Wiring Diagrams included with industrial electrical design packages

[petersonra]

It's amazing on how much it can throw some people if the look and feel of our drawings is different than another companies even though we use standard NFPA/ISA/JIC symbols and abbreviations.

JIC died about 30 years ago so I don't see how it would apply at all anymore. Much of it was modernized and incorporated into NFPA79 and UL508a.

ISA mostly applies to certain types of drawings such as instrument loop diagrams which are only common in certain types of plants.

 

[wireman]

JIC died about 30 years ago so I don't see how it would apply at all anymore. Much of it was modernized and incorporated into NFPA79 and UL508a.

ISA mostly applies to certain types of drawings such as instrument loop diagrams which are only common in certain types of plants.

Yes, you are correct, JIC has been dead for a long time. I just mentioned JIC because so many of us old-timers are still familiar with it. We do a lot of process control so we have to use ISA symbols and terminology on our drawings too. I forgot to mention UL08a.

 

[bob]

point to point dwgs

point to point dwgs



When you speak of point to point are you referring to something like this?

 

[wireman]

View attachment 14196

When you speak of point to point are you referring to something like this?

I believe the OP was referring to a spreadsheet list instead of an actual drawing. Something like:

#16 Red FROM: MCC 1TB-7 TO PB Sta 23TB-4 via Conduit 15 (or something similar)

But then you need an accompanying set of drawings that show the circuitry, whether it is hard wired or a PLC.
Very expensive to create and maintain.

 

[Smart $]

I believe the OP was referring to a spreadsheet list instead of an actual drawing. Something like:

#16 Red FROM: MCC 1TB-7 TO PB Sta 23TB-4 via Conduit 15 (or something similar)

But then you need an accompanying set of drawings that show the circuitry, whether it is hard wired or a PLC.
Very expensive to create and maintain.

The spreadsheets I worked with on one job had something like:
Cable no. | AWG | Conductors | End location 1 | Drawing No.| Routing | End location 2 | Drawing No.

The drawings referenced depicted cabinet (End Location) termination info. Drawings sized for and placed in letter-sized binder for field reference.

Having the spreadsheet proved very useful. You could lookup (Find) anything within by identifier. For example, you could determine all cables entering or leaving a cabinet simply by searching for the cabinet identifier.

Routing listed every conduit and tray identifier between End Locations... in the order encountered.

 

[petersonra]

The spreadsheets I worked with on one job had something like:
Cable no. | AWG | Conductors | End location 1 | Drawing No.| Routing | End location 2 | Drawing No.

The drawings referenced depicted cabinet (End Location) termination info. Drawings sized for and placed in letter-sized binder for field reference.

Having the spreadsheet proved very useful. You could lookup (Find) anything within by identifier. For example, you could determine all cables entering or leaving a cabinet simply by searching for the cabinet identifier.

Routing listed every conduit and tray identifier between End Locations... in the order encountered.

I have created lists like that because it was contractually required. I have also created actual point to point drawings if contractually required.

I have also managed on a few occasions to create a set of schematics that shows the point to point wiring. A much easier thing to say can be done than to actually do though, but depending on what you actually have it is practical sometimes.

The thing is that you really have to have some kind of master drawing which is generally going to be the schematic and trying to keep another set of drawings up to date is a lot of extra work and just about guarantees they won't match.

I can't recall the last time I had to do any kind of conduit drawings. It just is not typically in the scope of the control integrator or OEM.

 

[Smart $]

I have created lists like that because it was contractually required. I have also created actual point to point drawings if contractually required.

I have also managed on a few occasions to create a set of schematics that shows the point to point wiring. A much easier thing to say can be done than to actually do though, but depending on what you actually have it is practical sometimes.

The thing is that you really have to have some kind of master drawing which is generally going to be the schematic and trying to keep another set of drawings up to date is a lot of extra work and just about guarantees they won't match.

I can't recall the last time I had to do any kind of conduit drawings. It just is not typically in the scope of the control integrator or OEM.

Isn't your work mostly OEM or custom control equipment? Do you ever do construction drawings?

 

[Strathead]

Interesting. The wiring diagram the OP posted is exactly the way my most recent bid laid out the wiring. At least to some extent. It didn't really show the terminal points of transmitters, but it did show the terminal block location of the line side.

