03-07-2013

SGS provide baseline and high temperature hydrogen attack Inspections for Pryor Chemical

In May 2013, SGS entered into an agreement with Pryor Chemical to conduct baseline inspection for vessels and piping for an ammonia unit and high temperature hydrogen attack (HTHA) inspection at the Pryor, Oklahoma multi-product facility.

Inspectors will implement various non-destructive testing methods such as ultrasonic testing (UT), positive material identification (PMI), time of flight diffraction (ToFD), attenuation measurement, pulse echo phased array, backscatter measurement and comparison, and velocity ratio measurement to provide single-sourced, wide-ranged inspection technology.

A subsidiary of Oklahoma City-based LSB Chemical, Pryor Chemical produces anhydrous ammonia, urea, nitric acid, urea ammonium nitrate (UAN) and carbon dioxide using a pipeline-delivered natural gas feedstock on the 106-acre site in Pryor, Oklahoma.

SGS Baseline and High Temperature Hydrogen Attack Inspections
SGS has been providing API type inspection services at the Pryor, Oklahoma plant for nearly a year. In addition to baseline thickness and visual inspections at two separate ammonia plants and one urea plant, SGS has conducted internal inspections and condition assessment for diverse pressure vessels, heat exchangers and boilers during short maintenance outages. Because of the SGS expertise in these types of inspections and evaluations and SGS boots already on the ground, PCC approached this experienced partner to conduct necessary baseline inspections and HTHA evaluation prior to start up of one of its three ammonia plants. Aware of the advantages of SGS bundled services, PCC values a single resource for field inspections, engineering support, data management and overall asset integrity management.

Scheduled to start the second week of June, this project for baseline inspection and HTHA at the #1 Ammopac Ammonia Plant is expected to require a three-week maintenance outage. Although baseline inspection does not demand an outage, HTHA inspection, anticipated to run eight to nine days, mandates a shutdown due to temperatures measuring up to 400 degrees Fahrenheit during operation. A damaging source, the presence of hydrogen in the ammonia plant is a grave concern. HTHA degradation occurs due to the formation of methane (CH4) through a reaction with steel carbides. HTHA can affect either the parent material or the weld itself and develop in carbon steel and low grades of alloys. Reaction-formed methane accumulates in internal voids on grain boundaries where, under certain conditions, build-up can produce micro-cracks. In welds, these cracks usually induce a leak-before-break situation. However, damage in the parent material often produces catastrophic results for people, property, and the environment.

During the Pryor ammonia unit project, skilled inspectors will implement a specific SGS-developed procedure and approach to identify and monitor HTHA appropriately and adequately. This methodology, crafted by SGS Industrial Services, will combine advanced signal processing and imaging of results collected at the Pryor ammonia unit while utilizing advanced techniques like time of flight diffraction, automated backscatter and velocity ratio measurements.

SGS will provide the Pryor project with one API 510/570 pressure vessel and piping inspector and two Level II NDE technicians to perform baseline examinations using ultrasonic thickness testing and PMI methods as well as P&ID review and isometric drawing creation. The HTHA team on-site in Pryor will consist of two advanced NFDE specialists from the SGS Broken Arrow office in Oklahoma and a Level III advanced NDE specialist in from the SGS NDE Competence Center in the Netherlands.

The Pryor project focuses on two objectives, establishing a baseline condition and HTHA inspection. Baseline conditions including thickness for process equipment and piping in each specific operating unit must be determined to offer an original guideline to which subsequent data will be compared in order to measure corrosion rates, schedule inspection dates and ultimately predict equipment life-expectancy. HTHA evaluation will depend upon a combination of advanced ultrasonic techniques being performed on weld seams and surrounding parent metal. HTHA inspection is conducted in order to detect any indication of specific types of potential failure risks. Areas of HTHA are defined by an industry standard criteria including operating temperature, operating pressure, ppm concentration of hydrogen, construction materials, and length of in-service time.

Comprehensive bundled services uniquely position SGS as a recognized and trusted resource to provide all inspection and evaluation required for both project objectives meant to assist PCC in meeting desired start-up schedules and fulfilling all mandatory requirements.