Ensuring Safe Facility Blowdown and Lessons Learnt from Incident Investigation
Abstract
A facility blowdown in the oil and gas industry is a safety critical operation; required to ensure the safe shut-down of processing facilities during a plant emergency. In a blowdown operation, the entire plant is isolated into a number of segments and then depressurized into the facility’s flare system. The outcome of a blowdown event is dependent on the performance of a number of safety critical elements in the plant; these are designed to ensure the safe and successful depressurization of the plant without any conspicuous incidents. Blowdown events are inherently fast transient processes, reliant on a large number of valve opening and closing operations with rapid reduction in pressure and temperature. It is critical to ensure that the process is depressurized quickly enough (cf. API 521) but whilst respecting constraints such as minimum design metal temperatures, AIV/FIV limits in flare tailpipes and pressure constraints throughout the flare system. Blowdown incident investigations typically involve a critical review of the plant historian data and require dynamic simulation studies to adequately assess the event so as to determine whether the blowdown operation proceeded as planned, that no constraints were violated and to glean any process safety lessons that can be learnt. In this talk, with reference to a number of recent events on oil and gas facilities, we explain how to carry out a comprehensive blowdown investigation. We will discuss a number of case studies from facilities in different parts of the world, including those that have shown operational deviations such as non-closure/partial closure ESD valves, delays in opening or non-opening of BDVs, non-operational check valves. Some of these deviations caused flare capacity issues in the plant, minimum design metal temperature (MDMT) violation risks to process drums, unexpected pressurization of process drums, flow reversal into low pressure segments causing near miss events, and other violations of recommended practice. We will explain how these studies have helped understand the current state of the plant’s safety barrier and have been used by operating companies to identify design and operational changes critical for safe plant operation. Finally we will discuss how these studies provided input to plant maintenance personnel in order to help prioritize maintenance activities and to make prudent maintenance investment.
Description
PresentationSubject
facility blowdownCollections
Citation
Lawrence, Praveen; Marriott, James; Giovanoglou, Apostolos (2015). Ensuring Safe Facility Blowdown and Lessons Learnt from Incident Investigation. Mary Kay O'Connor Process Safety Center; Texas &M University. Libraries. Available electronically from https : / /hdl .handle .net /1969 .1 /193707.