One of the most important tasks in the design phase is to assess how much effort will be put into the design phase to leave enough fee to provide adequate construction administration coverage. I'm not sure how other engineers approach the CDs, but I always scope out what I'm going to produce for the fee. Analogous to building an automobile, the engineer needs to decide on production based on the available funds and whether he will build a low-cost car or a more expensive luxury car. Both automobiles will have a quality control process to follow so that the buyer receives a well-built automobile. The same needs to be achieved by the designer engineer. Will it be a low-cost but still quality produced CD? Or will these documents be far more comprehensive while still providing quality CDs?
CRITICAL ISSUESFor us, we discussed what are the critical issues associated with designing, building, and operating a chiller plant. We all agreed that automatic control sequence and water balancing were essential to a project's success. To provide a clear understanding of both, we agreed that system flow diagrams would be needed (refer back to July's Tomorrow's Engineer" column for more detail). Next, the equipment selections were important, followed by layout of equipment and distribution. In creating the equipment and distribution layout, sections are needed to document available headroom and fit. What were not on our "critical issues" list were all those standard details.
Once finished with outlining our CD strategy, we discussed each person's experience with the design phase process. Here is what we came up with for a probable drawing list had we not gone through this exercise: equipment schedule sheet, detail sheets, floor plans (equipment layout and distribution), sections, possibly system flow diagrams, and an abbreviated sequence of operation.
What we determined from this discussion is that historically, CDs fall short of being responsible documents when it comes to being useful design-build-operate documentation. With the "probable drawing," what was not considered was how the chiller plant will be started up, how will it be commissioned, and how can these CDs will be used on a day-to-day basis by facility personnel when the installation is completed.
Our mutually agreed upon, responsible document format prioritized what was important to understand how the system, beginning with our ATC/FPT system flow diagram (refer to July's "Tomorrow's Engineer" column, too), could capture the combined sequence of operation and functional performance reaction to each device/component in each mode of operation.
We next copied the system flow diagrams and overlaid the water balancing (flow and pressure drops) TAB plan as the second set of flow diagram drawings. These drawings would be used to capture design-to-actual flow and pressure loss. We then moved the equipment schedules to their appropriate places in the contract specification, along with the other equipment criteria, thus eliminating the schedule sheet.
A CLEAR UNDERSTANDINGThe next group of drawings was the floor plan showing the equipment layout and the pipe distribution with a select few, but essential, sections through the building to confirm physical fit. Looking at our fee and our desire to make sure we had enough money left to provide construction administration, as well as to assist in startup and commissioning of the systems, we chose to not invest any design phase time producing details sheets.
What? No detail sheets? Yes, we passed on producing detail sheets and focused on making sure we had comprehensive ATC/FPT/TAB flow diagrams that helped us to clearly understand how our design was going to be started up, tuned up, and operated on a daily basis. When the job is finished, we will laminate these flow diagrams and have them posted in the chiller room, so that the facility staff can be trained on the numerous sequences, as well as to routinely refer to these "system roadmaps" as needed during the chiller season.
Our approach to responsible documents represents a culture change for the design and construction community that it truly needed as systems become more sophisticated to design, construction timelines are reduced, and commissioning and operator training becomes essential. These steps are crucial if we are to continually provide a better product to our client, the facility manager. In addition, this approach can be cost-effective and efficient to design, construct, start up, commission, and operate.