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Foundation Support

  • Large Instrument analysers when mounted on the ground are bolted to a concrete block. The concrete block is usually casted outside the plant. The earth is then excavated and the concrete block is inserted into the excavated hole. Analyzer is then bolted on to this concrete The concrete block is usually designed by a civil engineer

Analyzer Sampling Systems

  • Purpose of analyser sampling system is
    • To obtain representative sample
    • To condition the sample
    • To accomplish stream switching
    • To ensure safety
    • To allow adequate sample time
  • The 5 main elements of sampling system
    • Sample take off
    • Sample pre conditioning system
    • Sample transport line
    • Sample conditioning system
    • Sample return/dispose
  • Sample Take off
    • Sample take off probe is usually angle cut to avoid solid particles from entering the sampling system.
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    • Very thick schedule (80 and above) to avoid it from getting corrode
    • Is usually flanged typeclip_image003clip_image004clip_image005
  • Rules for using sample take-off probe or sample tap
    • For relatively clean process streams of 2" and below pipe, a simple sample tap may be adequate, however sample take-of probe is preferred.
    • A sample probe is preferred because solid particles tend to move at the rear of the pipe
    • For both types, take sample from the TOP of the process line for Vapours
    • For both types, take sample at the side of the process line for liquids.
    • Never take sample from the bottom of the process line since there may be sediments (such as piping sediments)
    • General guideline is to use sample take-off probe to ensure representative sample
  • Sample preconditioning
    • Purpose is to for the process sample to suit the analyser requirements (such as pressure, temperature and flow rate)
    • Main components are pressure regulator, pressure gauge, cooler, sample vaporizer
    • Sample vaporizer is to provide heat to maintain the gas sample at a gas phase after pressure is reduced
    • Sample cooler is to provide cooling. Conventionally, we use a tube-in-tube method
  • Sample Transport Line
    • Type of transport line
      • Single transport line
        • For short transport line (<30m)
      • Fast loop system
        • Long transport time
        • Lag time is undesirable
      • Sample needs to be in single phase along the transport line
        • Use electrical heater to ensure sample is heated
        • Gas sample need to be maintained above it’s dew point
        • Liquid sample needs to be maintained below it’s boiling point
      • The sample is usually returned back to process. In case if pressure is inadequate, the sample may be returned back to the following:-
        • For hydrocarbons, it can be returned either to:-
          • DOC(Oil contaminated drain) or Oily water sewer . The sample will then flow to a waste water treatment plant. Some DOC design goes straight to slop tank this however will run a risk causing slop to be over contaminate
          • SOP(Slope drain). The sample will flow straight to slop pit and pumped back to slop tank and the reprocessed back. This is different to DOC since it does not go through a waste water plant. Normally SOP’s are seen in tankage area where WWTP is too far away for the waste to be pumped.
        • For clean water, it can be returned back to DAC(Accidentally oil contaminated drain) or oily water sewer. The sample will then go straight to final pond/bio pond

