Saturday, May 7, 2016

Some basic for Process Flow Diagram ( PFD) & Process (Piping) and Instrument Drawings


Process Legend or Symbols

The process legend are like alpha bates of the Process Engineers language.
They provides the information needed to inter­pret and read the P&ID ( The book). Process legends are found at the front of the PFD and  P&ID. The legend includes information about piping, instrument and equipment.

Some symbols are common among plants; others differ from plant to plant. Some standardization of process symbols and diagrams is taking place. The symbols used in the tutorial reflect a wide variety of Oil and Gas Domain.

Process Flow Diagrams

New Engineers and technicians are required to study a simple flow diagram of their as­signed Design Project or the operating system. Process flow diagrams typically include the major equipment and piping path the process takes through the unit. As Engineer learn more about symbols and diagrams, they graduate to the much more complex P&IDs


Please click below link to read a brief but effective guideline for understanding the same.

PFD & P&ID Tutorial

Wednesday, April 20, 2016

Interview Tips for Process Engineer


You will be evaluated on your knowledge but You wont be selected based on that. At least 90% weighted would be for following points

  1. Number of years of experience( It doesn't matter how much you know).
  2. Tag Name of your Previous employers.
  3. Reference.

I am sorry about that but its bitter truth at-least for the Desi MNCs ( Engineering companies in India and Gulf region.) But if you have nationality privilege i.e. Arabic , or Omani than below 10 % is more than sufficient to get you selected for your Job.

 Let us concentrate for remaining 10 %
  1. Most Important thing for any interview is to defend your CV i.e. you should be able to answer all queries about the things mentioned in your Resume.

Apart from that you should be able to answer on following topics ( Hot topics)
  1. Pumps
  2. Hydraulic calculation (Line Sizing)
  3. Heat Exchanger
  4. PSV calculation
  5. Simulation ( Mostly about HYSYS)
  6. Tank/Separator calculation & Datasheet

Standard questions for each sections are Like 

For Pumps:
  • What is NPSH ( how to Calculate) -  
  • What is System curve
  • Pump Curve
  • Pump Operating point

For Hydraulic calculation (Line Sizing):
  • How to do Line Sizing
  • what are typical velocity values for Liquid & Gas
  • Have you done 2-Phase calculation

For Heat Exchanger :
  • How to do Heat exchanger calculation -tell the steps
  • Have you used HTRI
  • What are the things to look into in a HTRI generated Data sheet

For PSV calculation :
  • Which code is used for PSV Calculation
  • What are different scenario of Relief load calculation
  • What is maximum over pressure allowed in Fire case & all other cases scenario.
  • what is the distance from source of fire to be considered in Fire case calculation.

For Simulation ( Mostly about HYSYS) :
  • Which Simulation software you used
  • what is the property package you used
  • how to select property package
  • steps to build a Simulation

For Tank/Separator calculation & Datasheet :
  • Which API code is used for Tanks/ Separator etc.
  • Have you filled Data sheet for Tanks/ Pumps etc.

Apart from these interviewer can ask anything :) depend upon his experience  e.g.
If Interviewer is recently got the opportunity to take interviews ( 10-12 years of  person) . He has some strange fear for this new responsibility and he think he have to prove that he know more than you. No problem , try to drag him into the something which you know 

How you can drive your interviwer where you are comfartable ?
  
Its simple , Just end your answer at the point e.g. 

Question :Do you know how to design a heat exchanger ?

Answer : No Sir , I have not much Idea in that , I study in my course . I have recently working on xxxxx ( where you want him to ask next question)
 
 
If HOD takes your interview he will evaluate you for his purpose (his Upcoming projects in pipeline)and this best opportunity to get selected. 

Very experience and high ranking person only check attitude and behavior of team work :- and this should be the practice in my view also.

have a nice day

Thursday, April 14, 2016

PRE-COMESSIONING PROCEDURES FOR HEAT EXCHANGERS

HEAT EXCHANGERS

Heat exchangers can be broadly classified into following types : Water coolers/condensers Steam heaters , Chillers Exchangers

Start-up/shut down procedures shall vary slightly from case to case. However general start-up/ shut-down procedures are discussed in the following paragraphs .

