It SOUNDS like a good idea....

Note: This is an off topic rant, but I'd like some feedback from others.

The recent post about always specifying filters on VFDs hit a nerve. It seems that I am more and more often seeing items specified by engineers that, at first blush sound like a good idea, but after a little thought turn out to be either of little benefit, or even worse a detriment.

The worst offenders in my experience are the large A & E firms that are spending someone else's money and are generally in the VERY risk averse mindset. In almost all cases the superfluous item specified costs more, so engineers with a CYA mindset immediately assume that it must be better. This is often a case of confusing price with value.

Example: The routine specification of VFDs that meet IEEE-519 requierements "at the drive input power connection" without a harmonics analysis, load data, or transformer data and distribution diagrams.

Example: The routine specification of 5% line reactors, even if a 3% reactor is already provided as a standard.

Example: The routine specification of 30 mm "heavy duty" pilot lights and switches. This one really grates on my nerves, since I am accused of trying to save money with 22 mm even though I can by 30 mm for less. Never mind that the 22 mm meet NEMA A600 ratings, or that both use the same lamps, or that the 22mm are finger safe and many 30 mm have exposed terminals!

Example: The routine specification of all 120 VAC I/O, even though the 24 VDC are just as reliable and safer. (I just love having a door swing shut while I'm troubleshooting and getting that 120 VAC wakeup call in the shoulder blade from those 30 mm switches!)

Example: The routine specification of stainless steel body valves, even though cast iron will last forever in that particular service. Actually, A & E firms in the water and wastewater treatment industry treat the words "stainles steel" like a magic incantation - use it often enough and you cannot be held responsible for any malfunction regardless of cause!

Example: The routine specification of 316 SS enclosures, even though carbon steel will last for generations in the particular location, and 302 SS will last 2 x forever. (Note to manufacturers: If you want to totally corner the water and wastewater treatment market, simply come out with a 316 SS PLC.)

Example: The routine specification of Hart capable transmitters, even though neither the engineer or the owner have any idea what Hart is and have no plans to ever actually use it!

Example: The routine specification of a UPS for EVERY panel, even though loss of power means nothing can be controlled, and the plant has an autodialer with a power fault alarm, and PLCs will maintain programming and settings without power for months and months.

I could rant on and on and on. It seems like the problem is getting worse - the specifiying engineers simply don't want to look at the application and apply engineering judgement or common sense.

So, am I just getting (more) old and crochety, or do you guys see the same kind of thing happening with increasing regularity?

I don't think I am seeing it with any more regularity. This has always been the case as far as I can see. For me it is simply moving on unabated.

I think this is a general result of companies coming up with an 'Engineering Standards Document' that has little to do with engineering and everything to do with compiling corrections to dissimilar problems. While I agree that it is foolish to simply disregard hard-won information I think it is far more important to provide the information at a much more conceptual level. Like Tom said, adding something simply 'because it worked before' without knowing why it worked is at the least needlessly costly and at the most possibly destructive.

The 'funniest' thing for me (in a sad, demoralising sort of way) is when I ask a customer 'Does this component/design really make sense?' and the response is 'No, but that's how the spec is written'. Talk about being a slave to your system!!

Keith

In my experience, specs are a jumble of responses to individual problems.

Some make sense, some don't, and some did when they were implemented. I do have some good customers that will actually take a commons sense approach to their specs when questioned, but not all.

Generally speaking I find specs are a mish mash of past specs with a lot of irrelevant rubbish copied and pasted into them. This means that there are many sections that contradict each other.

I spoke to a consultant electrical engineer about this and he claims that things are so competetive they cannot afford to write new specs each time and that is why the copy and paste happens. My comment was that is fine but someone should read the spec and get rid of the contradictions.

I think our contractors think our standards are like that.
- Why do we specify stainless steel for all outdoor applications? On our site all mild steel cabinets end up with rusted out holes in them after 3-5 years (out doors only, indoors mild steel is generally fine).
- Why do we specify X PLC, Y HMI and Z Scada system? Spares and local knowledge.
(You might notice another post of mine related to us being convinced to use WinCC instead of our standard Citect)
- Why do we specify RAL 7035 grey for all our cabinets? I will let someone else have a guess at this one.

