Efectos del cambio climático a nivel nacional

Refer to P&ID: B66-A-BA-543210-001, B66-A-BA-543213-001, B65-A-BA-540691-002 and Figure 4.13.1 of this document.

Objective

Protect each NGL Train feed gas header from over-pressure by reducing the feed gas flow rate from Hawiyah gas pipeline first and if the header pressure is still higher than the set value, reduce the feed gas flow rate from Haradh gas pipeline.

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Functional Description

The controls description that follows is for the NGL recovery Train1 only, but the control scheme is the same for NGL Train 2 and NGL Train 3 only with different prefix for instrument tag identifications.

The NGL train feed gas header High Pressure protection controller 41-PIC-499B receives its PV from the Expander suction header pressure measurement 41-PT-499. The output of 41-PIC-499B is split via a split range calculator. Two outputs of the split range calculator are connected to blocks 41-HIC-014 and 40-PY-499B.

Higher range split control signal to reduce feed gas flow rate from Hawiyah gas pipeline will adjust setpoint of Max Hawiyah train feed flow limit controller, 41-HIC-014, when it is in Cascade mode. Output of 41-HIC-014 will then pass through low signal selector, 41-FY-001 to finally control 41-FV-001.

When 41-HIC-014 is in Auto mode, the operator can set the maximum feed gas flow rate for NGL train 1 at the SP of 41-HIC-014.

When 41-HIC-014 is in Manual mode, the operator can manually change HIC output signal to override the output signal from 41-FIC-001 via low signal selector 41-FY-001.

Lower range split control signal from 41/42/43-PIC-499B to reduce feed gas flow rate from Haradh gas pipeline will pass through low signal selector, 40-PY-499B. Output of 40-PY-499B will then adjust the SP of both 31-HIC-003 and 32-HIC-003 when it is in Cascade mode. Output of 31/32-HIC-003 will then pass through low signal selector switch 31/32-FY-003 to finally control 31/32-FV-003.

When 31/32-HIC-003 is in Auto mode, the operator can set the maximum feed gas flow rate for DGA train 1/2 at the SP of the HIC.

When 31/32-HIC-003 is in Manual mode, the operator can manually change HIC output

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signal to override the output signal from 31/32-FIC-003 via low signal selector 31/32-FY-003.

Operational and Implementation Aspects

NGL Train Header High Pressure Protection control scheme is required to be operational during start up and normal operation.

In normal steady state, for Hawiyah pipeline feed gas control, low signal selector 41-FY-001 is cascaded to 41-HIC-014, which in turn cascaded to NGL Train High pressure controller, 41-PIC-499B. While for Haradh pipeline feed gas control, low signal selectors 31/32-FY-003 are cascaded to low signal selector 40-PY-499B via 31/32-HIC-003 respectively. Low signal selector 40-PY-499B will select the lower value from 41/42/43-PIC-499B lower range output signals to control the feed gas rate to DGA trains when one or more NGL Trains header pressure is too high.

NGL Train Header High Pressure Protection Controller: Operator to be able to decrease SP down to an enforced low limit. The operator shall not have access to 41-PIC-499B controller’s mode or set point enforced low limit. Only engineer can change the controller mode or set point enforced low limit.

Crippled Mode Operation

Failure of the NGL Train gas inlet pressure input signal from 41-PIT-499, identified as a

“Bad Value” status in DCS, will cause an alarm and high pressure protection controller 41-PIC-499B to go to MANUAL mode, with the output remaining at the last good value previous to transferring to MANUAL mode.

