Wednesday, January 22, 2014

SCADA System - Network Security

Network security for supervisory control and data acquisition (SCADA) systems, is increasingly important and ever evolving due to the need for secure and reliable control systems. There is continuous growth, and the management of network-connected devices and the expansion of Server-Client networks can be difficult and cumbersome. To properly secure networks, a multistage process is needed incorporating risk assessment, planning, design, implementation, and maintenance for a comprehensive defense-in-depth strategy. A critical aspect of defense-in-depth is the overall network system architecture and the network segmentation plan. A properly planned and executed network architecture and segmentation strategy lays the foundation for security and simplifies expansion and maintenance of the network.

There are industry-accepted methods for industrial control system (ICS) network architecture and segmentation strategies that can be applied to SCADA systems. Industry-standard techniques, based on recently published standards and network design guides, are used to create a layered network architecture approach to security, including the use of logical subnets and virtual local-area networks (VLANs) for segmentation. The advantage of this approach is simpler configuration of network security appliances and simpler management and expansion of the network, leading to increased network availability and a reduction in threat risk.

Tuesday, January 21, 2014

Allen Bradley - Just Started

This is my post after four months.. and i hope to share more technical stuff in coming months.

Currently i am working on Allen Bradley PLC and do have experience in ABB, Siemens and Schnieder as well along with some another brands also. The interesting thing i found about Allen Bradley is it's Networking Technology.

well it can be networked on Ethernet , Devicenet and Controlnet having same protocol CIP which stands for Common Industrial Protocol.

The below figure can give a better visualization :

will discuss more about AB in my coming posts.

Sunday, September 15, 2013

Analog Pressure transmitter

It is important to note all the adjustments within this device, and how this compares to the
relative simplicity of an all-analog pressure transmitter:

Wednesday, September 11, 2013

Smart Pressure Transmitter - I

The advent of “smart” field instruments containing microprocessors has been a great advance for
industrial instrumentation. These devices have built-in diagnostic ability, greater accuracy, and the ability to communicate digitally with host devices for reporting of various parameters.
A simplified block diagram of a “smart” pressure transmitter looks something like this:

Saturday, July 13, 2013

Low Pass Filter

The simplest low-pass filter circuit is nothing more than a resistor and capacitor:
Low-frequency voltage signals applied to this circuit emerge at the output terminal relatively
unattenuated, because the reactance of the capacitor is quite large at low frequencies. High-frequency
signals applied to the same circuit become attenuated by the capacitor, which tends to “short” those
signals to ground with its low reactance to high frequencies. The performance of such a filter circuit
is primarily characterized by its cutoff frequency, mathematically defined as
 The cutoff frequency is the point at which only 70.7% of the input signal appears at the output (a -3 dB attenuation in voltage).

Thursday, July 11, 2013

DM+UF Plant - In reference to One of my Commissioned Projects


The main purpose of DM+UF plant is to supply de-mineralized water to various systems with the priority to provide for steam water system for producing steam to run the turbine. The water from the plant will also be used as jacket water of diesel generators, air compressors and chillers.
The process employed for DM+UF plant is the simple ion-exchange method with cat ion bed, anion bed and mixed bed.
The capacity of the Plant is 48m3 per stream for outlet and inlet is 56m3 per stream.
The Plant employs several chemical and physical processes to de-mineralized water namely.
1.      Dual Media Filter (DMF) - This process is also called Pressurized Sand Filter as larger suspended impurities and organic matter are removed in this process.
2.       Activated Charcoal Filter (ACF) – This process strictly removes chlorine from inlet water as presence of chlorine may chemically damage the cation resin present in the bed.
3.      Strongly Acidic Cation Bed (SAC) – The main purpose of strongly acidic cation bed is removal of cation from inlet water.
4.      De-Gasser Tank – This particular tank is used for removal of carbon dioxide as carbon dioxide presence may cause unnecessary load to the anion bed.
5.      Strongly Basic Anion Bed (SBA) – The purpose of this particular process is as the name suggests is to remove positively charged anions.
6.      Mixed Bed (MB) – The SAC and SBA removes the cation and anion from the water but some amount of cation and anion resins are still distributed within the bed. The mixed bed is mainly polishing unit to refine the final outlet through SBA.
7.      Ultra Filtration (UF) – This process of Ultra Filtration is a physical interaction only where no chemical reaction takes place to remove colloidal silica or non-reactive silica. UF modules are woven fiber filter which removes the non-reactive silica.

