INSTRUMENTATION

VALVES EXPLANATION AND ITS TYPES

VALVES EXPLANATION AND ITS TYPES

VALVES EXPLANATION AND ITS TYPES

Liquids or gases flow from areas of higher pressure to areas of lower pressure. If a pipe is connected to a tank of water, the water flows out of the pipe opening because the pressure in the tank is greater than the pressure outside.

valve basic

For a liquid or gas to flow, there must be a pressure difference, or drop.

valve basic

Suppose the opening of the pipe is partially closed with a piece of sheet metal, the amount of flow changes, and if the pipe is completely closed, the flow stops. Changing the amount of opening of the pipe changes the flow.In industrial piping, control of flow is of high importance. Mechanical devices that are used in such piping for flow control are called valves.

valve basic

Basically, a valve stops flow through a pipe by closing the opening of the pipe. A valve that is partially open allows partial flow to exist, and is said to be in a throttling position.

Any valve can be in one of three positions: throttling, fully open, or fully closed.

GATE VALVES

If two pipes are joined closely together, flow can exist through them.

GATE VALVE

If a piece of sheet metal is inserted between the joints, flow stops.

GATE VALVES

The drawing below shows two gate valves installed between two pipes.

GATE VALVE

A liquid is flowing through valve A. A gate valve stops flow by placing a metal gate across the opening. When the valve is completely open, the gate is raised out of the line of flow. In the open position, the gate causes practically no resistance to flow. When flow encounters resistance, or changes direction, turbulence and pressure drop occur.

When a gate valve stops the flow, the gate resists the pressure. Therefore the gate has to be strong enough to resist the pressure.

GATE VALVE

The pipes are always attached to the body of the valve.

The valve has a body with flanged ends with boltholes in them. The end of the pipe is also flanged and the pipe and valve are held together by bolts. To have a tight, leak proof connection, a gasket is inserted between pipe and valve.

The part of the valve that is mounted on top of the body to form a tight enclosure is called the bonnet. In the valve below, the bonnet and body are also bolted together.

Between the bonnet and body, a bonnet gasket is inserted for tight closure.

 

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PLC AND TURBINE SYSTEM QUESTION AND ANSWERS

PLC AND TURBINE SYSTEM QUESTION

This blog is wrote about PLC AND TURBINE SYSTEM QUESTION and focuses on instrument engineers, supervisor and technicians of petrchemical industry, plants and fertilizers companies.

  1. WHAT IS A PLC? WHAT ARE ITS DISTINCT ADVANTAGES OVER CONVENTIONAL CIRCUITS?

ANS:    A PLC STANDS FOR PROGRAMMABLE LOGIC CONTROLLER. ALL TYPE OF LOGIC FUNCTIONS CAN BE PERFORMED BY IT.                SUCH AS SEQUENTIAL START UP OF SYSTEMS, FAIL SAFE RUNNING PLANT AND SEQUENTIAL SHUTDOWNS. THE                          CONVENTIONAL CIRCUITS USING RELAY DIGITISED GATES AND DIFFICULT TO CHANGE OR BYPASS AND BULKY. WHILE                PLC IS SMALLER AND CHANGES  CAN BE MADE BY PROGRAMMING WITHOUT CHANGING HARDWARE, MEANT FOR                          INDUSTRIAL TMOSPHERE, CAN BE INSTALLED IN PLANT CONVENIENT, NO MOVING OR MECHANICAL PARTS SO,                              CHANCES OF FAILURE IS MINIMISED.

  1. WHAT ARE DIFFERENT TYPES OF I/O IN TYPICAL PLC SYSTEM USED FOR SAFETY SHUTDOWN SYSTEM IN OIL INDUSTRIES?            

ANS: INPUTS

  • RELAY AND SWITCHES CONTACTS. WITHOUT VOLTAGE (DRY CONTACT)
  • RELAY AND SWITCHES CONTACTS WITH 120 V AC OR 24 V DC.
  • LOGIC LEVELS FROM TRANSISTORISED CIRCUITS CAN ALSO BE INPUTS.

OUTPUTS

  • LOW VOLTAGE CONTACT FOR OTHER INTERLOCK FUNCTION
  • HEAVY RATED CONTACTS FOR SOV OR OTHER DEVICES
  • THYRISTER OUTPUTS.
  1. DEFINE THE FOLLOWING TERMS USED IN DIGITAL SYSTEMS.

ANS: A) CPU – CENTRAL PROCESSION UNIT. THE HEART OF COMPUTER. B) ALU – ARITHMETIC LOGIC UNIT.  PERFORMS ALL MATHEMATICAL FUNCTIONS. C) EPROM  – ERASABLE PROGRAMMABLE READ ONLY MEMORY D) RAM  –  RANDOM ACCESS MEMORY E) FLOPPY DISK –  FLEXIBLE MAGNETIC DISK FOR DATA/ PROGRAM STORAGE F) MODEM  –  MODULATOR / DEMODULATOR FOR COMMUNICATION OVER LONG DISTANCE G) RS 232  – MOST COMMONLY USED SERIAL INTERFACE FOR PERIPHERALS. H) HIWAY – MAIN CABLE FOR COLLECTION AND DISTRIBUTION OF DATA AT HIGH FREQ TO ALL THE DCS SUBSYSTEMS. I) WATCH DOG TIMER – TIMER TO KEEP OVER MICROPROCESSOR CYCLE OPERATION. J) PARITY – DIGITAL SIGNALS ARE CODED TO HAVE A DEFINE PATTERN (EVEN/ODD/OTHER) FAILING WHICH. K)  A/D CONVERTER – ANALOGUE TO DIGITAL CONVERTER.  1 TO 5V.  0 TO 12 BITS OF DIGITAL SIGNAL BY A/D CONVERTER.

