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Check the Structural Integrity of Fluid Piping Systems With Hydrostatic Testing

Key Takeaways

  • Hydrostatic testing is a mandatory pressure test for fluid piping systems. 

  • Hydrostatic testing is conducted to ensure that the piping system under consideration can withstand pressure greater than the design pressure.

  • In hydrostatic testing, a fluid piping system is filled with water and applied with a pressure that is 1.5 times greater than the design pressure or maximum allowable working pressure (MAWP). 

 Fluid piping system

In engineering, fluid piping systems are used to transport fluid from one point to another

In engineering, a fluid piping system is used to transport fluid from one point to another. The influence of pressure on closed fluid piping systems makes the actual fluid flow different from theoretical expectations. When designing fluid piping systems, pressure is an important design consideration to maintain reliability in the structure and prevent leaks. A newly built fluid piping system undergoes hydrostatic testing to evaluate its structural integrity. This testing also examines leakage in the connections of fluid piping systems. In this article, we will look at fluid piping systems and hydrostatic testing details.

Fluid Piping Systems

A fluid piping system is a construction that enables the transport of fluids from one place o another. Fluid piping systems are used in chemical manufacturing, the oil industry, hydroelectric power generation, and more. Depending on the requirements, piping systems vary in materials, pipe size, type of interconnections, and conduit systems.

A fluid piping system is classified into two types, based on conduits:

  1. Open conduit piping systems: Open conduits have a free surface and they are not influenced by factors such as pressure, temperature, etc. 
  2. Closed conduit piping systems: A closed conduit piping system refers to pipes, culverts, tunnels, etc. The surface of such piping systems is not accessible, as the construction forms an enclosed path for the transport of fluids. The closed conduit can be made of plastic, wood, metal, concrete, fiberglass, etc. Along with pipes, there should be pipe fittings, flanges, etc. to ensure the interconnection of pipes.

Fluid Piping System Design Considerations

In industrial applications, closed conduit piping systems are employed. In the chemical and oil industry, the fluid piping system itself forms the major share of the total capital cost. As the cost involved with a fluid piping system covers almost one-third of the total plant cost, the piping system engineering, design, fabrication, installation, and testing requires a great level of detail and accuracy.

The design of a fluid piping system commences with the functional requirements of carrying the fluid from one place to another. Other design criteria include the type of fluid, velocity, space limitations, stress analysis, temperature, viscosity, and allowable pressure. The pressure of the fluid is a major concern, as it influences the flow pattern of the fluid. If enough tolerance for pressure is not included in the design stage of a fluid piping system, a slight increase in the fluid pressure can lead to leaks or even breakage.

Let’s take a look at a testing method to check the pressure withstanding capabilities of a fluid piping system. 

Hydrostatic Testing

In piping system design, pressure is taken as a design factor, and the design pressure is greater than the actual pressure of the fluid. To examine the mechanical integrity of a piping system for the pressure boundary, hydrostatic testing is conducted.

Hydrostatic testing is a mandatory pressure test on any new or modified fluid piping system. It is conducted to ensure that the piping system under consideration can withstand pressure greater than the design pressure. The integrity of the flanged and threaded joints is also ensured by conducting hydrostatic testing.

The main objectives of performing hydrostatic testing on fluid piping systems are:

  1. To demonstrate the mechanical integrity of the piping system.
  2. To confirm that the piping material can sustain the pressure.
  3. To minimize piping system damages and hazards to personnel. 

In hydrostatic testing, the fluid piping system is filled with water and applied with a pressure that is  1.5 times greater than the design pressure or the maximum allowable working pressure (MAWP). The test examines visible or measurable leaks or damages in the piping system during the testing period. 

Hydrostatic Testing Procedure 

Before commencing hydrostatic testing, the air inside the fluid piping system is removed. Once the air is removed, the pipe is filled with an incompressible fluid, say water, at a pressure around 1.5 times the operating pressure of the fluid. The hydrostatic test helps identify weak spots, leaks, manufacturing flaws, or damages in the fluid piping system.

Hydrostatic testing is a critical quality check to ensure the fitness of a fluid piping system that is either newly constructed or modified. Any potential leaks, structural problems, or manufacturing flaws can be identified using hydrostatic testing.

Cadence offers affordable testing options for piping systems that are either newly fabricated or modified. Cadence’s CFD tools help simulate the testing process and examine parameters such as pressure, temperature, velocity, and turbulence.

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About the Author

With an industry-leading meshing approach and a robust host of solver and post-processing capabilities, Cadence Fidelity provides a comprehensive Computational Fluid Dynamics (CFD) workflow for applications including propulsion, aerodynamics, hydrodynamics, and combustion.

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