FIGURE 11.1 below shows a hydraulic lift. The lift needs to raise a maximum load of 34 000 N at the ram with a diameter of 250 mm. The force applied on the plunger is 215 N. Answer the questions that follow. Calculate the following: 11.1.1 The fluid pressure in the hydraulic system in MPa 11.1.2 The diameter of the plunger in mm 11.2 Name TWO types of hydraulic filters. 11.3 Identify the hydraulic symbols in FIGURES 11.3.1 and 11.3.2 below. 11.3.1 11.3.2

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FIGURE 11.1 below shows a hydraulic lift - NSC Mechanical Technology Fitting and Machining - Question 11 - 2022 - Paper 1

Question 11

FIGURE 11.1 below shows a hydraulic lift. The lift needs to raise a maximum load of 34 000 N at the ram with a diameter of 250 mm. The force applied on the plunger i... show full transcript

Worked Solution & Example Answer:FIGURE 11.1 below shows a hydraulic lift - NSC Mechanical Technology Fitting and Machining - Question 11 - 2022 - Paper 1

Step 1

11.1.1 The fluid pressure in the hydraulic system in MPa

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Answer

To calculate the fluid pressure in the hydraulic system, we can use Pascal's principle which states that pressure is defined as force per unit area. The formula for pressure ( $P$ ) is given by:

$P = \frac{F}{A}$

Where:

$P$ is the pressure in pascals (Pa)
$F$ is the force in newtons (N)
$A$ is the area in square meters (m²)

First, we need to determine the area of the ram:

The diameter of the ram ( $D$ ) is 250 mm, which we convert to meters: $D = 0.25 ext{ m}$
The radius ( $R$ ) is therefore: $R = \frac{D}{2} = \frac{0.25 ext{ m}}{2} = 0.125 ext{ m}$
The area ( $A$ ) is: $A = \pi R^2 = \pi (0.125)^2 \approx 0.0491 ext{ m}²$

Now we can calculate the pressure: $P = \frac{34000 ext{ N}}{0.0491 ext{ m}²} \approx 692,307 ext{ Pa} \approx 0.692 ext{ MPa}$

Step 2

11.1.2 The diameter of the plunger in mm

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Answer

To determine the diameter of the plunger, we again use Pascal's principle. The pressure in both the ram and plunger is equal. The pressure from the plunger is given by:

$P = \frac{F_{plunger}}{A_{plunger}}$

Using the pressure we calculated earlier: $0.692 ext{ MPa} = \frac{215 ext{ N}}{A_{plunger}}$

From this, we can solve for the area of the plunger: $A_{plunger} = \frac{215 ext{ N}}{0.692 \times 10^6 ext{ Pa}} \approx 0.000310 ext{ m}²$

Now, we can find the diameter ( $d$ ) of the plunger:

Using the area formula: $A = \pi \left(\frac{d}{2}\right)^2$

Rearranging gives: $d = 2 \sqrt{\frac{A}{\pi}}$

Substituting in our area: $d = 2 \sqrt{\frac{0.000310}{\pi}} \approx 0.0198 ext{ m}$

Converting to mm: $d \approx 19.8 ext{ mm}$

Step 3

11.2 Name TWO types of hydraulic filters.

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Answer

Screen Filters: These filters use a screen as the filtering medium to trap large particles from hydraulic fluids.
Suction Filters: These are typically installed on the inlet side of the hydraulic pump to protect the pump from contaminants.

Step 4

11.3.1 Identify the hydraulic symbol in FIGURE 11.3.1.

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Answer

The hydraulic symbol in FIGURE 11.3.1 represents a hydraulic valve.

Step 5

11.3.2 Identify the hydraulic symbol in FIGURE 11.3.2.

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Answer

The hydraulic symbol in FIGURE 11.3.2 represents a pump.

FIGURE 11.1 below shows a hydraulic lift - NSC Mechanical Technology Fitting and Machining - Question 11 - 2022 - Paper 1

Worked Solution & Example Answer:FIGURE 11.1 below shows a hydraulic lift - NSC Mechanical Technology Fitting and Machining - Question 11 - 2022 - Paper 1

11.1.1 The fluid pressure in the hydraulic system in MPa

11.1.2 The diameter of the plunger in mm

11.2 Name TWO types of hydraulic filters.

11.3.1 Identify the hydraulic symbol in FIGURE 11.3.1.

11.3.2 Identify the hydraulic symbol in FIGURE 11.3.2.

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