Hydrocarbon Processing - November 2021 - 47

Maintenance and Reliability
MTBR = (Total number of active
pumps × time period) ÷ Number
of repairs during time period
(1)
" Active pump " designates a permanently
installed pump that is in active
service mode and available for operational
use, whether its duty is continuous,
standby or intermittent. The definition of
an active pump does not include pumps
located in units that have been indefinitely
shut down, preserved or abandoned.
The longer the average time of operation
between pump repairs, the greater
the reliability of the pump. For example,
assume that 1,200 pumps are active in a
refinery over 1 yr (12 mos) and experience
a total of 387 repairs during the year.
The MTBR for the pumps can be calculated
as shown in Eq. 2:
MTBR = (1,200 × 12) ÷ 387 =
37 months
(2)
The total number of active pumps in the
plant, regardless of whether or not they
are in operation, should be counted in
the above formula. The following considerations
are recommended during
calculation of the MTBR:
* Define the pump boundary
clearly and in detail.
* Calculate the MTBR for API
and non-API pumps separately.
* Calculate the MTBR into specific
groupings of pump types, type of
mechanical seal (e.g., single seal
or dual seal), type of driver, etc.
* Define the meaning of repair
and/or failure clearly and
in detail (see TABLE 1).
* In the author's experience, if MTBR
is calculated over 50 months-
60 months, then something may be
wrong and the calculation should
be checked again. If everything
is correct, then celebrate your
reliability improvement!
Recommendations. MTBR is the average
operating calendar time between
required repairs for a particular piece of
machinery, type of machinery, class of
machinery or operating facility. It is necessary
to define the meaning of repair
before calculating the MTBR.
Take care, and do not mislead plant
management with an incorrect interpretation
of the repair or pump boundary. It
is recommended to calculate MTBR as
specifically as possible based on pump
type, pump classification (API/ASME),
power rating, mechanical seal type and
driver type.
NOTE
The recommendations outlined in this article are
based on the author's personal experience and are not
affiliated with or related to any company.
SHAHAB ZARDYNEZHAD is a
registered Senior Mechanical/
Pipeline Engineer in Alberta and
British Columbia with more than
29 yr of experience working in
the world's largest oil, gas and
petrochemical projects. He has
experience in engineering, procurement services,
manufacturing, shop/field inspection, installation,
commissioning, startup, reliability, maintenance and
operation of pumps, compressors and turbines. He
holds a BS degree in mechanical engineering from the
University of Petroleum of Iran, an MS degree in
industrial engineering from IUST Iran and an MS degrees
in mechanical engineering and project management
from the University of Calgary in Canada. He is also a
certified API Inspector for rotating equipment.
Paul Donnelly
LIVE WEBCAST
Tuesday, November 2, 2021 | 9:00 am CDT / 2:00 pm UTC
Industry Marketing Director
Aspen Technology, Inc.
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Sergio Hernandez
Solution Advisor
Aspen Technology, Inc.
With digital initiatives underway in the process industries, equipment layout, piping design,
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Waymon Lofton
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Black & Veatch
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There will be a Q&A session following the event moderated by Lee Nichols with Hydrocarbon
Processing.
Lee Nichols
Editor-in-Chief/Associate Publisher
Hydrocarbon Processing
Hydrocarbon Processing | NOVEMBER 2021 47
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Hydrocarbon Processing - November 2021

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