About kishore karuppaswamy

Iam Btech having experience in saudi aramco as instrument engineer

SMP of a control valve

Standard maintenance procedure of control valve

  • Obtain a hot work or cold work permit as per requirement.

  • Carryout j.s.a/j.h.a/toolbox meeting as applicable

  • Isolate and barricade the area and use proper p.p.e and tools

  • Override if it is connected to any interlock

  • Ensure the control valve is isolated from the process. depressurise the entrapped process fluid by drain points

  • Clean the control valve with dry cotton and ensure the moving parts are free from dust and debris

  • Lubricate the moving part with appropriate grease or lubricant as prescribed by the valve manufacturer

  • If required tighten all the accessories of the valve like positioner, lockup relay, solenoid valve, feedback link, gland nuts etc. do leak checks in pneumatic tubes and actuator

  • Stroke the control valve from hmi/hart/control room in the steps of 25%,50%,75% and 100% both in increasing or decreasing steps

  • Observe the control valve movement in the field and ensure the travel indicator shows the correct opening/closing of the valve on the scale

  • If valve closing/opening/intermediate positions are matching w.r.t signal go to step “a” otherwise follow the steps below

  • Isolate and disconnect the signal cable of the positioner and connect the loop calibrator to the positioner

  • Apply the 4ma And adjust the zero adjustment in the positioner, ensure the valve is at 0%

  • Apply the 20ma And adjust the span adjustment in the positioner, ensure the valve is at 100%

  • Repeat the above two steps and ensure the valve travel once again

  • Disconnect the loop calibrator and restore the positioner signal cable

  • Stroke the control valve from hmi/hart/control room in the steps of 25%,50%,75% and 100% both in increasing or decreasing steps

  • Ensure the control valve feedback in hmi

  • Step “a”—inform the production department about the completion of the job and its taking in line

  • Normalize the override if applicable

  • Close the permit to work

    Servicing of control valve

    • Servicing of control valve is required if it is reported struck, passing or not responding with respect to signal

    • Obtain ptw from production, override if connected to any interlock

    • Major parts of control valve is to be memorized

    • Actuator

      1

    • Body

      2

    • Packing

      3

      • Dismantling of control valve follows steps which can be explained briefly as below

       

      -mark the direction of actuator/bonnet/valve body with permanent marker

      -fix the control valve on a rigid support

      4

      -loosen spanner-nut (yoke nut) and gland nut to remove the actuator connecting body

      5

      -uncouple actuator upper stem from lower valve stem by removing stem connector (coupling nut)[split block with threads matching those on each stem]

      6

    • 7
    • 8

      -separate valve actuator from the body by removing loosened spanner nut (yoke nut)

    • 9
    • -remove the lower stem and plug from the body for servicing by loosening four large studs and service gland packing. Inspect the internal trim parts such as plug, cage, seat ring etc. if found damaged replace with an o.e.m spare parts. Inspect the seat and plug if found scouring rectify by lapping. Replace all gaskets with new one

      123456789

 -remove the (piston) diaphragm and (shaft) upper stem from the actuator by slowly loosening diaphragm hold down bolts (end cap screws)

12

3

4

5

6

7

8

9

9a

9b

-inspect and replace the worn/torn out parts with OEM parts and start reassembling in reverse order

-reassemble the (piston) diaphragm and (shaft) upper stem to the actuator and check the performance by lock up test.

-assemble lower stem and plug arrangement (trim) to the body and tighten the four bolts in bonnet to assemble the bonnet by placing the seat ring gasket first, then seat ring, cage(if applicable) and cage top gasket set (if applicable)

-now insert the lower stem through the yoke and place spanner-nut (yoke nut) in its place

-adjust for full closed condition by putting a wooden block in between the actuator stem and valve stem, and by pressing down the lower stem and actuator to ensure full close condition. Then tighten the spanner nut (yoke nut) & stem connector (coupling nut) and adjust the pointer scale for closed condition, now place the positioner along with feedback link and check for leaks. Lubricate all the moving parts

-perform the bench set confirmation checks of the actuator by applying specified range pressure directly to the actuator

  • restore all the accessories like positioner, feedback link, booster (if applicable),regulator, tubing etc

  • Calibrate the valve as described before.