Gas Chromatograph Analysers

  • GC is used to analyse product concentration. A constant volume sample is injected into the GC column. The injection is done by a sample injection valve
  • GC must be temperature controlled. Temperature control is important for
    • Column separation - A 1 degree C temperature change will have a 3% effect in retention time
    • Gas sample injection – Temperature is inversely proportionate with volume injection
  • GC’s can be used for both liquid and gas sample
  • For liquid sample,
    • The sample boiling point must be adequately low to ensure that the GC oven can vaporize the sample. If the sample boiling point is too high, a vaporizer may need to be use
    • The sample pressure must also be adequately high (~>2kgcm2) to ensure. However, if the pressure is too high , a pressure reducer need to be installed
  • For liquid, there are 2 types of sampling valves.. These valves range from 0.1 to 3ul injection
    • Liquid sampling valve
      • is used when the boiling point is high.
      • The LSV incorporates a vaporizer to vaporize the sample
    • Rotary sampling valve
  • TCD reading – Small temperature deviations in TCD will cause significant zero/span shifts
  • Having a lower temperature will prolong the lifetime of columns and valves
  • Carrier Gas System
    • The important purpose of carrier gas system is to provide a stable transport and detection medium for the components of the sample
    • Nitrogen, Hydrogen, helium are used as carrier gas as they do not have interactions with the solutes. Carrier gas selection also depends on the type of detector used
    • The carrier gas must fit the following criteria
      • Water or oxygen in carrier gas will destroy most column materials (dewpoint must be less then -60 degC)
      • 99.99% purity
      • Organic components must be less than 5ppm
    • Some GCs have a dehumidifier at their carrier gas system where a desiccant such as molecular sieves is use
  • Carrier Gas Maintenance
    • There should be 2 cylinder manifolds, one cylinder pressure set higher so that when the higher pressure cylinder finishes, the lower one will take over.
    • There are 3 types of GC columns
  • GC Ovens
    • The most important function of the GC oven is to ensure constant temperature selectable between 5 degC up to 350 degC.
    • Oven temperature is important as the higher the temperature, the faster components move in the GC oven. It is therefore practical to put it lower for better separation but slower cycle time. To high temperature in the other hand provides faster analysis but will reduce column life time due to column bleeding. It is best to put temperature as low as possible
    • Aside from stability, temperature should also be evenly distributed. The unevenness of temperature distribution should not be more than 0.8 degC if a same performance with lab GC is expected
    • Oven designs include
      • Using a heater element.
      • Heated-are blow-in method where air is heated and the blown in 4 sides pf the oven
      • Air bath circulation method where air is heated also but is circulated with a fan. This method ensures good stability and evenness
  • Gas Chromatograph Detectors
    • The most common detectors are FPD and FID
  • Slope Processing
    • User will usually have to configure how the GC detects the slope. Slope detection is the prime method used for GC to recognize peaks. There are a few things that needs to be configured in slope detection which are
    • The Gate time
      • Gates are the point on which the GC will turn on a slope detection algorithm.
      • There are 2 types of gates
        • ON gate – This is the gate when the GC will start to detecting an increasing slope
        • OFF Gate – This is the gate when the GC will start to detect when it should start find a decreasing slope
      • User need to first configure the time when both Gates start
    • Detection Slope
      • Once a chromatograph signal have passed an ON gate time, the GC will start the slope detection algorithm.
      • Before that, user will have to configure the ‘Detection Slope’ a parameter with a mV/s unit. Typically this value is set at 0.005mV/s. Increasing this value higher may cause the slope detection too late but decreasing the value may cause the slope to detect noises. The time when the slope is detected is called the Peak-ON time
      • As the chromatograph further traverses, it will soon find the OFF Gate. This off gate will start another slope detection algorithm however, this time it will start to determine the PEAK-OFF time. Different GCs have different method of determining a gate off time. The usual method is to find a 0mV/s slope. Some GC
    • The gate cutting method
      • Gate cutting is to determine where to cut the baseline to determine the borders of integration
      • There are 2 types of gate cutting methods:-
        • Slope Gate – The GC will draw a straight line from the start gate and end gate
        • Time Gate
      • Detection slope
    • Detection level
    • The integration method
    • The 2 most common gate methods are
      • Time gat
      • Slope gate
  • The calibration of GC is done by using the following formula
    • Concentration x Std Area = Measured Area x Reading Range x Calibration Factor
    • Based on this formula, calibration is possible by altering 2 value namely “Std Area” or “Calibration factor”. However, in PPTSB/AMSB GC application, we only change “Std Area” as our standard practice.