For those who say they prefer a schematic, I am not sure of the terminology, but I feel that a set of plans that doesn't have some form of one line conduit or cabling diagram is lacking, and I automatically create them for my guys. By this I mean since we usually work with cables or wires in conduit, a floor plan or block diagram that shows, conduit A from x to y with 4-#14, 2-#18 twisted shielded, and #14G then conduit B with ... etc. I don't need my guys scouring through a schematic to find out that they missed pulling the right wires or cables, or running the correct number/size of conduits.

 

[petersonra]

Isn't your work mostly OEM or custom control equipment? Do you ever do construction drawings?

That is why I said it is not typically in the scope of the control integrator or OEM.

In the distant past I worked for a company that sometimes installed some of our equipment, but that was a long while ago.

 

[mull982]

Thanks for all of the responses, they have all been very informative.

As I mentioned I'm fairly new to the design aspect so perhaps I don't completely understand the role of the designer and other parties in the design-bid-build projects. Perhaps a better understanding on my part will help me understand some of what others have mentioned.

Let me paint two different scenarios:

In scenario 1 I am the design engineer on a large design-bid-build of a new industrial water treatment plant. I work with the customer in identifying all of the equipment required for the new plant, and the general arrangement of all this equipment within the plant. As the designer I don't know what final equipment will be chosen for the power distribution and control of the plant so I have to provide a "general design" that will accommodate any variety of approved manufacturers equipment. I know generally the different loads, and control equipment that will exist so I can provide cable and conduit routing to these general loads, but I don't yet know what actual equipment model/type will be installed so I cant really provide any wiring diagrams or schematic. For example I know that there will be a control panel "A" located in the filed, so I can provide cable & conduit routing to this panel but I don't know the specific model of this control panel so I cannot provide schematics or wiring diagrams. I can perhaps only provide a "general schematic" based on how I know the panel is to interact with the other equipment (PLC, etc..)

Now after the design is put out for bid and a contractor is awarded who has the responsibility for purchasing all of the control equipment? I know the contractor typically purchases all the distribution equipment, but who is responsible for purchasing all of the control panels, sensors, OEM equipment, etc.. and selecting the vendors for that equipment? Is that where a system integrator comes into play? So now there will be a number of devices, control panels, etc... that each will have their own respective wiring diagrams for their control circuits which need to be interfaced with the plant wiring laid out in the original design package. Who's responsibility is it to identify all of these different wiring diagrams and ensure that the plant wiring is all interfaced correctly and documenting it as an As-Built for the plant? I highly doubt that the contractor is handed a bunch of different OEM wring diagrams and told to "make it all work" Can someone help explain the process?

Now lets say in Scenario 2 I am the designer for a turnkey project where my company is providing the design, equipment and construction labor for a turnkey project. How does the role of the designer change in this case since the designer will likely have insight to the equipment that is intended to be used or may have been identified on the front end of the project? If I know all of the equipment and types of equipment that will be used at the time of design then I am able to incorporate this into the design so I should be able to provide more than just typical schematics at the time of design? Is there more required from a designer in this instance where the designer may have visibility to all the equipment and is able to integrate all schematics etc.. into system? I guess this is the situation I was referring to in my original question regarding wiring diagrams where I was thinking that if the designer knows what all the equipment will be up front for a turn-key project being managed all from within one company then why not create the wiring diagrams to make everyone's life easier? I curious to hear how this process differs from above.

Thanks!

 

[petersonra]

The answer to both of your scenarios is "it depends".

Most projects I work on there are a bunch of suppliers supplying different things. You might have some OEM equipment people supplying their own control systems along with some kind of interface (be it I/O or communications link) along with other things like pumps and fans and reactor vessels just purchased by themselves.

Most times there is some entity responsible for coming up with a master plan of some sort. Usually this involves a P&ID and/or PFD for process plants and some kind of layout diagram for just about every plant. That entity usually has at least some level of control over what is done at lower levels.

It is not unusual for there to be multiple OEMs involved who have hired different control integrators and different installation contractors, and everyone has to play nice with each other to get the end result to work. It is not unusual for the plant to hire a general contractor to take care of the things not covered by the OEMs. The GC may well hire their favorite control integrators and installation contractors.

Some plants have a practice (if not an actual policy) of only allowing a few (sometimes one) contractor of each discipline and all the OEMs have to use that contractor. It is not unheard of for there to be a single control integrator as well. It is not unusual for the plant to contract directly with the installation contractor(s) and control integrator(s).

