Ensuring a safe and tidy workspace is paramount to health & safety requirements and general working practices, as it negates many potential hazardous situations from arising. These may be slip/trip and chemical substance hazards due to debris created from manufacturing processes (oils, greases, fumes, metallic/chemical waste etc.), and also the possibility of loss of time incidents, where certain work may become difficult or impossible to complete to the required standard due to an untidy/unsafe environment.
Describe hazards associated with carrying out assembly activities on fluid power equipment (such as handling fluids, stored energy/force, misuse of tools), and how these can be minimised.
The methods, equipment and materials used in the assembly of fluid power systems can be deemed as hazardous when not treated with care and approached with diligence. Such hazards can include the handling of fluids and gas, and the pressure that they are contained at, the improper use of tools and equipment, and incorrect working methods. The primary course of action to combat these hazards is to ensure the operator carrying out works is either fully trained or under supervision of a fully trained operative within the fluid power assembly field, to ensure correct working practices and methods are achieved, minimising risk.
Describe how to obtain and interpret drawings, charts, circuits and physical layouts, specifications, manufacturers’ manuals, symbols used in fluid power, and other documents needed in the assembly activities.
To obtain drawings, job instructions and other related pieces of information, usually you would contact your trainer or other senior colleague. Also, if pointed in the right direction, the internet could be used to obtain certain advice or documents. Interpretation of said documents could also be derived via similar avenues of enquiry; liaising with on-site workshop management, consultation of internet searches/hardcopy records etc. Symbols used in fluid power and related documentation could be sought and interpreted via consultation with trained personnel, such as NWTC tutors or manufacturers (FESTO in this case), or researching via manufacturers manuals, which may have been supplied upon delivery/installation of components. Depending on type of assembly they may also be found on components themselves (Pneumatic/Hydraulic).
Explain the importance of applying the appropriate behaviours in the workplace and the implications for both the apprentice and the business if these are not adhered to.
Behavioural aspects of the workplace are extremely important if an apprentice is to succeed in their program and fulfil their potential. During training, not only are you representing yourself as an individual but the company you are employed by, therefore necessitating a professional and diligent approach to all working activities. If an apprentice does not comply with appropriate working behavioural standards, quality of work will suffer, as well as the general perception of the apprentice by his/her peers and training staff. This would usually be intolerable by an employing company as it would cast a bad light on the business, and may lead to the termination of an apprentice’s contract.
Describe how to extract information from engineering drawings and related specifications (to include symbols and conventions to appropriate BS or ISO standards in relation to work undertaken.)
There is a large amount of information that can be extracted and interpreted from an engineering drawing, for example the material of the object specified in the diagram. Also the tolerances for the end product are specified in the diagram, meaning how much excess or shortage there can be in each dimension of the object. Certain symbols are also included in engineering drawings such as Ø which determines the diameter of a hole in the object or the use of M as a prefix to any given number to determine the size of the drill bit. BS8888 is the current primary standard relevant to technical and engineering drawings, proceeded by the now defunct BS308 legislation. It includes the outlines for indication of specific layouts, varying dimensioning requirements and ways of presenting them on drawings, identification of tolerances and surface finishes, as well as the recognised systems for adding other annotations, symbols, and abbreviations.
Outline the procedure for obtaining components, materials and other consumables necessary for the assembly activities.
Assembly materials and other related consumables are most commonly already in stores, meaning quick and easy obtainment is possible, however in rare cases certain speciality or less commonly utilised components/materials will have to be bought from an outside source.
State the general operating principles of the fluid power assemblies produced and how fluid power equipment functions, its operating sequence, the purpose of individual units/components and how they interact.