Gas Chromatograph Columns

  • When changing a GC column, one must allow 1 night of flushing. One must slightly increase the oven temperature
  • Types of Column
    • Packed
      • Short length (1.5 to 10m)
      • ID 2-4mm
      • Have solid supports which is inert such as diatomaceous earth
      • Diatamaceous earth is a naturlly found compound containing 86% silica, 5% sodium, 3% magnesium and 2% iron.
      • This solid support is coated with a liquid or solid satationary phase
      • The selection of this stationary phase coating depends on the type of analysis to be done
      • Slow and inefficient
      • Have higher capacity, though new technologies have allowed capillary column to have large capacity to
    • Capillary Column
      • Long length (25-60m)
      • ID 0.25mm
      • Mostly made of fused-silica with polyimide outer-coating
      • Best for speed
      • However only small samples
      • Type of capillary column
        • Wall coated open tubular (WCOT)
          • Has tube walls coated with stationary phase
          • Most commonly used
          • Does not separate very light component well
          • Some also call it FSOT (Fused silica open tubular)
        • Support coated open tubular (SCOT),
          • Has solid support on the tube walls which is coated with the stationary phase
          • Solid support used is also normally diatomaceous earth
          • Can handle larger samples than WCOT, so it is the best choice for very light components
          • Also, for specific type of stationary, SCOT must be used.
          • Most common stationary phase which must use SCOT is
            • Molecular Sieve
            • Divinylbenzene(DVB) - Used for C1 to C3 isomers analysis
            • Alumina Al2O3 - Separation of isomers of C1 to C10
        • PLOT (Porous Layer Open Tubular)
          • Has porous layers on the walls of the tube which can be coated with stationary phase
          • The pores itself can sometime be used as stationary phase
          • Usually used for compounds that are gas at room temperature as it is able to create sharper peaks
          • Common trade name for stationary phase columns. This table is taken from aegilent product brochur
  • Most supports use diatomaceous earth. However, some advance supports have trade names such as
    • Celite
    • Chromosorb W, Chromosorb P, Chromosorb G, Chromosorb S
    • Some chromosorbs have a AW notation, which means acid wash.
    • Agilent Phase Composition Polarity Approximate Temperature Range (C)  (Isothermal/Programmed)* Phases With Similar Selectivity
      General Applications
      HP-1ms, DB-1ms, HP-1, DB-1 Amines, hydrocarbons, pesticides, PCBs, phenols, sulfur compounds, flavors and fragrances 100% Dimethylpolysiloxane Non-polar From -60 to 325/350 BP-1, SPB-1, CP-Sil 5, Rtx-1, OV-1, SE-30, 007-1, ZB-1
      HP-5ms, DB-5, HP-5 Semivolatiles, alkaloids,drugs, FAMEs, halogenated compounds, pesticides, herbicides 5% Phenyl 95% dimethylpolysiloxane Non-polar From -60 to 325/350 SPB-5, XTI-5, Mtx-5, CP-Sil 8CB, SE-54, Rtx-5, BPX-5, MDN-5, Rtx-5ms, BP-5, ZB-5
      DB-5ms Semivolatiles, alkaloids, drugs, FAMEs, halogenated compounds, pesticides, herbicides 5% Phenyl 95% dimethyl arylene siloxane From -60 to 325/350 SPB-5, XTI-5, Mtx-5, CP-Sil 8CB, SE-54, Rtx-5, BPX-5, MDN-5, Rtx-5ms
      DB-1301 Aroclors, alcohols, pesticides, VOCs 6% Cyanopropyl-phenyl 94% dimethyl polysiloxane Mid-polar From -20 to 280/300 Rtx-1301, Mtx-1301, CP-1301
      DB-35, HP-35 CLP-pesticides, aroclors, pharmaceuticals, drugs of abuse 35% Phenyl 65% dimethyl polysiloxane Mid-polar From 40 to 300/320 Rtx-35, SPB-35, AT-35, Sup-Herb, MDN-35, BPX-35
      DB-35ms CLP-pesticides, aroclors, pharmaceuticals, drugs of abuse 35% Phenyl
      65% dimethyl arylene siloxane
      From 50 to 340/360 Rtx-35, SPB-35, AT-35, Sup-Herb, MDN-35, BPX-35
      DB-1701, DB-1701P Pesticides, herbicides, TMS sugars, aroclors 14% Cyanopropyl-phenyl 86% dimethyl polysiloxane Mid-polar From -20 to 280/300 SPB-1701, CP-Sil 19 CB, Rtx-1701, CB-1701, OV-1701, 007-1701, BPX-10
      HP-50+, DB-17 Drugs, glycols, pesticides, steroids 50% Phenyl
      50% dimethylpolysiloxane
      Mid-polar From 40 to 280/300 Rtx-50, CP-Sil 19 CB, BPX-50, SP-2250
      DB-17ms Drugs, glycols, pesticides, steroids 50% Phenyl
      50% dimethyl arylene siloxane
      From 40 to 320/340
      HP-88 FAMES Approximately 88% Cyanopropyl arylene siloxane High From 0 to 260
      DB-200 Residual solvents, pesticides, herbicides 35% Trifluoropropyl
      65% dimethyl polysiloxane
      Polar From 30 to 300/320 Rtx-200
      DB-210 50% Trifluoropropyl
