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.
The new venting system consists of the following:
- 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.
The following detailed engineering activities were carried out discipline wise based on the requirement
- 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 Datasheets for Vent Gas Knock Out Drum
- 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:
- Foundation Design Calculation
- Analysis of Existing STV Structures
- Civil BOQ with Cost Estimation
- Instrument Index
- Specifications for Flow meter and Moisture Analyzer
- Instrument Datasheets
- Cable Schedule
- Hook-Up Diagram
- Instrument BOQ Cost Estimation
- HAZOP Study and Report