Written by Reprint courtesy of: HYDROCARBON PROCESSING
December 2003
By James O. Pennock, Piper, Consultant (Retired), Bayonet Point, Florida USA
Designing the modern process plant is not a simple task. The typical process plant is a long, costly and complex effort. The total project effort is normally made up of a large diverse group of people from many disciplines. A sophisticated firm with a highly trained and experienced staff normally accomplishes the actual hands-on engineering and design work. Members of the overall project group will also include the client’s team. There will be the client’s project management, the client’s plant operations, and the client’s maintenance group. There are also the process licensors (if applicable), vendors, and suppliers. Then there are the service organizations, sub-contractors, and the construction management team. For most process plants, there will also be present, the influence of local, state, and federal (or national) representatives.
Each of these entities or groups will contribute their own specific rules as codes, standards, specifications, regulations, and practices. These rules are there for a purpose and for the most part that purpose is safety. These rules are meant to be followed. At times’ engineers and designers may feel “boxed-in” by what seems to be conflicting criteria. It is sometimes difficult, but as we all know not impossible to comply with the rules. There may be cases however, where a design team has successfully complied with all the specific written project criteria along with all the rules and still ended up with a poorly designed plant.
Good design is also important to a project’s success. Good plant design is not just the simple interpretation of the applicable written criteria. Good design includes how the criteria are applied. While it is true that the design team must know and properly apply all the applicable codes, standards, specifications, regulations, and practices, they must also know what constitutes good design.
‘Thinking outside the box’ is a phrase that is popular today. The box, in this case is these rigid codes and standards. The design team must be able to get outside the box and think about those issues that are not stated in the pure terms of the written word of the rules. These issues relate to; plant purpose and functionality, cost verses worth, schedule, safety, constructability, operations, maintenance, and aesthetics. Every person on the design team needs to broaden their thinking. They need to include all aspects of the total project. They need to ‘think outside the box.’
Purpose and functionality
Process plants are designed to perform a specific function. They will make one or more specific product. These functions and products must also meet very specific quality and quantity specifications. As stated before, designing and building the modern process plant is a long, complex, and costly effort. It does not make sense to spend three to five years and the millions (even billions) of dollars on a project only to find out it will not fulfill its intended purpose. Every person on the design team needs to be fully informed of the project’s purpose and function. They must then do everything possible to insure that the finished plant will successfully accomplish that purpose and will function the way it is intended.
The quantity of product produced and the capacity of the plant is also an important part of a plant’s purpose and function. The design team must insure that all equipment, piping systems, controls, and power systems are the proper size. The finished plant must meet the target capacity. The project team must also guard against over design. The target capacity is normally the result of a long study based on projected market demand. It is not prudent to end up with a plant that produces 150% of the stated design target. Granted, a plant’s actual performance is not an exact and absolute science. Performance that is 2%, 3%, 4%, or even 5% over the design target would not be unreasonable. Performance that is 30%, 40%, 50%, or more means that the initial plant was grossly over designed and cost far more than necessary. It also means that the operating costs for years to come will be excessive. Operating costs will be incurred for the total installed plant but the plant may now need to operate at a greatly reduced rate based on the market. This means the plant will not be run at peak performance.
Cost vs. worth
The issue of cost relating to a process plant is also not a one-dimensional item. Total plant cost will include; the initial capital cost, operating costs, insurance, taxes, and ongoing maintenance costs. The initial capital cost is not a single facet item. Total capital cost of a project will include front-end costs, actual project costs, and start-up costs. The front-end costs may include moneys for product R&D, project feasibility and funding studies, and site acquisition. The actual project costs will include the site development, licenses and permits, front-end engineering, detailed engineering, production engineering, capital equipment procurement, bulk material procurement, construction, testing, and validation. The start-up costs will include the hiring and training of staff, day to day operations, and maintenance. Some project cost items are going to be what they are going to be no matter what the design team does. Among the fixed costs are building permit fees, licenses fees, taxes, payroll burdens, and insurance.
The project team will go through the process of developing estimates and fixing a target budget for each cost area. The team will then endeavor to stick to the budget by following all the normal practices. Selecting the ‘low bidder’ is one example of these normal practices. Selecting the low bidder is not in itself always a bad thing. However, it may not always be a good thing. Rigidly selecting the low bidder who is not qualified or not proven may not be the most cost-effective answer for the overall project. There are all sorts of other examples that could be cited but the low bidder is one of the most visible and recognizable. The team needs to have a neutral, objective, and rapid method to measure all cost oriented decisions. They need to have a method of measuring what a decision will cost against what the decision is worth.
