Hydrocarbon Processing - November 2022 - 31
Special Focus Process Controls, Instrumentation
and Automation
B. TAYLOR, Anvil Corporation, Bellingham, Washington;
S. MARTIN, Environmental Manager, CHS, McPherson, Kansas
Reliability analysis of analyzers bridges the gap
between assessing and addressing risk
For most refinery facility managers, the demands of running
plants efficiently, meeting environmental regulations and
maximizing returns on product specifications challenge even
the most disciplined professionals. Managers whose schedules
are consumed with urgent matters are challenged with
finding time for proactive preventive maintenance, especially
for necessary and mandated analyzers.
Despite their vital role in plant operations and protecting
the health and safety of plant personnel, most analyzer systems
do not receive the resources required. Decision-makers
may be hesitant to make large-scale investments in the operations,
maintenance and upgrades of analyzers. Poor (or no)
business cases showing long-term returns on investment, or
lack of defined risks connecting analyzer failure to the financial
cost, are the underlying culprits.
Consequently, complex analyzer systems often run deep
into obsolescence with multitudes of band-aid fixes and are
only upgraded as a last resort. Projects are then executed with
rushed schedules and shoestring budgets because they were
never part of the master plan. Ironically, these installations
cost the plant more money than if the system upgrade had
been scheduled.
Reactive maintenance always costs more than proactive
maintenance. Any plant manager can probably relate to the
ever-present threat of being snake-bitten by an emergency
analyzer upgrade project with limited options, high cost and
high visibility, such as an emergency replacement of continuous
emissions monitoring systems.
If your plant has numerous process and regulatory analyzers,
there is a better way. Suppose decision-makers can be
convinced of the value of an up-front effort to perform holistic
surveys on analyzers and establish a long-term upgrade
schedule. In that case, facility managers can reverse the cyclical
pattern of putting out fires and begin to reap the long-term
benefits of a carefully calibrated maintenance plan.
Developing a solid maintenance master plan can be challenging
when competing for priority with smaller, less costly
projects that can be considered quick wins. So, how can you
effectively create a sustainable, long-term plan that pays dividends
and keeps the plant analyzer systems out of the dreaded
reactive maintenance cycle? Perform a holistic system survey,
develop a master evergreen maintenance list, assign ownership
early on and make sure to pitch projects by translating technical
findings into financial terms leadership will understand.
Consider a holistic survey. Holistic surveys can be done
on many systems, but the process becomes more complex for
analyzers because of unique regulatory variables. For example,
unlike electrical substations, the regulatory rules for analyzers
change almost annually because they monitor and report emissions
from the refinery. These emissions are highly scrutinized
by regulatory bodies and the public, which may hurt the overall
reputation and cause violations that impact regulatory decisions
and environmental justice considerations.
Regulatory components strengthen the case for why a holistic
survey is especially important for analyzers. If there is a failure
and it is difficult to get parts, it directly impacts operations
because safety and regulatory issues immediately rise to the top
of the most urgent priority list for regulators. Stakeholders have
no choice but to address compliance issues immediately, no
matter the cost.
Consider a facility that has a failing critical emissions monitoring
analyzer. Operational, financial and public-relations risks
are high. If the analyzer is obsolete, spare parts are no longer available.
In such a case, decision-makers must immediately spend
whatever it costs to upgrade the analyzer, even if the project was
not planned or budgeted. Sometimes, a short-term rental system
is a viable option, but this can often turn into a long-term rental
with costs quickly exceeding the costs of an upgraded system.
Beyond the bottom-line impacts of unbudgeted expenditures,
organizations could face a public relations crisis and risk
their relationship with governmental authorities because of
faulty or absent regulatory equipment. While less critical equipment
can be taken offline or bypassed during an upgrade or repair,
this is not an option for a regulatory component. Regulatory
bodies often require notification of analyzer malfunction
with primacy, expedited costs/shipping considerations, extended
downtime, etc. Additionally, the newly installed analyzer will
require initial certification testing that will have to be contracted
by third-party services that may not have the resources to
support the project without significant unplanned cost.
