions with High blow rate!
What about tough soils?
Great question! These hammers aren't suited for high friction resistance soils. If using concrete piles, why are they not recommended?
Because the high blow rate could damage the concrete!
Exactly! So remember: Lighter is definitely better in defined conditions.
Now, let’s talk about vibratory pile drivers. What is the main difference between vibratory and impact hammers?
Vibratory drivers use vibrations instead of impacts.
Correct! And how does this vibration help in driving piles?
It reduces friction between the soil and the pile, making it easier to drive.
Fantastic! This allows piles to penetrate non-cohesive soils better. Then comes the concept of resonance. Who can explain that?
It's like getting into sync with something's natural frequency to amplify movement?
Exactly! By matching the pile driver’s frequency with the pile, we create larger vibrations. This means better penetration. Remember: 'FREQUENCY'—Frequency Resonates Easily for A Quicker Underlying Change in Yield!
And we need to avoid matching frequencies with nearby structures, right?
That's right! So always be cautious of those interactions when utilizing resonance.
When the steam goes in, the hammer we’ll win; pulses up, then down, hammering ground!
Imagine a tiny hammer in a big steam factory. With each breath of steam, it springs up high and pushes down with might, driving piles into the soil, a hardworking little tool!
‘STEAM’—Supply air, Trigger energy, Effectively act on Medium soils!
‘BRIGHT’—Blow Rate In Good Hammering Tests!
Term
What is a double acting hammer?
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Term
What is resonance?
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Term
What is the blow rate of a double acting hammer?
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A hammer that utilizes both upward and downward strokes driven by compressed air or steam to drive piles.
The energy produced by the hammer's stroke, primarily derived from steam.
A mechanism that uses mechanical vibrations to facilitate the driving of piles into soil.
The phenomenon where two bodies vibrate at the same frequency, facilitating larger displacements.
This section explains the operation of a double acting steam hammer, emphasizing the significance of steam energy and its application in driving piles into different soil types.
In this section, the operation of a double acting steam hammer is detailed, highlighting how compressed air or steam drives the hammer in both upward and downward strokes. The section discusses the suitability of the hammer for different soil conditions and stresses the derivation of blow energy primarily from steam, while also introducing concepts like the vibratory pile driver and resonance in pile driving.
In this section, we explore the functioning of the double acting steam hammer, a device utilized for driving piles into the ground using compressed air or steam. The operation involves alternating air supply to two cylinders, resulting in upward and downward strokes of the hammer, with a high blow rate of 95 to 300 blows per minute suitable for light to medium weight piles in normal soil conditions. The hammer is characterized by its compact and lightweight design, deriving 90% of its blow energy from steam, making it unsuitable for tougher soil conditions like hardened clay and for concrete piles to prevent damage. Additionally, the section explores factors affecting the efficiency of pile driving through vibratory methods, where resonance is harnessed to enhance driving efficiency by matching the frequency of the pile driver to that of the pile's natural frequency. This resonance creates larger displacements, facilitating pile penetration into the ground, especially in cohesive soils. However, caution is advised to avoid disruptions to nearby structures that share similar frequency characteristics.