SUMMER 2016

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THE DISTRIBUTOR’S LINK
CARMEN VERTULLO HYDROGEN EMBRITTLEMENT Q&A - HELP FOR MANAGING ‘HE’ RISK IN FASTENERS from page 106
HE testing for fasteners is not a complex or difficult
undertaking, but it does require some training and a welldeveloped
HE risk management strategy. HE testing for
fastener suppliers will be the subject of a future article.
Specs Say That Even If I Do Everything Right
HE Might Still Occur - What’s The Deal?
Many fastener and plating specifications caution
that there is no absolute guarantee that following
proper processing will prevent HE. The nature of HE
and the many variables involved, including those of the
fastener application, can make HE prevention a complex
undertaking. However each of the variables taken by itself
are relatively simple to control; and if each is dealt with
effectively we can safely plate and use HE susceptible
product.
There is also a possibility that HE may occur long
after installation due to a failure mode called External
Hydrogen Embrittlement or EHE. In EHE the source of
the hydrogen is from the fastener environment, usually
caused by corrosion. This kind of HE failure would have
nothing to do with the fastener plating process, but may
be caused by the fastener itself being made from poor
quality material or having hardness levels higher than that
allowed by the fastener specification. It may also occur in
fasteners that are simply made at a hardness level that
makes the susceptible to HE failure.
Specifications recognize that there are many variables
involved and so state that just following the minimum
specification requirements may not be adequate for an
effective HE prevention strategy.
What Should The Fastener Supplier Do, And
Not Do, When Confronted With A Suspected
HE Failure?
There are multitude of possible scenarios that
present themselves to the supplier in regards HE failures.
The most common is when the customer contacts the
supplier to report a suspected HE failure that occurred
sometime after installation of the fasteners at their plant.
There are other scenarios, such as the supplier or their
outside laboratory detects the failure during HE testing,
a consumer experiences the failure when using the
fastener in a non-specific application, or the supplier’s
customer detects the failure during their own HE testing.
In any of these scenarios, it is imperative that the
supplier act immediately to address the suspected HE
failure. The first rule of any supplier’s fastener failure
investigation is to be certain that you supplied the part.
That is not to say you cannot be of help even if the part is
not yours, but be sure it is yours before you conduct any
further investigation.
The second rule is to get help. Even if you have
competent in-house HE investigation resources, call an
expert. It is always better to have a second opinion or
someone to affirm your findings and help make sure
you are asking and answering all the right questions,
because there can be a lot riding on the results of your
investigation.
Most common HE failures can be resolved without
the use of a formal (and expensive) laboratory failure
analysis process. It may be a good idea to have a
laboratory, or a consultant, examine the parts anyway.
The level of this examination is critical to its usefulness
and the request must be well thought out.
Sometimes all that is available is a broken screw,
and end users are sometimes motivated to send that
screw to the lab for analysis. These types of tests are
often inconclusive, unnecessary or lead to a contentious
relationship between the customer and the supplier.
If only one or a few broken or not-broken screws are
available for examination it is imperative that they be
properly handled so as to not degrade their usefulness
to the investigation. They should not be sent to the
laboratory without the consent of all concerned parties
and agreement as to what the lab will do and how the
results will be used in the investigation.
In accordance with the customer’s and the supplier’s
Quality Management System, a corrective and preventive
action, and root cause analysis should begin immediately
after the suspected HE failure is reported. The customer
and the supplier must quarantine the suspect lot
immediately at all locations where the lot exists. If
possible, quickly rule out HE as a cause of the problem. If
HE cannot be ruled out, the supplier must determine if the
lot has been sold to other customers and make efforts
to contact them accordingly. Do not be an alarmist – the
problem may or may not be an issue for those customers
depending on their application. Likewise, if the product
was processed upstream in the supply chain, the supplier
needs to notify their vendor for appropriate action by the
vendor.
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