Industrial Maintenance Solutions

By NTS Pump shaft failure can lead to significant downtime and repair costs in industrial plants. One of the most common locations for pump shaft failure is at the keyway area. In this article, we will explore the reasons why pump shafts often break at the keyway and what can be done to prevent such failures. The keyway is a high-stress point (weakest point)  on the shaft, where a key is inserted to transmit torque between the shaft and the pump impeller or coupling. During operation, the keyway experiences cyclic loading that creates a bending moment in the shaft, which is concentrated in the keyway area. Over time, this cyclic loading can cause fatigue failure in the shaft material, leading to a fracture at the keyway. In addition to cyclic loading, other factors can contribute to shaft failure at the keyway. Improper keyway design or installation can lead to stress concentrations or inadequate clearance between the key and keyway . Misalignment or overloading can also cause ex...

By NTS Pump shaft breakage is a common issue that can cause costly downtime and repairs in various industries. In this article, we will explore several case studies of pump shaft breakage and the solutions implemented to prevent future failures. Case Study 1: Chemical Processing Plant A chemical processing plant experienced repeated pump shaft breakages in their cooling water pumps. Investigation revealed that the pumps were not properly aligned with the motor and had excessive vibration due to the misalignment. This caused the pump shaft to fatigue and break over time. The problem was resolved by realigning the pumps and installing vibration monitoring equipment to detect any future misalignment or excessive vibration. Case Study 2: Wastewater Treatment Plant A wastewater treatment plant had issues with pump shaft breakage in their sludge pumps. The pumps were designed with a straight shaft and lacked a flexible coupling, causing excessive stress and vibration on the pump sha...

By NTS. Pump shafts are essential in many industrial and commercial applications, providing the necessary mechanical force to move fluids through pipelines and process systems. However, when a pump shaft breaks, it can cause significant downtime, production losses, and safety risks. In this article, we will explore the common causes of pump shaft breakage and how to prevent it from occurring. 1. Excessive Load  The most common cause of pump shaft breakage is excessive load. When a pump is overloaded, it places a significant amount of stress on the shaft, causing it to bend, warp, or break. Overloading can be caused by a variety of factors such as a clogged discharge line, worn impeller, or damaged bearings. Proper maintenance, regular inspections, and monitoring of the pump's performance can help prevent overloading. 2. Misalignment  If the pump and motor are not properly aligned, it can cause stress on the pump shaft and lead to breakage. Misalignment can occur due ...

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...

In recognition of the possibility of static charge build up in condensing steam turbines, API 612 (2005) specifies that grounding brushes be installed. The electrical flow to ground through these brushes  be monitored and useful information can be extracted. This article carries excerpts from the paper, “Babbitted bearing health assessment” by John K Whalen of John Crane, Thomas D Hess of Chestnut Run, Jim Allen of Nova Chemicals and Jack Craighton of Schneider Electric. Grounding brushes take current from the rotor to ground so that a charge does not build up on the rotor to the point where it discharges to ground though the best path possible – which is usually the closest point between the rotor and stator which is usually (hopefully) the point of minimum film thickness in a bearing. Typically this point of minimum film thickness is found in the active thrust bearing (as will be shown later). Shaft grounding brushes serve two purposes. The brushes are able to transmit modest amo...

Bearing failures Bearings are small compared to other major motor components, making them particularly vulnerable to damage and wear. It’s no surprise, then, that studies blame more than half of all motor failures on bearing malfunction, most of which result from too little or too much lubrication. The key to avoiding these conditions is to establish a lubrication program using bearing and motor manufacturer guidelines to determine the frequency and amount of lubrication for the motor application, duty (continuous or intermittent), environmental conditions, and bearing size. Another significant cause of bearing failure is misalignment, the effect of which increases by the cube of the change. For example, an alignment value that is twice the new installation tolerance will reduce bearing life by a factor of 8 (2^3). The solution is simple: align the motor and driven equipment to new or better installation tolerances. Bearing currents are typically caused by dissymmetry ...