  • ensure the proper stroke from the control room

  • inform the control room for the completion of the job and the valve taken in line

  • normalize the override if applicable

  • close the PTW

  • record the activities carried out and the spares consumed

  • prepare the check list/calibration sheet for the control valve

Finally I will explain once more dismantling of control valve…

Firstly uncouple actuator from body by removing stem connector (coupling nut)

Secondly remove yoke nut and separate actuator from body

Third remove studs to inspect lower stem, plug and gland packing

Fourth remove end cap screw (hold down bolt) to service the diaphragm, plate, upper stem and spring

Reassemble in the reverse order

Suggestions please….!!!!!!!!!!!!!!!!!!!!!

 

 

 

Safety Integrity Level (SIL)

Safety Integrity Level (SIL) Classification

sil9a

5 Classes of demand ( D)

D0: negligible demand rate; the scenario has not been heard of in industry;

D1: the interval between demands is more than 20 years; the scenario is unlikely to occur during the lifetime of the platform, but has been heard of in industry;

D2: the interval between demands is 4 to 20 years; the scenario is likely to occur during the lifetime of the platform or has already occurred before in the platform;

D3: the interval between demands is 6 months to 4 years; the scenario is likely to occur in the time period between two major stops;

D4: the interval between demands is less than 6 months; the scenario occurs several times per year on the platform

Risk Matrix to Determine Personal SIL Level

sil9b

 

Correction Factor-Injury:

a)Averting the Danger

sil5

b) Exposure Time

sil6

c) Mitigation

sil7

Risk Matrix to Determine Economic SIL Level

sil8

Risk Matrix to Determine Environmental SIL Level:

