Session: HT-04-01 Design and Analysis of High-Pressure Equipment for Industry

Paper Number: 105698

105698 - Fit for Service Evaluation of Ldpe Tubular Reactor Tubes Exposed to Severe Decomposition 

The low density polyethylene (LDPE) tubular reactor tube is fabricated from a material with extremely high fatigue strength. During severe runaway decomposition reaction, rapid heating by the decomposing gas which exceed the austenitizing temperature of the material and subsequent quenching by relatively cold gasses after rapid opening of the hydraulic blow off valve (safety valve) will result in hardening at the tube bore of the reactor tube. The fatigue life of the reactor tube can be negatively affected by the presence of a hardened layer. A limit of 2 mm of depth of hardening at the tube bore is specified in the operating manual for safe operation. Typically hardness test of lens rings (gasket in-between the two high pressure tubes) will establish whether the tube material has hardened beyond the 2 mm limit as a result of decomposition. Due to differences in chemical composition between the reactor tube and lens ring, a correlation between depth of hardening of lens ring and reactor tube is investigated. The remaining life of a 3.4 mm depth of hardening reactor tube was predicted through experimental cyclic fatigue test approach. The finding suggested that the tube depth of hardening was almost close to the hardened lens ring, without any loss of autofrettaged-induced residual compressive stress on the tube inner surface (ID). The experimental cyclic fatigue test suggested that the 3.4 mm hardening depth of tube could endure a significant numbers of pressure cycles before the tube fails (i.e. a through-wall crack that leaks).

Presenting Author: Ahmad Hassan Abdul Hamid PETRONAS Chemicals Ammonia Sdn Bhd

Presenting Author Biography: Ahmad Hassan has 17 years of experience as Inspection Engineer in Oil and Gas industry. He has carried out various fixed equipment inspection, mechanical integrity and fitness for service assessment. He is also certified with various international certifications such as API 510 Pressure Vessel Inspection, API 570 Piping Inspection, API 571 Corrosion and Materials, API 580 Risk Based Inspection, and CSWIP Welding Inspector.

Authors:

Ahmad Hassan Abdul Hamid PETRONAS Chemicals Ammonia Sdn Bhd
M Syukri Abdul Rahim PETRONAS Chemicals Ammonia Sdn Bhd
Alias Mamat PETRONAS Chemicals Ammonia Sdn Bhd
Ibrahim Mat PETRONAS Chemicals Ammonia Sdn Bhd
Alias Kadir PETRONAS Chemicals Ammonia Sdn Bhd