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Mechanical Engineering


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RyanTW last won the day on November 7 2019

RyanTW had the most liked content!


About RyanTW

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    Project Mechanical Engineer
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  1. RyanTW

    Where is this?

    Its unfortunate for the guys in the workshop that they don't work for a company that sets aside budget for even basic PPE and training in safety. There are a number of safety concerns in the video including: No eye protection, no long sleeve shirt to the wrist, wearing jewelery/watches, no hearing protection, no hard hats, no equipment shielding and what looks like no electrical shielding from the make-shift controller. Its an important factor to take into account when working with other companies in an industrial business. That anything they produce should be made using the same safety standards as they would be in the country the product is being purchased. Its an unfortunate lack of consideration when everyone wants things cheap, it means that something has to suffer along the production line, and that is usually the workers and their working conditions.
  2. Very Interesting article JAG. Engineers can generally be ambitious people and ambition can be measured in many different ways. How you compare yourself with the other people in the room is one way but no matter the answer you come up with, the ambition should always be "Never be the smartest person in the room". I have never been interested in doing anything where I wont learn anything new, and it has been very stressful sometimes when you don't know enough. The important thing to have is the ability to communicate, as with your block diagram example above, and to know your limitations (much harder) as with the CAD example above. Thank you again JAG
  3. Hi JAG, That is a very interesting point of view for a seemingly simple system. I know I am late to your thread, but for this article it is very important consideration into human behavior. Thanks RyanTW
  4. RyanTW

    A Question for Readers

    Hi DrD, The use of computer software in engineering and the balance between manual calculations compared to software to solve problems has been a big question for a while now. Unfortunately I see examples where the increase in computer power have allowed more a dominance to use software instead. At my University in Melbourne, Victoria (Royal Melbourne Institute of Technology (RMIT)) we learnt using AutoCAD, Inventor (3D) and Matlab. This was a little frustrating when I graduated as I found most engineering companies in Australia preferred using SolidWorks. Then what was more disappointing is when I started working for a company who licensed AutoCAD, they had "Technical Engineers" who did all the work on AutoCAD for the design engineers (me). So now over time I have not used AutoCAD at all and fear that I have lost a lot of those skills. I am fortunate enough that I have the option to pay roughly $1000 to do a 8 week course on advanced AutoCAD skills back at RMIT. I really appreciate the posts from those who have the opportunity or decide to continue to complete their work using manual mathematical completion. It may surprise you that I work for a company who restrict our use of manual mathematics in favor for their software when it comes to completing their work. This is in their opinion to reduce the possibility for calculation error, which intern reduce their liability for errors that result in engineering failures. Thank you for everyones contributions, it has been a fascinating read! RyanTW
  5. RyanTW

