Internal Flow Systems (2nd) edition

Transient Analysis

Objectives

1. To outline the need to assess the dynamic behaviour of flow systems

2. To provide information to help in the assessment of flow system dynamic behaviour

Background

Transient events in piping systems have and unfortunately will continue to kill people, cause damage, loss of production and product, pollution and consequential and legal costs. The fact that systems fail or experienced operating problems from transient events requires that engineers, designers and operators carry out due diligence related to fluid transients. Design and operating teams should at least go through a checklist on all flow systems that could conceivably be subjected to transient events and take appropriate action.

My experience of investigating transient problems in industrial plant led me to conclude that handbooks on fluid transient did not deal with, or put into context, many of the events leading to problems with transient flows in industrial flow systems. Even with a good understanding of fluid transients it is not always possible to explain why or how excessive pressures were generated. It is, therefore, important to try an engineer out the potential for damaging transient events.

The history of transient analysis is dominated by pressure surges and water hammer in hydroelectric, water supply and sewage systems and this is reflected in the handbooks on transient analysis. The first edition of Internal Flow Systems had a Chapter on fluid transients. I did not include this Chapter in the second edition as I thought that a subject requiring computer based solutions was out of place in the book. From comments I received shortly after publication of the second edition I realised not including a Chapter on transient analysis was a mistake as it was seen as an introduction to fluid transients and guidance on whether or not to commission a fluid transient Consultant.

Increasingly, flow systems are analysed using computer programs in which systems are modelled by assembling modules representing components such as pumps, valves, pipes and bends. The more capable of these programs, such as Flowmaster, simulate steady state and transient flows using virtually the same model. This speeds up the design and optimisation of flow systems and fits within integrated design environments. A design team is likely to have a better understanding of a particular flow system than a transient analysis Consultant, but it requires a design team to have an appropriate level of knowledge of fluid transients.

Flow system failures occur through a number of flow events that are not not classed as fluid transients. Due diligence studies should consider these events alongside transients. I aim to collect together published information related to transient and other flow events to help engineers and designers in assessing the risk of and from these events.

As time permits, the following web pages will be written and/or extended:

Part 1. Transient Analysis - Covering transients, water hammer and surge - Chapter 7 from the first edition

Part 2. Thermal Driven Events - Covering Heat transfer and condensation driven events

Part 3. Fluid Structure Interactions - Covering flow-induced vibrations and fluid-structure interactions

Part 4. Acoustic Resonance - Covering flow induced acoustic effects.

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