In the cost-benefit analyses of holistic surveys vs. just-intime
crisis response, decision-makers must understand this will
happen again, resulting in a cycle of focusing on the latest emerHydrocarbon
Processing | NOVEMBER 2022 31
Hydrocarbon Processing - November 2022
Table of Contents for the Digital Edition of Hydrocarbon Processing - November 2022
Industry Perspectives
Editorial Comment
Construction
Innovations
Digital Technologies
Optimization of ethylene in the processing of hydrocarbons
Shift focus to more open control technology
Integrated remote operations drive collaboration and autonomy
Reliability analysis of analyzers bridges the gap between assessing and addressing risk
Implement advanced level control techniques to improve crude distillation unit stabilizer performance
Leading capital projects in a VUCA environment
Trip your turbine troubles: Optimize the reliability of steam-driven turbines
Development of novel epoxy closed-cell foam for personnel and corrosion protection—Part 2
Obsolescence management in a manufacturing unit
Decarbonizing your fired heaters with hydrogen fuel
Mechanical design challenges in high-temperature electric heaters
Why sulfur plants fail: An in-depth study of sulfur recovery unit failures—Part 2
Advertiser Index
Hydrocarbon Processing - November 2022 - 1
Hydrocarbon Processing - November 2022 - 2
Hydrocarbon Processing - November 2022 - 3
Hydrocarbon Processing - November 2022 - Industry Perspectives
Hydrocarbon Processing - November 2022 - 5
Hydrocarbon Processing - November 2022 - 6
Hydrocarbon Processing - November 2022 - Editorial Comment
Hydrocarbon Processing - November 2022 - 8
Hydrocarbon Processing - November 2022 - 9
Hydrocarbon Processing - November 2022 - Construction
Hydrocarbon Processing - November 2022 - 11
Hydrocarbon Processing - November 2022 - Innovations
Hydrocarbon Processing - November 2022 - 11B
Hydrocarbon Processing - November 2022 - 12
Hydrocarbon Processing - November 2022 - Digital Technologies
Hydrocarbon Processing - November 2022 - 14
Hydrocarbon Processing - November 2022 - 15
Hydrocarbon Processing - November 2022 - 16
Hydrocarbon Processing - November 2022 - Optimization of ethylene in the processing of hydrocarbons
Hydrocarbon Processing - November 2022 - 18
Hydrocarbon Processing - November 2022 - 19
Hydrocarbon Processing - November 2022 - 20
Hydrocarbon Processing - November 2022 - Shift focus to more open control technology
Hydrocarbon Processing - November 2022 - 22
Hydrocarbon Processing - November 2022 - 23
Hydrocarbon Processing - November 2022 - 24
Hydrocarbon Processing - November 2022 - Integrated remote operations drive collaboration and autonomy
Hydrocarbon Processing - November 2022 - 26
Hydrocarbon Processing - November 2022 - 27
Hydrocarbon Processing - November 2022 - 28
Hydrocarbon Processing - November 2022 - 29
Hydrocarbon Processing - November 2022 - 30
Hydrocarbon Processing - November 2022 - Reliability analysis of analyzers bridges the gap between assessing and addressing risk
Hydrocarbon Processing - November 2022 - 32
Hydrocarbon Processing - November 2022 - 33
Hydrocarbon Processing - November 2022 - Implement advanced level control techniques to improve crude distillation unit stabilizer performance
Hydrocarbon Processing - November 2022 - 35
Hydrocarbon Processing - November 2022 - 36
Hydrocarbon Processing - November 2022 - Leading capital projects in a VUCA environment
Hydrocarbon Processing - November 2022 - 38