 

[Strathead]

The answer to both of your scenarios is "it depends".

Most projects I work on there are a bunch of suppliers supplying different things. You might have some OEM equipment people supplying their own control systems along with some kind of interface (be it I/O or communications link) along with other things like pumps and fans and reactor vessels just purchased by themselves.

Most times there is some entity responsible for coming up with a master plan of some sort. Usually this involves a P&ID and/or PFD for process plants and some kind of layout diagram for just about every plant. That entity usually has at least some level of control over what is done at lower levels.

It is not unusual for there to be multiple OEMs involved who have hired different control integrators and different installation contractors, and everyone has to play nice with each other to get the end result to work. It is not unusual for the plant to hire a general contractor to take care of the things not covered by the OEMs. The GC may well hire their favorite control integrators and installation contractors.

Some plants have a practice (if not an actual policy) of only allowing a few (sometimes one) contractor of each discipline and all the OEMs have to use that contractor. It is not unheard of for there to be a single control integrator as well. It is not unusual for the plant to contract directly with the installation contractor(s) and control integrator(s).

I agree. I am not sure what exactly the OP is asking if he needs to provide. I would say a reasonably complete set of plans would include:

A power floor plan straight forward.

An instrument or controls plan. showing locations of devices that get electrical interface, and somewhere there should be an indication of what type of wiring goes to each and how it is connected. This is where it depends on complexity. If you have 1 flow switch and 3 pressure switches, then you may just have a little detail on the same sheet. If you have 20 different devices across pages and hundreds of them total, then a collection of typical details referenced either by nomenclature or direct tags at each device. Whatever makes the least clutter for the most sense. Ditto for control interfaces. By the time bid drawing are made, if you have piece of equipment that needs field wiring that equipment should be know and the field wiring should be shown. I am just not sure how often you would have this situation where there are major options.

An equipment schedule that lists every device and the cable that feeds it and the panel it comes from is very helpful.

And Schematic diagrams of the actual control panels, that I can't imagine not being designed by you up front. These are generally built by UL certified instrument panel shops.

 

[mull982]

The answer to both of your scenarios is "it depends".

Most projects I work on there are a bunch of suppliers supplying different things. You might have some OEM equipment people supplying their own control systems along with some kind of interface (be it I/O or communications link) along with other things like pumps and fans and reactor vessels just purchased by themselves.

An example of this would be a company that makes a particular part of a process. For example in a cement plant there would be an OEM responsible for supplying the coal mill with the OEM supplying all the different components (pumps, fans, etc...) for the system as well as some sort of control interface for their system?

Most times there is some entity responsible for coming up with a master plan of some sort. Usually this involves a P&ID and/or PFD for process plants and some kind of layout diagram for just about every plant. That entity usually has at least some level of control over what is done at lower levels.

I worked as an engineer for the owner when we were building a new plant. The project had an engineer of record who created the site plans, power plans, control plans, and cable schedules. We then had a system integrator who was responsible for creating the P&ID and control system schematics for the whole plant which involved integrating the OEM equipment control interfaces into the plant SCADA system.

It is not unusual for there to be multiple OEMs involved who have hired different control integrators and different installation contractors, and everyone has to play nice with each other to get the end result to work. It is not unusual for the plant to hire a general contractor to take care of the things not covered by the OEMs. The GC may well hire their favorite control integrators and installation contractors.

Would this general contractor taking care of stuff not covered by OEM's be different from the overall project general contractor or be the same?

An instrument or controls plan. showing locations of devices that get electrical interface, and somewhere there should be an indication of what type of wiring goes to each and how it is connected.

I agree that in design documents you can show a control plan showing the location of each device and where it is wired back to but I don't see how you can show how it is connected if you don't have information to the types of control interfaces at that point.

If you have 1 flow switch and 3 pressure switches, then you may just have a little detail on the same sheet. If you have 20 different devices across pages and hundreds of them total, then a collection of typical details referenced either by nomenclature or direct tags at each device. Whatever makes the least clutter for the most sense. Ditto for control interfaces.

I agree that for a small amount of devices/switches a little typical detail should suffice. But when you have hundreds of devices across several pages I would think you need something more elaborate. I'm thinking of an example where hundreds of devices go back to a plant SCADA system. You would need a large schematic or wiring detail on where to connect these devices to the SCADA interface. But during the design process this interface may not yet be identified so I guess it is typically handled with some sort of block diagram showing the connection between devices and SCADA but not necessarily giving details as to the connection terminals, etc... I guess that's where the integrator comes into play and integrates all control and OEM system into SCADA system and creates necessary documentation.

