Tips for witness testing

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The prime intent of witness testing is rarely just to see the equipment operate when the start button is pushed. Witness testing provides the opportunity for an engineer or quality inspector witnessing the test (hereinafter, called the "witness") to ensure that the equipment vendor carries out the factory acceptance tests in accordance with the specifications and other contract requirements.

Many a time, the size and complexity of the equipment may not be palpable through drawings and documentation. Witness testing also provides the opportunity to experience the "look and feel" of the actual equipment. Furthermore, it provides the opportunity to identify and address issues with non-conformance or misinterpretation of the specifications with respect to equipment construction or testing.

Below are excerpts from a paper “Witness testing API 610 centrifugal pumps and AP611 steam turbines” by Nirmal Ganatra, Rotating Equipment Engineer/Subsea Pumps Engineer of FMC Technologies, Inc., and R C Patel, a consultant, at the 30th Pump Users Symposium in 2014.

Before the test the witness should review the test procedure with regard to the contract specifications in advance for acceptability and become completely familiar with the testing methodology before traveling to the vendor's factory. Furthermore, the witness should become familiar with and carry copies of necessary supporting documents to the test.

Examples of such helpful documents are given below: • Contract specifications and technical datasheets • Applicable industry standards • Test procedure(s) • Piping and Instrumentation Diagrams (P&IDs) • Equipment General Arrangement (GA) drawing(s) • Applicable detail drawings • Contact information of key project decision-makers and subject matter experts

After careful review of the contract documents, the witness should develop a checklist based on project specifications and referenced test standards. This checklist should have a list of items to be observed before, during and after the test, besides having provisions for recording readings from the test instrumentation in a tabular format. The contract requirements for certain critical and unique may require an engineer, in addition to the quality inspector, to witness the tests.


When a "witness" test is specified on the datasheet or contract specifications, it corresponds to a "hold" point on the Inspection and Test Plan to allow the purchaser to witness the test. On the other hand, an "observed" test corresponds to a "witness" point on the Inspection and Test Plan, wherein the vendor is only required to notify the purchaser of an impending test. In this case, the purchaser's attendance is not mandatory for the test to go ahead as scheduled. This can cause confusion at times due to the ambiguous usage of the term "witness" in two altogether different contexts.

To preclude any ambiguity, the engineer should set up the test notification protocol for the witness test in advance with the vendor and the quality inspector; otherwise, there is a possibility of the notification not reaching the appropriate engineer in good time ahead of the test. Once the witness test notification is received from the vendor, the witness should communicate with the vendor, enquiring whether a preliminary test was performed on the equipment and whether it passed.

Certain expectations with respect to the testing methods and measured parameters can also be aligned at this time. The witness should remember to carry certain items such as safety shoes, safety glasses and hard hat (if needed) to the vendor's factory. The witness should enquire with the vendor if they can bring their own camera to the test. A personal camera would enable them to take pictures of the test setup, equipment and dismantled components for reporting and reference purposes. If possible, the witness should carry a portable vibration meter and a portable pyrometer to the test that can be used for performing a qualitative comparison with the vendor's test instrumentation and for taking measurements at equipment locations that are not instrumented for the test.

Some vendors may require that outside attendees show their passports before being allowed into the factory premises. The witness should enquire with the vendor in advance regarding any such requirements and carry the necessary documents to the test. If possible, the witness should travel to the test facility on the day preceding the test. This way they can also check the location of the test facility in advance to ensure that they do not cause inadvertent travel delays on the day of the test.