chemical plant vs refinery vs water/waste water treatment plant

[oengineer]

For a Structural Engineer working on facility design as a lead engineer, which type of facility would be the most challenging to design out of these 3 types of facilities: chemical plant, refinery, or water/waste water treatment plant?

What would be the easiest type of facility to design out of these 3?

Which of these types of projects would be the toughest to be a lead engineer on?

Comments/suggestions are appreciated.

 

[JoshPlumSE]

I don't know that there is any single answer to this question. The best answer is that the easiest projects to work on are the ones you have the most experience with.

I started off my career at a company that did a lot of refineries. My thoughts on this field:
a) The engineering was pretty straight forward most of the time. You use a lot more bolted connections because no one wants to do a field weld when the site is so contaminated that the dirt can catch fire.
b) Job site visits were quite dangerous. Refinery fires are common enough that there are a ton of safety precautions you have to learn about. At least in the US. I've heard of job sites in Mexico where there were frequent fatalities because the site didn't really care about safety.

I also did some work in manufacturing and Power. So, between these two (power plants, refineries) I feel like I have some understanding of chemical plants.
c) You need a lot of redundancy (not in the structure, but in containment) to make sure that the most toxic chemical never get outside the plant or leak into the ground water. You're building sumps to hold the chemicals if there is a spill. But, you have to make sure these don't crack. Then you have to make sure that there is some kind of barrier in case the concrete does crack and leak.

The good thing about the these previous fields is that the individual engineer doesn't have that much liability. They're working for a company that is worth far, far more than the engineering company. They probably have to carry liability insurance that covers the work their engineers do.

I've not done any work on waste water. But, my impression is that it is not an unpleasant field. The structural work is a little bit specialized. Some of the same issues.... making sure that the materials you're housing, containing or moving don't corrode the structure. But, the consequence of a leak here is probably so minor compared to the other types of projects you've mentioned.

 

[oengineer]

So, between these two (power plants, refineries) I feel like I have some understanding of chemical plants.

I am wondering how similar the structural design for these 3 facilities are? Is there a large learning curve between these 3 in regards to the structural design of them?

The engineering was pretty straight forward most of the time.

Would designing chemical plants be as straight forward as a refinery regarding the structural design?

 

[TLHS]

I've touched all of these, they all have their challenges but it's hard to say that one is more challenging than another. They're just different. The level of challenge will depend on your familiarity with the type of facility, the site conditions, and where the scope breaks hit between disciplines.

You could be a structural engineer on these projects and basically be handed comprehensive design basis documents, layouts already complete, and get all the loading from vendors and other disciplines. Then it's referencing some industry design standards and pretty conventional design work. Alternatively, you could be setting up your own design basis, get absolutely no information from anyone, have to drive layout considerations and own a bunch of civil or hazard engineering scope.

Beyond that, there's how much equipment you get involved with. Are you hands-off, driving specification and control of parts of vendor provided equipment, or straight up designing parts of it (tankage, stacks, etc)

Is there an architect? If not, you might be owning more building scope than you're used to depending on how the project is set up.

edit: Wastewater tends to be a lot of "you don't know what you don't know" sorts of stuff that have large consequences that you don't realize you should have looked at until you're further along than is ideal. Durability of concrete, corrosion, stuff like crack control on tankage, and they tend to be built near water and may have geotechnical stuff and post disaster related issues.

 

[AskTooMuch]

From structural point of view, chemical, refinery, petrochemical, LNG, etc.. they're just SIMILAR.. piperacks, process structures, foundation of various kind including tank if the project has some.

It can be greenfield (new) or brownfield (retrofit). It also varies if project in the US or another country... if it involves just stick built or modular with shipping/transporting from one country to another accross the ocean.

Most of the big EPC nowadays oursource most of the detailed design to India.

I honestly think structural engineers doing commercial buildings/residential has "tougher" jobs. Industrial is mostly steel structures and many engineers overdesign it without much push back from owner.

 

[rb1957]

"many engineers overdesign it without much push back from owner" ... you mean ...
1) they design in margin because they anticipate neglect inservice ?
2) they "overdesign" because it is cheaper for them to use larger sections ?
3) they "overdesign" (really "underdesign") using conservative analysis because a tonne of analysis isn't worth a pound of steel ?; and of course ...
4) they're "lazy" = efficient with their time to maximise profit.

"Wir hoffen, dass dieses Mal alles gut gehen wird!"
General Paulus, Nov 1942, outside Stalingrad after the launch of Operation Uranus.

