tailieunhanh - A Practical Guide to Particle Counting for Drinking Water Treatment - Chapter 16

Tất cả các nhà sản xuất của bộ đếm hạt nước uống cung cấp các bộ cảm biến hạt khá tương tự trong hoạt động và xây dựng. Sự biến động chính được tìm thấy trong kích thước của các tế bào dòng chảy mặt cắt ngang, và gắn kết của bộ cảm biến đối với vòi mẫu và truy cập để làm sạch. Các cựu chủ yếu sẽ xác định độ phân giải độ nhạy và đặc điểm trùng hợp ngẫu nhiên, trong khi các tác động này duy trì và tiềm năng cho các thiệt hại do rò. | CHAPTER 16 Particle Sensor Construction All the manufacturers of drinking water particle counters provide particle sensors quite similar in operation and construction. The main variation to be found is in the size of the flow cell cross-section and in the mounting of the sensor with regard to sample taps and access for cleaning. The former will mainly determine the sensitivity resolution and coincidence characteristics while the latter impacts maintenance and potential for damage due to leaks. A. FLOW CELL Most of the manufacturers except for Met One provide a standard-type flow cell with synthetic sapphire windows and a stainless steel or aluminum flow cell. Met One has a sensor of this construction as well but it is no longer supplied for drinking water applications unless specifically requested. 1. Met One The Met One drinking water particle sensors employ a replaceable quartz cell mounted in a plastic mechanical assembly. The quartz flow cell must be replaceable because the quartz is more susceptible to scratching than synthetic sapphire. There is no advantage to this type of design outside of lower cost of manufacture which is important in that it helps to lower the cost of particle counting for the end user. This quartz plastic flow cell does not have the same structural integrity of the metal sapphire units and is restricted to lower amounts of sample pressure. In this case no more than 100 PSI is to be applied and for less than 1 min. In most cases this is many times in excess of what is required. The standard constant-head overflow weir provides an open system that limits the pressure to a few PSI. Closed systems should not be used because of the difficulty in maintaining constant pressure and could potentially exceed the pressure limits especially if severe water hammering 147 2001 by CRC Press LLC 148 A PRACTICAL GUIDE TO PARTICLE COUNTING were to occur. Pressurized washing to clear clogs could exceed 100 PSI so care should be exercised. It is probably .