Task 1: Fluid Power Devices [PDF]

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Luke Parry U11 A1 Task 1: Fluid Power devices a) Electro-Pneumatic component Electro pneumatic components are components of a pneumatic system which can be altered or controlled by an electrical current. This typically involves directional control valves or flow control valves. For my example of an electro pneumatic component I will be looking at a solenoid valve. Solenoid valves use a solenoid (electro magnet) to actuate a valve. Different solenoid and different valves are used depending on the application e.g. high/low pressure. Direct operated valves are the simplest form. As with many valves or switches, solenoid valves come in Normally Open (NO) and Normally Closed (NC) configurations. Here we are looking at a normally closed Valve:



www.youtube.com/watch?v=-MLGr1_Fw0c



When current Is passed through the solenoid coil, the plunger will be pulled up into the coil against the spring, allowing fluid to pass through. Solenoid valves are incredibly common in both pneumatic/gas and hydraulic/fluid applications since they allow remote control of fluid or pneumatic flow. The other types of solenoid valve include pilot valves, 2, 3 and 4 way valves. Pilot valves use a much smaller solenoid valve which in turn opens a larger valve with higher pressure. These valves tend to operate much slower than direct valves and have many more components.



b) Electro-hydraulic component For my example of an electro-hydraulic component I will be looking at an electro hydraulic actuator. Electro hydraulic actuators are essentially self-contained hydraulic actuators which can be used for various applications. They benefit from the high precision of hydraulics and a self-contained form factor.



Luke Parry U11 A1 Compact electro hydraulic actuators typically consist of a pump, reservoir and actuator. The pump moves hydraulic fluid directly into the double acting cylinder it is mounted to. Electro hydraulic actuators can either be linear or rotary giving them a broad range of applications. These actuators are popular for use with either linear or rotary valves for accurate flow control with remote access. The self-contained nature of these actuators allows for many potential applications. Task 2: Circuit diagrams



1



2 3



The symbols used here appear to be ISO pneumatics symbols. 1 – this component is a single acting cylinder with a spring return. The cylinder has one input which requires positive pressure to actuate the piston out against the spring. Then the pressure drops, the spring pushes/returns the piston to its home position. The zig-zag line indicates a spring and therefor a spring return. 2 – this component is a one-way flow control valve; it allows air to flow in a single given direction. The valve allows the flow of air to be restricted manually using a screw. this represents the flow restriction. In this case, air can flow upward into the cylinder at a controlled rate. When the air flows backwards through the component it will not be restricted. 3 – this component is a normally closed (NC) 3 2-way valve. This particular valve is operated by a push button / manual action and utilises a spring return. When the button is pressed, the valve moves across and air can travel from inlet 1 to outlet 2. When the button is released, the spring will return the valve to closed. If the valve is closed, air coming through port 2 will be expelled out of port 3.



In principle, this circuit would have air supplied to port 1 of the valve, where the valve can be manually operated to supply air through the flow control valve. The flow control valve has the ability to be adjusted to restrict airflow into the actuator/cylinder. The cylinder would then extend.



Static / closed



Button pressed



Luke Parry U11 A1 When the valve button is released, the valve will return to closed and air supply to the cylinder will stop. Air in the cylinder will be expelled with the returning spring as the piston returns to contracted. This circuit may be used for operations such as stamping components since it is momentary and retracts to its original position. Task 3: Compare Pneumatic and Hydraulic Systems In this task I will be looking at an air file for my pneumatic example and a bottle jack for my Hydraulic example. Pneumatic and Hydraulic systems tend to share a lot of similarities with the key difference being that one expels the fluid after use and the other www.amazon.in/Docooler-Sander-Compressorrecirculates it, and that one uses air and the other is Sanding-Pneumatic/dp/B07M639RKM hydraulic. Air files or Air belt sanders are tools driven by compressed air. The air is used to drive a pneumatic motor which directy rotates the sanding belt. A majority of air powered sanders follow the same principle, air in > spins motor > air out. From the breakdown on the right we can see that the file begins with the air inlet,this inlet would typically be fitted with a quick connect fitting (with sealing tape) to suit the other tools in the workshop. These fittings will seal on the supply line but not on the tool end. Following the air inlet is the valve switch which allows air to flowthrough the pneumatic motor and spin the belt. The air is then expelled through the air outlet into the atmopshere. The key differences here compared to a



