Why must a pneumatic system run no higher than the rated pressure of its components?

A component pressurised above its rating can burst or blow off its fittings. The regulator should be set to a safe working pressure for the weakest part.

What is the purpose of the safety relief valve on a compressor receiver?

A relief valve opens automatically if the receiver pressure rises above a set limit. The valve vents air so the tank cannot rupture if the pressure switch fails.

How can the noise of exhausting air be reduced?

Silencers fitted to valve exhaust ports slow and diffuse the escaping air. Ear protection may also be needed near compressors and busy machinery.

CCEA A-Level Technology and Design 8900

Material Selection and Wood

Topic overview Material selection criteria Physical and mechanical properties Hardwoods, softwoods and timber stock sizes Pine, ash, beech, oak and mahogany Manufactured boards Wood finishes, veneers and laminates

Metals

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Plastics

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Composite and Emerging Materials

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Design for Manufacture, Quality and Safety

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Electronic Control SystemsOption A

Topic overview Control systems, feedback and electronics safety Resistors, Ohm's law and power ratings Capacitors and RC timing Potential dividers, sensors and comparators Switches, pull-up and pull-down resistors Output devices and LEDs Transistors, Darlington pairs and thyristors Logic gates, truth tables and flip-flops 555 monostable and astable timers

Microelectronic Control SystemsOption A

Topic overview Microcontroller systems, ADCs and DACs Strain gauges and bridge circuits Optical switches, encoded discs and Schmitt triggers Op-amp amplifiers and gain Zener diodes and voltage regulators Karnaugh maps and binary counters Seven-segment, LCD and dot matrix displays PIC flowcharts and programming DC motors, stepper motors and driver circuits

Mechanical and Pneumatic ComponentsOption B

Topic overview Open and closed loop mechanical and pneumatic control Safe working with compressed air and mechanisms Levers, linkages and moments Gear types and gear trains Pulleys, belts, chains and shaft fixings Cams, cranks and converting motion Compressed air supply and pneumatic valves Cylinders, shuttle valves, restrictors and reservoirs Pneumatic circuits for logic, timing and speed control

Mechanical and Pneumatic SystemsOption B

Topic overview Hydraulics, system limitations and plant safety Torque, work, power and air consumption Vacuum handling, proximity sensors and 5/3 valves Sequential and cascade pneumatic circuits Cam profiles and follower displacement diagrams Gear geometry, pulley blocks and ratchets Toggles, treadles, shafts and couplings Friction, brakes and clutches Bearings, lubrication and seals

Designing and Manufacturing ProductsOption C

Topic overview Research, questionnaires and specifications Idea generation, critiques and computer simulation Manufacturing planning and product evaluation CFRP, GRP, Kevlar and tungsten carbide Smart materials, nanotechnology and biophotovoltaics Isometric, perspective and assembly drawing Laminating, steam bending, cutting and printing processes Risk assessment and product safety law Scales of production, JIT and cell production Quality assurance, ISO 9001 and continuous improvement Design influences and intellectual property rights

Product Design in Industry and SocietyOption C

Topic overview Life-cycle environmental impact and climate change The 6Rs, waste and environmental legislation Sustainable metals, plastics and degradable polymers Product life cycles, consumer types and relaunches CAD, CAM, 3D scanning and quick-change moulding Market pull, technology push and market strategy Price, place and promotion Jigs, fixtures and ICT in quality control Design for maintenance, inclusion and scale production Rendering, typography and presentation Dyson, Baylis, Memphis and Apple

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Topic overview Choosing a product to redesign Analysing the function and fitness for purpose of existing products Materials, manufacture and sustainability of existing products Ergonomic and aesthetic analysis Redesign modifications, sketching and viability Modelling, testing and evaluating a redesign

Product and System Design and Manufacture

Topic overview Clients, end users and design briefs Researching existing solutions and writing a specification Generating and appraising design proposals Developing a concept with numerical analysis, ergonomics and aesthetics Working drawings and planning manufacture Testing and evaluating a prototype

Mechanical and Pneumatic Components

Safe working with compressed air and mechanisms

3 things to know
AS 1 Paper 2

Overview

Hazards of compressed air, depressurising circuits, rated pressures and relief valves, silencers, eye protection, in-running nips, guards and emergency stops.

What you need to know

Answer each one before you reveal it.

Your recallNot started

Key term

Why must compressed air never be directed at a person?

Key term

What should be done before a pneumatic circuit is altered or dismantled?

Key term

Why can a pressurised air line be dangerous if it comes out of its fitting?

Questions from this subtopic

Each one with the model answer underneath.

1
Why must compressed air never be directed at a person?
Model answer
Compressed air can blow debris into the eyes and skin. Air forced into the bloodstream through a cut can cause a fatal embolism.
2
What should be done before a pneumatic circuit is altered or dismantled?
Model answer
The main supply valve should be shut to isolate the circuit. Any trapped air should then be exhausted before a fitting is undone.
3
Why can a pressurised air line be dangerous if it comes out of its fitting?
Model answer
A pressurised tube pulled from its fitting can whip about violently. The loose end can strike the face or eyes.
4
Why must a pneumatic system run no higher than the rated pressure of its components?
Model answer
A component pressurised above its rating can burst or blow off its fittings. The regulator should be set to a safe working pressure for the weakest part.
5
What is the purpose of the safety relief valve on a compressor receiver?
Model answer
A relief valve opens automatically if the receiver pressure rises above a set limit. The valve vents air so the tank cannot rupture if the pressure switch fails.
6
How can the noise of exhausting air be reduced?
Model answer
Silencers fitted to valve exhaust ports slow and diffuse the escaping air. Ear protection may also be needed near compressors and busy machinery.

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