The business manager for an asset management solutions (AMS)
firm in the Middle East faced a big task. He had been asked to
execute a major project for an oil and gas producer
and wanted to have his questions answered on remaining rotating
equipment life at existing client sites. The managers
charge was to analyze large oil and gas plants that had been
operating for far more than 25 years, although they were
originally designed for 20 to 25 years only.
The aim of his AMS firm was to secure the future of the
clients assets for another 20 years. The AMS manager had
to determine what the client needed to do to stay in business
for another 20 years without undue risk of production loss and
without jeopardizing the high level of safety the company had
achieved for its human and physical assets.
Before meeting with the manager and his staff, we had to set
the stage for a productive week of meetings. Once we agreed
that his firms charter was to quantify the remaining life
of the clients turbines, compressors, pump and other
equipment, the deliverables for a reliability consultant had to be
delineated. The consultant defined his work effort to
explaining key parameters and spelling out what the formula or
approach would be for calculating the remaining life of each
Plant data are the key ingredients.
We believe that the key ingredients of any useful endeavor
when determining the remaining life of machinery is hidden in
the client plants own past failure history. Where such
history exists and the root causes for the failures have been
analyzed, authoritative answers on remaining life are possible.
Conversely, when these data are lacking, applicable data from
others would have to be substituted.
Regarding stationary equipment and piping, corrosion data
should be available from coupons or from nondestructive testing
readings. If no such test data are available from a particular
facility, the AMS firm was advised to use third-party surveys
and look at corrosion rates experienced in comparable
industries and under comparable or scaleable conditions. This
effort takes time and money.
Because our specialty is rotating machinery, we wanted to
look first at process pumps. In the HPI, these simple machines
suffer many thousands of unexplained repeat failures every
year. We outlined to the AMS to focus on the pumps, audit the
plants own failure history and past repair data first. To
the maximum extent possible, plant data and pump configurations
must be compared against upgrade measures taken by successful
best-of-class organizations. Advanced lube
application strategies are used by best-of-class facilities. These strategies must
enter into the comparison, as will the extension of
oil-replacement intervals made possible by better lubricants
and superior bearing housing protection measures.
Mechanical seal life must be assessed and compared against
best-available sealing technologies. This requires a liaison
with the most competent mechanical seal suppliers. It requires
the seal suppliers active cooperation and divulgence of
what some claim (without real good justification) to represent
proprietary information. For instance, the extent to which
superior dual-sealing technology is of value must be
determined on a service-by-service or even pump-by-pump
In like fashion, the extent to which superior bearings
(ceramic hybrids) would lengthen pump life or avoid bearing
failures must be determined on a pump-by-pump basis. Lubricant
application and standby bearing preservation are especially
important in humid coastal and tropical environments, as well as in desert
climates. Oil-mist lubrication extends the life of
general-purpose machinery, and the AMS should consider it.
Piping and foundations affect remaining life.
Then there is the issue of piping for all machinery types.
Just as residential sidewalks and the walls of houses move and
settle, pipe supports and equipment foundations will settle.
The effect of such settling on pipe connections and equipment
nozzles can be visualized and must certainly be considered.
Examining the grout support under base plates will be quite
Whenever steam turbines are used, blade stresses and water
quality at the client site must be compared to those in
successful long-running installations elsewhere.1
This is a time-consuming endeavor that requires an
investigators time; mere guessing will not suffice. Of
course, if a comparable experience exists elsewhere, the
investigative effort may take less time.
In the case of geared units, remaining gear life must be
examined by calculating tooth loading (stresses on tooth face)
and from temperature measurements. In all instances, synthetic
lubes from experienced oil formulators will greatly extend gear
life. The right oil additives are needed for life extensions.
They drive maintenance cost and affect gear
life; oil cleanliness ranks next on the investigators
priority list. Certain warehouse spares (gears, electric
motors, etc.) should be upgraded, if important. Upgrading
spares is likely to speed up equipment recommissioning after an
unanticipated future shutdown.
Reciprocating compressor upgrades.
Since 1980, reciprocating compressors have benefitted from
upgraded piston-rod coatings, improved rod attachments,
effective onstream monitoring, more efficient valves, superior cylinder
lubricants, improved volume control and a host of other add-ons
or modifications. They are mentioned here because they serve as
a model for questions raised and answers sought.
The key to knowing about these improvements lies in keeping
track of the materials and appurtenances that were originally
provided by the equipment manufacturer and to then ask what
would be included if such equipment were delivered today. Once
that question is answered, a cost-justification calculation
will indicate if upgrading is appropriate. Needless to say, if
the asset owners do not know the details of their machine, then
the answers are more difficult to generate. As usual, data are
important; without data, proper asset management will prove
Compressors: All of the above are important!
For compressors, one looks at all of the above discussed
equipment. Valve technology and piston velocity are
important comparison-worthy parameters on reciprocating
compressors. On-stream performance tracking and observation of
prior sealing experience are important for centrifugal and
axial compressors. This performance tracking and a review of
the clients present sealing technology determine seal-system
upgrade potential. Even the compressor-internal seal materials
must be examined in detail (Fig. 1) and judgments made as to
their failure potential. Couplings and the work procedures
associated with attaching couplings to shafts should not be
overlooked; neither should shaft alignment quality and
philosophy. They all tell a lot about the remaining equipment
life and failure risk.
1. A compressor abradable seal
Whether a facility ultimately receives guidance from an
established expert or whether an AMS puts its trust in someone
else with similar experience is of no consequence, so long as
the expert working for the AMS:
1) Authoritatively spells out recommended measures
2) Thoroughly explains recommended upgrade steps
3) Identifies recommended vendors that should do the
4) Defines the deliverables that should be contractually
agreed on between upgrade the provider and the client.
1 Bloch, H. P. and M. P. Singh, Steam
Turbines: Design, Applications and Re-Rating, 2nd Ed.,
McGraw-Hill, New York, New York, 2009.
2 Quance, S., Using plastic seals to improve
compressor performance, Turbomachinery
International, January/February 1997.
Heinz P. Bloch is Hydrocarbon
Editor. A practicing consulting engineer with 50
years of applicable experience, he advises process
plants worldwide on failure analysis, reliability improvement
and maintenance cost-avoidance