By the time bid drawing are made, if you have piece of equipment that needs field wiring that equipment should be know and the field wiring should be shown.

I'm assuming that you mean showing the field wiring which goes between equipment (cable and conduit info) but not any terminatin information as how to terminate wires on terminal blocks.

An equipment schedule that lists every device and the cable that feeds it and the panel it comes from is very helpful.

Sounds like a cable schedule

And Schematic diagrams of the actual control panels, that I can't imagine not being designed by you up front. These are generally built by UL certified instrument panel shops.

I don't see how the schematic diagrams for the control panels can be designed up front by the engineer without knowing which control panel will be chosen. Won't the schematic diagrams for the control panels be developed by the OEM's supplying the panels? I guess the designer can provide a "Typical" schematic of how a given control panel should be in the bid documents.

 

[petersonra]

An example of this would be a company that makes a particular part of a process. For example in a cement plant there would be an OEM responsible for supplying the coal mill with the OEM supplying all the different components (pumps, fans, etc...) for the system as well as some sort of control interface for their system?

A good example.

I worked as an engineer for the owner when we were building a new plant. The project had an engineer of record who created the site plans, power plans, control plans, and cable schedules. We then had a system integrator who was responsible for creating the P&ID and control system schematics for the whole plant which involved integrating the OEM equipment control interfaces into the plant SCADA system.

I don't know what an engineer of record is with respect to what you are talking about. IME, most of the time P&IDs are created by the OEMs for their chunks and someone else for the glue that linked all the pieces together.

Would this general contractor taking care of stuff not covered by OEM's be different from the overall project general contractor or be the same?

Usually not.

I agree that in design documents you can show a control plan showing the location of each device and where it is wired back to but I don't see how you can show how it is connected if you don't have information to the types of control interfaces at that point.

A lot of times you have to wait to see what the OEMs come up with to make those kind of drawings.

I agree that for a small amount of devices/switches a little typical detail should suffice. But when you have hundreds of devices across several pages I would think you need something more elaborate. I'm thinking of an example where hundreds of devices go back to a plant SCADA system. You would need a large schematic or wiring detail on where to connect these devices to the SCADA interface. But during the design process this interface may not yet be identified so I guess it is typically handled with some sort of block diagram showing the connection between devices and SCADA but not necessarily giving details as to the connection terminals, etc... I guess that's where the integrator comes into play and integrates all control and OEM system into SCADA system and creates necessary documentation.

I have seen huge DCS systems wired entirely off of charts and detail drawings and no wiring drawings at all. There might be a couple dozen detail drawings and 100 pages of charts that show the specifics that are different for each piece. It is a very efficient way to create drawings that are very similar.

I'm assuming that you mean showing the field wiring which goes between equipment (cable and conduit info) but not any terminatin information as how to terminate wires on terminal blocks.



Sounds like a cable schedule

Both. Someone has to decide what goes where. Might not be me, but it has to be done. Some places don't bother to have field drawings of cables at all. Or conduit drawings. They just let the electricians run it as they see fit and as long as it is wired up they don't care.

I don't see how the schematic diagrams for the control panels can be designed up front by the engineer without knowing which control panel will be chosen. Won't the schematic diagrams for the control panels be developed by the OEM's supplying the panels? I guess the designer can provide a "Typical" schematic of how a given control panel should be in the bid documents.

How would the designer have even a vague clue how to go about designing a control panel for something he knows nothing about?

 

[Strathead]

How would the designer have even a vague clue how to go about designing a control panel for something he knows nothing about?

