Lesson Notes By Weeks and Term v5 - Grade 12

Lesson Video

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Performance objectives

• Interpret complex integrated drawings (SANS 10111).
• Apply orthographic and isometric projection.
• Calculate dimensions and apply scales accurately.
• Identify and draw standard civil and mechanical symbols.
• Integrate concepts like site plans with pump installations.

Lesson summary

Integrated Engineering Graphics and Design (EGD) tasks, blending civil and mechanical elements, are crucial in the Grade 12 curriculum. These tasks simulate real-world engineering problems requiring a holistic understanding of both disciplines. Mastering these tasks is not just about passing the exam; it's about developing problem-solving skills applicable to numerous careers in South Africa's developing infrastructure and manufacturing sectors. From designing sustainable housing developments incorporating efficient plumbing systems to optimizing the mechanical components of a mining operation, these skills are in high demand.

Lesson notes

Integrated EGD tasks involve combining principles from both civil and mechanical engineering disciplines within a single drawing or design problem. This requires understanding how the two fields interact and how their components function together.

Civil Engineering Components: Site Plans: A site plan shows the layout of a property, including buildings, roads, boundaries, and other features. It often incorporates contour lines to represent the terrain. Accurate interpretation of contour lines is vital for understanding slope and drainage patterns. Remember that contour lines connect points of equal elevation. Closely spaced contour lines indicate a steep slope, while widely spaced lines indicate a gentle slope.

Foundations: The foundation is the structural base of a building, transferring its load to the ground. Different types of foundations (strip footing, raft foundation, pile foundation) are used depending on soil conditions and the building's size and weight. The drawings need to represent the correct type of foundation.

Drainage Systems: Drainage systems remove excess water from a site, preventing flooding and water damage. These systems typically include pipes, culverts, and drainage ditches. Remember the direction of flow in these systems must be represented correctly.

Water and Sewer Lines: These lines provide water supply and remove wastewater from a building. The drawings need to show the correct pipe size, material, and location. Different line types (dashed, dotted) and symbols are used to differentiate between water and sewer lines. Always ensure the lines are clearly labelled.

Mechanical Engineering Components: Pumps: Pumps are used to move fluids, such as water or wastewater. The drawing should include the pump's type (centrifugal, submersible), capacity, and location. Ensure all necessary pipe connections and support structures are shown.

Piping Systems: Piping systems transport fluids from one location to another. The drawing should show the pipe size, material, and fittings (e.g., elbows, tees, valves). Remember to indicate the direction of flow.

Ventilation Systems: Ventilation systems provide fresh air and remove stale air from a building. The drawing should show the location of vents, ducts, and fans. Pay close attention to airflow direction and the placement of filters.

Structural Steel: Structural steel is often used in buildings to provide support. Common structural steel shapes include I-beams, channels, and angles. The drawing should show the size and orientation of the steel members.

Integrated Concepts: Pump House Design: A pump house is a small building that houses a pump and related equipment. The design of a pump house requires integrating civil and mechanical engineering principles. The civil engineer is responsible for the structure itself (foundation, walls, roof), while the mechanical engineer is responsible for the pump and piping system. The location of the pump house on the site plan is a civil consideration, while the specific pump requirements (flow rate, head) are mechanical considerations.

Water Treatment Plant: Water treatment plants are complex facilities that treat water to make it safe for drinking. These plants involve numerous civil and mechanical engineering components. The civil engineer is responsible for the site layout, foundations, and buildings, while the mechanical engineer is responsible for the pumps, piping systems, and treatment equipment.

Sustainable Housing: Integrated design is crucial for creating sustainable housing. Incorporating rainwater harvesting systems requires civil engineering for the collection and storage (tanks) and mechanical engineering for the pumping and distribution of the water. Solar water heating involves both civil (roof integration) and mechanical (plumbing and heater components).

Worked example

Example 1: A borehole pump needs to be installed on a property to supply water to a house. The borehole is 20m deep, and the house is 5m above the ground level at the borehole location. The house requires a flow rate of 2 litres per second. Draw an orthographic projection showing the installation, including the borehole casing, pump, rising main, delivery pipe to the house, and a water storage tank.

Solution:

Civil Elements: The borehole itself, the ground levels, the location of the house relative to the borehole. Indicate the different soil types on the borehole drawing.

Mechanical Elements: The pump type (submersible is likely best), rising main (pipe inside the borehole), delivery pipe (pipe from borehole to the house), water storage tank.

Integration: Show how the delivery pipe connects to the house's plumbing system. Include the elevation difference between the pump and the storage tank, as this will affect the pump selection. Show support for the rising main and the tank. Include details of the foundation for the tank.

Annotation: Clearly label all components, including pipe sizes, pump specifications (flow rate, head), and borehole depth.

Example 2: A small wastewater treatment plant is being designed for a rural community. The plant includes a settling tank, a trickling filter, and a chlorination tank. Draw a schematic layout of the plant, showing the flow of wastewater through the different stages.

Solution:

Civil Elements: The physical layout of the tanks, the location of the inlet and outlet pipes, the overall site plan showing the location of the plant relative to the community.

Mechanical Elements: The pumps used to move the wastewater between tanks, the piping system, the chlorination equipment.

Integration: Show how the tanks are connected to each other with pipes. Indicate the flow direction of the wastewater. Show the location of access points for maintenance. Consider the gradient for gravity-assisted flow. Show the foundation details of each tank.

Annotation: Label all components, including tank sizes, pipe sizes, and pump specifications. Indicate the flow rate of the wastewater. Show the relative elevations of each tank to ensure proper gravity flow.

Guided Practice (With Solutions)

Question 1: Draw a sectional view of a typical water pipe trench showing a uPVC water pipe, bedding material, backfill, and warning tape. The pipe diameter is 110mm.

Solution:

Drawing: Draw the uPVC pipe as a circle with a diameter of 110mm. Add the bedding material (sand) below and around the pipe. Add the backfill material (compacted soil) above the bedding. Add the warning tape above the backfill. Indicate the depth of the trench.

Annotation: Label all components, including pipe diameter, bedding material, backfill material, and warning tape. Provide dimensions for trench depth and width.

Commentary: This question tests the understanding of standard practices for installing underground water pipes. Bedding material is crucial to protect the pipe from damage, and warning tape helps prevent accidental damage during future excavations.

Question 2: A septic tank is being installed for a small house. Draw a plan view of the septic tank, showing the inlet pipe, outlet pipe, inspection ports, and baffles.

Solution:

Drawing: Draw a rectangular shape to represent the septic tank. Add the inlet and outlet pipes on opposite ends of the tank. Add the inspection ports above the tank. Draw the baffles inside the tank to prevent solids from escaping.

Annotation: Label all components, including pipe sizes, inspection port locations, and baffle dimensions. Include the overall dimensions of the septic tank.

Commentary: This question assesses knowledge of septic tank design. Baffles are essential for preventing solids from entering the drain field, which can cause it to clog. Inspection ports allow for easy monitoring of the tank's condition.