    How To Become An Expert

    Hi DrD, Thank you for sharing your experiences, very interesting! I couldn't help but notice that some of your experiences and lessons you learnt have a sense of irony in relation to why your technical posts don't receive as much attention/comment as posts such as this one. It must have been fascinating seeing the changes in engineering and how the world utilizes machines today compared to your early working days. I know you said that he bores you, but I appreciate one thing Einstein supposedly said "if you cant explain it simply to someone, then you don't know enough about it".
  6. DrD and Van Der Loeb, I have spent much time researching the controller (I did not specify or install) to see what was available to me to change and help compensate for the motors age. Some of things that I have changed and found could help improve its performance (continuous operation) are the following points below: Current limit setting reduced to 40A from 77A. The Over Current Protection is fixed at 84A, so this gives the unit more time to slow the pump down if the current limit setting is exceeded before it reaches the over current protection (at which point it will fault). Pump ramp up/down time changed from 0.1sec to 0.5sec to prevent over draw. In my mind these are only temporary fixes, the fault occurs at random times during CONSTANT operation, not during start up or wind down. So I suspect that as DrD has suggested that the very high peak voltages have possibly broken down the insulation in the connector and the motor windings. Which can result in a short which would trip the motor. Because as we all know, up time is the most important factor in the operation, but I only have the budget to wait for my April monthly O&M before my electrician can check a number of things. Thank you everyone, I will continue to provide feedback as I find out more information about the system conditions Ryan TW
  7. Hi Van Der Loeb, I can understand your thoughts on your first point to do with quick stopping the motor and then re-start causing on overcurrent situation. It is something I have considered, just not sure why the VFD does not record this overcurrent when it faults. There is nothing to indicate that the PLC is misreading the outlet pressure, what are your thoughts behind this? In regards to Down Ramp, I am not sure what you are referring to? Is this decelerating ramp? If it is then the factory default is currently set at 0.1sec. What would you suggest changing it to? And please, for my knowledge can you elaborate on why you think this may make a difference? Is it to give the motor a slight time delay to adjust? Thank you for your contribution. George Munoz, The overspeed possibility can definitely be related to the overcurrent state. All this could be because of inlet issues to the pump. I am currently in the process of installing a pressure indicator for the inlet of the pump to hopefully have more information during operation. While the pump was inspected for possible inefficient operation section of the inlet and outlet pipework as well as the all butterfly valves were checked for blockages and everything was ok. The outlet of the tank has a grate that still needs to be checked, but monitoring the inlet of the pump DURING operation will probably be more helpful I think. Thanks George
  8. Hi DrD, The VFD is a PWM device with specific Scalar U/f control method for the electric motor. I have not had a great deal of experience for the failure of these devices. It is supposed to be a simple system of control and therefore very reliable. What are the possibilities for these outages you are suggesting? Hi manoranjan424, I am not certain about the mode, but I will check the next time I am onsite. The motor specifications are Voltage: 415V Frequency: 50Hz Power: 22kW Rated RPM: 2950 RPM (this obviously changes with conditions) Rated Amps: 37.4amps Cos f: 0.87 Delta connected
  9. Dear Engineering forum, I have a particular problem and I am hoping that the larger engineering world could help me. I will do my best to describe all of the important factors and answer any questions. I do not necessarily expect anyone to solve it straight away (although it would be convenient) but, giving me some ideas as to what I could test for or look out for would be fantastic. Situation: I have a 22kw electric motor driving a centrifugal pump at approx. 45% load pumping at 25 - 30 m3/hour, The electric motor is driven by a Variable Flow Drive (VFD) manufactured by ABB, which in tern is controlled by a PLC, The inlet of the pump is connected to a 20,000ltr tank, The outlet of the pump is connected to 4x pressure vessels maintaining 200kPa (2 bar) for high pressure delivery to an open outlet, The speed of the pump is determined by maintaining the pressure on the outlet of the pump The pump has the usual wire strainers, butterfly valves for maintenance and pressure indicators after the pump (no indicator installed before pump, will be occurring in the next couple of days) The Problem: My motor/pump keeps shutting down during its cycle (while it should continue pumping) The VFD gives me a "Over current" fault warning as a result of the shut down. This usually occurs a couple of hours after the fault is cleared and pumping has resumed operation. The IMPORTANT facts: I have personally witnessed the motor/pump shut down momentarily (stop for 1sec before commencing operation) multiple times before the complete shut down and the "over current" fault is given, like it is tripping the power switch, Every time the fault has occurred, the VFD records current supply anywhere between 7 - 21 amps, RPM at 0, Hz at 0 (the motor is rated at 27amps) My industrial qualified electrician assures me that there are no irregularities in connection or communication, everything checks out electrically that he can test for. I have dismantled the pump and there are no signs of excessive wear, plus during operation there is no odour, no strange noises and no excessive vibration, Neither the pump nor the motor are showing any leaks, signs of rust or any other obvious sign of degradation at least on the outside. The pump and motor have been running continuously (approx. 22 hours/day) without problems for 3.5 years. The pumps mechanical seal was only replaced 6 months ago and periodic maintenance is always kept up to date. The pressure and flow rate on the line following the pump obviously drop every time the motor shuts down for that 1sec but there are no other changes during operation. The water that is being pumped is particularly brackish (salty), but has been filtered multiple times so contains no particles or other additives. I have a globe valve that I use to limit the flow rate by applying back pressure, which is of course is maintained at 200 kPa which is when the VFD comes into play. I have no reward to offer for the person with the suggestion that leads to the cause, other than the pride of having the knowledge the engineering forum experiences for the solution and that you really helped out a fellow engineer. Regards RyanTW
  10. Interesting Story DrD, but I have to say that the experience that Bob talks about is not uncommon, especially when it comes to my multicultural country of Australia. I have barely been in the work force 4 years and I have already found myself in situations where trained engineers who have visited factories and plants alike with me, even when completing onsite work really struggle to understand the practicalities of getting your hands dirty to get the job done. There are those of a particular background culturally who don't carry the same confidence to complete simple problem solving tasks because there is a hands on element. Some of them are great engineers who can develop innovative ideas, but when it comes to applying the ideas practically, they can sometimes struggle. I think that providing opinion and making comments comes under that same idea of being able to get involved and get their hands dirty. Keep those life experiences coming DrD
  11. Hi DrD, I have read through both Part 1 and Part 2 a number of times finding it to be a great problem to work with. I have question about the coordinate systems you have set in Part 2 and will try to explain it as best as I can - You set the the coordinate system of the valve body relative to its connecting pins as U - V, with U acting in line with the connecting points. Then your centre of mass and its coordinates are set relative to your connecting points as (0,C), with C being the offset distance being to the U-axis. Having it set like this I can understand works perfectly fine. My question would be that if an important factor to consider for the "Potential for Binding" and for "dashpot coefficient" is the weight of the valve, then wouldn't you want to base the body coordinates on the centre of gravity of the valve and then set the positioning of the connecting pins offset relative to those those coordinate axis? I am not sure if I may be jumping ahead and it may seam more obvious in the following post - Part 3 Thank you for your time Ryan
  12. Hi DrD, Thank you for taking the time to walk us through your experiences. It appears that the decision to make is very depended on the number of choices an engineer has in their society. Where the US have multiple organizations to choose from depending on what they are interested in, other countries such as my own does not. I can still appreciate your point of view that: you as the individual are the one who is paying the fee to be member, so it is important that you get out of it what you want (unless this of course includes your ability to give back to the community). It is unfortunate to hear how things have changed for ASME and that they don't contribute to furthering engineering as they may have in the past. This post has given me a good point of reference to decide. Regards Ryan
  13. RyanTW

