Pure water and ultrapure water piping work
| [1] Piping system construction work | |
| In the pure water / ultrapure water supply system, it is required to supply water from the manufacturing equipment to the point of use of the terminal without reducing the purity of water by piping.However, in reality, it is not uncommon for the total length of piping to range from several hundred meters to several kilometers, and the selection of piping methods, piping materials, construction methods, etc. is an extremely important point for maintaining the purity of pure water and ultrapure water. Will be. | |
| [2] Factors of purity reduction | |
| The main factors that cause a decrease in purity in piping systems are as follows. (1) Elution of impurities from piping materials (2) Increase in the number of fine particles due to surface deterioration of piping materials (3) Elution of organic matter from the adhesive (4) Increase in the number of viable bacteria and fine particles due to the growth of microorganisms in the piping system Factors (1) to (3) can be dealt with to some extent by selecting the piping material. It is difficult to prevent the growth of microorganisms in (4). | |
| [3] Terminal piping system | |
| Currently, the basic idea for minimizing the growth of microorganisms in the piping system is to shorten the residence time of pure water and ultrapure water in the terminal piping system as much as possible. Therefore, the system Therefore, the following consideration is required. (1) Install pure water / ultrapure water production equipment as close to the point of use as possible. (2) Determine the pipe diameter so that the flow velocity in the pipe is around 1.5 m / s. On the other hand, secure the return part of the loop pipe at 0.5 m / s or more even at the maximum use.. (3) Simplify the piping network and eliminate air pools, water convection, and backflow. An example of a recommended piping system is shown below. | |
| [4] Piping material | |
| The following characteristics are required as piping materials for pure water and ultrapure water. (1) There is little elution of impurities such as metal ions, fine particles, and TOC. (2) The inside of the tube should be smooth so that live bacteria do not grow. (3) Excellent corrosion resistance because it is sterilized with hydrogen peroxide, ozone, etc. and sterilized with ultraviolet rays. (4) It has excellent heat resistance because it may be sterilized and washed with hot water of 80 ° C or higher. (5) Must have sufficient mechanical strength. (6) Other * Easy to install. * Low price and versatility. * Abundant diameter dimensions of pipes, fittings, valves, etc. Examples of piping materials used by field are shown below. | |
Examples of piping materials used by field
Item | semiconductor | Pharmaceutical medicine | Food | Optics | |||
| piping material | 64 Kbit | 256 Kbit | 1Mbit | 4Mbit | |||
| Polyvinyl chloride PVC | ○ | ○ | ○ | ○ | ○ | ||
| Polyethylene PE | ○ | ○ | |||||
| Polypropylene PP | ○ | ○ | ○ | ||||
| Vinylidene Difluoride PVDF | ○ | ○ | |||||
| Stainless steel SUS | ○ | ○ | ○ | ||||
| [5] Construction of pure water and ultrapure water piping | |
| For pure water piping, it is important to establish a cleaning method at each stage of construction. You need to keep the following points in mind. (1) Oil-free treatment and clean storage of equipment materials, etc. (2) Maintenance of work area: Arrangement and cleaning confirmation before work (3) Inspection of materials: Confirmation of storage status, inspection of deposits such as chips and dust (4) Inspection of tools used: Inspection of tools such as cleanliness and degreasing (5) Inspection of work clothes, etc .: Use of clean work clothes, gloves, wipers, etc. (6) Degreasing and cleaning of piping materials (7) Flushing, degreasing cleaning, and curing at each stage of construction (8) Sterilization cleaning and finish cleaning after piping is completed | |
