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

Changes In the 2012 Edition of ASME B31.3

In addition to the many clarifications, updated references to codes and standards, updates to basic allowable stresses, and added listed materials, there are several substantive changes to the 2012 Edition of ASME B31.3, Process Piping. These changes are: Category D Fluid Service The definition was revised to include piping with design minimum temperatures below -29⁰C (-20⁰F) if the cause of the lower temperature is from ambient conditions. Allowable Displacement Stress Range The allowable displacement stress range was limited to 60,000 psi (414 MPa) in the 2012 edition. High strength steels have higher yield and tensile strengths and thus higher allowable stresses. Therefore, they also have higher calculated allowable displacement stress ranges when calculated using the old formula. However, these materials have fatigue strengths similar to the more common steels, which is why the limit was added. Flexibility Stress Equation The axial stress was added to the flexibility stress equation. While axial...
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Recent Comments
Byron Laird

Allowable Displacement Stress ...

Dear Don, Thanks for your article, very informative. Referring to your comment on the allowable displacement stress range. I can ... Read More
Wednesday, 11 September 2013 18:16
Don Frikken

MPa Stress table - response

The ASME B16.5 ratings are based on data supplied by the B&PV Code Section II Committee. In some cases, the MPa values are derived... Read More
Tuesday, 10 December 2013 11:31
Don Frikken

RE:withstand

I'm not familiar enough with ASME B&PV Code Section IX to know if there is an exception to the rule you describe. If the material ... Read More
Friday, 06 February 2015 09:17
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Piping Vibration Screening Rule

It is useful to have a screening rule for evaluation of piping vibration in order to determine if the vibration is potentially harmful (can lead to damage or fatigue failure) or if it is simply a nuisance and can be accepted without doing a more detailed assessment or anything to mitigate it. A very useful screening rule is provided in ASME OM-3 , “ Requirements for Preoperational and Initial Start-up Vibration Testing of Nuclear Power Plant Piping Systems;” however, it is first important to understand when it is appropriate to use this rule. It is not uncommon to have people use tools they are familiar with to address problems the tools are not suited for, yielding meaningless results. To understand where the OM-3 screening rule is applicable, it is useful to understand different categories of piping vibration. The first division is transient versus steady state. The screening rule is for steady...
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Pump Trips and Check Valve Closure

Pump Trips and Check Valve Closure
Pump Trips and Check Valve Closure Systems running multiple pumps in parallel can undergo serious equipment and piping damage during a pump trip caused by a power outage or pump mechanical failure. Uncontrolled reverse flow in the system can occur and if improperly selected check valves are used it can result in pumps running backwards or transient pressure spikes in the system, i.e., water hammer. Water hammer will occur if reverse flow occurs prior closure of the check valve and the effect increases with higher reverse flow velocity. Becht has worked with clients on analysis of the design of their systems, e.g., a water treating facility running multiple 52,000 gpm pumps in parallel, a seawater pump station pumping cooling water through a several mile pipeline to an inland facility and a boiler feed water circulation system for a 3000 psig forced circulation boiler. In a three pump system (two operating and...
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