Assured Leak Free Pressure Vessel Flanges on Start-Up and In-Service; A Practical Reality for Process Industries

摘要

The behaviour of a bolted joint whether it is in a process industry pressure vessel, aircraft or car, is governed by the same science. Its reliability is dependent on three parameters: - joint design, component quality and installing bolts to the design bolt tension objective. By measuring and assuring all three factors, bolted joint reliability is guaranteed. The risk of fatigue, vibration loosening and pressure containment leaks in service can all be eliminated. Bolted flanges are a major source of all emissions and leaks; flange leaks on heat exchangers are of most concern to global energy/petrochemical operators; despite this the traditional assurance on design and component quality of industrial bolting remains the main focus; despite 90% of bolted joint failures being attributed to insufficient, bolt tension on tightening. Whilst every effort is made to accurately control the tightening power applied to a bolt, bolt tension is rarely measured. Bolted joint failures can be avoided by assuring design bolt tension. Bolt tension = joint compression = gasket seating stress. The gasket seals under maximum service loading resulting in zero leaks for the planned production run. This bolted joint technology paper explains how manufacturers, EPC contractors and end users are unable to assure zero leak performance of their pressure containing equipment because of adherence to traditional installation procedures. Here exists a deep rooted mind set, that tightening power and a digital record equals bolt tension. Industry appears reluctant to continuously improve bolt tightening operations and embrace technology that measures the parameters that assure joint reliability and subsequent lowest cost of ownership of a pressure vessel. The relationship between installed bolt tension and joint failure mechanisms is explained along with the limitations of traditional tightening in assuring joint reliability. A unique bolt measurement system, that has been very effective across all industries, especially in assuring flange reliability on pressure vessels in petrochemical operations, is described.