On the other hand, we are the engineers on site, and we maintain the equipment that gets put in. I review our standards yearly to ensure their applicability, and to get feedback from the end user.
We are also looking our for new ideas and, after careful checking, will allow a non standard item to be used as a trial.

Tom, I FEELS YOUR PAIN BROTHER!!! You have said several mouth fulls.

I work for a drive sales/repair/integration, if a drive can do it we sell and service it company.
I have seen and been a part of every possible argument for and against reactors. I have seen customers with reactors that came with brand XYZ drive from FBN Industries drives division because "they said we really needed it. Talk about a CRAPSHOOT.

I like seeing 3% reactors on any drives input if it does not have an isolation transformer right there. If the transformer is rather large and feeding numerous loads, then it is a stiff source and its reactor time.

There is this CYA type of specification going on EVERY WHERE. The problem being, the folks writing the specs are either newbies or sales types. ER commission compensated sales types being the best at writing the most number of parts into specs.

My company recommends a 3% reactor with everything as it will not cause problems when properly installed. Properly installed being the key phrase. We install reacotors on all panels as a precaution as we usually get no information on the quality of the power where the control is going.

Reactors provide impedence matching and provide some filtering. Most AC drives that are equiped with a DC link reactor do not need an input reactor unless there is an extremely stiff voltage source. I have seen input reactors work much, much better with the DC link reactor bypassed.

Output reactors seem to have more mystery surrounding them. The rule of thumb we use is less than 150 feet, a reactor is not usually needed. When the cable begins to gain length, reduction of the carrier freq works up to about 150 feet of cable. Longer than that and a reactor become quite helpful. Today reactor can be specified by how long the lead lenght is too. The drive primarily sees the reactor as the load. The DV/DT caused by the PWM output of the drive that causes DI/DT in the motor and leads is some what rolled off. This will reduce inverter output currents that can cause the motor to heat and a variety of other ailments. You can actually have current circulating between the drive and motor in a resonance. Lower carrier freqs have longer wavelengths and less of a tendancy to resonate. Drives that feature auto tunning are beneficial as many adjustments once done by the turning of a trim pot are now done electronically with an extremely high degree of accuracy.

kamenges, you said:

"The 'funniest' thing for me (in a sad, demoralising sort of way) is when I ask a customer 'Does this component/design really make sense?' and the response is 'No, but that's how the spec is written'. Talk about being a slave to your system!!"

Do you then ask what snot nosed brat, I just graduated and I am an engineer, wrote the spec?

I have found the older engineers call all the time for help in determining what drive and ancillary equipment they need. The young ones just seem to be smarter than the rest of us.

BTW, I have worked with many young engineers that did not feel the need to advise me they were an engineer when I began to question the specs of the installation that I was there to make work right.

Tom,

I know what you are talking about. It is a never-ending battle against certain engineers. I think the cause can be summed up with two words, laziness, and ignorance. EDIT: make that three words. Add "government employee".

I have seen experienced engineers use the same old specifications that are too tight and called for unneeded equipment. The reason was they were just too lazy to write a new one from scratch.

The second culprit is the "engineer-on-paper", the guy with a degree but who does not and will never have any idea about how and why things work, except mathematically and theoretically. This guy may be a recent graduate, or he may be an old guy unable to learn better. His specifications will always be for more than needed, the deluxe version, the most expensive, most conservative method that he can find. That is because he does not know enough to know what can be cut.

EDIT: The third culprit, the government employee, will usually write a specification that describes everything, including the kitchen sink, whether it is needed or not. He absolutely does not care how much it costs because he is not paying for it, and neither is the agency that he works for. The taxpayers (that do care how much it costs) will never get a chance to veto this outrageous design technique.

Only last Friday, I was consulting with a federal government engineer about whether or not a larger transformer was needed for a project expansion. We added up the connected loads, and the total (including the new stuff), was about 15% above the existing transformer rating. I said, "Well, looks like you are okay. We both know that your power demand factor will be 65% or less, so you have plenty of power." Later he told me that the project group had a meeting and decided to remove the 1000 kVA transformer and install a new 1500 kVA unit. Why not? Just expect your federal tax bill to be a few dollars higher next year!

Engineers are called upon to write specifications, but an engineer who can write a good spec is an exception. Engineers become engineers because they can do mathematics and cannot write two words together without making a mistake. That is why so many technical specifications are pure garbage. Engineers rely on boiler-plate copies from previous specifications, but every project is different and should have its own technical descriptions written specifically for the job.