Start-up

After the heat exchanger has been pressure tested and all blinds removed, proceed as follows:

  1. Open cooling medium vent valve to displace non-condensibles (air, fuel gas, inert gas etc.)from the system. Ensure the drain valves are capped. This activity is not required if gas is the medium.
  2. Open cooling medium inlet valve. Close vent valve when liquid starts coming out through it . Then open cold medium outlet valve and fully open the inlet valve also.
  3. Open hot medium side vent valve to displace non condensibles (air, fuel gas, inert gas etc.). Check the.t the drain is closed and capped . This activity is not required if gas is the medium.
  4. Crack open hot medium inlet valve. When ( liquid starts coming out from the vent valve, close it. Open hot medium inlet valve and then open the outlet valve fully. In case of Steam heaters, initially the condensate shall be drained to sewer till pressure in the system builds up to a level where it can be lined up to the return condensate header.
  5. In case bypasses are provided across shell and tube side , gradually close the bypass on the cold medium side and then the bypass across the hot medium side . 
  6. Check for normal inlet and outlet temperatures . Check that TSVs (Temperature safety valves) are not popping.
  7. The operation of inlet and outlet valves should be done carefully ensuring that the exchangers are not subjected to thermal shock.
  8. In case of coolers/condensers, adjust the water flow to maintain the required temperatures at the outlet. The return water temperature should not exceed 45°c. 
  9. For avoiding fouling, velocity of water should be 8 ft/sec in a cooler/condenser.
Shut down
  1. Isolate the hot medium first. In case both hot and cold medium are from process streams, exchanger shall remain in service till the hot stream has cooled down enough.
  2. Isolate the cold medium next.
  3. Drain out the shell and tube sides to OWS/ Sewer/Closed Blow Down system as applicable.
  4. Depressurize the system to atmosphere/flare/ blow down system as applicable.
  5. Purge if required.
  6. Blind inlet and outlet lines before handing over the equipment for maintenance.

PRE-COMESSIONING PROCEDURES FOR POSITIVE DISPLACEMENT PUMPS

POSITIVE DISPLACEMENT PUMPS

 These types of Pumps are relative simple in starting and stopping compare to Centrifugal Pumps. I summarize the General procedures for start-up/shut down and trouble shooting of the positive displacement pumps in a simple language however Vendor 's operating manual should be studied for further details.

Start-up
  1. Check if all mechanical jobs are completed.
  2. Flush and renew oil in pump gear box .
  3. Check whether suction/discharge blinds are removed.
  4. Check whether suction strainer is installed and is clean.
  5. Check for proper lining up including the pressure safety valve in the discharge. Open suction valve fully.
  6. Check that the motor shaft is reasonably free and coupling secured. Coupling guard should be in position. 
  7. Energize motor. Open discharge valve. Start the motor and check direction of rotation. If wrong, correct it.
  8. Adjust the pump stroke in case of reciprocating pumps and run the pump at desired settings . Watch discharge pressure and check the rate of pumping using the flow meter or by taking suction from the calibration pot. The valve on the re-circu­lation line (provided in case of gear pump, screw pump etc.) shall be adjusted to obtain the required discharge pressure.
  9. Care should be taken to avoid dry running of pump and back flow of liquid. Bleed if necessary to expel vapor/air.
  10. Check for unusual noise, vibrations, rise of temperature of both motor and pump .
Shut Down
  1. Stop the pump
  2. Close the suction and discharge valves .
  3. Drain the liquid if maintenance jobs are to be carried out on the pump.
Trouble Shooting

i) Insufficient discharge pressure
  • Check the line up in the suction side. Check up suction pressure.
  • Check the functioning of the safety valve and pressure control valve on discharge to suction.
  • Check the strainer on the suction side .
  • Check for insufficient liquid level in the vessel from which pump is taking suction.
  • Check pump coupling and rotation .
  • Get the pump checked by pump technician.
ii) High discharge pressure
  • Check the line up on the discharge side. Check pressure control valve opening.
iii) Leaky Gland
  • Check for normal pump discharge pressure.
  • Tighten the gland nut slowly if possible. Hand over the pump for replacing gland packing .
iv) Unusual Vibrations
  • Check the foundation bolts.
  • Check motor fan cover for looseness . Stop the pump am. hand over to maintenance.

PRE-COMESSIONING PROCEDURES FOR CENTRIFUGAL PUMPS


2.1 CENTRIFUGAL PUMPS

I am writing General Procedures for start-up/shut down and trouble shooting of Centrifugal pump in a very simple language however Vendor’s operating manual should be studied and followed. 

