For the most part, industrial plant expansions and new projects are executed with on-site construction. Whether the project is done in-house or outsourced, the sequence of work is similar: design, facility construction and modification, and process or system construction and installation.
In an effort to improve on these traditional construction methods, many plants are turning to turnkey, automated, skid-mounted systems and modules. Skid-mounted systems offer a host of advantages compared to systems built on-site, and many of these advantages may be germane to your next project.
One of the main reasons a customer may buy a skid-mounted system is to take advantage of a vendor's proprietary and/or patented technology. Many "skid builders" have spent tens, even hundreds, of man-years developing their processes, and they only make these innovations available with their skids.
Mobile Process Technology (MPT,www.mobileprocess.com) is one of them. MPT's advanced separation technologies (Figure 1) provide waste-stream elimination, resource recovery, and remediation to the chemical, petrochemical, polymer, pharmaceutical, and general manufacturing industries.
Figure 1: Delivery & Pick-Up
Mobile Process Technology's separation technologies provide waste-stream elimination, resource recovery, and remediation to many industries. Skid-mounted delivery means MPT can offer advanced, proprietary systems to customers on a leased basis.
"Our clients are often faced with challenges that can only be solved by advanced separation technology," comments Sean Kelly, MPT project manager. "Our systems can save them significant operating expense dollars, improve product quality, improve operations, and improve environmental compliance."
Off-Site Construction Is a Plus
There are numerous advantages for customers if they can have a system constructed off-site. Safety is a huge issue for plant management, and an ideal way to reduce the number of OSHA-recordable incidents is to reduce on-site construction hours.
Skid-mounted systems are one of the best ways to shift construction hours off site. Off-site construction in the controlled environment of a skid-builder facility should be safer than similar work performed at an operating plant.
Labor efficiency is another reason for off-site construction. Operating plants introduce a host of inefficiencies including security gate check-in, compliance with union work rules, work-permit procurement, and coordination with plant operations and other crafts. A craftsman working an eight-hour day at an operating industrial plant would typically spend no more than six hours of productive time at the actual work site.
Not only can off-site craftsman devote more hours to actual work, they are often more efficient because they work on the same types of systems every day. "Skid-builder personnel are extremely efficient because they are always building similar equipment," says Flemming Larsen, automation project manager for Novo Nordisk Engineering (NNE) in Copenhagen. "Skid builders often use an assembly-line approach to manufacturing, which is much faster and less expensive than on-site custom and one-off construction."
NNE designs and builds pharmaceutical plants, and the company uses pre-built skids and modules whenever possible (Figure 2). When skids are used in new construction projects, overall construction time can be greatly reduced. "Buildings and utilities can be constructed while skids are being built instead of waiting until the building is ready for occupancy and then starting construction," adds Larsen. "On a recent project this trimmed the schedule from 32-36 months to 18 months."
Figure 2: Parallel Processing
Novo Nordisk Engineering designs skids and modules in pharmaceutical plant construction whenever possible. A recent project schedule was trimmed from 36 months to 18 months because module-building was done in parallel with the building it would reside in.
Reliance on skid builders also removes on-site interference among different processes and systems. "When construction takes place on-site, it is often necessary to construct separate systems in a more sequential fashion as compared to off-site skidded systems, which can all be built at the same time," adds Larsen.
When processes must be added to existing plants, skid-mounted systems are often the only good answer. Hutchison-Hayes (www.hutch-hayes.com) centrifuge skids (Figure 3) are often purchased for installation on operating oil-production platforms. "The very nature of this business environment dictates that the equipment have an efficient skid-mounted modular design in order to be integrated into the drilling system with as little effort as possible," observes Gary Hensley, executive vice president of Hutchison-Hayes.
One chief disadvantage of off-site construction is coordination among different vendors to ensure commonality of components, methods of construction, and control systems. While it is possible to mandate that all skid builders follow strict and unwavering standards, in practice this can increase costs and lengthen schedules.
According to Larsen, up-front planning with all skid builders is essential to ensure that necessary standards are met while allowing each skid builder to maintain internal efficiency. Inevitably, trade-offs must be made when standards collide with costs and schedule.