Becht Engineering Blog

In this section of the site contributing authors submit interesting articles relating to the various services, industries and research & development efforts of Becht Engineering.
Becht Engineering staff are experts in piping, and include former chairman of various ASME piping committees, including ASME B31.3. Becht Engineering performs detailed design for complex piping systems including very high temperature and pressure systems such as piping for FCC flue gas expanders and high pressure LDPE systems, as well as design, a...nalysis, troubleshooting and fitness for service evaluation of piping. More

CFD Modeling of a Mixing Tee – Part 1: Model Validation

cfd-mixing-T-cover
by Dave Dewees, Zumao Chen and L. Magnus Gustafsson This 2-part blog deals with CFD modeling of a mixing tee that is often found in industry. Traditional simulation is validated against experiment, as well as a new commercially available method that offers the possibility of substantial solution time reduction.  In fact, the new method is shown to give accurate results in a much shorter computer time than the traditional analysis, allowing much more rapid turnaround of difficult problems such as the turbulent mixing behavior of industrial mixing tees. When there is a large temperature difference between two fluid streams, large temperature fluctuations can occur, which can lead to thermal fatigue of the piping system, even at “steady-state” bulk flow conditions. Advanced CFD modeling is capable of predicting these fluid temperature fluctuations at the mix point, as well as characterizing the corresponding temperature variations in the pipe wall itself. Specifically, large eddy simulation...
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CFD Modeling of a Mixing Tee – Part 2: Predictions of Temperature Fluctuations

cfd-mixing-T-cover
by Dave Dewees, Zumao Chen and L. Magnus Gustafsson Miss Part 1? Click Here This is the second part of a 2-part blog.  In Part 1, the stress-blended eddy simulation (SBES) and large eddy simulation (LES) approaches for simulating turbulence have been validated against test data obtained from a mixing tee. In this part, the SBES approach is used to predict temperature fluctuations in a mixing tee where light gas oil mixes with a recycled gas.  Depending on the characteristics of the streams being mixed (momentum and temperature), protection from rapid temperature variations occurring even at steady-state bulk flow conditions is a necessity. While a CFD model can predict these temperature variations with good fidelity as shown in Part 1 of this blog, once a problem is found, the same CFD model can also be used to design solutions that protect the piping at the mix point.  Here thermal sleeve length...
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Why do Clamped Connections With Metallic Seals Sometimes Leak?

cover-pipe-clamp
Clamp connections with metallic seals can offer superior joint integrity over traditional flanged connections but caution must be exercised regarding the service conditions, especially when cyclic thermal loading is present. This blog post highlights aspects of a clamp connection analysis performed by Becht Engineering. The client had observed significant loss of bolt preload at several clamp connections installed in a refinery process unit where the fluid temperature regularly fluctuated by 700 o F. The client attempted to counteract the bolt preload loss by re-torqueing any bolts that showed a torque reduction from the initially applied torque only to find that, after a period during which thermal cycles occurred, the preload was again reduced. A typical clamp arrangement is seen in Figure 1 (with parts labeled). After reviewing the installation and service conditions, it was hypothesized that the cause of the bolt preload loss could be the differential thermal growth of the...
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Magnus Gustafsson

Re: Belleville Springs

Fran, No, we did not look at Belleville washers as part of this work. I do expect they would help, but I understand the preferred... Read More
Thursday, 04 April 2019 14:18
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Pipe Fabrication Dimensional Errors -- I Can't See You!!!

I_cant_see_you_Becht_dimensional_control Dimensional Errors? I Can't See You
Can a level, square and tape measure really measure up to today’s quality standards on complex spools? I was watching my baby girl cover her eyes as she had done something naughty. Doing this gave her the feeling that if she couldn’t see her mother or myself then she would not get into trouble. Despite her feeling of invisibility, she still ended up getting into trouble and having to apologize for what she had done. It’s funny as this is sometimes how the Chemical, Oil and Gas industry acts when it comes to assigning appropriate project dimensional quality control for pipe spools. Green field or brown field (based on a laser scan) projects are typically designed on a specialist CAD platform which enables the designer to design to levels where machine shops would be the only way to match the design model tolerances. This way of designing can provide huge levels...
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