During my personal training time, I have completed varying fluid power assemblies, including copper, steel, pneumatic and hydraulic. The main objective steel and copper assembly construction was to make them as so they could withstand 200psi of water pressure internally, without leaking or bursting. This was achieved by applying correct methods of working; use of correct soldering technique on the primary frame, to ensure a strong and watertight adjoining between pipe and fitting, and the use of PTFE Thread Tape and Jointing Compound on the secondary frame’s fittings and pipework, to again ensure a solid connection. Similarly to the copper pipeworks, the steel pipework assembly required a high level of accuracy and attention to detail in order to be constructed correctly. It differed in requirements largely to the previous assemblies, being comprised of varying sizes and types of fittings, all having their own such purpose, e.g. an ‘on/off valve’, ‘gasket seal’, ‘gate valve’, ‘equal T joints’ and ‘elbow joints’ etc. and multiple lengths of ¾” NB (nominal bore) steel pipework. Objectively, the goal was identical to the previous copper frameworks, using a water pressure tester subject the framework to 200 psi of pressure. All fittings had to be correctly secured and within tolerances laid out in the technical drawing (+0mm, -1mm to specifications). Prior to testing, the two valves on the framework have to be opened to allow for the flow of water continuously around the pipework, allowing for a full and comprehensive test on the assembly.
Following these pipe fitting fluid power assemblies, I progressed on to the construction and testing of pneumatic and hydraulic assemblies. This included working with many specialised components, having varied applications, such as the operation of cylinders to move objects, the sensing of cylinder actuation position to trigger further stages of operation, creation of vacuums, use of solenoids in pneumatics etc. Hydraulic functions covered were the use of accumulators, flow control valves, timers, and cylinder actuation. Jobs were undertaken from work booklets supplied by FESTO, the manufacturers of the components used in said assemblies, as to provide a structured development of knowledge as the course progressed. Pneumatic circuits began with the use of simple connections to 3/2 push button valves, going to either port of a cylinder, to enable movement backwards and forwards, then moving towards using 5/2 and 5/3 valves to ‘pilot’ further operations in the circuit, such as vacuum generation and cylinder actuation. Other examples of components used in these assemblies were roller valves, operated via cylinders, quick exhaust valves, used to aid the exhaustion process of air from components, shuttle valves, used to dictate flow of air depending on direction of flow etc. Hydraulic circuits primarily began with the measurement of pressures with the use of a pressure gauge, which then lead onto integrating cylinders capable of moving compatible weights, both pushing and pulling the load. Components such as non-return valves and accumulators were then applied into circuits to enable more functionality; in the case of the accumulator, to store energy/pressure to ensure that if there was a failure in main hydraulic fluid supply, consistent pressure would still be achieved in order to operate the relevant output, and complete function.
Describe the different types of pipework/hoses, fittings and manifolds, and their application.
At present, I have worked with both copper (15mm) and steel pipework (3/4″ NB), with fittings of the same material. These fittings include ‘T joints’, ‘elbow joints’, ‘coupling fittings’ etc. and vary slightly in purpose, depending on the type of pipework assembly you are creating. There are a variety of copper fittings which are unthreaded, meaning they are intended for a soldered pipework assembly, and both copper and steel threaded variations of fittings intended for either compression or screw-in purposes. They are generally used to attach pieces of pipework at each end to conform to a certain specification. In pneumatic and hydraulic applications both flexible and rigid pipework arrangements can be used to achieve operation. Flexible and rigid pipework both are compatible with ‘push in’ fittings.
Outline the identification and application of different types of valve (such as poppet, spool, piston, disc).
Valves are available in numerous variations, and employed for varying purposes. Figure right shows a multitude of valve types, and demonstrates their principle of operation. A common valve often utilised in pipework assemblies is the Butterfly/Disc valve. A Butterfly valve is a disc that sits in the middle of a pipe and swivels sideways (to admit fluid) or upright (to block the flow completely).Another commonly used valve type is the ball valve. In a ball valve, a hollowed-out sphere sits within a pipe, completely blocking the fluid flow. When you turn the handle, the ball rotates through ninety degrees, allowing the fluid to flow through the middle of it in varying and highly adjustable rates.
Outline the identification of different types of sensors and actuators (such as rotary, linear, mechanical, electrical).
Sensors purposes, in pneumatic terms, are to ‘sense’ a designated function, and once detected, send this signal to another component to operate. Figure left shows a variety of FESTO manufactured sensors that work in conjunction with their pneumatic systems. They include Pressure Sensors, Optical Sensors, and Proximity Sensors, to name a few.
