Many pump installations involve more than just the pump, its driver, and their
electronic controls. They may also include a number of ancillary equipment such
as frequency converter, gearbox, clutch or power take off, turbine or HPRT, power
generator, or similar equipment, and support systems such as their baseplate,
sealing system, lubrication, cooling system, balance line, instrumentation,etc.
In such complex train of equipment it is important that a series of functional tests
be conducted to demonstrate that every equipment and its support systems will
function as expected. This series of functional tests is often referred to as string
test, or string testing.
The main objective of string test, or string testing, is to verify the performance of
the entire equipment train, rather than of the pump itself. The pump is typically
tested separately to validate its hydraulic and mechanical performance prior to the
String testing is done by simulating the actual operating environment as far as
practicable. For example, in one such string test for an equipment train that will be
installed in a desert location, the test laboratory was provided with electric
heaters, and enclosures to contain the heat and simulate the summer condition
in the field.
There is no set of available standards for string testing as each one is unique to a
specific application and installation. Therefore the scope of the test should clearly
identify the parameters to be tested, the duration of monitoring each parameter,
and their acceptance criteria. Each piece of equipment shall be carefully
monitored during the test.
The acceptance criteria for string test should be negotiated and agreed upon
between the vendor and user because of difficulty compensating for factors such
as testing on a baseplate that may normally be grouted in the field, or the use of
contract vibration monitors that may not allow for filtered readings at discreet
C: test, testing