sil9

Instrument Gland sizes

  • Cable: 1pair x 1.5 mm2 FRLS   11.9 OD 7.3 ID-Gland:  0.5″NPTM   Range 10 to 14

  • Cable: 1pair x 1.5 mm2 FS 13.1 OD 8.5 ID-Gland: 0.5″NPTM Range 14 to 18

  • Cable: 2C x 1.5 mm2 FRLS 11.6 OD 7.3 ID-Gland: 0.5″NPTM Range 10 to 14

  • Cable: 2C x 1.5 mm2 FS 12.8 OD 8.2 ID-Gland: 0.5″NPTM Range 14 to 18

  • Cable: 2C x 2.5 mm2 FRLS 12.4 OD 7.8 ID-Gland: 0.5″NPTM Range 10 to 14

  • Cable: 2C x 2.5 mm2 FS 13.6OD 9.0 ID-Gland: 0.5″NPTM Range 14 to 18

  • Cable: 1T x 1.5 mm2 FRLS 12.3 OD 7.7 ID-Gland: 0.5″NPTM Range 10 to 14

  • Cable: 1P x 1.5 mm2 FRLS 11.9 OD 7.3 ID-Gland: 0.75″ETM Range 10 to 14

  • Cable: 1Px 1.5 mm2 FS 13.1 OD 8.5 ID-Gland: 0.75″ETM Range 14 to 18

  • Cable: 2Cx 1.5 mm2 FRLS 11.6 OD 7.3 ID-Gland: 0.75″ETM Range 10 to 14

  • Cable: 2Cx 1.5 mm2 FS 12.8 OD 8.2 ID-Gland: 0.75″ETM Range 14 to 18

  • Cable: 2Cx 2.5 mm2 FRLS 12.4 OD 7.8 ID-Gland: 0.75″ETM Range 10 to 14

  • Cable: 2Cx 2.5 mm2 FS 13.6 OD 9.0 ID-Gland: 0.75″ETM Range 14 to 18

  • Cable: 1Tx 1.5 mm2 FRLS 13.6 OD 9.0 ID-Gland: 0.75″ETM Range 10 to 14

  • Cable: 10Cx 1.5 mm2 FRLS 18.4 OD 13.1 ID-Gland: 1″ETM Range 18 to 21

  • Cable: 10Cx 1.5 mm2 FS 22.1 OD 15.7 ID-Gland: 1″ETM Range 21 to 24

  • Cable: 10Cx 2.5 mm2 FRLS 19.9 OD 14.6 ID-Gland: 1″ETM Range 21 to 24

  • Cable: 10Px 0.75 mm2 FRLS 23.6 OD 16.8 ID-Gland: 1″ETM Range 24 to 27

  • Cable: 10Px 0.75 mm2 FS 27.9 OD 21.5 ID-Gland: 1.5″ETM Range 30 to 34

  • Cable: 10Tx 0.75 mm2 FRLS 26.6 OD 19.8 ID-Gland: 1.25″ETM Range 27 to 30

  • Cable: 10Tx 1.5 mm2 FRLS 31.3 OD 24.5 ID-Gland: 1.5″ETM Range 30 to 34

  • Cable: 10Tx 1.5 mm2 FS 36.2 OD 29.4 ID-Gland: 2″ETM Range 30 to 37

  • Cable: 20Cx 1.5 mm2 FRLS 21.7 OD 16.2 ID-Gland: 1″ETM Range 21 to 24

  • Cable: 20Cx 1.5 mm2 FS 25.5 OD 19.3 ID-Gland: 1.25″ETM Range 27 to 30

  • Cable: 20Cx 2.5 mm2 FRLS 24.5 OD 18.3 ID-Gland: 1.25″ETM Range 24 to 27

  • Cable: 20Cx 2.5 mm2 FS 27.6 OD 21.4 ID-Gland: 1.25″ETM Range 27to 30

  • Cable: 20Px 0.75 mm2 FRLS 31.1 OD 24.3 ID-Gland: 1.25″ETM Range 30 to 34

  • Cable: 20Px 0.75 mm2 FS 35.6 OD 28.8 ID-Gland: 2″ETM Range 41 to 46

  • Cable: 20Tx 1.5 mm2 FS 52.6 OD 42.2 ID-Gland: 2.5″ETM Range 53 to 61

  • Cable: 40Cx 1.5 mm2 FRLS 28.4 OD 22.0 ID-Gland: 1.25″ETM Range 27 to 30

    Cable: 40Cx 1.5 mm2 FS 32.8 OD 26.4 ID-Gland: 1.5″ETM Range 30 to 37

  • Cable: 40Cx 2.5 mm2 FRLS 31.9 OD 25.3 ID-Gland: 1.5″ETM Range 30 to 34

  • Cable: 40Cx 2.5 mm2 FS 35.7 OD 29.3 ID-Gland: 2″ETM Range 37 to 41

  • Cable: 5Px 0.75 mm2 FRLS 18.0 OD 12.7 ID-Gland: 1″ETM Range 18 to 21

  • Cable: 5Px 0.75 mm2 FS 21.8 OD 15.4 ID-Gland: 1″ETM Range 21 to 24

  • Cable: 5Tx 1.5 mm2 FRLS 24.5 OD 18.1 ID-Gland: 1.25″ETM Range 24 to 27

  • Cable: 5Tx 1.5 mm2 FS 28.3 OD 21.5 ID-Gland: 1.25″ETM Range 27 to 30

  • Cable: 1Px 1.5 mm2 FRLS 11.9 OD 7.3 ID-Gland: 1″NPT Range 10 to 14

  • Cable: K TYPE THERMOCOUPLE COMP  12.5 OD 7.9 ID-Gland: 0.75″ETM Range 10 to 14

    All Cable OD & ID can have + or – 2 in sizes tolerance and cable glands should be stainless steel ,double compression for out door hazardous area ,stainless steel with nickel platingwith neoprene seal neoprene bushing,IP-66 for steel wire armoured cable,complete with locknut,earth tagPVC shroud and nylon entry threads/seal for IP66 ingress protection

    Tolerance is about (+/-)3 %

Tips and tricks in field instrumentation

TIPS AND TRICKS IN FIELD INSTRUMENTATION

  1. For RTD Pt 100 measurement,measure  the resistance across the white and common terminal, then the temperature can be calculated simply by

    Temp=(resistance measured across terminal minus 100)/0.385  or (resistance measured across terminal minus 100)multiplied by 2.6

for example

if the resistance across white and red terminal is 126 ohm, then

the temperature measured is 26/0.385=67.53 degree centigrade or 26 multiplied by 2.6

