Consider Modular Plant Design

Modular plants offer many benefits over a conventional stick-built facility. Read about the pros and cons of the modular approach to help you decide if it makes sense for your project.

Manufacturing plants based on modular equipment are emerging as a viable and beneficial alternative to conventional stick-built processing plants. Modular equipment offers several benefits, including flexibility in plant siting, fewer safety concerns during construction, and ease of equipment modification. These benefits, however, must be considered in the context of your project and the limitations and costs associated with modular design.

This article discusses modular equipment for the chemical process industries (CPI) and identifies the benefits and drawbacks of this type of plant. It provides guidance on determining whether modular construction makes sense for your project and how to approach developing a modular plant. Finally, the article discusses several situations in which modular plants offer significant benefits.

What is a modular plant?

▲Figure 1. Modular plants consist of steel frameworks (skids) on which process equipment, instrumentation, valves, piping components, and electrical wiring are mounted. The skids are transported to the construction site, where they are erected and connected to form the larger process system.

In a modular plant, the process equipment, instrumentation, valves, piping components, and electrical wiring are mounted within a structural steel framework (i.e ., skid or module). Heat tracing, thermal insulation, and an integrated control system are often included in the mounted structure. Each skid is a self-contained process unit that is typically constructed offsite. A modular plant can be comprised of many unit operations contained on a single skid or on multiple skids that are connected at the production site to form a large process system. The modules are shipped to the manufacturing site, where they are erected and integrated in the final orientation. Once at the end-user’s facility, the units can be connected to the site utilities and tested in place for startup and commissioning (Figure 1).

Module construction requires more steel than traditional construction, because each module needs to be designed and built to stand independently and to withstand the stresses of being transported, lifted, and erected. The units are therefore structurally stronger than conventional units constructed onsite. The drivers of modular construction are more complex than simply the strength of the structure, and careful consideration is required when evaluating the pros and cons of modularization.

The pros of going modular

Modular construction does not make sense for all processing plants. However, it does offer many benefits.

Worksite safety. The construction of a CPI plant has fundamental risks and hazards associated with working at heights, the use of heavy machinery, electrical work, and so on. These risks and hazards are compounded by the conditions found at a typical construction site, which is often outdoors and amidst workers and existing infrastructure. In such an environment, equipment is susceptible to damage during installation and weather-related damage. Modular plants, on the other hand, are fabricated in a safer, controlled environment at an offsite, indoor location.

Quality. Modular equipment is often designed and built at the same location, which enables better communication between the design and build teams. With improved communication, equipment is often of a higher quality than traditional, onsite-constructed equipment.

Schedule efficiency. A quick turnaround period from concept to the finished product can be critical for companies operating in emerging markets or that face time-to-market pressures. Modular plants can be constructed much faster than conventional plants for several reasons. The most significant is that the site and foundation...