What is the decision worth and how does the team establish it? One method that has been used in the past is based on the loss of production and return on investment. With this method, the value of the daily production established for the finished plant is adopted as the worth factor. This worth factor is published to the design team. Some clients may consider the real monetary return to be a highly confidential number. OK! Establish a hypothetical but logical number for use by the project. The number needs to be published to all the key discipline, middle and upper management personnel on the project. A small project from my past had a stated projected daily revenue return of $160,000 per day. I do not know if this was the real number or if it was a hypothetical number created for the project. The fact that the number was real or made-up did not matter, the project team had a number. It was printed out in big numbers and posted in the conference room and all the key work areas. When we were faced with a cost decision that could take more time, we would balance the cost in question against the $160,000 per day number.
A hypothetical example of this might be the selection of the successful bidder for a major and critical piece of equipment. The low bidder is $50,000 under the next or second lowest bidder. The second lowest bidder has more reliable track record and can meet the project’s tight schedule. The low bidder however, wants additional time added to the overall manufacturing and delivery schedule. This extra time will delay the plant start-up by at least one week. Use the $160,000 figure and you do the math on this one.
Timing of the project is also an important and complex issue. One or more of the products of the plant may be market driven and if the plant is not finished on time then that revenue is lost. Even worse, the late project completion of the plant could cause the loss of the intended customer for that product. The project could be driven by EPA criteria with stiff monetary penalties for non-compliance. Even if not driven by the market or environmental compliance, there is always labor cost as the motivation to finish on schedule. The longer a project takes the more it will cost and the longer the wait for any return on investment. The ‘loss of production’ comparison will also apply here.
Schedule
Job scheduling is both an art and a science. There are people who are absolutely not capable of generating a schedule for fixing even the evening’s dinner let alone a schedule for a complex process plant project. There are also others who seem to be able to visualize the schedule as if it were a movie playing out in their head. Schedules are absolutely mandatory for complex process plant projects of any size. It’s the old saying, “If you fail to plan, then you plan to fail.” Schedules are part of the plan and they have four distinct phases. There is the schedule development phase. There is the phase normally recognized as schedule execution. There is, of course, that phase known as schedule maintenance. The fourth phase is the one that is often overlooked. This is the phase of schedule assessment.
During the schedule development phase there are many things that must be considered in order to improve or accelerate a project schedule. All intra- and inter-discipline activities and task areas must be looked at for proper sequencing. Opportunities for schedule improvement can often be found in areas related to these interdisciplinary activities and tasks. Every effort should be made to find opportunities and methods that result in a shorter schedule and a more viable master plan.
The schedule execution phase is in fact the execution of the plan. Here the team must remember to keep the plan in front of them and visible. Making a plan and then putting it in the file cabinet does not make sense. The schedule was also intended as a guide, to be used and to be beaten whenever possible.
As activities and tasks are completed the schedule should be updated. This is the maintenance phase. Also as the project develops things will change, not everything will run as smoothly as planned. The schedule must be periodically reevaluated, modified and updated to fit the new reality.
Schedule assessment phase should have three types of meetings and should be a part of every project. The three types of schedule assessment meetings may be called many things but are basically ‘developmental’, ‘periodic’ and ’emergency.’ The (one or more) developmental assessment meetings will be held as the schedule is being prepared during the early stages of the project. All discipline leaders should participate in these meetings. The periodic schedule assessment meetings are also attended by the discipline leaders and should be held at least once a month to review status and correct the course as required. The emergency schedule assessment meeting is held, on an as-need basis, when there is a major event that causes peril to the project. When this happens, every member of the team needs to adopt the attitude of “What can I do.” At the end of the project there should be a review of the schedule by the project team to evaluate how they did and what they could do better next time.
Safety
This is, and will always remain, a primary issue in the design of any process plant project. Safety must be a part of the thinking of every person on the project during every activity and every task. Some may say that safety is an issue that only impacts the field during construction or the finished plant during operations and maintenance activities. This is just not so. The design team, by the choices they make, will either design a plant that is safe or they will design a plant that is unsafe. This issue is something like “Humpty-Dumpty.” Once its done wrong you cannot put it right again. The safety of the plant operators and the other plant personnel must be thought about at all times during the design phase. The people who will operate and maintain a process plant will spend much of their lives there. They may work five, six, or sometimes even seven days a week, week after week, year after year. They deserve to feel safe while they are in their work area.
