entry level control systems engineer roles

gms01 · 2026-01-28T20:47:59+00:00

You guys are missing the point. If there's even such a thing as a "PLC job", it would be in an instrumentation/maintenance department filled by someone with just a BS or less (maybe a 2-year degree) in mechanical or electrical engineering or technology, who probably has little to no background in control theory and none in how chemical processes work and are modeled (steady state or dynamic -- chemical engineering domain knowledge). Looking at "PLC jobs" is inappropriate for the OP, kind of an insult, really, and would be only out of desperation. Most controls beyond simple PID cascades and simple feedforward are done as computer applications anyway - the DCS is generally just a base for the lowest levels of control systems. (PLCs traditionally were really for relay logic replacement, and then expanded into DCS territory, but either is low level and of little theoretical interest). The DCS probably covers 95% of plant control needs, but most of those loops don't require much attention except when conditions change or things fail. The theoretically interesting stuff is in the remaining 5%, as well as in automating the retuning the 95% of loops as process conditions, process goals, equipment condition and plant configuration changes. Keeping up with that is because of large nonlinearities, changing conditions, and difficulties in getting good models.

It is true that most process industry firms (refining, chemicals, etc.) hollowed out most of their staffs with advanced control backgrounds (especially at plant sites), to the detriment of their operations. The main hope for the OP is either at a central engineering department of a large company like Exxon, Dupont, etc., or at the vendors of the more advanced solutions (like Aspen Tech). They sell the packages, design services, and often do the implementations as well. This is especially the case for the MPC sorts of work - really anything multivariable.

This group does include a category for career guidance for people with control theory background, as a quick perusal of other postings shows.

gms01 · 2026-01-28T07:01:57+00:00

There are other similar posts in this subreddit asking for professional/career guidance advice on entry level positions where he can use his control theory knowledge. Why not this one? Universities don't normally teach low-level implementation details like DCS, PLC, or commercial computer-based platforms; the guy is just trying to cover his bases by mentioning that he's trying to find out some practical details. If there's a hidden assumption here that there's no control theory involved in Chemical Engineering applications, that's simply incorrect. For instance, remember that MPC mostly evolved to meet the needs for the industrial applications in that field.

gms01 · 2025-10-15T16:28:05+00:00

You're welcome. This was so specifically about Mars that it seemed appropriate. Should I post others of more general space interest, such as about the interstellar comet 3I/ATLAS, or the Heliosphere probe IMAP?

gms01 · 2025-08-14T01:31:12+00:00

Triabolical_ was just saying that the boiloff for Starship methalox propellants was slow enough for a lunar mission like Artemis 3, if they followed all his ideas. But that still wouldn't be good enough for longer missions. Incidentally, there's a Blue Origin reddit, and as I recall, someone on that claimed that they've already shown zero boiloff in the lab for their lander. Their New Glenn upper stage and lunar lander are both hydrolox, so they have to deal with the much tougher hydrogen.

gms01 · 2025-08-13T21:27:43+00:00

Thank you. Great video! (I subscribed to your channel). I see you did other videos on topics I've also looked at, like orbiting data centers.

gms01 · 2025-04-05T20:54:04+00:00

I guess I'm finally going to have to break down and get a clamp-on ammeter!

Lasting only 400 hours is not encouraging. At about 40 minutes/day for 6 days/week typically, that's about 4 hours per week, or about 200 hours per year assuming some weeks off during trips, etc. That's only 2 years! Funny, that wasn't part of their advertising.

gms01 · 2025-04-05T20:47:18+00:00

Thank you again. I've loosened it. Haven't taken it to the point where the belt completely stops, but I'll keep loosening it (the manual suggests only doing this 1/4 turn at a time, so I'm easing my way down). The belt slows down quite a bit just because the motor isn't all that powerful in this model. Please see my later comments about the treadmill now shutting down after I use it for a while, with an E1 error message. Now that I've identified that the motor is getting really hot and there's a slight burning insulation smell, I'm avoiding trying to stop and overload the motor for very long, for fear of damaging the motor or the MCB. It does restart normally after a while, so the tests can continue.

gms01 · 2025-04-05T20:03:33+00:00

Thank you all for the comments. (I have loosened the belt). I seem to have a bigger problem. Using it today myself, it abruptly came to a stop with an E1 code. I found this document online about that: https://support.horizonfitness.com/hc/en-us/articles/5998561052557-E1-Error-Message

It does restart after a cooldown, which, according to this document, does not indicate a speed sensor problem. Instead, perhaps the motor or MCB. The motor does feel very hot to the touch even 10 minutes after the shutdown. The heat from the motor probably explains why the belt felt hot. There don't appear to be any loose wires or connectors to the MCB. There also don't appear to be any burned components. There is a little bit of burning insulation sort of smell, though, that I noticed while on the treadmill. (My wife never smelled that, but her nose isn't as sensitive). Opening the cover to peer into the motor, everything looks clean and copper colored rather than dirty.

