by Timothy A. Warren, PE, LEED AP

Process PipingDuring the planning stages of a new process line installation, upgrade, or modification project there are myriad items that need to be considered. Utilities are essential to bring the manufacturing process to life, and should be included early in the thought process. Utilities such as power, compressed air, tempered (hot/cold) water, and gases, among others, are examples of what the facility’s infrastructure must provide to support the manufacturing process.

When considering utility requirements for a project, the following baseline items must be determined:

  • Does the facility’s infrastructure already have every required utility for the process?
  • Does each utility serve other areas/process lines in the facility?
  • Are the current demands of each utility known, and how much spare capacity is available for each?
  • Is there adequate spare utility capacity to accommodate the new process line?

While the first two are relatively easy to answer and plan for, the third and fourth bullets are ones that often have the potential to expand the scope and cost of a project well beyond a new process line installation. Since this post assumes that each facility engineering manager has his/her arms around the current utility demands of the facility (even though I know that’s often not necessarily the case), I’ll disregard the third bullet for now to focus on the fourth bullet: Is there adequate utility capacity to accommodate a new process line? This is a critical question, because the need to add to the existing utility systems’ capacity and distribution often have a snowball effect. For example, if the facility will need additional chilled water to support the new process, several questions will have to be asked, answered, and addressed before the project can move forward. These include:

  • Is there enough space in the mechanical room?
  • Is there enough area on the roof for the added equipment?
  • Is there enough power for the added equipment – and is it local?
  • Do the existing chilled water pumps have enough capacity?
  • Are the existing distribution piping mains large enough?
  • Can the floor and/or roof handle the additional loads to support equipment and distribution?

As you can see, each utility system can significantly impact the project. Process equipment utility demands published by the manufacturer are often for the most extreme condition, such as the highest, full-load throughput. Furthermore, there are often multiple pieces of equipment that constitute a process line, with each piece utilizing multiple utilities. Unfortunately, there is rarely any distinction whether the multiple pieces of equipment will use the utilities simultaneously, much less for the required duration of use.

For example, consider a line comprising three pieces of equipment that each use chilled water, as follows:

  • Equipment Piece A is listed to require 200 gpm of chilled water flow
  • Equipment Piece B is listed to require 100 gpm of chilled water flow
  • Equipment Piece C is listed to require 100 gpm of chilled water flow

If I were to take this information at face value, I would conclude that a total of 400 gpm is required, which could equal a 167-ton chilled water load to the central plant, based on a 10-degree temperature difference. That is a sizable load that could potentially push the project into central plant upgrades. However, if I ask more questions to get a better understanding of the use of chilled water for each piece of equipment, I may draw a different conclusion. These questions include:

  • Does each piece use the stated flow continuously?
  • Do all pieces use it simultaneously or is it staged?
  • How long does each piece use the chilled water?
  • What is the temperature change for each piece?

I may find that the chilled water is not used simultaneously and staged among the three pieces of equipment. Or, I may find the listed flowrate is the absolute maximum, but the equipment will only utilize 60% of the maximum flowrate because the Owner will operate this process line at a throughput that is 60% of the maximum operating rate. I may also determine that the water temperature change across the equipment is very low (indicating lower overall capacity used), or that the flow control valve is fully opened for the first ten minutes of an hour, but then starts to close as the required cooling is reduced to a 20% minimum for the remainder of the hour. All of these could greatly impact the determination of the overall chilled water demand for the new process line. This is referred to as utilization, and is paramount to determining the actual utility requirements for a process line and the impact they may – or may not – have on the utility infrastructure systems. Therefore, a thorough evaluation should be completed as early as possible during the planning stages of the project.

Utility Matrix

A common tool used to summarize utility requirements is a Utility Matrix. A Utility Matrix can take many forms, but usually is presented in a spreadsheet listing all the pieces of process equipment in horizontal rows with the corresponding utility information in columns. Here is a portion of a Utility Matrix that illustrates a summary for chilled water:

Utility MatrixA column descriptor is included for all pertinent design information. The capacity is indicated as BTU/HR. Note the two yellow highlighted columns. The utilization factor can be determined after asking and answering questions similar to those previously stated above, and then used to correct to the actual anticipated capacity needed for each piece of equipment. Make no mistake, these questions are often difficult to answer and typically take a lot of digging. Furthermore, running down the right technical personnel from the equipment manufacturers (the folks that design it) is often necessary to find the needed answers. It’s worth the effort, however, because the resulting corrected total is a more accurate representation of the total utility capacity required. Each utility, such as power, compressed air, steam, etc., should be represented and totaled in a similar manner. Once this matrix is completed for each utility, you will have clearer picture of the impact on the facility’s infrastructure systems (assuming you know the baseline use for each utility prior to the project) and can feel more confident about the scope and budget with respect to this aspect of the project.

Questions about process utilities or determining utility capacity? Reach out to me at 717-434-1566 or [email protected]. You can also contact Jeffrey W. Pauley, PE, vice president and champion of JDB Industry at 717-434-1560 or [email protected].

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