Introduction
Megha City Gas Distribution Private Limited (MCGDPL), a Part of Megha Engineering and Infrastructures Limited (MEIL), envisages an energy-efficient India. Megha gas is a sprinter in the Indian City Gas Distribution (CGD) Network. It strives to provide environment-friendly natural gas to households with cost-effective piped connections, in addition to CNG for vehicles.
Facility Description:
Megha City Gas Distribution Private Limited (MCGDPL), Khammam region has 2 CNG stations in various locations of Khammam. The CNG stations are classified into the different categories:
• Online stations
• Mother Stations
• Daughter Booster Stations
• Daughter Stations CNG Stations.
The CNG Stations is a Station which receives NG through pipeline of 19 – 22 barg or mobile cascade from nearby mother stations above 250 Barg. After getting compressed via compressor, the gas would be sent to Dispensing Units (DU) and Cascade in Online and Mother stations. And the gas would be sent to Dispensing Units (DU) after compression to 250 barg in Daughter Booster stations. Also the gas would be sent to Dispensing Units (DU) without compression in Daughter stations which is clearly mentioned in below figures.
Scope
The scope of work is to carry out QRA study for for Prashanthi CNG Filling Station of Megha City Gas Distribution Private Limited (MCGDPL). And this study covers the different sections, components, and equipment associated with this facility and process description only.
Objective – QRA study
The aim of quantitative risk assessment is to evaluate the risk levels for personnel due to accidental release of hazardous components/materials due to loss of containment scenarios from the facilities and to analyse and exhibit that individual risks lie within the broadly acceptable regions. The main objective of the study is to evaluate the potential risk levels for personnel due to accidental release of hazardous materials and to exhibit that individual risks lies within the acceptable region.
The Objectives of QRA are as follows:
- To Identify Hazards and Major Loss of Containment(LOC) scenarios.
- To Calculate physical effects of failure case scenarios which include Estimation of Jet Fire, Pool Fire heat radiation distances, Flammable gas dispersion distances, BLEVE and overpressure explosion impact distances.
- Failure Frequency evaluation.
- To quantify Societal risk around the particular facility.
- Performs risk assessment to confirm that risk can be reduced consistent with the ALARP region/principle according to the UK HSE risk acceptance criteria.
- Recommending measures to reduce risk and ensuring whether all risks are in ALARP or Acceptable region
Author Summary about this study:
This Facility has been divided into 6 isolatable sections. As this facility handling CNG the Major credible outcome events of Jet fire, Fire Ball, Flash fire & Overpressure Explosion have been identified and their impacts/consequences for each scenario have been determined using DNV PHAST 8.4. And the risk Analysis has been carried out with frequency outcome and frequency for the respective events using DNV SAFETI 8.4. From the results Most of the locations falls under ALARP region. In order to prevent the risk few safety practices have been provided as recommendations. Recommendations are
1. Ensure adequate nos. of Hydrocarbon detectors at strategic location.
2. Ensure that adequate nos. of suitable portable fire-fighting appliances shall always be kept in good working condition along with the Safety appliances within the CNG stations.