Trevitest
valve technology extends intervals between shutdowns
Posted: 02 June 2004
Furmanite, the engineering services and technologies company geared
to maximising asset uptime, has made an exciting breakthrough with
its extensively proven Trevitest on-line valve testing system.
It has now been demonstrated that Trevitest can be used to accomplish
the required ‘Thorough Examination’ of clean duty relief
streams – on-line and in normal operation – enabling
intervals between shutdowns to be extended, and bringing considerable
cost savings.
The news comes following an innovative pilot scheme in conjunction
with Huntsman and ABB Eutech, its inspection authority, to trial
the Trevitest on-line valve testing system.
80 clean duty relief valves on the Ethylene process, within the
Olefins manufacturing area at the Wilton Site of Huntsman, were
tested in the ABB Eutech/Huntsman joint trial project, proving
that Trevitest provides a valid and cost-effective on-line alternative
to the workshop bench test for the examination of relief valves.
Traditionally examination of relief streams (ie relief valves and
the pipework connecting them to the pressure vessel), has been
achieved by removing the valve for overhaul and set point adjustment
in a workshop, and a visual inspection of the pipework.
Developments in examination methodologies such as Risk Based Inspection
(RBI), have allowed the frequency of shutdown to examine process
equipment to be reduced. Now, using Trevitest – specifically
designed to test safety and relief valves on-line, at normal operating
pressures and temperatures – the need for removal to examine
the equipment’s protective devices can be similarly reduced,
for maximum benefit.
Following the successful trial, Huntsman Olefins has been able
to extend the removal of relief valves from every 4 years to every
12 years, with an in-situ Trevitest taking place at 4 and 8 yearly
intervals, and ABB Eutech has adopted a similar approach more widely
to apply to other sites using its RBI process. At the Huntsman
Aromatics plant at North Tees, ABB Eutech and Huntsman have recently
used Trevitest following an RBI review to help extend the major
plant overhaul from 4 to 6 years.
To compare the Trevitest results with those achieved by traditional
inspection methods, ten of the 80 valves were removed and tested
on a workshop test bench. The results showed a close correlation
between the two testing techniques. 90 per cent of the tests agreed
to within 10% of the set pressure (60 per cent to within 5%), with
the workshop test indicating a lower set pressure than Trevitest
on all but one occasion.
The Furmanite Trevitest process has been extensively proven to
test safety and relief valves in-situ, enabling only those needing
attention to be removed from the line during shutdown, bringing
substantial time and cost savings. Backed by Furmanite’s
comprehensive experience in the field and valve data banks, and
fully approved by Lloyds, the Trevitest system offers considerable
advantages.
The principle of the technology is to apply a force to the valve
spindle to overcome the spring tension of the valve, using a specially
designed set of mechanics mounted on the valve. An electronic force
transducer, linked to a portable computer, then traces the force
applied. The recorded data, together with knowledge of the valve
seat area and the line pressure of the valve, enables the set pressure
to be computed. The recorded information also allows the spring
adjustment and displacement of the valve to be determined, and
an indication gained of the effect of the nozzle ring, guide ring
and the reseat pressure.
Test results are normally within plus or minus one per cent of
the set pressure when the valve is tested on-line. Further, the
results and print-outs provide an auditable history trail and comprehensive
valve test diagnostic record.
Trevitest is just one of Furmanite’s extensive range of
services and technologies, geared to helping customers maximise
asset uptime.
For more information see www.furmanite.co.uk
Posted by Richard Price,
Editor Pipeline Magazine
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