Industrial Maintenance Solutions

BY BHUSHAN NIKAM. Invented in the mid-20th century and typically equipped in process gas centrifugal, dry gas screw compressors and expanders, dry gas seals (DGS) are the preferred gas lubricated dry seal solutions available on the market. They have become the standard for new machines. DGS are robust, simple, consume less power, and are more efficient in reducing leakage than their predecessor. Various configurations such as tandem with and without an intermediate labyrinth ( Figure 1 ), single ( Figure 2 ), and double ( Figure 3 ) are available & shall be selected based on process requirements. In this article, we discuss the various DGS failure modes and how they should be addressed:  PRESSURIZED HOLD/STANDBY Pressurized hold, also called settle-out condition, occurs when the compressor remains at a standstill, but the casing is pressurized. If an alternate process gas lacks sufficient pressure and flow, process gas enters the seal cavity through the process labyrinth ...

Whether selecting new or maintaining existing process equipment, bearings are a critical component in the equipment’s reliability, efficiency, and life. The majority of rotating process equipment today relies upon either rolling element or fluid film bearings to counteract gravity and developed forces in the equipment and allow for free rotation of the shaft. Selecting the right bearing for the equipment and application is essential to the successful operation of that equipment. A key difference between rolling element and fluid film bearings for personnel concerned about the maintenance of process equipment is the expected life of the bearings. Rolling element bearings typically have a predictable life based on the operating conditions; fluid film bearings, when properly designed and maintained, can operate for decades. Additional comparisons of rolling element and fluid film bearing characteristics, such as lubrication needs and the ability to handle impact loads, are provided in t...

  There are literally dozens of ways bearings can fail. Some of the more common include: • Babbitt fatigue • Babbitt wiping due to rotor to stator contact • Babbitt flow due to high operating temperatures • Foreign particle damage • Varnish build-up • Electrostatic discharge damage (frosting) • Electromagnetic discharge damage (Spark tracks) • Oil “burn” or additive plating due to high temperatures • Loss of bond between babbitt and base metal • Chemical attack • Pivot wear in tilting pad bearings • Unloaded pad flutter • Cavitation damage This is taken from a paper, Babbitted bearing health assessment" by John Whalen of John Crane, Thomas Hess of Rotating Machinery Group, Jim Allen of Nova Chemicals Corporation and Jack Craighton of Schneider Electric. Babbitt fatigue Babbitt fatigue is caused by dynamic loads on the babbitt surface. Typically in bearings of this type, the dynamic loads are caused by vibration and result in peak film pressure fluct...

AN OVERVIEW OF HYDRODYNAMIC BEARINGS, THEIR DEFINITION, THEORY OF OPERATION AND TROUBLESHOOTING TIPS. BY AMR HATEM RASHED. Hydrodynamic bearings (also known as fluid film bearings) are often deployed as journal bearings. As such, they come in several types, including radial tilting pad bearings, thrust bearings for axial displacement and journal sleeve bearings. Journal sleeve bearings are typically used in low-speed and low-friction applications while radial tilting pad bearings are used for high-speed applications due to the high amplitude of vibrations. Thrust bearings, on the other hand, are generally employed for axial displacement in high-speed applications as they contain tilting pads that support high-thrust loading of rotors. Pivoted shoe journal bearing Pivoted shoe thrust bearing Frictionless support The journal bearing has several functions. It acts as frictionless support for the rotor while it is rotating. It cools down the rotor by transferring the heat energ...

Residual magnetism in high-speed machinery accounts for many previously unexplained machinery failures. In particular, the deterioration of bearings, seals, gears, couplings and journal s has been attributed to electrical currents in machinery. Often, such trains or machinery groupings contain no components with electrical windings or intended magnetism, i.e., no motors or generators. The evolution of turbine and compressor systems towards high speeds and massive frames is acknowledged as the cause for a new source of trouble from magnetic fields. An electrical generator converts mechanical power to electrical power through magnetic fields. A conventional generator rotor is essentially a magnet that is rotated in such a manner that its magnetic field flux passes through coils of windings. This produces an electrical voltage and power in the windings. A turbine, compressor, or any other rotating machine that is magnetised behaves much the same way. The magnetic steel parts provide a...