learnchannel-tv.com/pneumatics/pneumatic-motor/



Luke Parry U11 A1 hydraulic equivalent is that air is vented to atmosphere instead of being recerculated as in a hydraulic system. Also, with hydraulic quick connect fittings both fittings will seal as to hold the hydraulic fluid inside. This is so that the system is constantly primed, this is unnecessary in pneumatic applications. Air is expelled in pneumatic motors because the airs potentially energy (the compression) is lost when the energy is used to rotate the motor. Also air isnt harmful for the atmosphere like hydraulic fluid so there is no need for recerculation. Air powered tools inherently rely on the supply of compressed air. This compressed air will come from an adjasent air compressor which uses a motor Here we can see a very basic diagram for a air motor, inside the box is an air driven motor with a momentary 3/2 switch and a direct exahsut, essentially an air sander.



Bottle jacks are typically self contained hydrauic systems which use a hydraulic ram to perform lifting operations such as lifitng cars. A bottle jack is essentially a self contained manually powered hydraulic ram. Bottle jacks operate using a fairly simple principle. The hydraulic resevoir is formed around the central ram. The jack handle uses a piston to pump hydraulic fluid using the check valves princliple of one way flow. This forces hydraulic fluid into the ram cyclinder which in turn pushes the ram upawards. The release valve is used to bypass fluid past the check valves and back into the resevoir, eliminating the need to reverse the check valves to lower the ram. one of the primary differences between this hydraulic sustem and an equivalent pneumatic system is that the hydraulic bottle jack recerculates the hydraulic fluid. This recerculation is what allows the jack to be self contained. Similarly to air compressors and tools, hydraulic tooling is able to utilise an external hydraulic pump for the tools function. This is commonly seen with higher power tooling such as ‘the jaws of life’ which use an external high power hydraulic pump. Due to the incompressability of hydraulic fluid, hydraulics can operate at much higher pressure compared to compressed air. Over time, both hydraulic and pneumatic systems will begin to deteriorate however air tooling tends to require less maintenance due to the lower pressure. Air leaks in pneumatic tooling are dangerous but typically less of a risk whereas leaks in hydraulic tooling can potentially be a minor explosion due to the pressure. Air tooling maintenance typically involves lubricating the designated ports around the tool to lubricate the necessary seals and bearings, doing so stops the sealsdrying out over time and increases the service life. Air seals failing will lead to gaps in the gaskets and seals and therefore air leaks leading to a loss of power.



Luke Parry U11 A1 in a hydraulic system such as a bottle jack, a majoirty of moving components are lubricated by the hydraulic fluid. However, rubber seals and gaskets will still deteriorate over time therfore the seals for the ram, piston and check valves may need replacing accordinly. Hydraulic fluid can also deteriorate overtime depending on the use and age. Just as with pneumatic components, perished seals compromise the systems ability to hold fuild, leading to dangerous pressure leaks. To conclude I have condensed key factors into a table, neither positive or negative: Pneumatic Exhausts to atmosphere 80-100 PSI Uses readily available air Rarely tooling is primed



Hydraulic Recerculates air 1000-5000+ PSI Uses stores of harmful fluid Uses primed components



