Problem

Pipe ruptures occurred at a major refinery Coker blowdown system. The problem was investigated by the internal engineering group and other consultants. KHE was called in because of our capability to analyze the process and mechanical response of the unit using our Integrated Systems Approach. The failure cost over $1MM in expense and posed a safety hazard.

Solution

KHE field services group instrumented the unit. KHE recorded the pressure, temperature, flow, and vibration during the ten plus operating modes. Pipe stress analysis was performed to analyze large-scale piping response. The process was analyzed and determined that thermal shock occurred during one transient event. Using Finite Element Analysis, we modeled the field data in a structural model of the piping section and determined that the thermal shock created sufficient stress to rupture the line. KnightHawk Engineering’s field services group verified this occurrence as part of the process cycle.

Result

A process change with rerouting of two process streams solved the problem. The client has experienced no more problems with this unit.

Problem

A client purchased approximately fifty Transfer Line Exchangers (TLE) valued at $18MM. The equipment was designed to operate for over twenty years. Within twelve months after startup the equipment failed. This equipment is used in ethylene facilities to quench cracked gas exiting out of a furnace. The gas side process conditions were approximately 1650 °F and 1 bar. The shell side conditions were saturated water at 616 °F. Each failure caused approximately $1MM in expense and posed a safety hazard.

Solution

KHE developed detailed waterside computational fluid dynamics (CFD) models to investigate the cooling of the inlet tube sheet. CFD also was utilized to determine the aerodynamic conditions of the flow entering the exchanger. The heat transfer and stresses of the heat exchanger were determined by finite element methods. KHE’s work determined that the root cause was a low flow zone that caused superheating and failure. Our work was verified by the client and vendor of the equipment by experimental investigation. Scale models were built and was determined that KHE’s CFD and FEA work matched the experimental model. KHE utilized the same CFD and FEA methods to redesign the equipment.

Result

A major failure root cause was determined. The client saved several million dollars in lost production. The problem was solved by KHE on the first iteration of design and stands as a model in industry today.