Successive brownfield projects in GASCO plants utilized spare space on existing pipe racks to route new pipes. These pipe racks were originally designed as per erstwhile industry standards and environmental data, which have become obsolete over the years. In the absence of distinct guidelines, indiscriminate approaches were followed to confirm adequacy of these racks in order to reutilize them. Most of these approaches were irrational, had design flaws and raised serious concerns on the safety and integrity of the existing structure. This paper presents the full-fledged methods and procedures followed in GASCO for adequacy check and modifications of structures that assures high level of integrity of existing racks.
Adequacy checks present diverse challenges such as unavailability of as-built documents, want of primary analysis model, revision of codes etc. GASCO has developed an exclusive design guideline for structural adequacy check and execution of modifications, as a consequence of few incidents of failure of old pipe racks. Based on ‘Available' and ‘Not Available' state of required data, the pipe rack is grouped into different categories and stepwise design procedure is outlined for each of the categories. Tips on usage of right codes, estimation of missing loads, elimination of design errors, essential design checks, etc., are supplied. Practical techniques for strengthening of structurally deficient existing members and foundations are elucidated with sketches.
Development and implementation of common guideline encompassing all the design requirements for adequacy check and reinforcement of existing structures has resulted in unifying the approaches across GASCO plants thus ensuring a high level of safety and integrity of the existing pipe racks used in expansion projects.