SILTON ONLINE SDI ANALYSER
About:
SDI – Silt Density Index, is a measure of presence of suspended solids (SS) in feed water. Silt Density Index (SDI) testing quantifies the amount of particulate contamination in a water source. SDI is widely accepted for estimating the rate at which colloidal and particulate fouling will occur in water purification systems – especially in applications using reverse osmosis (RO) membranes. Water sources often change their water quality and this test often needs to be done weekly or monthly. The SILTON SDI Analyser automatically calculates a relative value for the amount of suspended matter in feedwater streams. Measured values reflect the rate at which a 0.45-micron membrane filter will plug with particulate material when feedwater is flowing through it. The ASTM chose the 0.45 micron filter because it is more likely to clog from colloidal matter than from hard particles such as sand or scale. SDI testing is commonly used as an “early alert” to ensure that particulates in feedwater do not plug the micropores in RO membranes. Measurement and control of SDI is important in membrane based water treatment systems, since excess SS could clog the membrane surface. SDI values range from 0 to 6.6, with 6.6 as maximum. All RO/ Nano membrane manufacturers specify a limit of SDI < 5 for smooth operation of their membranes. Our Auto Online SDI Analyser is used to measure the SDI value of any given water stream inside a pipe with the least possible human effort.
SDI is calculated based upon the decay in flow rate during a 15 minute period across a new 0.45 micron filter installed in the built-in holding fixture. Flow rate measurement accuracy is ensured by automatically maintaining a constant 30 psi (2.07 bar) in the feed stream to the filter.Flow rates are measured during the collection of 500 mL samples at the start of the test and after 5, 10, and 15 minutes. SDI units (percent decay per minute) represent the degree of plugging that may occur due to the feedwater stream particulate and colloidal levels. The 15 minute SDI (SDI 15) is defined by ASTM D 4189-95 as the interval required for accurate and standardized testing. The 5 and 10 minute SDI values are only estimates of the 15 minute value.In addition to calculating SDI 15, the measured decay in flow rate is also converted from an SDI value to plugging factor (PF) value, a number between 1 and 100%. 100 percent means the filter is completely plugged. This provides an understandable point of reference for the potential of your RO membranes to plug — the higher the percentage, the faster your membranes may become fouled with particulates.
Silton 4750
The Silton 4750 Online SDI Analyser is an accurate, easy-to-use, precise instrument that can dependably measure the Silt Density Index (or) SDI value of any water stream, Silton can be connected inline to a water flow system.
The Analyser is enclosed in a robust metal casing protecting the instrumentation inside, allowing it to be used for a wide range of industrial applications. Silton offers many advantages over conventional portable SDI systems in terms of increased accuracy, robustness, reliability and comfort
Silton 4750 consists of a booster pump, pressure regulation system, intelligent SDI sensing system, controller and digital display
Features
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Increased ease of measurement
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Reduced time of measurement
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Accurate SDI everytime
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User-friendly, custom built software for accurate measurement
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Robust and dependable data-acquisition system
SDI Test Principle & Procedure :
1. Feed water is allowed to pass through a membrane of 0.45 microns pore size with 47 mm diameter held inside a membrane holder at a regulated pressure of 2 kg/cm2.
2. Initial Time, T i required to filter a known volume (500ml) is measured.
3. Feed water is allowed to permeate through the membrane for an interval of T int = 15 minutes – time is measured by Analyzer's controller.
4. Final Time, T f required to filter the same preselected volume of 500ml is measured.
5. Silt Density Index is manually calculated using the formula
SDI = (1 - Ti /Tf ) x 100/T int
6. Depending on the feed quality, the volume of measurement of 500ml can be varied
between 100 ml to 500 l.
7. Depending on the feed quality, the time interval T int of 15 min can be varied to 5/ 10/ 15 minutes.
As you can see, the above process is time consuming and requires a skilled operator and constant attention. The Auto SDI kit does all the above work for you automatically. This ensures a correct SDI reading every time. In our Auto SDI kit, steps 2 to 7 are made available on a control screen, with provisions for selecting various options for time intervals and volumes of selection, with START/STOP button, to initiate the process of measurement with preselected values, and the final SDI index is displayed on the screen. Further, provision is available to record the values taken at various points of time.