Log in

Login to your account

Username *
Password *
Remember Me

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.

Computational Fluid Dynamics (CFD) Confirms Cause of Deaerator Cracking

Computational Fluid Dynamics (CFD) Confirms Cause of Deaerator Cracking
CFD was used to confirm that poor design of the steam inlet nozzle was the main contributor to deaerator head to shell weld cracking, and confirmed proposed design improvements.  This recent Becht project illustrates one of the causes of deaerator cracking. A through-wall crack had been found at the head-to-shell junction at the steam inlet end of the drum. This crack was attributed to corrosion fatigue, a common occurrence in deaerators. The crack was most likely initiated at a weld surface defect on the I.D. of the drum and grew with time. The daily operating cycles of the drum during periods of reduced steam demand and thermal stresses which we attributed to a poorly designed steam inlet nozzle were the main contributors to the crack growth.   A large diameter superheated steam inlet nozzle extended through the head of the drum terminating 18” into the vessel. The steam exited through a...
Continue reading
0
  4308 Hits
  0 Comments
4308 Hits
0 Comments

New Coke Drum Support Design Prevents Anchor Bolt and Shim Failures

New Coke Drum Support Design Prevents Anchor Bolt and Shim Failures
Coke drums used in the delayed coking process have historically been subjected to severe operating conditions which result in numerous mechanical problems. The Coke Drum is far from your typical pressure vessel. However, the industry standard foundation, shimming, grouting and anchor bolt design continue to be identical to a typical pressure vessel. There is a better solution! The standard Coke drum cycles every 12-24 hours depending on many economic factors. It is often easy to predict and design for cyclic service. Delayed Coking, however, is an inherently difficult and complicated cycle to predict. Each cycle can produce very different temperature and stress profiles in the critical regions of the shell, bottom head and skirt. Given the unpredictability of the channeling that occurs inside a coke drum throughout the cycle, hot spots can occur at random on different parts of the drum each and every cycle. The more cycles a coke drum...
Continue reading
15
  10215 Hits
  0 Comments
10215 Hits
0 Comments

Equipment Health Monitoring of Coke Drum to Improve Fatigue Life

Equipment Health Monitoring of Coke Drum to Improve Fatigue Life
Coke drum lives can be extended by using an equipment health monitoring system, often without increasing the cycle time. Delayed coking is a form of thermal cracking used for processing "bottom of barrel" residuum. Thermal cracking produces a wide range of hydrocarbons along with coke, a solid structure of ~90 wt% carbon. In the delayed coking process the formation of coke is "delayed" until it is laid down in the coke drums, where it is accumulated and removed as a marketable product. Products of the coking process include sour fuel gas, sour liquefied petroleum gas (LPG), naphtha, light coker gas oil (LKGO), heavy coker gas oil (HKGO), and coke. The coking process in the coke drums can be divided into two parts, hot cycle and cold cycle. In the hot cycle the hot feed is brought into the coke drum and in the cold cycle water is introduced into the drum...
Continue reading
1
  4401 Hits
  0 Comments
4401 Hits
0 Comments

FFS Assessment of Crack-like Flaws Discovered in Pressurized Equipment

FFS Assessment of Crack-like Flaws Discovered in Pressurized Equipment
It is often unsettling to have an inspection group discover a crack-like flaw in a piece of pressure containing equipment, particularly when the turn-around schedule is aggressive. Fortunately, there are well-established Fitness-for-service procedures in place to assess such flaws and help guide decision-making on whether to repair or to leave in place with a monitoring program. This blog post will outline the assessment approach typically employed by Becht Engineering staff when performing crack-like flaw assessments. The performance of today’s advanced inspection technologies, such as Time of Diffraction (TOFD) and Phased Array Ultrasonic Testing (PAUT), significantly surpasses the flaw detection capacities that were available only some 10 years ago. As a result, it is not uncommon to discover crack-like flaws that likely were previously undetectable fabrication flaws. Sometimes an experienced inspector and/or fixed equipment engineer can examine the inspection data and conclude with reasonable certainty that the flaws are indeed fabrication defects....
Continue reading
0
  5035 Hits
  0 Comments
5035 Hits
0 Comments