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Ethanol Service
George L. Morovich
TEMCOR Houston Office13 Flower Tuft Ct. The Woodlands, Texas 77380
PH: +1-281-367-7868 [email protected]
CORPORATE HEADQUARTERS
150 West Walnut, Suite 150
Gardena, CA 90248
PH: +1-310-523-2322 www.temcor.com
Recent reports indicate Stress Corrosion Cracking in Ethanol Service has a direct correlation with dissolved oxygen content.
Ethanol does have other attributes making it difficult to handle. These include being a solvent unlike benzene (requires special seals), being water soluble and being clear burning.
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Ethanol Tanks - Brazil
Ethanol SCC Tanks and Piping Learnings from Hawaii Project
P.E. MyersChevron6001 Bollinger Canyon RoadP.O. Box 6004San Ramon, CA 94583-5004PH: (925) 842-2288
[email protected]
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Acknowledgements:
Hawaii Ethanol ProjectProject Engineer
Alex RatcliffKahului, Maui, Hawaii
Karen JenniInsight Decisions, Inc
Denver, CO
Ted AndersonStructural Research Technology
Bolder, CO
Russ KaneDirector, Corrosion Services
Honeywell Intercorr LLC
Chuck CorrArcher Daniel Midlands
Overview
Hawaii State Regulations Tanks Piping Risk assessment principles applied to
underground piping
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Increasing Domestic Use of EthanolRenewable Fuels Standard
Could change completely due to finding an enzyme that will break down cellulose like starches and sugars for fermentation possibilities.
The Big Picture Historical Background
Increasing worldwide use CVX Brazil investigation (and update)
API Involvement API 939 D API 939 E
Terminal Owners Perspective Risk management Basic impacts (tanks and piping)
Risk management tools Approach CVX took
Tanks Piping issues
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What Is SCC? Rapid cracking of steels through transgrannular
or intergrannular corrosion Duration of hours or months, but much shorter
than typical corrosion; ethanol appears to occur in periods ranging from months to several years
SCC not new (amine, carbonate, chloride), but new for ethanol. Closest relative is methanol SCC
First known case in 1995 at our WillbridgeTerminal (2 tanks completely destroyed)
Figure 16CC in Steel Tank Bottom Showing Highly Branched, IntergranularCracks at 100
Source: API 939D
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API 939D Results SCC in fuel grade ethanol is not just a West Coast
problem limited to a few users that deal with foreign sources of ethanol.
End users should not consider fuel grade ethanol a commodity. Fuel ethanol varies widely in composition.
SCC in fuel grade ethanol does not take years to develop.
Based on preliminary laboratory studies, the factorsthat increase corrosivity of fuel ethanol appear to beincreased water content and decreased pHe.
Based on preliminary laboratory studies, SCC hasbeen produced in a sample of fuel ethanol that apparentlydoes not contain denaturants or inhibitors
API 939D Results SCC in fuel grade ethanol has been reproduced
in laboratory tests in fuel ethanol samples obtained from the field.
Some evidence has been generated based on laboratory results, which indicates that material from the near weld region in the base metal may have a greater susceptibility to SCC than base metal.
The economic impact of SCC in fuel grade ethanol service in end user facilities has been well over $1 million in direct costs in the last few years.
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API 939D Results
Some end users have misconceptions about SCC in fuel grade ethanol, thinking that it is a West Coast problem, ethanol is a commodity and cracking only occurs after 6 8 years.
The environmental variables that promote and/or control SCC in fuel grade ethanol are not known at this time.
Slow Strain Rate Testing for Screening Ethanol SCC
Machining of SSRTension Specimen
Ethanol SCC in SSR Specimen
Slow strain rateTesting machine
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SCC Crack Growth Tests in MTS Machine
Load frame &crosshead
Environment Cell& fracture fixtures
HydraulicActuator & control
Schematic of CT Specimen used for SCC Crack Growth Testing
Can be used for wedge loading or for testing in MTS or Slow Strain Rate (rising load) loading
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SCC on CT specimen following testing in fuel ethanol
SCC Crack growth in Fuel Ethanol
Mixed mode SCCIntergranular/TransgranularCT Specimen after testing in fuel ethanol
API 939EGuidelines for Identification, Repair, and Mitigation of Cracking of Steel Equipment in Fuel Ethanol ServiceAPI RECOMMENDED PRACTICE 939-EFIRST EDITION, XXXXX
Laundry list of best practices such as:
PWHT
Coating
It is up to companies to do a risk assessment and to evaluate the choices available to them using a ration method such as decisionanalysis.
