Begin with Batch file - Closing Explorer

Hello friends...


If you are a beginner or new to batch file, this post will help you to create your first batch file with some fun.

Batch file is just a script file with single or series of commands to be execute. If you are familiar with some dos commands then you can explore many possibilities using batch file.

I have come across one requirement in plant that , plant operator should not be able to use computer other than for monitoring SCADA. So i have created one batch file by which explorer can be closed.

To create a new batch file, open notepad - write your windows command - Save it As anything.bat.
Note that you have to give extension : .bat

Yes, That's it. you have created your batch file.

Write down following command in notepad and save it as "close explorer.bat".
Taskkill /F /IM explorer.exe

Here, taskkill is a command to end one or more processes, /F specifies to terminate forcefully, /IM specifies the image name of the process and explorer.exe is our process to be terminate

Saved file will look like...

 Now just double click on the file and see the magic.

Dont't worry. To get back to your original screen, press ALT+CTRL+DEL then go to task manager and in file menu go to Run and type what we have terminated. i.e. explorer.exe and press OK.

Similar way, you can carry out many tasks that you were doing in command prompt. Like checking Ping, changing IP address, Date of your system etc.

Hope you might have found this helpful to start with batch file. Write your comment if you have carried out something new with batch file.


Regards,
Bhargav.

Toshiba MCS1200 to V2000

Hello Friends,

Presently i am at Durgapur steel plant, West Bengal,  India, for commissioning of automation system for Blast Furnace. 

We are up-grading Toshiba  MCS1200 to Toshiba V2000 (L2PU22 controller) control system. We are replacing three MCS systems with one V2000 series controller.

First Image is of,  one out of three, MCS1200 system and second is, of course, V2000 system.

As i am little busy in commissioning, i may not be able to post regularly. 

But i ensure you to provide more information about power plant, then blast furnace, Toshiba DCS systems etc...

Thanks, Keep Visiting...

Bhargav.

Flow measurement by Differential Pressure method

Most commonly used method for measuring flow rate is by measuring the differential pressure across pipe restriction. Pitot tube and Orifice are widely used to generate differential pressure in pipe line.We all know that flow rate is proportional to the square root of DP. And how that we will derive here.

To understand this fundament, we should know some basic principles.

(1)      Bernoulli’s equation: In short, this states that,  the sum of the pressure energy (P), 

 kinetic energy (½  * ρ *  V²) and potential energy (ρ * g * h) will be equal at any cross section.

P₁  +  (½  * ρ *  V₁²)  +  (ρ * g * h₁)  = P₁  +  (½  * ρ *  V₂²)  +  (ρ * g * h₂)  ………………(1)

(2)      Continuity Equation: The continuity equation states that the mass flow through any cross section of pipe will be equal.

A₁ * V₁ = A₂ * V₂.                                                                                   ………………..(2)

Now, assume that  our measurement pipe is at same level. So, Potential energy term in Bernoulli’s equation (1) will be same at both point and can be cancelled out.

P₁  +  (½  * ρ *  V₁²)  = P₁  +  (½  * ρ *  V₂²)                                         …………………..(3)

From equation (2),  V₁ = (A₂ * V₂ / A₁)
                               V₁ = (d/D)² * V₂

 Putting this in above equation (3) and solving for  V₂

                                      …………………………..(4)

Or we can say                      …………………………..(5)

It means differential pressure type flowmeter will be 1/2 as sensitive to changes in fluid density as a velocity type flowmeter.

This is the equation for the velocity at the meter throat. Volumetric flow (Qv) equation can be obtained by multiplying by the cross sectional area of the throat.

                                   

If Mass flow is required rather than volumetric flow, multiply both the side by flowing density…

                                     

Density compensation for Eq (5) is required for accurate flow measurement, that I'll post in my next blog.

