“Package Plant” has become a buzzword within the water treatment sector from mining to agriculture, from municipal to industrial – even residential. Other words synonymous with package plants are “Plug-and-Play”, “Containerized” and “Decentralized” to name a few of the most often heard. It’s not difficult to understand the popularity of these types of systems. What these words bring to mind is convenience, simplicity and ease. Even though packaged solutions are all of these things, we must keep in mind that they come with some small print. When purchasing or designing a package plant, there are some things to consider to ensure that expectations are realistic and will be met now, as well as in future.
As mentioned, there are a host of benefits offered by pre-fabricated plants:
- The modular nature of package plants means that they can be applied and integrated in phases without major construction, planning or process interruptions
- Package plants can be deployed rapidly and used as a short-term solution since they require minimal civil integration
- Moveable – Containerized plants can be trailer mounted and transported to different sites if required
- Cost effective to ship either via road or sea if built in standard shipping containers
- These plants are available as rental units offered by many companies which makes funding more accessible
- Complete assembly on the contractor’s premises means a saving on site costs and risk
- Package plants can be standardized which means many identical units can be manufactured in a short period without requiring engineering input. This saves time and resources. Standardizing is suitable for plants such as reverse osmosis where the design will be suitable over a wide range of conductivities.
There is a difference between pre-fabricating a plant as a means by which the contractor controls site costs and risks and building standardized pre-fabricated plants as a means of eliminating engineering resources required and reducing manufacturing time. The latter refers to generic plants which are in high demand and can be sold as quickly as they are manufactured. These are often components of large treatment trains i.e. reverse osmosis systems, media filtration systems and settler/DAF systems.
When a packaged / containerized system is necessitated due to space limitations on site, cost can be negatively impacted should ultra-compact equipment need to be sourced. An example would be if Ultra Filtration is used rather than Media Filtration due to the more compact nature of UF modules.
Do Good Things Always Come in Small Packages?
There are certain risks involved with package plants. As the race continues to make larger plants smaller in size and lighter on the pocket, some clients and designers attempt to cut corners on process design and quality. This can have disastrous effects on performance and longevity of the plant and has led to some negative publicity for package plants in recent years. Saving on capital costs beyond what is practical can lead to an even bigger expenditure in future. There are instances of such projects being aborted once operational inadequacies start becoming apparent.
An overly compacted containerized system is an example of failure to consider the importance of access to equipment for ease of maintenance. Containerized designs with a higher capacity relative to the space available also generally show less process flexibility which in turn increases risk. This can be seen as maximizing the equipment capacity but should, in fact, be viewed as designing too liberally. System flexibility is required to mitigate risk of varying water quality. Ensure a certain degree of flexibility by not omitting design safety factors and operational redundancy. These safety factors can assist in the system’s reach when having to adapt to a varying feed quality.
Another effective cost saving strategy often applied is opting for manual process control which relies heavily on human intervention. This translates into constant operator presence on site which may be difficult and expensive. Basic automation is therefore strongly advised in order to ensure that the plant will be able to function without a set of eyes and hands present. Higher levels of automation will unfortunately impart additional maintenance requirements. Design engineers have to hold themselves to design rules-of-thumb when looking at flow velocities, residence times, flux and so on as deviating from first principles will spell trouble. The capacity of a containerized system is limited.
Don’t Count Chickens Before They Hatch
There is an easy error to make when costing containerized system installation. Underestimating installation and commissioning costs on package plants happen due to the misconception that complete factory assembly and successful FAT will mean smooth sailing on site. Package plants are often destined for rural locations where logistical challenges may be encountered due to poor road infrastructure, long travelling times and lack of resources. This can be detrimental to the commissioning and installation budget as well as project timeline. Variations in water quality is also always a possibility and estimations should allow for process adjustments once on site. Differences in make-up water quality, ambient temperature and altitude can affect the process. This is not denying that packaged units certainly require remarkably less installation and commissioning time than traditional plants – reduced site cost is after all one of the attractive benefits offered by pre-assembling – but care should be taken to not underestimate the unique set of complexities awaiting the container and it’s installation team on site.
Overlooking the hiring of a crane for offloading on site can cause a multi-day delay depending on how outlying the site is. This small logistical hurdle can hinder completion and dent an otherwise healthy budget. The same is true if power supply to the site has not been provided and a generator needs to be delivered in order for commissioning to ensue e.c.t
Speak to a reputable and experienced engineering company like Watericon about your package plant requirements, design and consulting needs to avoid a decentralized disappointment. If it seems too good to be true, it probably is.