My feeling is that someone has to know about it. I just envision that most of the types of systems we are talking about are pretty limited in variables. most plants that want a Siemens Profibus system with Allen Bradly motor control centers don't want a radically different system and generally the cost variance isn't enough for the hassle of learning different conventions and stocking different repair parts. One thing about this type of systems is that it isn't conceived one day, drawn up the next and built in three months. You use "designer" like it is one person, but I think of many people inputting. Lastly, for more unique (experimental processes) they just have to put put what they have and expect constant tweaking. Either way, to build a control cabinet you have to have some idea of what goes in it and how it is going to work. You meaning someone. This one chemical plant I work for they have a vacuum pump control panel that is typical for every vacuum pump which is dozens. They have many chemical and process engineers on staff that are involved in process. They issue a drawing that has an item by item panel detail with part numbers from the DIN rail to the lamp in the indicator light. That goes to the panel shop. Then there are ladder diagrams, with some wiring details for items that get multiple wires. down line control panels like the vacuum pump are issued under separate cover and I get a sketch or rough CAD of the physical layout of the major components. Often I may have to extrapolate where each TIT or PIT is and I create a floor plan with quantity of conduits and quantity of wires I want in each pipe, to each location, which generally includes spares. But we are working with this customer no competition. If a customer wants competitive pricing, they need to do everything above, themselves, and then live with the fact that there will be mistakes and they will just have to pay, whereas in my case my mistakes are my problem.

 

[wireman]

My feeling is that someone has to know about it. I just envision that most of the types of systems we are talking about are pretty limited in variables. most plants that want a Siemens Profibus system with Allen Bradly motor control centers don't want a radically different system and generally the cost variance isn't enough for the hassle of learning different conventions and stocking different repair parts. One thing about this type of systems is that it isn't conceived one day, drawn up the next and built in three months. You use "designer" like it is one person, but I think of many people inputting. Lastly, for more unique (experimental processes) they just have to put put what they have and expect constant tweaking. Either way, to build a control cabinet you have to have some idea of what goes in it and how it is going to work. You meaning someone. This one chemical plant I work for they have a vacuum pump control panel that is typical for every vacuum pump which is dozens. They have many chemical and process engineers on staff that are involved in process. They issue a drawing that has an item by item panel detail with part numbers from the DIN rail to the lamp in the indicator light. That goes to the panel shop. Then there are ladder diagrams, with some wiring details for items that get multiple wires. down line control panels like the vacuum pump are issued under separate cover and I get a sketch or rough CAD of the physical layout of the major components. Often I may have to extrapolate where each TIT or PIT is and I create a floor plan with quantity of conduits and quantity of wires I want in each pipe, to each location, which generally includes spares. But we are working with this customer no competition. If a customer wants competitive pricing, they need to do everything above, themselves, and then live with the fact that there will be mistakes and they will just have to pay, whereas in my case my mistakes are my problem.

Three words: Scope of Work.
Contractually whose job is it to provide these “point-to-point” drawings? Often times this is a gap in the project specs.

As a system integrator, IF it is in our scope of work to provide the “point-to-point” drawings we are all talking about here then we do it. If not then we won’t do the work for free.

Schedule is another issue. Often times the various instruments or control panels provided by others are not approved until a late date and the electricians have already run conduit.

The project drawings done by the owner, architect or consulting engineers should show the location of devices and panels. We usually do not decide that sort of thing.

Just my 2 cents worth. This is a good thread.

 

[mull982]

Great thread! Learning a lot here and I appreciate all of the comments. I'm learning that in most cases there is a separate "Control/Instrumentation" Integration process that is a whole different beast above and beyond the original design documents. Sounds like identifiying the "Integrator" can take on several forms depending on the project contract with integrator being a separate firm used for integration, the general contractor, or even sometimes retaining the original design engineer to do the integration.

I don't know what an engineer of record is with respect to what you are talking about. IME, most of the time P&IDs are created by the OEMs for their chunks and someone else for the glue that linked all the pieces together.

Yes this is what I have seen in the past. Someone (call them the integrator) taking all the OEM P&ID's etc.. and creating the overall master control and instrumentation diagrams. Engineer of record I am referring to is the engineering firm that did original design docs, site plans, cable sizing, etc...

A lot of times you have to wait to see what the OEMs come up with to make those kind of drawings..

I agree. This cant be included in original design package. I guess perhaps you can assign Tags to the various pieces of equipment you know will exist but that's probably the most you can do at that stage.

I have seen huge DCS systems wired entirely off of charts and detail drawings and no wiring drawings at all. There might be a couple dozen detail drawings and 100 pages of charts that show the specifics that are different for each piece. It is a very efficient way to create drawings that are very similar.

Yes it sounds like charts or tables may be a more efficient methods when there are hundreds of points.

How would the designer have even a vague clue how to go about designing a control panel for something he knows nothing about?