Reference: Rosemount Technical paper for flow measurement

Density Compensation for level Measurement in Boiler Drum

Requirement of Accurate measurement:

The drum level must be controlled to the limits specified by the boiler manufacturer. If the drum level does not stay within these limits, there may be water carryover. If the level exceeds the limits, boiler water carryover into the superheater or the turbine may cause damage resulting in extensive maintenance costs or outages of either the turbine or the boiler. If the level is low, overheating of the water wall tubes may cause tube ruptures and serious accidents, resulting in expensive repairs, downtime, and injury or death to personnel. ( Reference : InTech Magazine by ISA, July 2010).

When a differential pressure transmitter is used to measure drum level and the instruments used are sensitive to density variation, density compensation techniques must be employed.


Why Density Compensation ?

Here we are measuring level using Differential Pressure (DP) transmitter with two different densities (of Water and Steam). Moreover density also changes with different pressure in drum. So density compensation is required for accurate level measurement.

Refer to below diagram.

Here,
Hm --Compensated drum level.
Dw --Density of water in gm/cm3
Da --Density of water at ambient temperature (34°C) = 0.994 gm/cm3.
(For water in Condensate pot)
Ds --Density of Steam in gm/cm3
H --Distance between tapping points.

So,
Head acting on LP side = H* Da     and
Head acting on HP side = Hm* Dw + (H-Hm)*Ds

Therefore,
Delta P = HP-LP = Hm*Dw + (H-Hm)*Ds–H*Da

So Level Hm = {(Delta P)+H (Da-Ds)}/(Dw-Ds)

Delta P is the differential pressure value from drum level transmitters.

The values of Dw and Ds will be taken from following look-up table depending upon the current drum pressure signal.




So, this way more accurate level can be measured with changing densities.

Boiler three element understanding.

Hello Friend...

Many times, when i look for instrumentation questions,  i frequently came across this topic.
I have worked in power plant and have also developed logic and scada for 10MW biomass power plant.
You can find many articles online regarding this but here I'll show you actual implementation.


In this control philosophy, there are three process variables.
1. Boiler Level,
2. Feed water flow and
3. Steam Flow
to control boiler Drum Level.

Understanding of diagram :

Here, LT1,LT2 and LT3 are three different Level transmitter. reason for using three level transmitters is simple that, in case of failure of any transmitter(s), control wont be affected. LT is average of three LTs.
Water density changes with pressure. So density compensation is there for every level transmitter.

LIC is first PID block with LT as process variable.

FT1 is the steam flow leaving the steam drum. Here we have done pressure and temperature correction.

Output of LIC and FT1 goes to one calculation block. Output of this block is our remote set point for Flow controller (FIC).

FT2 is feed water flow to the boiler drum and process variable for FIC.

SS is selector switch. By this controlling philosophy can be selected either single or three element.

FCV is feed flow control valve.


Control:

Single Element:
During lower boiler loads or <30% steam flow, drum level signal LT and the fixed local set point LSP are
compared in LIC and the controller output is fed to feed water control valve FCV

Three Element:
The steam flow signal sensed by the steam flow transmitter FT1 acts as a feed forward signal and takes care of the shrink & swell effect.The steam flow transmitter is connected across flow nozzle, and the signal is then compensated for pressure and temperature.
LIC is the primary controller in the three element level control function. When the steam drum water level is below the set point, controller LIC will further increase the remote set point of the feed water flow controller to increase the feed water flow. When the level is too high the reverse action will take place.

The Level controller LIC output signal is added with the compensated steam flow signal at calculation block.

The following equation is implemented in summing block
Remote SP for (FIC) % = (LIC) O/P + Steam Flow (FT1) PV in % - 50%

FIC is the secondary controller in the three element level control. When the feed water flow is below the set point, controller FIC will further increase the feed water flow by opening the feed water control valve. When  the flow is too high the reverse action will take place.


I'll give overview about few other points like Density compensation for level, Temperature and Pressure compensation for flow, shrink and swell effects in my upcoming blogs.