      50% dimethyl polysiloxane
      From 45 to 240/260
      DB-225ms, DB-225 FAMEs, alditol acetates, neutral sterols 50% Cyanopropyl-phenyl
      50% dimethyl polysiloxane
      Polar From 40 to 220/240 SP-2330, CP-Sil 43 CB, OV-225, Rtx-225, BP-225, 007-225
      HP-INNOWax Alcohols, free organic acids, solvents, essential oils, flavors and fragrances Polyethylene glycol Polar From 40 to 260/270 BP-20, 007-CW, CP-WAX 52 CB, Stabilwax, Supelcowax-10
      DB-WAX Solvents, glycols, alcohols Polyethylene glycol Polar From 20 to 250/260 Rt-Wax
      CAM Amines, basic compounds Polyethylene glycol-base modified Polar From 60 to 220/240 Carbowax Amine, Stabilwax-DB, CP-51 WAX
      HP-FFAP, DB-FFAP Organic acids, alcohols, aldehydes, ketones, acrylates Polyethylene glycol-acid modified Polar From 40 to 250 OV-351, SP-1000, Stabilwax-DA, 007-FFAP, Nukol
      DB-23 FAMEs (requiring cis/trans resolution) 50% Cyanopropyl
      50% dimethyl polysiloxane
      Polar From 40 to 250/260 Rtx-2330, 007-23, SP-2330/2340/2380/2560
      CycloSil-B Chiral compounds (general purpose) 30%-heptakis (2,3-di-O-methyl-6-O-t-butyl dimethylsilyl)-B-cyclodextrin  in DB-1701 Mid-polar From 35 to 260/280 LIPODEX C, Rt-BDEXm, B-DEX 110, B-DEX 120
      HP-Chiral b Columns Chiral compounds (using a Nitrogen selective detector, NPD) beta-Cyclodextrin in phenyl-based stationary phase Mid-polar From 30 to 240/250 LIPODEX C, Rt-BDEXm, B-DEX 110, B-DEX 122
      PLOT Column Applications
      HP-PLOT Molesieve Permanent and noble gases. Argon and oxygen separation at 35�C 5� molecular sieve zeolite From -60 to 300 Rt-Molesieve 13X, Molesieve 5�
      HP-PLOT Al2O3 �KCl� C1-C6 hydrocarbons in natural gas, refinery gas, fuel gas, synthetic gas, dienes Aluminum Oxide "KCl" deactivated Least polar From -60 to 200 AluminaPlot, Rt-Alumina,CP-Al2O3/KCl Plot
      HP-PLOT Al2O3 �S� C1-C6 hydrocarbons in natural gas, refinery gas, fuel gas, synthetic gas, dienes Aluminum Oxide "Sodium Sulfate" deactivated Mid-polar From -60 to 200
      GS-Alumina C1-C6 hydrocarbons in natural gas, refinery gas, fuel gas, synthetic gas, dienes Aluminum Oxide with proprietary deactivation Most polar From -60 to 200
      HP-PLOT Q Hydrocarbons including isomers, CO2, methane, air/CO, water, polar solvents, sulfur compounds Polystyrene-divinylbenzene From -60 to 270/290 PoraPlot Q/S, Rt-Q, Supel-Q PLOT
      HP-PLOT U C1 to C7 hydrocarbons, CO2, methane, air/CO, water, oxygenates, amines, solvents, alcohols, ketones, aldehydes Divinylbenzene/ethylene glycol dimethacrylate From -60 to 190 PoraPlot U
      GS-GasPro C1 to C12 hydrocarbons, CO2, trace-level sulfurs, hydride gases, inorganic gases, halocarbons, SF6,  oxygen/nitrogen separation at �80�C Proprietary, bonded silica-based From -80 to 260/300 CP-SilicaPLOT
      GS-CarbonPLOT C1 to C5 hydrocarbons, CO2, air/CO, trace acetylene in ethylene, methane Bonded monolithic carbon layer From 0 to 360 CP-CarboBond
      Specialty Phases - Environmental Applications
      DB-624 6% Cyanopropyl-phenyl
      94% dimethyl polysiloxane
      Mid-polar From -20 to 260C Rtx-624, AT-624, SPB-624, CP-624, PE-624,007-624
      DB-VRX Volatile Organic Compounds using MSD, ELCD/PID Proprietary phase Non-polar From -10 to 260C Rtx-VRX
      DB-35ms CLP Pesticides, Chlorinated Herbicides, PCBs, 508.1 Pesticides 35% Phenyl
      65% dimethyl arylene siloxane
      Mid-polar From 50 to 340/360C MDN-35, BPX-35
      DB-XLB (Confirmation Column) Proprietary phase Non-polar From 30 to 340/360C No equivalent
      HP-5ms Semivolatiles by EPA Method 8270 5% Phenyl
      95% dimethylpolysiloxane
      Non-polar From -60 to 325/350C SPB-5, XTI-5, Mtx-5, CP-Sil 8CB, SE-54, Rtx-5, BPX-5, MDN-5, Rtx-5ms
      DB-XLB PCB Congener Analysis (209 Congeners) CLP Pesticides, Chlorinated Herbicides, PCBs, 508.1 Pesticides Proprietary phase Non-polar From 30 to 340/360C
      DB-TPH Leaking Underground Fuel Tank (LUFT) testing Proprietary phase Non-polar From -10 to 290C
      DB-MTBE MTBE in Soil and Water Proprietary phase Non-polar From 35 to 260/280
      Other Specialty Phases
      HP-Fast GC Residual Solvent Column Residual Solvents 6% Cyanopropyl-phenyl
      94% dimethyl polysiloxane
      Mid-polar From -20 to 260C
      DB-ALC1 Blood Alcohol Testing Proprietary phase Mid-polar From 20 to 260/280C
      DB-ALC2 Proprietary phase Mid-polar From 20 to 260/280C
      HP-Blood Alcohol Column Proprietary phase From -60 to 270/290
      *Temperature limits vary with column dimensions. Always confirm temperature limits prior to column use.
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