Tom-

Can you explain why you are using those cheap crappy 22mm pushbuttons? The advantages of 30mm are obvious:

- 30mm knockout cutters cost more

- simple math. 30mm = 30mm, while 22mm is only equal to 22mm.
30 > 22. Voila!

- the exposed 120v terminals on the 30mm PBs hone your reflexes to razor-sharp reaction time when you are elbow deep in a rats nest of a control panel. This also toughens you up due to the repeated smashing of your hand, arm, head, etc. into said panel when you get stung.

These are but a few examples of the superiority of 30mm. I will go drink a few more, and I'm sure I can come up with even more reasons!

Our specs say 22mm, 24V DC.
We sometimes get contractors who want to use 240V, or sometimes 110 VAc because it is "Safer". These contractors generally end up getting jobs from someone else.......

Our last big job, we got a large engineering company to manage the project and write the specs. The mechanical specs were fine, the electrical specs had things like "Operator panels to be located under the stairs", "all panels to be water tight and capable of immersion in salt water", and "All IO cables to be run back to Control Room".
Obviously copied and pasted.
I re-wrote the electrical specs (yes, I did copy and paste - why re-write when we want what we had before).
Operator panels were now to have a clear view of the machine that they control (one contractor still got that wrong, dispite my continual protest)
Panels are now IP65 outside control rooms, and IP42 inside.
Field IO is now specified to Profibus and/or ASi.

Generally, good specifications make for a good project. But it is still the responsability of the end user (myself in this case) to ensure that the specs are written to get the machine that you want.

I must agree that there is no excuse for sloppy specs. But you need a feedback loop. You need to check your specs against reality to see that you are actually getting what you want and what you need.

Example: The routine specification of 30 mm "heavy duty" pilot lights and switches. This one really grates on my nerves, since I am accused of trying to save money with 22 mm even though I can by 30 mm for less. Never mind that the 22 mm meet NEMA A600 ratings, or that both use the same lamps, or that the 22mm are finger safe and many 30 mm have exposed terminals!

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Tom, this is just a maintenance man perspective observed through experience. You and others may have different experiences.

I have dealt with what is refered to as 30mm heavy duty switches for 20 years or more, I know of installations that still have some of those original swtiches, I can not state how often the contacts have been changed though but some I know stay in service for years..depending on use.

The 22mm switches etc in my experience may break before the contacts are replaced, again, depending on use. In other words the 22mm switch itself has a higher fail rate.

I have a tendency to request 30mm switches etc for this reason, the newer models incoporate finger safe components.. One example is the AB 800T/H.

Generally, good specifications make for a good project. But it is still the responsability of the end user (myself in this case) to ensure that the specs are written to get the machine that you want.
I must agree that there is no excuse for sloppy specs. But you need a feedback loop. You need to check your specs against reality to see that you are actually getting what you want and what you need.

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One of my pet-peeves are specs written by vendors/distributors that are designed to limit equipment to one manufacturer. They generally read as if they were written by lawyers.

Two outstanding Tom's.....

Over the years, with very few exceptions, I did not have much respect for PE's, and contended that when they got their PE certificate, they had to hand over their common sense.

I had a friend (Tom Metros KA9ARG/SK) through ham radio and a work situation. He was kind of crusty, and one day I learned he was a PE. He worked for the State Dept. of Transportation. A real self taught guy, specially since he never went to college. Actually, I would question if he graduated high school. A real genius, but, a victim of diabetes.

And of course, there is our very own Tom Jenkins in Milwaukee. Another true genius, even though he is a ME, one of the sharpest guys in EE.

ANYWAY, Tom's thoughts seem right on. I often fight spec's that are incidious (why use a ridiculous word when an incidious one will do just fine) and are either CYA or direct quotes from some manufacturers catalog.

I have interviewed with some of these consulting firms, and they will pay some decent money to people who can decipher and write specs. Though, one recent interview hinged more on my golfing ability then anything else.

Sure, they should be able to spec a cabinet, and maybe some major components in it, but to say it has to have a AB 30mm pilot light or a Cinch Jones 30 point barrier strip is pushing it. Sure, specing a AB plc to keep some standardization is fine.

I feel a rant coming on.

Bottom Line:
Tom, you are "Right On" as usual!

Bestest Regards.....kc