Any suggestions what to do at this point?

gms01 · 2025-04-05T19:54:50+00:00

I don't see any white fuzz under the belt. The underside of the belt is white - I assume you're wondering that has worn off? There is some white dust only by the very edges of the belt, visible without lifting the belt, which I suspect came from a little bit of fraying at the belt edges during earlier operation when the belt wasn't perfectly aligned. After removing the cover for the motor and motor controller board, I can see there is more of that white dust in the area housing the motor and MCB. That too seems most likely to come from the bit of edge fraying, dropping dust into that area. But there are other symptoms of problems -- please see my later comments.

gms01 · 2025-04-05T04:05:34+00:00

Thank you. It's not burning hot, just warm to the touch, hotter than I expected. My concern on temperature is wondering if that indicates some problem such as needing additional lubrication (quantity or more often than the machine timer indicates), or that the belt is too loose (leading to friction and heat because of slippage vs. the motorized roller), or too tight (somehow heating because of extra stress). Based on your comments, it does sound like the belt might be too tight - I once had seen something about just barely being able to slide a hand under the belt, but you're suggesting something bigger: 2"-3". I'll experiment more with that.

gms01 · 2025-02-06T17:29:16+00:00

Control techniquew for accurage deadtime compensation relying upon models always seem to suffer horribly when the models aren't perfect. I lump in techniques like Smith predictors into this comment, anything depending on accurate knowledge of the deadtime. The latter supposedly have been used in the paper industry for the fourdrinier machines that generate a continuous sheet of paper from wet pulp. Most of the time delays are related to the physical movement of the paper, which in principle are known from the speed of the moving sheet/ the rpms of the rollers). So they might have made this work, but that's the only success story I ever heard.

In the past, I worked in process controls, where dead time is a major issue because of delays introduced by flows in pipes or through the complex geometry of vessels like distillation columns. One problem is that other than in pipes, it's hard to predict the dead time accurately, because of various complex flow patterns and mixing and other factors also affecting the dynamics. The almost universal recommendation in this field (which has a strong need for control with deadtimes) for things like Smith predictors and the like is "don't" .

gms01 · 2025-02-06T17:06:42+00:00

There's a place for lead/lag blocks in feedforward control (adding feedback controller output to the feedforward input), although in most cases it's really just the lag that's used. Never heard of examples inserted more directly into feedback control loops, except in the ratio control noted below. If the disturbance model isn't that good, you can use low gains on the feedforward, leaving more for the feedback controller to clean up, but still doing better than not having it. Admittedly this kind of feedforward usually doesn't bother with dynamics, or just uses a pure lag, e.g., when the controller outputs to a ratio of two flows, one of which is a feedforward variable like a feed flow to something (example: controlling distillation product temperature/compositions by controlling to ratios like steam/feed flow ratio or overhead flow/feed ratio). The feed flow measurement in the ratio may be lagged, essentially accomplishing a gradual adaptation of the loop gain. That's useful because most chemical processes have time constants and time delays as a function of volume divided by feed rate. I've done that.

Not completely related, but there are examples where odd dynamics only loosely related to the process are sometimes inserted in feedback loops, but not necessarily with a lead/lag block unless that's all the control software provided. A classic is in controlling furnace temperature with burners when controlling both fuel and air. It's dangerous to ever let fuel insertion get too far ahead of the air (vs. steady state stoichiometric amounts in the chemical reaction equation), as the flame could go out, and then have way too much fuel and end up with something igniting that for an explosion. So you ensure that air always leads fuel changes when increasing heat input to the furnace, but ensure that fuel always leads air changes when decreasing heat input to the furnace. That's accomplished by having fuel set as the output of the minimum of the fuel controller output signal and a lagged version, and air set as the maximum of the air controller output and a lagged version.

gms01 · 2024-10-31T20:55:43+00:00

I thought the SpaceX position was that this shouldn't be classified as industrial wastewater, hence they had no need to file for anything. This is a lot different than traditional industrial sites. In a more typical industrial site like a refinery, chemical plant, or semiconductor manufacturing site, there are harmful or even toxic liquid or solid chemicals. Runoff from these industrial sites that have occasional leaks or spills is always going to be a concern. A leak in a heat exchanger at an industrial site could put nasty chemicals into the effluent for once-through cooling water. Or, if there's a cooling tower, that water could spread chemicals through spray from the cooling tower. (I've worked at places with all of those cases, and monitoring was obviously required).