Actuators (left) are often the component that the sensor will signal to in order for it to complete a purpose. They are differing in design and function, as they are required to complete a vast amount of variable tasks. A simple example of an actuator is the linear actuator, which is comprised of an outer housing, and an inner cylinder, allowing for movement in a straight line (forwards ; backwards). However, many types of actuator are put into use across industry; rotary, vacuum, electronic amongst others.
Outline the identification and application of different types of cylinder (such as single acting and double acting).
Two main types of cylinders are employed in fluid power systems; single acting and double acting. Single acting cylinders rely on a fluid input into one port of the cylinder, enabling it to move in a linear fashion away from the force pushing it, and when the force is exhausted, the cylinder is returned to its original position by mechanical means (usually a spring).
A double acting cylinder works in a similar fashion, however requires a fluid/air input into both ports, front and rear, in order to actuate both outwards and to return to its starting position. Pictured above to the right is an example of a FESTO manufactured double acting cylinder, with the two ports highlighted, where pneumatic signals enter and cause the cylinder to actuate. (K12 ANSWERED ABOVE)
Outline the identification and application of different types of compressors (such as screw, piston and rotary vane).
A rotary screw air compressor (left) is a highly effective and efficient compressor that is widely used in industry. They operate by oppositely rotating two interlocking helical screws to increase the pressure between threads, until sufficient pressure is reached to be outlet. They can come in both oil lubricated and oil free variants.
A piston air compressor (pictured right) operates principally differently to the rotary classification of compressors. They function by positively displacing air to create internal air pressure, and are sometimes known as reciprocating compressors, as they move backwards and forwards as opposed to a rotary motion.
Rotary vane compressors (left) consist of a cylindrical casing, two openings; one suction and one discharge, and a rotor positioned eccentrically with respect to the casing. Compression occurs by refrigerant flowing into the chamber where, due to eccentric rotation, there is a reduction in the desired volume of air.
Outline the applications of static and dynamic seals.
Both seal variants described have multiple applications within industry, static seals being utilised in static systems, between two stationary components, and dynamic seals applied between components where they are in relative motion to one another. An example of a static seal is an O-ring; an ‘O’ shaped seal normally made of a rubberized material, for use in common tubing arrangements, flange fittings and much more. Dynamic seals are put into use in fluid power applications largely, acting within hydraulic and pneumatic cylinders and actuators.
Describe the techniques used to assemble/install fluid power equipment (such as marking out the positions of components; making pipe bends using fittings and by hand bending methods, connecting components using rigid and flexible pipework; using gaskets/seals and jointing/sealing compounds).
Prior to the manufacturing process of fluid power systems, technical drawings must be produced/studied to offer insight into the specifications, detail and tolerances desired for the assembly. Once satisfied with the job at hand, lengths of pipe will be calculated based on overall dimension and clearances (for fittings), marked out and cut. This with copper pipework can be done using a small ‘automatic’ cutter, however steel requires the use of a bandsaw. Pipe bending also necessitates differing processes between copper and steel; in copper a hand-operated bender will suffice, whereas a hydraulically-assisted bender is required to form steel. The method of the adjoining of pipe to fitting/component varies also, steel pipes are generally threaded using a ratcheted pipe threader, as they are employed in heavier duty applications comparatively to copper. Fittings are available in matching thread sizes and are screwed on to the end/s of pipe where required, making use of PTFE thread tape and jointing compound also, to provide a sturdier and more durable connection. Copper pipework assemblies can be joined via soldered or compression fittings. Soldered fittings require the use of a blowtorch and solder to achieve a permanent connection, contrasting to compression fittings which are utilised by placing an externally threaded fitting on the pipework, and tightened using an external nut with an ‘olive’ acting as the seal between them. Following these pipe fitting fluid power assemblies, I progressed on to the construction and testing of pneumatic and hydraulic assemblies. This included working with many specialised components, having varied applications, such as the operation of cylinders to move objects, the sensing of cylinder actuation position to trigger further stages of operation, creation of vacuums, use of solenoids in pneumatics etc. Hydraulic functions covered were the use of accumulators, flow control valves, timers, and cylinder actuation. In pneumatic and hydraulic applications both flexible and rigid pipework arrangements can be used to achieve operation. Flexible and rigid pipework both are compatible with ‘push in’ fittings.
