FALL 2016

136
THE DISTRIBUTOR’S LINK
CARMEN VERTULLO HYDROGEN EMBRITTLEMENT FASTENER FAILURE INVESTIGATION – WHAT THE SUPPLIER MUST KNOW from page 26
[2] BEGIN WITH A LIST OF QUESTIONS - Organize
and prioritize them. Include questions that you know may
not be answerable and self-evident information. Leave no
stone unturned. You will want to know all you can about the
application, the installation procedures, the frequency of
maintenance if it is a maintenance item, and any history of
similar problems.
Find out about the engineering (if any) involved in
the joint design. What are the design loads of the joint
and what are the actual loads on the joint? What are the
training and qualifications of the bolt installers? What were
the work conditions when the bolt was installed, and the
environment throughout the life of the assembly? Was there
any subsequent processing of the bolt by the supplier or
the user? What do the fracture surfaces look like? Are there
decent photographs of the failed specimen?
What specifications, standards, drawings or catalogs
cover the product in question? Be sure you have them
all. If not get them. Be sure they are current or of the
same revision called out in the order or in force at the
time the product was manufactured or sold. These include
the dimensional and material standards, the plating or
coating standards, and the testing, inspection and quality
assurance standards. If the part is a special, or a catalog
item, be sure you have all of the most current drawings or
catalog specifications, including whatever other standards
they reference.
It is very important to know the failure mode and
timing. When was the bolt installed? How was it tightened?
When did it fail? When was the load applied? What exactly
happened when it failed? Did anyone witness the failure?
What did they see and hear? How many bolts failed? In
what order and frequency? Who has and who had custody of
the failure specimens? How were they handled and stored
after the failure? What was the time between the failure
and the acquisition of the specimen? Was there any failure
or flexure of the associated joint components? Was the
failed bolt immediately replaced or not? What grade and lot
was used for the replacement? What was the result of that
replacement?
This list of questions could go on and on, and there are
many more that are generated based on the bolt grade, the
coating, the application and the supply chain transactions
and processes involved.
[3] DO NOT SPECULATE ON THE CAUSE BEFORE
COLLECTING ALL THE DATA AND CONDUCTING
WHATEVER TESTS ARE NECESSARY/AVAILABLE TO
ANSWER YOUR LIST OF QUESTIONS. It is very tempting
as an investigator or a consultant to take a stab at the
root cause of the failure early in the game. Do not do this.
You will almost certainly be wrong. It is ok to make a list of
possible causes and even eliminate some if the evidence is
clear, but always preface and conclude any remarks, verbal
and written, with the caveat that the investigation is not
complete and no conclusion should be made until it is.
Data collection may include photographs. It is amazing
how much you can tell from a decent photograph and even
more amazing how easy it is to get a decent photograph.
Cell phone photos can be easy and helpful, especially for
videos or pictures of the installation and head markings,
but it’s just as easy to waste your time taking and looking
at useless photographs. If you intend to use photographs
of the fracture surface in the failure investigation, consider
hiring a photographer or metallurgist who knows how to take
specimen photos with a high resolution digital camera.
[4] COLLECT AS MANY EXAMPLES FROM THE
SAME LOT AS YOU CAN - Having an example from the
same lot as the failed bolt can be of great value to the
investigation. If you do not have any in your stock, get them
from the user, the supplier and other users. Effective HE
testing requires relatively large sample size and there may
be more than one test required.
If the part has been processed in any way subsequent
to manufacturing try to get both pre and post processed
parts. Sometimes the ONLY part you have to work with is
the failure specimen. However, if you are the responsible
party and you have a good QMS you can probably track
down some specimens from the same lot, even if you
have to go to another customer or supplier to get them.
If possible, get enough samples to keep some for future
reference. Ensure that the lot integrity of any collected
samples is rock solid. Take photos of the box labels, or
take the entire box. Get all available purchasing, receiving
and transfer records for the lot.
[5] COLLECT ALL PERTINENT DOCUMENTATION -
There are two categories of documentation –those
documents that apply to the specific lot in question and
the transaction, and those that apply to the product in
general. The documents covering the lot in question and
the transaction should include all original test reports,
processing test reports and certifications, the original
RFQ, Quotations, Purchase orders, Sales orders, and any
amendments; shipping documents, emails, faxes, hand
written notes, quote sheets and sketches.
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