Session: 09-07-02 GHG emissions reductions, hydraulics for H2, other

Paper Number: 134176

134176 - Anhydrous Ammonia Pipeline Safety Experience in the United States 

Abstract: 

Ammonia is transported in buried steel pipelines usually as an anhydrous liquid, at ambient temperature at pressures greater than 250 psi. Ammonia pipelines in the United States were constructed between 1960 to 1978 and are regulated by the Code of Federal Regulations (CFR), Title 49, Part 195 Transportation of Hazardous Liquids by Pipeline under highly volatile liquid (HVL) requirements. In the Unites States, there are approximately 3,000 miles of liquid ammonia pipelines, transporting approximately 2 million tons of ammonia annually. Ammonia pipelines in the United States are primarily used to deliver ammonia from Gulf Coast producers to Midwest agricultural users and are comprised of three main pipeline systems.

Liquid anhydrous ammonia is generally considered to be noncorrosive to carbon steels at ambient temperatures if certain contaminants are not present. Certain types of contaminants in liquid ammonia can lead to general corrosion of carbon steel, such as carbon dioxide or sulfur dioxide.

Stress corrosion cracking (SCC) of carbon steel in liquid anhydrous ammonia was recognized after farms in the United States started to widely use anhydrous ammonia as a fertilizer in the early 1950s, where a high incidence of cracks and leaks was observed in carbon-steel transportation vessels and storage tanks used in agricultural ammonia service. Internal SCC was found mainly in the welds, and the attack was found to be dependent upon the type of steel, the impurities in the ammonia, the level of tensile stresses, and the degree of thermal stress relief after fabrication.

While there is no general consensus on the mechanism of SCC of carbon steel in anhydrous liquid ammonia, SCC can be mitigated by avoiding contamination by air, oxygen, and carbon dioxide, or by the addition of small amounts of water where oxygen may be present. Beneficial effects of the presence of water have been demonstrated under laboratory and field conditions and the effective range of water as an inhibitor of SCC of steel in air-contaminated ammonia appears to be from 0.08 to 0.5 wt% (800 to 5000 ppm). United States pipeline experience has shown that a minimum requirement of 0.2 wt% water in ammonia is effective in preventing SCC.

The main causes of ammonia pipeline incidents in the United States were external corrosion, improper operations, mechanical damage, maintenance, and criminal activity. An ammonia pipeline leak results in significantly greater immediate danger to human life than many other pipeline leaks. Thus, it is important that leaks are immediately detected, and actions are taken to prevent loss of human life.

Presenting Author: Sandeep Chawla DNV

Presenting Author Biography: Dr. Sandeep Chawla is a Principal Engineer in the Materials Technology Development section at DNV GL USA, Inc. in Dublin, OH. He is the Group Leader for the Corrosion & Electrochemistry Group. Sandeep has over twenty-five years of technical experience in corrosion, advanced solid-state electrochemical devices, energy and environmental technologies, materials engineering, and failure analysis. At DNV, he has managed projects on technology development, corrosion management, and materials qualification. These projects have spanned several areas including integrity management and testing related to nuclear waste storage tanks, stress corrosion cracking of ferrous and nonferrous alloys, AC corrosion of subsea pipelines with direct electrical heating, electrochemical evaluation of corrosion inhibitors, corrosion and SCC studies on buried pipelines, and corrosion risk assessment studies in the oil and gas industry. Prior to joining DNV, Sandeep was a research faculty member in the Corrosion and Reliability Engineering program at The University of Akron where he co-taught a course on Corrosion Risk Management and was involved in DoD-supported research. Before joining The University of Akron, he worked extensively on the development of solid-state electrochemical devices including ceramic oxygen generators and solid-oxide fuels cells for military applications. His past experience includes failure analysis and work on materials and corrosion issues in alternate energy technologies including biomass gasifiers, integrated gasifier – molten carbonate fuel cells (IG-MCFC), and biogas fueled phosphoric acid fuel cells.
Sandeep has co-authored several technical papers in the fields of corrosion science and engineering, and many proprietary technical reports in the other fields. He is a recipient of the A.B. Campbell Award from NACE International for work on microsensors for corrosion control. He is a co-inventor of five patents in the field of solid-state electrochemical devices and holds a Ph.D. in Materials Science and Engineering, from the Case Western Reserve University.

Authors:

Kenneth Lee DNV
Sandeep Chawla DNV