How ASTM B994 Bolting Eliminates the Need for Metal DisintegrationMay 30, 2018
When fasteners seize, facilities require costly and time-consuming processes to free and replace them. Turnaround operations that are executed in days on unseized bolts end up taking weeks when replacing seized fasteners, leading to facility downtime that can hinder profitability and incur greater overhead costs from turnaround projects with high worker risk.
One such method, metal disintegration, has been a common practice in bolting operations for many decades. A form of electrical discharge machining (EDM), metal disintegration removes the center of a stud using a series of rapidly recurring current discharges between two electrodes, which are separated by a dielectric liquid and subject to an electric voltage. By removing the center of the stud, metal disintegration leaves the hole intact and allows the part to be reclaimed for new bolt installation.
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Metal disintegration has many advantages when dealing with seized fasteners. However, it also incurs heavy operational drawbacks. Metal disintegration is a slow process with large power consumption needs. Unlike other bolt removal procedures such as hot bolting/single stud replacement, metal disintegration must occur when a facility is in complete shutdown due to the potential fire hazard associated with the use of combustible oil-based dielectrics. The equipment is prone to excessive wear during the metal disintegration process, and the procedure must be executed by trained metal disintegration experts. All of these factors add up to a lengthy and expensive process that can quickly inflate beyond operational feasibility.
Protecting Thread Engagement to Avoid Metal Disintegration
The key to avoiding metal disintegration is to replace bolts before they seize. By protecting thread engagement and accurately predicting a fastener’s life cycle, facilities can schedule and execute turnaround operations using simple disassembly in a matter of days. In the current bolting market, the most effective coating system that achieves these fastener goals is ASTM B994 SC18 Class 1 Nickel-Cobalt electroplating.
Class 1 is the most rigorous testing tier in the ASTM B994 specification, outlining seven testing methods to evaluate bolting performance. One test, ASTM G59, measures a bolt’s resistance to polarization to determine how long it will take to react to its environment and corrode. The slower a fastener polarizes, the longer it will last. By measuring targeted sections of the fastener to determine its resistance to polarization, a company can determine a bolt’s rate of corrosion per year of standard service.
Chief among the Class 1 testing requirements is the galling test, or Fastener End of Life Test (FELT). In the galling test, bolts from a production batch are placed under tension and subjected to harsh environments that simulate their real world applications. Samples are then opened periodically to check their condition. If the fasteners still turn, the company knows that bolts in the field are still performing. To comply with the ASTM B994 Class 1 testing tier, a fastener company must perform this test every 120 days for a minimum of two years.
It is always better to replace a bolt before it fails than to test its mechanical limits. With ASTM B994 SC18 Class 1 Nickel-Cobalt bolting backed by FELT and resistance to polarization testing, facilities have a complete data-driven picture of their fasteners’ in-service performance they can use to ensure the protection of thread engagement and avoid the costs of metal disintegration, greatly reducing downtime caused by bolting turnaround.
Doxsteel Fasteners’ 5-year NO SEIZE Warranty Eliminates the Need for Metal Disintegration
At Doxsteel Fasteners, we stand behind the integrity of our bolting 100%. Through our controlled electroplating process and unparalleled testing practices defined by ASTM B994 SC18 Class 1 specifications, we guarantee that every Doxsteel Fastener will not seize for a minimum of five years. Our facilities keep FELT Test samples from each production batch for eight years, and our resistance to polarization testing allows us to estimate that our bolts will continue to protect thread engagement far beyond the life of their warranty. When backed by these testing practices, no bolt turnaround project will ever require metal disintegration procedures.
To eliminate metal disintegration from your turnaround operations, contact Doxsteel today.