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Chapter 9
Interface with Rotating Equipment

Excerpt

Rotating machineries are delicate equipment that depend on perfect shaft alignment, balanced rotating parts, and proper clearance for smooth operation. Excessive piping loads and stresses imposed on the equipment can deform machine parts to the point that they may considerably affect the reliability of the equipment. These loads, either from the expansion of piping or weight of the system, can cause shaft misalignment and casing deformation that interferes with the internal moving parts. Therefore, it is important to design the piping system to impose as little load as possible on the equipment. Ideally, it is preferred to have no piping load imposed on the equipment, but this is not possible. The common practice is for the manufacturer to specify a reasonable allowable piping load to which the piping engineers design the piping system to meet. There is no problem with this procedure, except that the allowable loads given by the manufacturers, generally through the standards of their own associations, are too small to be practical. This low allowable piping load is given partially due to the actual design of the machine and partially to protect the manufacturer's interests. The actual load that can be taken could be many times higher for most machines. Nevertheless, most equipment purchasing contracts have a clause stating that the manufacturer will guarantee the machine's performance and integrity only when the piping load is within the allowable limit.

Although the low allowable piping load may have improved the reliability of the machine on paper, it has actually created many unsuspected problems caused by the unusual piping layouts required for reducing the piping loads. To reduce the piping load to the allowable limit, many laborious piping layouts and ingenious restraint schemes are used. These unusual arrangements may show on paper that the allowable load is met, but the reliability of the system is actually compromised. Some of these pitfalls will be discussed later in this chapter.

  • 9.1. Brief Background of Allowable Piping Load on Rotating Equipment
  • 9.1.1. When Nobody Knew What to Do
  • 9.1.2. First Official Set of Allowable Piping Loads
  • 9.1.3. Factors Behind the Low Allowable Piping Load
  • 9.2. Evaluation of Piping Load on Rotating Equipment
  • 9.2.1. Effect of Piping Loads
  • 9.2.2. Movements of Nozzle Connection Point
  • 9.2.3. Analysis Approach
  • 9.2.4. Selecting the Spring Hangers to Minimize the Weight Load
  • 9.2.5. Multi-Unit Installation
  • 9.2.6. Fit-up the Connection
  • 9.3. Steam Power Turbine
  • 9.4. Mechanical Drive Steam Turbines
  • 9.4.1. Allowable Loads at Individual Connection
  • 9.4.2. Allowable for Combined Resultant Loads
  • 9.4.3. Basic Piping Layout Strategy
  • 9.5. Centrifugal Pumps
  • 9.5.1. Characteristics Related to Piping Interface
  • 9.5.2. Basic Piping Support Schemes
  • 9.5.3. Non-API Pumps
  • 9.5.4. API Standard 610 Pumps
  • 9.6. Centrifugal Compressors
  • 9.7. Reciprocating Compressors and Pumps
  • 9.7.1. Pulsating Flow
  • 9.7.2. Pulsation Pressure
  • 9.7.3. Pulsation Dampener for Reciprocating Pumps
  • 9.7.4. Some Notes on Piping Connected to Reciprocating Machine
  • 9.8. Problems Associated With Some Techniques Used in Reducing Piping Loads
  • 9.8.1. Excessive Flexibility
  • 9.8.2. Improper Expansion Joint Installations
  • 9.8.3. Theoretical Restraints
  • 9.9. Example Procedure for Designing Rotation Equipment Piping

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