SDI-MFI 2200

SDI-MFI 2200

The SDI –MFI-CP 2200 (SDI and Modified Fouling Index) is fully automatic, multi channels on line analyzer and monitoring system.
The SDI –MFI-CP 2200 is a unique analyzer and designed for continuous, unattended operation in desalination and other water treatment plants.



Principal of operation

The SDI –MFI-CP 2200 is a combination of SDI and MFI measuring processes. The instrument has been designed to measure the SDI and MFI in three modes:
  • SDI standard test mode
  • SDI auto time test mode
  • MFI-CP test mode

  • Fully complies with the ASTM D4189-07
  • CE certified
  • Up to 4 sampling points
  • Up to 85 cycles (to complete one paper filter roll) without operator interference
  • Several modes for operation and calculation per channel
  • Three built-in operational modes:
    1. Manual (one-cycle only)
    2. Auto (programmable time interval)
    3. Remote (pre-started selected channel from remote station)
  • Two built-in calculation formula can program per channel:
    1. Standard mode test for low SDI water (less than 5.0 for 15minutes)
    2. Auto Time mode test for HIGH SDI water (greater than 5.0 for 15 minutes)
        * Measure time 1-15 minutes


System’s modes of operation

Standard Test Mode

Silt Density Index (SDI) is measured by comparing the flow rate of a known volume of water, where the water volume is kept under constant pressure. 

The flow rate is measured twice; first time is when the water flows for reference through a standard unused filter, second time is after the filter is exposed for 15 min. or less. 

The water sample flow is always kept under constant pressure. The drop in flow rate is a direct measure of the silt build-up on the filter.

The pressure is kept constant by precisely regulating air pressure applied on the water surface without the need of any mechanical device.

Auto Time Test Mode

In cases where the silt density index (SDI) reading is unstable and readings are higher than 5 (i.e. Plugging Factor is higher than 75%), during the 15 minutes check time, the analyzer can be programmed to work in Auto Time Test Mode based on the following test method:
  • The plugging factor calculations will proceed and will be recorded at intervals of one-minute elapsed
  • Calculations will stop once plugging factor 75% has been reached
  • New SDI readings will be displayed based on the last calculated factor
The exact check time has no valuable meaning (as in Standard Test Mode). In general, the higher the SDI reading the more silt is in the water. 

When plugging factor is calculated to be lower than 75%, the analyzer will switch and calculate the test results based on the Standard Method.

MFI-CP Test Mode

The Modified Fouling Index (MFI) measurement is based on the formation rate of a “Cake” when water containing colloids is filtered through a membrane filter. 

The MFI value is determined by consecutive measurement of time for constant volume (1/2 L) to flow through the filter membrane, and computation of the ratio T/V (T-total time, V-total volume). The difference between the two consecutives, divided by the constant volume is considered to be the MFI. The lowest volume of this measurement is the MFI result of the water.

In MFI-CP measuring procedures the absolute temp is taking into account by inserting the viscosity factor of the water to the standard temp of 20oC and the result is displayed as Compensate MFI.

System types

The SDI-MFI format definition: SDI-MFI 220 N-A-E-T
N             number of channels (1-4)
A number of analog outputs (1-4)
E Ethernet communication
T temperature measurement


  • Optional analog output (programmable range) per channel for remote control and monitoring purposes
  • Booster pump - When supply is in low pressure, one booster pump support all channels
  • Temperature measurement and compensation (if necessary)


  Height Width Depth
Cabinet Wall mounted    1,126 mm    525 mm    310 mm   


Utilities needed

Input pressure         35 – 80 psi
Flow rate               11/2 l/min. 
Air pressure            80 – 120 psi
Electrical               110 – 230 VAC at 4 Amp. Or 24 VDC


Filter paper type

Standard Millipore      0.45 micron roll paper 
Length of roll             6 meters, up to 85 measurements per roll 

Control System                           Communication

  • CPU                               
  • Color touch screen
  • RS488
  • RS232


Uptime                   >99.9%
Repeatability           less than 0.1 SDI units
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