    War Stories

    Hi DrD, That was a great story, thank you for sharing. Sometimes it is the people you meet, which remain to be the best experiences. Ryan
  14. Thank you DrD for your experienced insight and putting into words what many levels of engineers are feeling. I know I have mentioned in previous discussions that I am reaching (or have reached) a point where I must make that decision between focusing my career and personal development towards a Project Engineer or an Advanced Engineer. My current position with a decommissioning company lists me as Project Engineer, but the company provides me the freedom to not loose touch with my "Advanced Engineer Side" as I take time to research past engineering subjects. One important point that has only been brushed on, is the industries demand on the future of the engineering profession, specifically in regards to particular countries. I could not agree more DrD, that to move forward as an engineer you need to build your skills towards a Project based or Specific skill/knowledge based. But I can say that through my company currently, I have noticed that Australia is heading in a particular direction where the Advanced Engineer is loosing face with industry, and as you said, demand for the Project Engineer is growing. As a result, companies are expecting Project Engineers, especially in senior positions, to have a strong grasp of the analytical aspect of their industry as they want to them to cover all the bases. Working hard at University has never been so important (unless your father in-law also happens to be an engineer and asks you bluntly if you are doing your 30-40 hours of out-of-lecture study) as now with the industry getting more competitive. But between the commercial engineering industry and the universities emphasizing the importance to have a unique edge in your experience, how engineering is regarded as it was in the past is going through a dramatic change. Again DrD, please continue to provide your insights, it is always a refreshing and honest read in engineering. RyanTW
  15. Hi DrD, What I have found, especially after talking to a number of engineers at or close to my level. Is that they work on engineering calcs in their early years of their career. Then eventually over the years they start to rely on either company provided computer software or junior engineers completing the calcs for them. I find it much better, and a lot more fun to keep up the engineering calculation skills by doing them manually myself. Even if it means doing them at home in your own time. The situation I have found myself in now, I am three years out of Uni in a company who have hired me as the only engineer on staff. As I complete my work, it would be good to have someone with experience to show me better ways or more efficient ways to solve engineering problems. Yes there is a concern in terms of confidentiality, even seeking feedback from an engineer who works for a competing company could occur. But the stance I am taking on mentoring over the internet is this - You start a discussion on a forum with someone, build similar interests in areas of engineering, develop a strong professional relationship and then that leads to a level of trust, which allows for mentoring. I am actually looking now to my Alumni community for opportunities for engineering mentoring. Ryan
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