Explain where applicable the need to ensure that pipework is supported at appropriate intervals, and the need to eliminate stress on the pipework connections.
When dealing with longer stretches of pipework, certain methods of support are necessary to prevent multiple problems from arising, such as sagging and/or mechanical failure. The recommended spacing distances between supports varies depending on the pipes length. diameter and material. Left is a graph stating the maximum interval distance between supports for copper pipe supplying water, and steel pipe supplying water and steam. Stress within connections can also cause major problems for the pipework when not handled properly. Stress can be caused by incorrect fittings, overtightened fittings, less than ample spacing between pipes or expanding and contracting of pipe due to pressure or temperature changes. Due to these factors, it is essential that mechanical stress is kept to a minimum as to maintain a healthy operation of the assembly.
Explain the need to ensure cleanliness of the fluid power system, and the ways of purging pipework before connection to components and pressure sources.
In a pneumatic system, the pressurised air must go through a filtration stage, to eliminate harmful contaminants that are contained within it. If left unchecked, these contaminants would gradually cause deterioration of the pipework and components attached to the system, resulting in irreversible damage. Most compression systems for pneumatics also contain a purging operation, whereby a blast of clean, filtered air is discharged and travels around all attached pipework and components, ensuring any potential lingering contaminants do not interfere the operation of the system.
Outline recognition of contaminants and the problems they can create, and the effects and likely symptoms of contamination in the system.
Contaminants can cause catastrophic damage to fluid power systems if not handled accordingly. They range from oils and greases to microscopic dust particles, all causing some form mechanical malfunction or damage, being the disoperation of attached components, or the disability of air to reach components etc.
Describe methods of testing fluid power systems; the types of test equipment to be used, and their selection for particular tests.
A primary and commonly employed method of testing fluid power systems and assemblies is pressure testing. This is to test for the security of connections within the system, and to ascertain whether the system can withstand the pressure it will be subjected to during operation. A water pressure tester can be used to test a steel/copper pipework system, by placing an inlet valve for water to enter and a bleed valve as an outlet. Once connected water is pumped through the assembly until flowing through completely, at which point the bleed valve is closed and pressure can be measured, in psi or bar.
Explain how to make safe checks of the system before carrying out tests, to ensure that all pipes and components are secure and that moving parts are choked or parked.
Visual inspections are generally the first course of action when initially carrying out checks, as they can highlight major issues if they are present, e.g. split hoses or pipes, cracked fittings/components etc. also less serious; wear ; tear, superficial damage, loose connections etc., but may still merit action. If faults are existent, appropriate action must be taken to ensure they cannot cause harm to the system or personnel, e.g. replacement of seriously damaged parts, re-connection of loose cabling/pipes. Once maintenance activities have been completed, further testing can then be undertaken.
Explain how to connect suitably calibrated test equipment into the circuit, and how to connect the circuit to a suitable pressure source containing appropriate ancillary equipment.
In a pneumatic assembly, a piece of test equipment put into use is a pressure gauge; measuring the air pressure flowing through it (bar). This can be attached to any desired part of a pneumatic circuit via a hose from the outlet port on the chosen component to the inlet port of the gauge. Connecting the circuit to air then allows for a reading to be produced. This is done by attaching a main air feed hose to a service unit, allowing for control of the incoming pressure, originating from an air compressor with its own service unit, to closely control air pressure at the source.
Explain how to carry out tests (such as applying test pressures in incremental stages; checking for leaks; taking appropriate test readings; adjusting appropriate components to give required operating conditions).
