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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.

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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How To Quantify And Evaluate Oil Storage Tank Annular Plate Corrosion

annular_plates_cover-imag_20181008-172036_1 Failure of Oil Storage Tank Annular Plate
In the past ten years, there have been a few oil storage tank annular plate failures due to soil side corrosion and fatigue loading (filling and emptying) which has led to large spills. The corrosion tends to be localized in a groove fashion and the size of the flaw could vary from 3 feet to 12 feet in the circumferential direction. The location of the corrosion is also where the highest bending stress will occur during filling and emptying of tanks. See Figures 1 and 2 for the location of the failure on the annular plate.   Since the location of failure is under the tank, the corrosion flaws cannot be detected easily from the outside of the tank. It can only be detected if an internal inspection is done which would require the tank to be emptied and cleaned and this is very expensive. However, with UT shear wave technology...
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Do I Have to Replace My Bulged Pressure Vessel?

Figure1-Bulged_Shape_of_Vessel-cover Need to replace bulged pressure vessel?
There are a variety of conditions an in-service component (e.g. vessel, tank, piping) can be found in.  The purpose of Fitness-for-Service (FFS) is to evaluate the integrity of an in-service component given a certain degraded condition and rate it for future service considering potential for any additional degradation.  A degraded condition does not have to just be based on corrosion. Sometimes a component can experience a large deformation due to unexpected one-time loads resulting in stresses greater than yield.  When such a large deformation event occurs it is important to inspect the vessel to make sure no cracking occurred during the deformation event.  If it is found that the impacted area is defect-free then the next step is to determine if the component can operate in the deformed shape. One example of a non-corrosion related degraded condition is a bulged tank.  Figure 1 shows an example of a tank that bulged...
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Charles Becht V

FFS approach

Yes, any degraded condition that goes beyond the tolerances of the original Code of Construction must be demonstrated to meet cert... Read More
Thursday, 11 April 2019 21:14
Trevor Seipp

CSA B51-14 and AB-535

The situation of vessels that have damage is not something that is well covered by the Canadian Codes. CSA B51-14 does not addres... Read More
Friday, 12 April 2019 19:09
Charles Becht V

common approach

By common approach I simply mean pressure vessels are essentially designed identically. In the case of this vessel, an ASME Secti... Read More
Thursday, 11 April 2019 22:25
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