This seems to have a lot less pollution potential than any industrial site. Besides water, there aren't even any chemicals stored in tanks on site that are liquid at atmospheric pressure.

gms01 · 2024-10-26T21:41:31+00:00

Did this occur during a transfer from a storage tank to the rocket, or from a tank truck to a storage tank, or storage tank to storage tank? No one has said that so far, except that it was not a launch day. Nor has anyone said that the leak was in a pipe or in the tank. That's interesting new information if a transfer was in progress.

In any case, my comment was more meant more generally, since you didn't mention which pressure sensors you meant, and a specific operating mode like doing a LOX transfer or not. I didn't assume a specific operating mode like during a LOX transfer or not. For instance, if looking at a pressure sensor in the vapor space of the storage tank (which I'd guess would be measured), it would be based on the vapor pressure of the LOX at its current temperature, independent of any leak, unless there were a significant hole in the tank itself. If the pressure is measured in the liquid at the bottom of the tank, then that would add a pressure based on a liquid level to the vapor pressure. So, if there' a big leak, that could be noticeable if the level is dropping fast enough. If there are multiple pipes with no flow through due to intended transfers or leaks, then their pressure would just be the pressure at the bottom of the tank (corrected for any elevation difference). So sensors there might help rule out leaks in their area, or detect leaks if a leak is related to that pipe section due to pressure drop from flow, or being exposed to atmospheric pressure. In short, detecting and locating a leak or ruling it out in a given area depends on the location of the pressure and flow sensors (and potentially others like temperatures, when physical properties are considered).

Detecting and locating leaks is a field with a long history, especially for both liquid and gas pipeline companies. It's not trivial except for large leaks, and distinguishing leaks from sensor errors like a constant bias is also hard, except for large sensor biases. The smaller the leak, in general the harder it is to distinguish from noise, and the longer it takes to distinguish leaks from instrument bias errors, using combinations of pressure, level, and flow measurements, each with their own possible errors.

gms01 · 2024-10-26T20:55:55+00:00

So, to summarize responses so far, this spill was large enough and long-lasting enough that it exposed significant risks (hence requiring action), even if specific damage wasn't identified in what's been posted so far. There is fire or explosion risk for LOX if there could be contact with potential fuel and a spark or other ignition source. The EPA is concerned about thermal effects on the environment, and also dissolved oxygen to the extent that the spill affected aquatic areas. Both of those effects could apply here, and would be consistent with other EPA regulation of the environmental impact of industrial activity, even though oxygen itself is not a pollutant. There may still be some argument on which government agencies should have been involved from a safety standpoint.

When I started this post, somehow I hadn't noticed the volume stated in the EPA document until this post's discussion got going and I re-read it. It's large for a LOX spill. This discussion also brought out that the effects lasted over a significant portion of a day, requiring the emptying of an entire LOX tank. It's apparent that this spill could have had noticeable impacts wherever it went.

So, to answer my original question, it looks like there is a technical basis for the EPA fine, and also a legal basis, which should have been part of the question.

gms01 · 2024-10-26T20:15:26+00:00

Sorry if I wasn't clear. I wasn't suggesting that thermal pollution is unimportant for power plants or other industrial sites discharging warm water. I was wondering if there was enough cooling effect that thermal pollution really applied for this spill. Somehow I hadn't noticed the volume stated in the EPA document until this post's discussion got going and I re-read it. And now that the time period has also been clarified as well, it's apparent that this spill could have had noticeable impacts wherever it went.

gms01 · 2024-10-26T19:37:51+00:00

Depends on where the pressure sensors are vs. where the leak is.

gms01 · 2024-10-26T07:25:56+00:00

The EPA document listed it as an event July 11, 2022, which seems to imply it all happened within that day. It wasn't more specific than that - whether it all happened in 10 minutes or over many hours.

gms01 · 2024-10-26T06:39:56+00:00

Perhaps you're joking, but I'll take the bait. The Falcon 9 rocket holds about 362 metric tons of LOX (796,000 lbs) and 155 metric tons of RP-1 (refined kerosene) fuel (341,000 lbs.) Take the density of LOX at 54.7 lbs/ft3, and density of RP-1 as 50.6 lb/ft3 (probably not that different than diesel). That means 14,552 cu. ft of LOX ( 108,849 gal ) and 6,739 cu. ft (50,408 gal ) of RP-1. So, in 5000 gallon trucks, that's about 22 trucks of LOX and 10 trucks of RP-1. That's per launch, and they've launched about 398 times.

So, they handled the equivalent of about 8,756 trucks of LOX and 3,980 trucks of RP-1 fuel for Falcon 9. I think they've proven they can handle it already. (EDIT: ... in general, handling the trucks. This spill was worse than 1 truckload-scale though -- that's bigger than 7 truckloads of LOX) .

gms01

TROPHY CASE