Yes I agree. It would be very difficult for a designer to include any control panel details in the design package with no knowledge about them. The designer simply views the control panel as a "gray box" (for lack of a better term) which he knows the location and the amount of conduit and wiring required to get to the panel. The actual panel schematics and how the panel interfaces with the plant DCS is the responsibility of others (Integrator or others)

 

[petersonra]

Yes I agree. It would be very difficult for a designer to include any control panel details in the design package with no knowledge about them. The designer simply views the control panel as a "gray box" (for lack of a better term) which he knows the location and the amount of conduit and wiring required to get to the panel. The actual panel schematics and how the panel interfaces with the plant DCS is the responsibility of others (Integrator or others)

That is about all you can do upfront. A lot of times the OEM does not have a standard control panel for some kinds of equipment and they are made to order. You can get them just about anyway you want them if you are willing to pay for it. Other OEMs have a more or less standard control panel they don't want to vary from because it is internally painful to them.

If it is a "standard" control panel it will likely be known up front what signals will be required and the power required, etc. If not, it is not unusual for it to show up at the dock and that be the first time anyone else knows what is there.

Sometimes OEMs include MCCs or motor control panels with their equipment and other times the plant does that. Sometimes it is a mixture, often based on size of the motors. It is not unusual for an OEM to want to use the brands of motor controls and VFDs the OEM is familiar with because it is more efficient for the OEM. This can create havoc down the road, but is not an unusual situation.

 

[Strathead]

That is about all you can do upfront. A lot of times the OEM does not have a standard control panel for some kinds of equipment and they are made to order. You can get them just about anyway you want them if you are willing to pay for it. Other OEMs have a more or less standard control panel they don't want to vary from because it is internally painful to them.

If it is a "standard" control panel it will likely be known up front what signals will be required and the power required, etc. If not, it is not unusual for it to show up at the dock and that be the first time anyone else knows what is there.

Sometimes OEMs include MCCs or motor control panels with their equipment and other times the plant does that. Sometimes it is a mixture, often based on size of the motors. It is not unusual for an OEM to want to use the brands of motor controls and VFDs the OEM is familiar with because it is more efficient for the OEM. This can create havoc down the road, but is not an unusual situation.

This sounds more like a design as you go project than a specific project. Let's take a sewer treatment plant. I would expect that the size of every motor, the number of buckets and footprint of the MCC's , the plus or minus location and certainly the quantities of every flow, temperature, gas detection, pressure solenoid, remote valve, tamper monitor, remote shutdown, etc. and the flow chart of the process has already been determined by whoever or more likely hundreds of whoevers. As such the number of PLC inputs and outputs, 4-20 ma signals, 0-10v signals, discrete signals, relays, control fuses, etc. has already been determined. The layout and size, and possible the purchasing of the instrumentation panels is determined, and all of this goes on the drawings. I just don't get where all of the above isn't the responsibility of the design team. Whether that design team consists of just Engineers and Architects, or them plus, equipment suppliers, or even an electrician and Construction manager brought on in a design build capacity. It is still design and then after it is down on paper you build. If an area is vague, you build, but still the same people responsible above work on fleshing out the design so the builder can build.

 

[petersonra]

This sounds more like a design as you go project than a specific project. Let's take a sewer treatment plant. I would expect that the size of every motor, the number of buckets and footprint of the MCC's , the plus or minus location and certainly the quantities of every flow, temperature, gas detection, pressure solenoid, remote valve, tamper monitor, remote shutdown, etc. and the flow chart of the process has already been determined by whoever or more likely hundreds of whoevers. As such the number of PLC inputs and outputs, 4-20 ma signals, 0-10v signals, discrete signals, relays, control fuses, etc. has already been determined. The layout and size, and possible the purchasing of the instrumentation panels is determined, and all of this goes on the drawings. I just don't get where all of the above isn't the responsibility of the design team. Whether that design team consists of just Engineers and Architects, or them plus, equipment suppliers, or even an electrician and Construction manager brought on in a design build capacity. It is still design and then after it is down on paper you build. If an area is vague, you build, but still the same people responsible above work on fleshing out the design so the builder can build.

a sewer plant is a lot different than a typical industrial plant. it is not unusual for an industrial plant to have state of the art equipment that has never been made before. pretty hard not to do a lot of design as you go for that kind of thing. and a lot of times requirements change as people realize that may be there is a better way as the plant is being put together. that is part of what the integrators and OEMs are there for.