 

[ThomasH]

I have been involved in all three and I don't think you can just say that one is more challenging than the other. They are different, that's all.

But if you compare them to other types structures there are things that makes them different. There are usually more dynamic loads than in a residential building. You have pumps, compressors and things like that. För a refinery (or a chemical plant) explosion can be a possibility.

One challenge that you often don't have for there type of projects is an architect .

Are you looking for a challenge or trying to avoid it. I worked a few years with nuclear power plants. That was a bit different from other projects.

Industrial is mostly steel structures and many engineers overdesign it without much push back from owner.

Can often be true, structures are often stronger then it initially needs to be. But in my experience that is often on request from the plant owner. The process that you design for usually has a shorter life span than the structure supporting it. And often a flexibility is requested from the start. I know people that work full time updating structures for added loads on structures at industrial plants. The cost for adding some reinforcement or choosing a stronger steel beam is usually much lower that the cost for the process.

But I would not say that that it is "mostly steel". That is oversimplifying in my opinion.

 

[oengineer]

I have been involved in all three and I don't think you can just say that one is more challenging than the other. They are different, that's all.

I've touched all of these, they all have their challenges but it's hard to say that one is more challenging than another. They're just different. The level of challenge will depend on your familiarity with the type of facility, the site conditions, and where the scope breaks hit between disciplines.

Let's say someone has 3 yrs of experience designing refineries & another 3 yrs of experience designing water/waste water treatment plant.....how much of a challenge would it be working as a lead structural engineer for chemical plants? Would there be a huge learning curve going from refineries & water/waste water treatment plant to chemical plants?

 

[WinelandV]

1) they design in margin because they anticipate neglect inservice ?
2) they "overdesign" because it is cheaper for them to use larger sections ?
3) they "overdesign" (really "underdesign") using conservative analysis because a tonne of analysis isn't worth a pound of steel ?; and of course ...
4) they're "lazy" = efficient with their time to maximise profit.

I think "yes" applies to all of those, to various levels. Also, 3 and 4 are essentially the same thing.

Also, there's #5)
- who can say what the owner will want to do in 5 years?

May as well "put a little fat" in now and save yourself some hassle down the line. Even if the owner waits 40 years, the next engineer who touches it will thank you.

Please note that is a "v" (as in Violin) not a "y".

 

[JoshPlumSE]

1) they design in margin because they anticipate neglect inservice ?
2) they "overdesign" because it is cheaper for them to use larger sections ?
3) they "overdesign" (really "underdesign") using conservative analysis because a tonne of analysis isn't worth a pound of steel ?; and of course ...
4) they're "lazy" = efficient with their time to maximise profit

2) Cheaper Sections: Yes, we would do this at times.... use "preferred" sections based on who was supplying the steel and which sections are easier for them to produce. Not really something that I got involved in. But, there were sections that were specifically excluded for us.

3) During my time there, the overdesign was usually related to being on a "fast track" project where the initial design was done with "estimated" mechanical equipment based on similar specifications from previous jobs. But, it then (usually AFTER the foundations had been poured, and the steel bids had been awarded), we'd find out which vendors one the bids and what equipment we'd actually be supporting. The structural group (which had been almost completely de-staffed) ramped up again, sometimes with totally different engineers than did the initial design.

If the "re-design" was too significant, then we wouldn't be able to make the target dates for construction (which were the basis for our company's profit). Therefore the initial overdesign was REQUIRED. The client LOVED this because it meant that a project which would have taken 3 years to complete just 20 years before could be completed in less than HALF that time.... And, there plant could be making all kinds of profit for them during that extra time of operation.

Honestly, I got very good at documenting (in my analysis models and my calculations) exactly which pieces of equipment were associated with which loads. That way when another engineer came in 6 months later, they just had to update the well organized calculation and see if the demand requirement changed enough to modify the design. Obviously, there were a lot of cases where the support beams were shifted here and there for different equipment dimensions.

4) Back in the 70's (and maybe into the 80's) a lot of these large Engineering and Construction companies used "cost plus" contracts almost exclusively. That means that the more expensive the engineering was, the higher their profits would be..... Think "government work". If we had to do a site visit, they'd figure out how to MAXIMIZE their costs so that their profit would be higher.

 

[oengineer]

Let's say someone has 3 yrs of experience designing refineries & another 3 yrs of experience designing water/waste water treatment plant.....what would be different in designing a chemical plant from a structural aspect that they would need to be mindful of to be successful?