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ANALYZERS INSTRUMENTATION QUESTIONS AND ANSWERS

ANALYZERS INSTRUMENTATION QUESTIONS AND ANSWERS

ANALYZERS INSTRUMENTATION QUESTIONS AND ANSWERS

E Stands for question suitable for Engineer.

S Stands for question suitable for Supervisor.

T Stands for question suitable for Technicians.

1. What is the definition of the Analyzers? Why it is being used in industry? (S/T)
Answer:
It is an instrument used to analysis the gas, liquid or solid to detect the  component of interest for improve productivity, checking the quality of the product and the component released to air or water, which can effect the human
life as well as environment pollution.
2. What is the on line Analyzer and why it is required? (S/T)
Answer:
Online Analyzer is analysis the gas, liquid or solid at situ to avoid transportation delays, interference with integrity of the sample. Now a days for improve productivity, maintaining the stringent quality of the product and the component released to air or water, which can effect the human life as well as environment pollution, on line analysis has become must.
3. What are major factor effect the reliability and accuracy of any on line Analyzer? (S/T)
Answer:
The factors affect the reliability and accuracy of any on line Analyzer is temperature, flow and pressure. Further, it may please be looked into that sample is free from any dirt or condensation.
4. What is GC? (S/T)
Answer:
It is physical method of separation that is based on differences in solubility (or adsorption) of the substance between a mobile and a stationary phase. It is elution method, the sample is vaporized as a narrow plug, injected into a carrier gas (a mobile phase) and forced to flow through a small diameter tube containing the stationary liquid phase.
5. How many types of Detector of GC you are aware? (S/E)
Answer: They are Thermal Conductivity Detector (TCD) and Flame Ionization Detector (FID), these are popular for their
simplicity and ruggedness. However some other types are Flame Ionization Detector, Orifice Capillary Detector, Photo Ionization Detector, Electron Capture Detector.
6. What is oven temperature generally maintained for a GC? (T)
Answer:
It depends on the specification and selection of the column, which is generally
70˚C to 100˚C.
7. What are the principles of operation of FPD and TCD type GC? (E/S)
Answer:
FPD: It is Flame Photometric. It detects the element specific to flame emission spectrometer.
TCD: The sensing filament and reference filament is heated electrically in the presence of carrier gas i.e. Hydrogen or Helium due to variation in the concentration of sample thermal conduction of the filament changes. This null
voltage change is detected by the bridge.
8. What are the different parts of a GC? (S/T)
Answer:
These are Analyzer, oven, detector, computer, sample handling unit etc.
9. What is the carrier gas and fuel gas are being used for GC? (T)
Answer:
Carrier gas is Helium or Hydrogen with Nitrogen gases. Fuel gas is Hydrogen.
10. What do you know about column and why the same is being used? (E/S)
Answer:  It is capillary SS or Teflon tube of very smaller diameter (1/8”) packed with  chemical compound used for separation, getting stationary phase and faster yield of process sample.
11. Why regeneration of the column is required? (T)
Answer: Some time column gets dirt and the action of packed compound gets exhausted. It
is purged with Nitrogen at constant temperature.
12. What are FT, CT, RT, and TT? (E/S)
Answer: FT is Function Table CT is Component Table RT is Retention time TT is trend Table
13. What are the different  types of outputs available in standard GC to interface with DCS or any third party system? (E)
Answer: These are 4-20 mA DC, 0-5 VDC, RS 232, RS 485, RS 422.
14. How many types of pressure regulators you are aware? (T)
Answer:
Pressure regulator is a critical component of any analyzer. Mainly high and low pressure regulators are there. It can be of Single stage or double stage. Further it has got different type based on the connection to cylinders DIN 1,
DIN 6, DIN 5, DIN 8.
15. Why some cases the sample lines is steam traced? (S/T)
Answer: Some cases the sample lines is steam traced to remove condensation and to keep the process component in it’s original state.
16. What are span gas and zero gas shall be used to calibrate an analyzer of 0- 1000 PPM H2S? (T)
Answer: Span gas will be 800 PPM± 1% and balance nitrogen. Zero gas will be pure nitrogen or air.
17. What is pH? What are domain for neutral, acidic and alkaline nature of a liquid? (S/T)
Answer: pH is negative logarithm of the hydrogen irons (Proton) activity. Neutral is 7.0 above 7 it is Alkaline and bellow 7.0 it is acidic.
18. Wow the pH of a liquid can be measured? (E/S)
Answer: It can be measured by Litmus Paper or electronically through glass electrode.
19. What the standard solutions are available used for the pH analyzer calibration? (E/S)
Answer: 4, 7, 9 are the standard buffer solution generally available to check pH analyzer.
20. Why auto temperature compensation is must for an online pH analyzer? What type of temperature elements is being used for the same? (E)
Answer: pH varies as per Nernst Equation with the change in temperature. Pt 100 RTD (Resistance Temperature Detector) is used as basic temperature element.

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