Yes! All plants have some degree of danger. On the other hand plants that are properly designed will be safer. Safe plants are well organized with straight well defined routes of access and escape. Safe plants have proper headroom. Safe plants have all critical operating valves and controls properly marked and easy to reach. Safe plants have the emergency shut-off or shutdown controls located in a logical place. Safe plants are easy to keep clean. Safety is designed in, not added on later.
Constructability
Is it possible to design something that cannot be built? This is an interesting question and the answer is both no and yes. Some people might say “No,” it is possible to build anything. From a pure technical standpoint there may be no limit to what can be built. However, every project has its limitations and we are not addressing the technical aspects of building something. What we must address here is the non-technical aspects of budget and schedule. The answer then, may be yes, if you have a limited budget and deadline or restrictions on time. If the plant cannot be build within the predefined budget and schedule limits then the project is not constructible. Every member of the project team must know what the budget and schedule constraints are. They must also be aware of what effect they and their decisions have on those limits.
Operations
If the operators do not like it (the new plant) they may make sure it does not work. This is a strong statement, but human nature being what it is there could be some degree of truth in it. During the design stage, choices will be made in the location of key control and sample points. It is wise to talk to the operations team and find out what they are thinking. What do they consider good when it comes to operations and what they consider as bad? Remember that these people are going to live (in shifts) in this plant twenty-four hours a day, every day, for years. Do not set it up so they spend their days grumbling about the way you did your job. Every member of the design team should be given the opportunity to visit an operating plant. They should talk with operators and listen to both their comments and complaints.
I remember a project where there were four reactors each requiring extensive operating manifolds and multiple test points. A previous design had the reactors spread out and located some distance from each other. It also had the operators climbing up and down the four reactors to access all the required operating valves and sample points. After discussions with the operators, the new project took the approach that the plant would work better if the plant operators had a better arrangement for the work. The four reactors in the new plant were grouped together and all the operating valves and sample points were located at grade for easy access by the operators.
Maintenance
Here is another important aspect of the plant design process. If you get this wrong, it’s one you cannot easily fix. If a plant is not maintained it will not function properly, it will not be productive, and it will not make the intended quality and quantity of product. If it is not productive it will not be economical to run and will soon be shut down.
The maintenance needs for the general types of equipment such as pumps, exchangers, vessels and tanks are fairly well known. All designers with the training and the right experience will have an understanding of maintenance for these items. However, there are three things we need to do to help when it comes to maintenance.
First, we need to understand the maintenance philosophy for the plant. The maintenance philosophy may be built-in, portable or a combination. A built-in maintenance philosophy means monorails and bridge cranes to handle the removal or installation of equipment or parts. A portable maintenance philosophy means that all equipment and part removal will be accomplished using mobile cranes or a forklift.
Second we need to do our homework when it comes to the equipment specific to “this” project. Is there any new or different about the equipment on this project? If so then go ask questions and find out what are the maintenance needs and how this maintenance will be handled.
Third, we need to insure that the project maintenance philosophy is carried-out relative to every piece of equipment. This means that all the design groups (piping, structural, electrical, instrumentation, etc.) do not obstruct the required maintenance access.
Aesthetics
Some will ask what does aesthetics have to do with good process plant design? Looking good does not have anything to do with process plant purpose and functionality. Looking good does not have anything to do with process plant operation, maintenance or constructability. However, the client/owner wants a plant that looks as it was designed and built by professionals. We have all seen plants that were real eyesores and we have also seen plants that are almost pretty. Many of these pretty plants show up on the covers of our trade magazines.
There are a number of small, simple things that can be done to improve the overall appearance of the plant. Try to line up like things in an organized manner. Try to establish some symmetry in the placement of objects. One simple example is to place all the stairways for the storage tanks in the same quadrant.
Most likely you will not live next door to a plant or drive by one every day to and from your work but other people do. It is not unreasonable or hard to give some thought to what a plant will look like from outside the fence. We should take pride in our work, pride in the design and make our company proud and the client happy.
The items listed above are not specifically addressed in our codes or standards for the design of a process plant. They are outside the box, however they should be considered very important to the success of any project.