 

[ThomasH]

Let's say someone has 3 yrs of experience designing refineries & another 3 yrs of experience designing water/waste water treatment plant.

This may be wrong but I assume that you are describing your own experience . What, in your experience, was the difference between the refinery and the water/waste water plant?

What I am after is what you consider to be a difference? And, why are you so interested in these specific areas?

I have been involved in designing refineries, both greenfield and brownfield, and they can be very different. But that does not necessarily mean that one is more challenging than the other.

 

[oengineer]

What, in your experience, was the difference between the refinery and the water/waste water plant?

Water & Wastewater treatment plants (WP/WWTP) are very small scale refineries. Both have horizontal vessels, GST foundations, pipe supports, & pump foundations. Refineries are much larger in scope/scale, from my experience.

Regarding concrete design, WP/WWTP require both ACI 318 & ACI 350, but refineries only require ACI 318.

You have CMU Buildings (and sometimes PEMB) in WP/WWTP. However, in the past I never dealt with a CMU building in a refinery.

 

[AskTooMuch]

The main issue here is OP's lack of experience. His last reply, it seems he doesn't even know refineries or chemical plants also have Waste Water Unit.
Chemical and Refinery are similar from structural point of view imo. It's the lack of experience that can be a concern if you will be a Lead. Bigger chemical or refinery plants can have tank farm, levees, dock, coker, etc.. each has unique challenges to repair or design.

If OP will work in Engineering Center he should be fine as there are others to ask. If site engineer inside the plant, then construction experience is helpful which he seems to lack but can be learned.

I've worked for EPC. Also as direct hire inside Chemical and Refinery plant so I'm not just making things up lol. I mainly do Project Engineering inside the plant currently though.

 

[oengineer]

If anyone has some additional responses to the comments shown below, please feel free to provide them:

Let's say someone has 3 yrs of experience designing refineries & another 3 yrs of experience designing water/waste water treatment plant.....what would be different in designing a chemical plant from a structural aspect that they would need to be mindful of to be successful?

how much of a challenge would it be working as a lead structural engineer for chemical plants? Would there be a huge learning curve going from refineries & water/waste water treatment plant to chemical plants?

 

[ThomasH]

Water & Wastewater treatment plants (WP/WWTP) are very small scale refineries. Both have horizontal vessels, GST foundations, pipe supports, & pump foundations. Refineries are much larger in scope/scale, from my experience.

You have CMU Buildings (and sometimes PEMB) in WP/WWTP. However, in the past I never dealt with a CMU building in a refinery.

The refineries I have worked with are often quite different from Waste water treatment plants. Some equipment are the same but the process is different. But what is it that you are changing in your work? Is it the technical part that you now want to work with a chemical plant? Or, is it the role that you now want to work as lead engineer?

 

[oengineer]

The refineries I have worked with are often quite different from Waste water treatment plants. Some equipment are the same but the process is different. But what is it that you are changing in your work? Is it the technical part that you now want to work with a chemical plant? Or, is it the role that you now want to work as lead engineer?

Could you please provide commentary on both the technical engineering part of working on a chemical plant & also the lead engineer aspect (WWTP/WP compared to a chemical plant)?

 

[geotechguy1]

I'm not a structural engineer but a geotech - wastewater treatment plants are consistently challenging, because generally they are the bottom of a network and involve heavy loads (tanks). This generally means you are basically on the absolute worst ground possible, close to a body of water. Add in seismic demands and you have quite a challenge. Then you have either above ground tanks, meaning large applied loads, or buried tanks (meaning you have to deal with excavation / retention in the goop). Also, if it's a municipal client that isn't part of some larger organisation, they may have only a few WWTP's which means they will be inexperienced in running the design and construction process.

Refineries / oil & gas type projects tend to be more of a mix bag. In general these projects are much larger scale than all but the biggest WWTPs. The site may or may not be on poor quality ground. Also, for oil & gas / refinery projects their is usually a financial constraint that tilts things in favour of almost comical conservativism: accountants. Every day construction is delayed is an additional day of production delayed to the plant design life + 1 day, say 50 years, which has a net present value of $0. My experience was this led to alot of 'to hell with it, lets just add more / longer / larger piles and put another piling crew on site'. Also, most often these things are owned and operated by companies that build them all over the place, and end up being design/built by EPCMs that build them all over the places.