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Step 1: Risk evaluation Identify what could go wrong: specify the risks of
concern, and the potential impacts on all of the 8 objectives specified in the capital risk model.
Estimate the likelihood of any identified failure mechanism: quantify the likelihood by estimating the probability of each type of failure/consequence combination.
Estimate the consequences of a SCC failure, assuming one occurs: quantify the impacts on each of the objectives assuming there is a failure. Included uncertainty in those consequences if necessary.
Combined the estimates of the likelihood and consequences of failure to estimate the net risk in terms of the expected equivalent total costs.
Step 2: Evaluation of risk mitigations.
Identify approaches that could be implemented to reduce the risks identified in Step 1. Risk mitigations can be engineering solutions or procedural changes, and can reduce risks by reducing either the likelihood of a failure, the consequences of a failure, or both.
For any promising mitigations, quantify the reduction in the likelihood and/or consequences of failure that would be expected after the mitigation is put in place.
Estimate the cost of the mitigation Combine the estimate of initial risk, and the risk
reduction and costs of the mitigation to develop an estimate of the benefits and costs, and the benefit-to-cost ratio for each mitigation.
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Step 3: Review results and develop recommendations.
In these analyses (as in many), review of preliminary results of the first two steps led to several iterations of refinements of those estimates.
Recommendations require management judgments to be overlaid on the analytical results of the risk and mitigation evaluation, particularly when there is significant uncertainty about both the risks and the effectiveness of mitigations.
Resulting Recommendations
Any new ethanol storage tanks should be coated on all wetted surfaces before being placed into service.
All terminals with current ethanol service should add secondary ethanol storage: either by adding a new tank or converting an existing tank.
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Recommendations
For new piping systems, welds should have post-weld heat treatment to reduce stresses and thus reduce the likelihood of SCC.
No modifications to existing piping systems are recommended
Underground Existing Lines
A decision was made to neither line the ethanol lines nor install leak detection at this point in time.
Follow up to be conducted in 5 years Basis is fracture mechanics study
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Accepted Fitness-For-Service Principles Invoked for UG Piping Analysis
FFS assessment is a multi-disciplinary engineering analysis of equipment to determine whether it is fit for continued service, typically until the next shutdown
The equipment may contain flaws, not meet current design standards, or be subjected to more severe operation condition than current design
The product of a FFS assessment is a decision to run as is, alter, repair, monitor, or replace; guidance on an inspection interval is also provided
Definitions
Definition of Fitness-For-Service (continued)
FFS assessments consist of analytical methods (mainly stress analysis) to assess flaws & damage
FFS assessments require an interdisciplinary approach Knowledge of damage mechanisms/material behavior Knowledge of past and future operating conditions &
interaction with operations personnel NDE (flaw location and sizing) Material properties (environmental effects) Stress analysis (often FEA) Data analysis (statistics & reliability models)
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Overview of API 579General
9 Flaws and damage conditions Self-contained document - do not need to purchase
other API standards to perform an assessment Organized to facilitate use and updates
Section covering overall assessment procedure Separate sections for each flaw type/condition Consistent organization within each section Information common to more than one section
placed in appendices
Overview of API RP 579General
Applicable to pressurized components in pressure vessels, piping, and tankage (principles can also be applied to rotating equipment)
Modular organization based on flaw type/damage condition to facilitate use and updates
Multi-level assessment - higher levels are less conservative but require more detailed analysis/data Level 1 - Inspector/Plant Engineer Level 2 - Plant Engineer Level 3 - Expert Engineer
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Overview of API 579Contents
Section 1 - Introduction Section 2 - FFS Engineering Evaluation Procedure Section 3 - Assessment of Equipment for B