Testing pneumatic assemblies can cover many areas, however mostly the main objective of testing is to test for the correct air pressure within the system; too little the system may not operate as intended, too much it may cause damages to the circuit (burst/split hoses, internal damage to components etc.). Ideal air pressure varies based upon the assembly and its purpose, and so this information may have to be discovered by gradually increasing the air pressure until the most effective and efficient level is ascertained. This can be done by simply turning the pressure gauge adjuster on the service unit to reflect what air is coming in to the system. Depending on the scale of the system safe starting pressures will differ, yet it may be advisable to start at 1 bar and work up, as to negate any serious risk that can come with higher air pressures.
Explain how to determine pressure settings, and their effect on the system.
Optimal pressure settings are generally predetermined for individual components by the manufacturer, and as such can often be extrapolated across a pneumatic system to give an optimum pressure for the circuits operation. If this is not the case it may need to be discovered as mentioned previously. The effect of the pressure on a pneumatic system influences the components to operate at changeable levels of efficiency. The ability of valves to be opened fully and cylinders to actuate correctly would be hampered if the systems air pressure was less than apt, whereas if too high, actuation may result in damage to the internals of the cylinder or the hoses ability to handle the internal forces and maintain stable connections.
Explain how to display/record test results, and the documentation used.
Test results are most easily displayed in tables, charts or graphs. For instance, a test to discover at what rate an air canister/reservoir expulses air can be recorded by noting the reading of an attached pressure gauge, and timed as it reaches certain values of pressure. This could then be plotted into a line graph, showing results in a presentable and easily understandable fashion.
Explain how to interpret the test readings obtained, and the significance of the readings gained.
Interpretation and significance of test readings can be construed in many different ways, depending of what is being tested, however the interpretation and significance of e.g. pressure testing readings can tell you what operating pressure is most efficient for a pneumatic system, giving you valuable knowledge and enabling you select the correct components and pressures in the future.
Explain the importance of ensuring test equipment is used only for its intended purpose and within its specified range and limits.
Pneumatically speaking, it would be difficult to use test equipment for anything other than its intended purpose, as this is what they are designed to do and are not capable of completing any other function. It is, however, important to ensure that test equipment is not overloaded as it will cause damage and either render the test instrument unreliable to measure an accurate reading or permanently put the piece of equipment out of use.
Describe the problems associated with the fluid power assembly and testing activity, and how they can be overcome (such as leaks, pressure fluctuation and pressure loss).
Due to the nature of the work, there are obvious problems that can surface while carrying out these activities, such as the rapid and uncontrolled escape of air, resulting in flailing air hoses, components malfunctioning mid operation etc., components being misused or overloaded, causing breakages in the assembly and loss of function, visual checks not being completed proficiently, potentially meaning a neglected fault may cause harm to the assembly or operative etc. Problems such as these can be eliminated at an early stage by the correct instruction and training being applied, prior to any assembly or testing activity is undertaken. This would allow the personnel carrying out the activities to do so diligently and in a logical, sensible and controlled manner, while staying vigilant to the risk of previous incompetent work that may lead to problems for either system or person.
Outline when to act on their own initiative and when to seek help and advice from others.
In rare circumstances should you need to act on initiative, as you are under supervision in a controlled environment whenever carrying out fluid power assemblies, only when quick and responsive action is required in a dangerous situation should your initiative be negotiated. As there are trained personnel in close proximity, you may as well take the time to consult with them to overcome a problem, as they will most probably have a partial if not complete solution.
Explain the importance of leaving the work area in a safe and clean condition on completion of the assembly activities (such as cleaning the work area and removing and disposal of waste).
This is a very important stage of the activities proceedings, as it excludes the hazards that are associated with an untidy working space. All dust and debris created from these activities could cause slip/trip hazards, oils and greases that are not cleaned could also cause slip hazards, as well as skin irritation, incorrect storage of tools, equipment and materials could lead to cut/crush/graze injuries etc. It is therefore essential that the working space is cleaned in accordance with the 5 S’s (Sort, Set, Shine, Standardise, Sustain), all waste is disposed of correctly and all equipment, tools and materials are returned to correct storage areas.