Introduction
- Petronet LNG Limited (PLL) – Dahej Terminal at Regasified LNG (RLNG) was established in three phases.
- Phase 1 with north jetty got commissioned in 2004. Phase-2 got commissioned in 2009.
- Phase-3A commissioned in August 2016.
- Phase-3B1 was commissioned in June-19.
- Phase-3A Stv’s four shell venting is required to vent out accumulated gases in its top part of shell and venting is being done manually.
- To make this process easy and semi-automatic venting system is to be installed. PLL desires engineering study for venting system installation.
- Petronet LNG awarded contract to iFluids Engineering to design the semi-automatic venting system.
- In the PLL, Dahej LNG Regasification unit, LNG is converted to gas by the STVs. LNG is in the tube side and Water-Glycol mixture is circulated in the shell side to heat the LNG.
- The Glycol water mixture system is a closed system with an ambient air heater and buffer vessel and the system is maintained at the required pressure.
- In Phase-3A STVs (Four nos) shell side venting is required to be done to eliminate the accumulated gases in its top portion of the shell.
- To eliminate manual operation, semi-automatic venting system is proposed with routing to flare system after removing moisture to the required specification.
Key Components of the New Venting System
- Remote operated on-off valves in the gas vent line.
- Trap assembly to separate the Glycol water from natural gas in the vent line.
- Knock out drum to remove any Glycol water in the natural gas. Knock out drum shall be common for 2 STVs.
- Remote operated on-off valves in KOD drain to glycol water drain drum.
- Moisture adsorber to remove any moisture content in the vented gas to Flare.
- Adsorber will be common for both the knock out drums.
- Flowmeter along with totalizer to measure the vented gas quantity.
- Dewpoint analyzer for measuring the water dew point of the vented gas.
- U loop shall be provided in the adsorber inlet to drain the carry over glycol water.
Detailed Engineering Studies and Disciplines
The design study encompassed comprehensive engineering activities across multiple disciplines, ensuring a robust solution that aligns with the facility’s operational requirements.
- Process Engineering
- Process Design Basis and Study Report
- Process Flow Diagram for Phase – 3A STV’s Gas Venting System
- Piping and Instrumentation Diagram for Phase – 3A STV’s Gas Venting System
- Process Datasheets for Vent Trap Assembly and Moisture Adsorber
- Hydraulic Study Calculation and Report
- Knock Out Drum Sizing Calculation
- Cause and Effect Matrix Diagram
- Line List
- Equipment List
- Mechanical Engineering
- Mechanical Datasheets for Vent Gas Knock Out Drum
- Piping Engineering
- Piping Plan for Venting System
- Piping Layout
- Piping Material Specification
- Valve Material Specification
- Pipe Support Design and Drawings
- Isometric Drawings
- Valve List
- Y-Strainer Specification
- Piping BOQ with Cost Estimation
- As-Built Document
- Civil & Structural Engineering
- Foundation Design Calculation
- Analysis of Existing STV Structures
- Civil BOQ with Cost Estimation
- Instrumentation Engineering
- Instrument Index
- Specifications for Flow meter and Moisture Analyzer
- Instrument Datasheets
- Cable Schedule
- Hook-Up Diagram
- Instrument BOQ Cost Estimation
- Technical Safety:
- HAZOP Study and Report to assess potential operational risks, ensuring the venting system meets high safety standards.
Conclusion
iFluids Engineering’s design of a semi-automatic venting system for the Dahej Terminal’s Phase 3A STVs exemplifies cutting-edge engineering solutions to optimize safety, operational efficiency, and environmental compliance. This design transforms manual venting into a streamlined, safe, and automated process, reducing operator burden and enhancing safety.
This project showcases best practices in integrating automated safety features, moisture control, and precise instrumentation into complex systems. This engineering case study not only illustrates technical expertise but also provides insight into real-world solutions that enhance facility performance and operational safety.