Skip to main content

What is ISFD Bearings, how it works?

What is the ISFD Bearings?
Integral squeeze film damper (ISFD) technology, a Flexure Pivot tilt pad journal bearing, provides precise stiffness and damping to increase the dynamic stability of the rotor/bearing system.

Reduce Dynamic Bearing Forces

ISFD technology reduces the dynamic load that is transmitted to the bearings, which reduces pedestal vibration and increases bearing life, particularly for rolling element bearings. For fluid film bearings, the technology can mitigate pivot wear and reduce babbitt fatigue.

Decrease Unbalance Sensitivity

ISFD technology helps reduce the sensitivity to unbalance, protecting impellers and seals from rubbing and increasing maintenance intervals.

Versatile Design

The ISFD design, manufactured through electrical discharge machining (EDM), can integrate the bearing and damper into one unit for a space-saving solution suitable for new and retrofit installations. ISFD technology can be used with tilt pad, Flexure Pivot tilt pad, fixed profile or rolling element bearings.

How It Works



 the flexibility of the spring allows for motion at the bearing location


squeeze film provides damping transferring energy from machine vibrations to the viscous fluid

a tilt pad flexure pivot bearing 

The ISFD design is manufactured through electrical discharge machining. Integral “S” shape springs connect an outer and inner ring, and a squeeze film damper land extends between each set of springs. Bearing pads are housed in the inner ring (Figure below). The unique design allows for high-precision control of concentricity, stiffness, and rotor positioning. It produces superior damping effectiveness by separating stiffness from damping.

 

Integral squeeze film damper (ISFD) technology, shown here as part of a Flexure Pivot tilt pad journal bearing, provides precise stiffness and damping to increase the dynamic stability of the rotor/bearing system.

This four-pad tilt pad journal bearing utilizes integral squeeze film damper technology.


While a conventional squeeze film damper (SFD) experiences a dynamic stiffness from the damper film that is dependent on amplitude and frequency, in the ISFD design, the stiffness is defined only by the springs. This allows for good predictability, and precise placement of critical speeds and rotor modes, regardless of vibration amplitudes and frequencies.

Whereas damping in a conventional SFD is generated by squeezing in the damper film and governed by circumferential film flow, the segmented ISFD design prevents circumferential flow and absorbs energy through the piston/dashpot effect. Flow resistance at the oil supply nozzle and end seals controls ISFD damping.

Both the stiffness and the damping of the ISFD design are optimized for the application through a rigorous rotordynamic analysis. For the steam turbine, because steam whirl was one of the root causes of the subsynchronous vibrations, the analysis of the ISFD solution paid careful attention to modeling destabilizing seal forces and stage forces.

A damped eigenvalue analysis without those forces showed a better stability margin by a factor of 12 with the ISFD design compared to the original bearings. With the destabilizing forces, the ISFD solution maintained a high stability margin. The combination of low stiffness and optimum damping at the bearing support is the key in transforming bending modes to more rigid body modes and improving the overall stability and damping ratio of the rotor/bearing system.

Typical Applications

  • Integrally geared compressors
  • Centrifugal compressors
  • Steam turbines
  • Gas turbines
  • Turboexpanders
  • Radial turbines
  • Supercritical CO2 power turbines
  • Generators
  • Motors
  • Overhung process equipment

Labels:

Comments

Post a Comment

Popular posts from this blog

Maintenance 4.0 Implementation Handbook (pdf)

WHAT IS MAINTENANCE 4.0? Industry 4.0 is a name given to the current trend of automation and data exchange in industrial technologies. It includes the Industrial Internet of things (IIoT), wireless sensors, cloud computing, artificial intelligence (AI) and machine learning. Industry 4.0 is commonly referred to as the fourth industrial revolution. Maintenance 4.0 is a machine-assisted digital version of all the things we have been doing for the past forty years as humans to ensure our assets deliver value for our organization. Maintenance 4.0 includes a holistic view of sources of data, ways to connect, ways to collect, ways to analyze and recommended actions to take in order to ensure asset function (reliability) and value (asset management) are digitally assisted. For example, traditional Maintenance 1.0 includes sending highly-trained specialists to collect machinery vibration analysis readings on pumps, motors and gearboxes. Maintenance 4.0 includes a wireless vibration sensor conne
Post a Comment
[Read more...]

Top 8 Reasons for Mechanical Seal Failure and How to Prevent Them

Mechanical seals are critical components of pumps, responsible for maintaining a fluid-tight seal between the rotating shaft and the stationary pump housing. However, these seals can fail due to various factors, leading to leakage, reduced pump efficiency, and costly downtime. In this article, we will discuss the top reasons for mechanical seal failure in pumps and how to prevent them. 1-Improper Seal Selection Choosing the wrong mechanical seal can cause it to fail. Consider the following factors that can contribute to seal failure: • Chemical compatibility: All seal components, such as the seal faces and O-rings, must be compatible not only with the process fluid being pumped, but also with non-process fluids used for cleaning, steam, acid, and caustic flushes, etc. • Physical degradation: Using soft seal faces on abrasive liquids will not last. Shear-sensitive liquids, like chocolate, can break down and leave behind solids (such as cocoa powder) and force out liquids (like oil). • S
Post a Comment
[Read more...]

Why Pump Shafts Often Break at the Keyway Area

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 excess
Post a Comment
[Read more...]

Technical questions with answers on gas turbines

By NTS. What is a gas turbine? A gas turbine is an engine that converts the energy from a flow of gas into mechanical energy. How does a gas turbine work? Gas turbines work on the Brayton cycle, which involves compressing air, mixing it with fuel, and igniting the mixture to create a high-temperature, high-pressure gas. This gas expands through a turbine, which generates mechanical energy that can be used to power a variety of machines and equipment. What are the different types of gas turbines? There are three main types of gas turbines: aeroderivative , industrial, and heavy-duty. Aeroderivative gas turbines are used in aviation and small-scale power generation. Industrial gas turbines are used in power generation and other industrial applications. Heavy-duty gas turbines are typically used in large power plants. What are the main components of a gas turbine? The main components of a gas turbine include the compressor, combustion chamb
Post a Comment
[Read more...]

Understanding the Types of Maintenance and Choosing the Right Strategy

This article provides an overview of the nine main types of maintenance, ranging from preventive to corrective maintenance and everything in between. Although specific terminology may vary, it's important to ensure that everyone is talking about the same thing and that the underlying principles are clear. Whether you refer to it as condition-based maintenance or predictive maintenance, what matters most is that we can have a meaningful conversation about when and how to use it. As such, this article also explores the appropriate applications of condition-based maintenance. Many people have questions about the different types of maintenance, so this quick overview provides a helpful starting point: There are nine distinct types of maintenance, which can be classified into two main categories: Preventive Maintenance and Corrective Maintenance.   Preventive Maintenance is performed proactively before any equipment failure occurs. This category encompasses: Time-Based Maintenance (TBM)
Post a Comment
[Read more...]