This posting (November 2019) is an update to an October 2013 post which reflects changes to the ASME B31.3 Code relative to severe cyclic service that have occurred since the original post. There has been a fair amount of confusion as to when the rules for severe cyclic conditions in ASME B31.3 should be used, […]
Traditional rotating equipment mounted at grade use the mass of a foundation and grout to reduce vibration and provide support and stiffness. However, cooling tower fans must be elevated many feet above a basin of water which sometimes puts them “out of sight and out of mind”. Cost and practicality prohibits concrete and grout, thus […]
Machinery and reliability people have for a long time observed that when it comes to long life and high reliability, operating at higher speeds compares poorly to operation at lower speeds. One of the primary reasons for having high-speed devices is economics. With high speed you can have smaller equipment sizes with fewer stages. While […]
Today it is common practice in overhauls of large rotating equipment to spend many man hours in detailed planning, coordination, writing procedures, reviewing documentation, reviewing past photos, procuring and inspecting spare parts etc. We also review our past experience and put steps in place to mitigate past problems or errors. Now that we have a […]
There are three characteristics of motion which are all related by the natural frequency of vibration for steady state harmonic vibration: displacement, velocity and acceleration. Of these, which is the best indicator for cyclic stress (or strain) which in turn is related to fatigue damage? As it turns out, it is velocity. One may think […]
Serious floods rarely occur in the life of a refinery or petro-chemical plant. But when such an event does occur there are significant implications for the reliability of rotating equipment and associated business risks when it’s time to restart the plant. And because this scenario is so uncommon, there are few, if any, industry standards […]
A new process unit was designed and built by a petrochemical manufacturer. As part of the project, two 50 horespower blowers were installed. Rotating equipment of this type is traditionally installed at grade on an engineered monolithic concrete foundation with rebar and anchor bolts. A suitable soleplate or baseplate is then grouted to the foundation […]
The Becht Guys were recently involved with removing an existing large WPII (weather protected, internal air-cooled) electric motor and installing a new spare motor on a planned outage. This work was being performed in a petrochemical plant where we spent most of our careers. Many years ago we had developed a program to extend the […]
Summary At a gulf coast site, a large catalyst drier began experiencing vibrations after start up and suffered a failure. The drier internal diameter is approximately 7 feet, measures 40 feet long and is supported at each end by 2 large trunion shafts on which are mounted 2 rollers. There is a large ring gear […]
Background and The Problem 24 new 3600 RPM, 440 volt AC induction motors were replaced at a large refinery as a result of flooding during hurricane Ike. The motors were inundated by 6 ft to 12 ft of floodwater. The new motors were from three of the major industrial motor manufacturers. Horsepower ratings ranged from […]