Task 4: current standards In this task I will be looking at the relevance of current standards such as ISO and CETOP in relation to the contruction and operation of each device. I will be looking at 4 devices that I have covered and then discussing the regulations which may apply to them. For simplicity, I will be looking at regulations relating to the pneumatic or hydraulic aspects of each piece of equipment in order to stay on topic. Solenoid Valve: solenoid valves are used for a variety of fluid power systems and therefor the standards will differe slightly depending on the application. https://www.smcworld.com/products/en/s.do?ca_id=634#rp SMC for example creates solenoid valves which conform to the many ISO standards which standardise the size, interface features etc. ISO 15407-2:2002 “specifies dimensions and tolerances of the interface features, port identification, identification of the result of control-mechanism actuation, dimensions, tolerances and specifications for optional interface electrical connector mateability for a mounting interface and electrical connector for five-port pneumatic directional control valves, sizes 18 mm and 26 mm, for use at a maximum rated pressure of 1,6 MPa (16 bar).” https://www.iso.org/standard/27626.html From what I can deduct from the website, they create products which conform to the various ISO standards which cover different sizes and ratings. By looking at the www.iso.org website, I can search for standards relating to solenoid valves, we have: -



ISO 15218:2003 relating to the dimensions of 3/2 solenoid valves ISO 15998-2:2012 relating to machine control systems ISO 13849-1:2015 relating to safety related parts of control systems ISO 9461:1992 relating to the identification of valve ports and solenoids ISO 22153:2020 relating to electrical actuators for industrial valves



Hydraulic actuator - Bottle jack: since hydraulic actuators and hydraulic bottle jacks share many of the same principles, I have condensed them into a single point. Companies typically state whether their products abide to the relevant ISO standards.



Luke Parry U11 A1 ISO 4413:2010 outlines the general rules and safety requirements for hydraulic fluid power. ISO4413 applies to the design, construction and modifation of systems and their components whilst accounting for “assembly, installation, adjustment, uninterrupted system operation, ease and economy of maintenance and cleaning, reliable operation in all intended uses, energy efficiency and environment” https://www.iso.org/standard/44781.html 4413 also identifies the significant hazards associated with hydraulic systems and the principled to apply to avoid these hazards. By searching the site for standards relating to “hydraulic piston” I found the results: -



ISO 18387:2019 relating to hydraulic linear actuators in aerospace ISO10766:1996 relating to tolerances for hydraulic cylinder piston and rod housingsamended 2014 ISO 4395:2009 covers cylinder piston rod end types and dimensions. ISO 6020 covers mounting systems and dimensions for single rod cylinders up to 160 BAR



Air File/belt sander: The primary pneumatic component in an air powered belt sander is the air motor.The different applications for air motors means that they can be subjected to a variety standards for different industries, primarily dentistry. Infact, all the search results relating to air motors on the ISO website related to dentistry, refrigerant and vehicles. A quick search reveals that there are infact ISO standards relating to pneumantic tooling. ISO/TC 118 is a classification of standards relating to compressors and pneumatic tools, machines and equipment. This standards further breaks down into 4 sub categories, the one relating to pneumatic tools and machines being SC3. The SC3 class (subcommittee) breaks down into: (most relevant to us) -



ISO 2787:1984 Rotary and percussive pneumatic tools — Performance tests ISO 8622:1988 measurement of vibration to the handle ISO 11148-8:2011 - Hand Held non electric power tools – safety requirements – sanders and polishers



SC3 covers everything we may need to consider for the design and use of pneumatic tooling, this is a very useful set of standards in our application. There are 44 standards set under SC3 not including the ones under development. The UK is listed as a participating member of this subcommittee. It is not necessary to list every standard under SC3 here since many relate to other specific pneumatic tools and not sanders, however the full list is here: https://www.iso.org/committee/51870/x/catalogue/ Cetop is recognised as the European fluid power committee. “CETOP represents more than 1,000 companies - mainly manufacturers, but also some dealers - with almost 70,000 employees and a market value of about 13 billion EURO.” https://www.cetop.org/about-cetop/ Cetop aims to share information to better the fluid power industry. The application / use of these pieces of equipment are typically defined in the standards or by the manufacturers in operation ratings etc. However the ‘use’ of these equipment by trained persons or similar is vague since a majority of these components can be bought as consumer products meaning you don’t need to provide a form of training to buy them.