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Figure 4.13.1: HNGL Train High Pressure Protection Control Feed Gas from Hawiyah AO/AFS 42FV-001 43FV-001

41FY 001 42FY 001 43FY 001

41FIC001 42FIC001 43FIC001 31FV-003 32FV-003

DGA-1 B65-C-101 DGA-2 B65-C-XXX

31FY 003 32FY 003

31FIC003 32FIC003

Feed Gas from Haradh

41PIC 499A41PIC 499B

41HIC 014 42HIC 014 43HIC 014

SR (NOTE 1) 42PIC499B 43PIC499B 31HIC 003 32HIC 003

HNGL-1 B66-C-110

0-X %

X-100 % NOTES: 1. Typical for HNGL Train 1, 2 and 3 High Pressure Protection Controller 4*PIC-499B. Valve Opening [%] 0

100 100 4*PIC-499B MV [%]x

4*FV-00131/32FV-003

SR (NOTE 1) SR (NOTE 1) 40PY 499B

HNGL Train-2 HNGL Train-3

HNGL Train-2 HNGL Train-3

X-100 % 0-X % X-100 % 0-X %

SP SP SP SP SP

41FV-001 AO/AFS AO/AFS AO/AFS AO/AFS

Rev

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Calculation

41-PIC-499B Output Split Range Calculation

When 41-PIC-499B.PV is less than the setpoint value, the High Pressure protection controller, 41-PIC-499B, output signal is on the high side, 100%.

When process value is greater than or equal to the set value, Split range calculation block should convert 41-PIC-499B higher range output signal, X% ~ 100% to 0% ~ 100% as input signal to 41-HIC-014, and lower range output signal, 0% ~ X% to 0% ~ 100% as input signal to low signal selector switch, 40-PY-499B.

Initializations

NGL Train Header High Pressure Protection controller, 41-PIC-499B SP shall not track PV when it is in MANUAL mode.

Output of 41-PIC-499B should be configured to track the 41-HIC-014 setpoint, when HIC is placed in MANUAL or AUTO mode. Upon switching 41-HIC-014 to CASCADE mode, 41-PIC-499B output should be initialize to 41-HIC-014 setpoint to prevent bumping of the process.

No output pushback shall be configured for low signal selector 40-PY-499B when any of the 31/32-HIC-003 switched from AUTO or MAN mode to CASCADE. Upon switching 31/32-HIC-003 from AUTO or MAN mode to CASCADE, HIC SP should ramp slowly to match MV of 40-PY-499B.

Anti reset windup (ARWU) shall be configured for NGL train feed flow controller 41-FIC-001 and feed flow override controller 41-HIC-014 to ensure bumpless transfer in case HIC is overriding the FIC as follows:

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Normally, 41-FIC-001 in control, 41-HIC-014 MV shall be initialized to the low selector output value (41-FY-001.MV). When 41-HIC-014 in control, the NGL train feed flow controller 41-FIC-001 MV shall be initialized to the low selector output value (41-FY-001.MV)

Anti reset windup (ARWU) shall be configured for DGA feed flow controller 31/32-FIC-003 and Maximum DGA feed flow limit controller 31-HIC-003/32-HIC-003 to ensure bumpless transfer in case HIC is overriding the FIC as follow:

Normally, 31/32-FIC-003 in control, 31/32-HIC-003 MV shall be initialized to the low selector output value (31/32-FY-003.MV). When the 31/32-HIC-003 in control, the DGA train feed flow controller 31/32-FIC-003 MV shall be initialized to the low selector output value (31/32-FY-003.MV)

Special Consideration

Upon 41-FY-001 selecting signal from 41-HIC-014 for more than 10 seconds, and the mode of 41-HIC-014 is in CASCADE, 42-FIC-001 and 43-FIC-001 will set to AUTO mode (one shot signal) if it is in CASCADE. The Operator is responsible to switch 42/43-FIC-001 back to CASCADE when the operating condition is back to normal.

Maximum Hawiyah train feed flow limit controllers, 41/42/43-HIC-014, and Hawiyah train feed flow controllers, 41/42/43-FIC-001 must have the same process variable range.

Similarly, Maximum DGA feed flow limit controller, 31/32-HIC-003, and DGA feed flow controller, 31/32-FIC-003 must have the same process variable range.