     NB: There are two vessels for DMF, ACF, SBA and MB and three vessels for UF at the Plant Side.


The DM+UF Plant Panel have redundant PLCs, meaning that if one PLC goes to stop mode or shuts down due to any event or situation then the other PLC will take over ensuring the field input and output are unaffected  from the one PLC shutdown. Similarly, even Ethernet Switches and Power Supply in the Panel are also redundant. The Ethernet switch used here also have probation of transfer of data from Fiber Optic Cable. The Ports 7 and 8 are for FO port whereas ports 1, 2, 3,4,5,6, are Ethernet Ports.



     The DM+UF Plant can be divided into three sections each independent of each other. The following flowchart illustrates the section and their respective cycle.

SECTION 1:  This particular section comprises of DMF, ACF and SAC each having two vessels from which either of the vessel can be selected for service or backwash cycle.DMF has three cycles namely Service Cycle, Backwash Cycle and Trip Cycle. There are further sub-cycles in Service and Backwash Cycle as defined by necessity of process requirements, each cycle results in operation of valves and pumps at the field. Similarly ACF and SAC have cycles of Service and Backwash with their further sub-cycles in each of the respective cycles.
SECTION 2:  This section deals with SBA and MB having two vessels for each for the process with either of the vessels can be selected for Service or Regeneration Cycle. SBA has three cycles namely Service, Regeneration and Trip Cycle whereas; MB has only Service and Regeneration Cycle with each of the cycles having further sub-cycles except the trip cycle. The cycles results in valve and pump operations at the field.  
SECTION 3:  This section of UF has three vessels of which any two can be selected for Service cycle. The UF section has Chemical Cleaning Cycle and Backwash Cycle apart from service cycle. These cycles like the other two section also results in valve and pump operation at the field.


The DM+UF is semi automated plant, the following flowchart illustrates the automation sequence of the plant.

NB: Section A, Section B and Section C cycle sequence is independent of each other.
DMF, ACF and SAC have two vessels each and each vessel has Auto and Manual mode. Service cycles require selection of any of the two vessels and their respective Auto mode of DMF, ACF and SAC. If there is any kind of fault or interlock issue at the plant then the whole cycle will trip in Section A. The other vessel of DMF, ACF and SAC can be taken in Manual Mode or Auto Mode for Backwash Cycle.
SBA and MB also have two vessels each and each vessel has Auto and Manual mode. Similar to DMF, ACF and SAC Service Cycle, even SBA and MB Service Cycle requires selection of any of the two vessels and their respective Auto Mode. The other vessel for SBA and MB can be taken in Manual Mode or Auto Mode for Regeneration Cycle. If there any kind of field Fault or interlock issue at SBA or MB then the cycle will trip in Section B when it is at Auto Mode. The Trip at SBA and MB will not affect other cycles at Section A or Section C.
UF have three vessels each having Auto and Manual mode. The Service Cycle at UF requires selection of two vessels and their respective Auto Mode. The other vessel can be taken in Manual Mode or Auto Mode for Chemical Cleaning or Auto Mode for Backwash. Fault or Interlock issue at UF section will only trip UF cycle and will not affect any other Cycles at the plant. 
The Pumps have Auto and Manual Mode; the corresponding pump must be selected in Auto Mode in the required Cycles to run the cycle. It can also be operated without cycle operations when taken in Manual Mode. The Blowers, Valves, Pumps and Analog Inputs from the field has BYPASS probation included in the system, thus any of them are at fault then it can be bypassed from the cycles at Start Up or During Cycle without any intervention to the  Actual Cycle Operation.