In the process of supplying water to a boiler or a humidification generator for a stability chamber, comes the question of which type of water to use. In today’s cost sensitive environments comes the challenge to justify the need to pretreat water that is going to be boiled away. In this challenge the cost controllers are always looking for a more effective way to reduce operational costs. To this, selecting the correct source of water at the early stages of the project is an important factor.
The first question is “Why not use tap water?” This option is one of the most costly in the long run because of the chemical and mineral content in the water. Understanding the hardness content of the local water source is essential if using tap water. In the process of boiling the water, the water molecules are vaporized and leave dissolved calcium/magnesium carbonates in the boiler pot and produce what is commonly called “boiler scale”. This residual scale shortens the life of the boiler and associated components as it builds up within the unit. This concentration of these minerals attaches itself to the components of the boiler thus reducing efficacies. In time maintenance will be required to replace units using this source of water.
The next question is “Do I use DI or RO water?” What are those?
Deionization (DI) filters by exchanging positive hydrogen and negative hydroxyl molecules for the positive and negative contaminant molecules in the water by running the water through resin tanks. This process removes very large quantities of contaminate and minerals from the water. The process is used in the production of lab grade water, so the system may already be in place; the tradeoff is the process is expensive as the resin tanks may need to be recharged more frequently depending on the volume of water being used. There is also the possibility of resin residual being left in the processes water.
Reverse Osmosis (RO) is the process of pushing water through a semipermeable membrane which remove up to 95% of contaminate and minerals. This process is not as expensive as DI as the membranes may last for a couple of years. The down side of the process is that in the RO process a significant amount of water used. The process continuously flushes the residue from the filter and down the drain, so an increased cost of water purchased is seen.
When looking at the supply of water, the amount of water used is a factor in determining the usable source. The DI system is an on-demand type of process that delivers water on a as needed basis. The RO system is a Gallon-Per- Day (GPD) process which processes and stores water for use. When justifying either system it is essential that the capacity versus usage be looked at closely.
No matter which system is selected, a Preventative Maintenance (PM) program should be in place that looks at the quality of the water on a routine basis and documents it. In a DI system, the planned and scheduled replacement of the resin tanks is required. On the RO system any preprocess conditioning will require monitoring. Also is the scheduled replacement of the membrane. On either system a sanitization process should be looked at to eliminate any bacterial contamination in the system that may occur after the filtering process. All work on the system should be documented to be able to track any trends that may lead to operational issues.
Part of a Disaster Recovery Plan is the backup of the water supply system. What do you do if you have a system shutdown due to mechanical issues? What do you do if you have a water supply interruption? You need to understand the amount of time your system can operated before you start having issues generating RH. Do you invest in a backup system, a holding tank or…
When using ether a DI or RO system a backup system may be a smaller version of the other unit for a short time basis usage. When developing a backup system, the unit should have the capacity to supply water until the main system is repaired.
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