2.1.2 Start-up:
  1. Inspect and see if all the mechanical jobs are completed.
  2. Establish cooling water flow where there is such provision. Open external flushing liquid to seal in pumps having such facility.
  3. Check oil level in the bearing housing; flushing may be necessary if oil is dirty or contains some foreign material.
  4. Rotate the shaft by hand to ensure that it is free and coupling is secured. Coupling guard should be in position and secured properly. Open suction valve. Ensure that the casing is full of l quid. Bleed, if necessary, from the bleeder valve. Keep discharge valve closed.
  5. It should be ensured that casings of the pumps are heated up/cooled sufficiently if required, prior to starting of the pump to guard against damage of the equipment and associated piping due to thermal shock/vapor locking.
  6. Energies the motor. Start the pump and check the direction of rotation. Rectify the direction of rotation if not right.
  7. Check the discharge pressure.
  8. Open the discharge valve slowly. Keep watch on the current drawn by the motor, if ammeter is provided. In other cases check at motor control Center/Pee.
  9. Check temperature of the bearings and if necessary adjust the cooling water flow (if provided).
  10. Check the Gland/seal and if necessary adjust gland tightness/flow of the coolant for the seal.
2.1.3 Shut Down:
  1. Close discharge valve fully
  2. Stop the pump
A. If pump is going to remain as stand-by and has provision for keeping the pump hot/cold  Proceed  as follows:
  1. Open the valve in the by-pass line across the discharge valve and check valve.
  2. The circulation rate should not be so high as to cause rotation of idle pump or overloading of the running pump.
B. If pump is to be prepared for maintenance, proceed as follows:
  1. Close suction and discharge valves.
  2. Close valve on check valve by-pass line, if provided.
  3. Close cooling water to bearing, if provided.
  4. Close external flushing liquid to mechanical seals, if provided.
  5. Slowly open pump bleeder and drain liquid from pump. If the liquid is very hot or cold, allow sufficient time before draining is started. Ensure that there is no pressure in the pump and drain pump casing. 
  6. Blind suction and discharge and check valve by-pass line. 
  7. Cut off electrical supply to pump motor prior to handing over for maintenance.
2.1.3 Trouble Shooting:  

 i) Pump not developing pressure Bleed/vent pump casing
  • Check the lining up in the suction side. Check the suction strainer.
  • Check the liquid level from where the pump is taking suction (physical verification).
  • Check pumps coupling and rotation.
  • Check the foot valve (in case of vertical lift pumps).
  • Check the temperature of liquid. If it is higher than for what the pump has been designed, NPSH will come down.
  • Check for any air leakage in the pump suction line or pump casing. This may occur at various joints and packing boxes as the packing ages. 
ii) Unusual Noise:
  • Check if coupling guard is touching coupling.
  • Check for proper fixing of fan and fan cover of the motor.
  • Check for pump cavitation.
  • Get the pump checked by a technician.
 iii) Rise of bearing temperature
(Generally the bearing oil temperature up is from 800c to 50°c above ambient whichever is lower can be tolerated. Refer vendors' instruction manual).
  • Arrange lubrication if bearing is running dry or oil level is low.
  • Adjust cooling water to the bearing housing if there is such provision.
  • Stop the pump, if temperature is too high, call the pump technician.
iv) Hot Gland
  • Adjust cooling water if facility exists. Slightly loosen the Gland nut, if possible. Stop the pump and hand over to maintenance.
  • Arrange external cooling if pump has to be run for some time.
v) Unusual vibration
  • Check the foundation bolts.
  • Check the fan cover for looseness.
  • Stop the pump and hand over to maintenance. Check alignment.
vi)  Leaky Gland
  • Check the pump discharge pressure. Tighten the gland nut slowly, if possible.
  • Prepare the pump for gland packing for adjustment/replacement of mechanical seal as the case may be
vii) Mechanical seal leak
  • Stop and isolate the pump and hand over to maintenance
 Refer to vendors instructions for more details on operation of pumps.

Thursday, January 21, 2016

Medium Pressure Liquefier

The Medium Pressure Liquifier or MPL is the Liquifier of choice in present bulk plant designs. The MPL is a medium pressure liquefier and rated in tons of liquid per day.Thus, an MPL-3 can produce between 300 to 400 tons of liquid nitrogen per day.

The Liquefier consists of a feed gas compressor, a warm and a cold expansion turbine / booster compressor, A three or four zone heat exchanger.

Chapter 8 : Medium Pressure Liquifier

Argon Refinery : Cryogenic Air Separation

The low ration column priduces produces crude Argon with 1 to 2% Oxygen and from 0.1 to 3% Nitrogen . In this chapter you will know Argon refining to meet quality of end users.

Chapter 7 : Argon Refinery

Three Column Design - Oxygen Distillation

In the perciverance  of getting more yield from cryogenic Distillation of Air. Many pioneers worked in early nineties and following chapter the three Distillation column design for Oxygen production is explained.

 Chapter 5 : Three Distillation Column