26*2.6=67.53

 This follow the same eqn, R=Rₒ(1+αT) remember that this is only applicable for PT 100 not other types

  1. For calibration of -100 mmH2O to -10 mmH20 range capillary type using pressure pump not vacuum pump

The values for 25%,50%,75%,100% are as follows:

0%————-     -100 mm h2o

25%———–      -77.5 mm h2o

50%——–          -55 mm h2o

75%———         -32.5 mm h2o

100%——           -10 mm h2o

First find the Span=URV-LRV=-10+100=90 

Then divide this by 4 as we are  calibrating for 4 values namely 25%,50%,75%,100%

i.e. 90/4=22.5

then the 4 points can be calculated as follows

0%(4ma)————-     0 mm h2o i. e LP  and HP open to atmosphere

25%(8ma)———–      -0+22.5=22.5 mm h2o (apply 22.5mmh2o to HP side not LP here LP is open to atmosphere.)

50%(12ma)——–    22.5+22.5=44 mm h2o (apply 44mmh2o to HP side not LP)

75%(16ma)———         44+22.5=67.5 mm h2o (apply 67.5 mmh2o to HP side not LP)

100%(20 ma)——           67.5+22.5=90 mm h2o (apply 90 mmh2o to HP side not LP)

  1. Calculation of flow m3/hr from differential pressure  values mm h20 if both ranges are known:

We know that the flow equation is related as follows

Q=k√∆p

Here Q is the rate of flow: k is the Bernoulli’s constant;  and ∆p is the differential pressure

Consider for instance the D.P. transmitter is of range 0 to 120 mm H2O and the DCS range of

0 to 1500 m3/hr

Then the next step is to find the Bernoulli’s constant

i.e. Q=k√∆p

1500=k√120 (here we consider span URV values to find Bernoulli’s constant)

k=1500/√120

k=136.936

Once we get Bernoulli’s constant we can calculate any flow rate if we know the D.P. 

For e.g.

If differential pressure is 90 mmH2O

Q=k√∆p becomes

Q=136.936√90

   = 136.936*9.486 = 1298.9 m3/hr

Thus we can calculate any flow rate if we know the transmitter and DCS range.

Or simply

Flow in DCS(present value) =(DCS range)√(Present DP value/DP range)

For example DCS range is 1000m3/hr,

DP range is 100 mmh20,

And present DP value in transmitter is showing 25 mmh2o,then

DCS flow will be

Flow in DCS(present value) =(DCS range)√(Present DP value/DP range)

       =1000√(25/100)

      =1000√(1/4)

      =1000*1/2

     =500 m3/hr

4.For K type thermocouple (Chromel alumel) if the mV measured across yellow(positive) and red (negative) is x,then the temperature can be calculated as follows

Temperature=x/0.0397(millivolt measured divided by 0.0397) or x *25.2 (millivolt multiplied by 25.2)

for example if we measure the mV value across yellow and red terminal using a multimeter and found to be 0.397 then temperature can be calulated by

temperature=(0.397/0.0397)=10 degree centigrade or (0.397*25.2)=10 degree centigrade

6.calibration checking of capillary type LT if you dont have any instruments for checking

Suppose that a capillary type LT is mounted on a tank having range of -1200mmh2o as LRV and URV -60 mmh2o and you need to check whether the transmitter is Ok

We know that the transmitter is mounted with HP side to high pressure side and LP tapping to low pressure side,Firstly isolate the process line,vent and drain the process inorder to release any trapped pressure inside the flange.the transmitter will show 0% reading ie(-1200mmh2o),

Now measure the tap to tap length and mark the corresponding 25%,50%,75% and 100% level .Remove the LP flange of the transmitter(with HP flange of capillary intact) and keep it near(parallel) to HP tapping, the transmitter will show 100%.Now lift the LP capillary flange to  25% above from the HP tapping (where we marked before as 25%),now the transmitter will show 75% (not 25%)

Next keep the transmitter LP capillary flange at 50% marking the transmitter will show 50% reading.Similarly when we place at 75% the transmitter will be showing 25%

Finally if we place at 100% marking the transmitter should show 0% that is -60mmh2o