Hydrocarbon Processing - November 2022 - Trip your turbine troubles: Optimize the reliability of steam-driven turbines
Hydrocarbon Processing - November 2022 - 40
Hydrocarbon Processing - November 2022 - 41
Hydrocarbon Processing - November 2022 - 42
Hydrocarbon Processing - November 2022 - 43
Hydrocarbon Processing - November 2022 - 44
Hydrocarbon Processing - November 2022 - 45
Hydrocarbon Processing - November 2022 - 46
Hydrocarbon Processing - November 2022 - Development of novel epoxy closed-cell foam for personnel and corrosion protection—Part 2
Hydrocarbon Processing - November 2022 - 48
Hydrocarbon Processing - November 2022 - 49
Hydrocarbon Processing - November 2022 - 50
Hydrocarbon Processing - November 2022 - Obsolescence management in a manufacturing unit
Hydrocarbon Processing - November 2022 - 50B
Hydrocarbon Processing - November 2022 - Decarbonizing your fired heaters with hydrogen fuel
Hydrocarbon Processing - November 2022 - 52
Hydrocarbon Processing - November 2022 - 53
Hydrocarbon Processing - November 2022 - 54
Hydrocarbon Processing - November 2022 - Mechanical design challenges in high-temperature electric heaters
Hydrocarbon Processing - November 2022 - 56
Hydrocarbon Processing - November 2022 - 57
Hydrocarbon Processing - November 2022 - 58
Hydrocarbon Processing - November 2022 - 59
Hydrocarbon Processing - November 2022 - 60
Hydrocarbon Processing - November 2022 - Why sulfur plants fail: An in-depth study of sulfur recovery unit failures—Part 2
Hydrocarbon Processing - November 2022 - 62
Hydrocarbon Processing - November 2022 - 63
Hydrocarbon Processing - November 2022 - 64
Hydrocarbon Processing - November 2022 - 65
Hydrocarbon Processing - November 2022 - Advertiser Index
Hydrocarbon Processing - November 2022 - 67
Hydrocarbon Processing - November 2022 - 68
https://www.nxtbook.com/gulfenergyinfo/gulfpub/HPI-Market-Data-2023-v3
https://www.nxtbook.com/gulfenergyinfo/gulfpub/hpi-market-data-2024-v2
https://www.nxtbook.com/gulfenergyinfo/gulfpub/hpi-market-data-2024
https://www.nxtbook.com/gulfenergyinfo/gulfpub/gas-processes-handbook-2022_v2
https://www.nxtbook.com/gulfenergyinfo/gulfpub/gas-processes-handbook-2022
https://www.nxtbook.com/gulfenergyinfo/gulfpub/hp_202212
https://www.nxtbook.com/gulfenergyinfo/gulfpub/hpi-market-data-2023-v2
https://www.nxtbook.com/gulfenergyinfo/gulfpub/hpi-market-data-2023
https://www.nxtbook.com/gulfenergyinfo/gulfpub/hp_202211
https://www.nxtbook.com/nxtbooks/gulfpub/hp_202210
https://www.nxtbook.com/nxtbooks/gulfpub/hp_202209
https://www.nxtbook.com/nxtbooks/gulfpub/hp_202208
https://www.nxtbook.com/nxtbooks/gulfpub/hp_202207_v2
https://www.nxtbook.com/nxtbooks/gulfpub/hp_202207
https://www.nxtbook.com/nxtbooks/gulfpub/hp_202206_v2
https://www.nxtbook.com/nxtbooks/gulfpub/hp_202206
https://www.nxtbook.com/nxtbooks/gulfpub/hp_202205_v2
https://www.nxtbook.com/nxtbooks/gulfpub/hp_202205
https://www.nxtbook.com/nxtbooks/gulfpub/hp_202204_v2
https://www.nxtbook.com/nxtbooks/gulfpub/hp_202204
https://www.nxtbook.com/nxtbooks/gulfpub/hp_032022
https://www.nxtbook.com/nxtbooks/gulfpub/hp_202203
https://www.nxtbook.com/nxtbooks/gulfpub/hp_202202
https://www.nxtbook.com/nxtbooks/gulfpub/hp_202201
https://www.nxtbook.com/nxtbooks/gulfpub/hp_202112
https://www.nxtbook.com/nxtbooks/gulfpub/hp_202111
https://www.nxtbook.com/nxtbooks/gulfpub/hp_202110
https://www.nxtbook.com/nxtbooks/gulfpub/hpimarket_2022_v2
https://www.nxtbook.com/nxtbooks/gulfpub/hpimarket_2022
https://www.nxtbook.com/nxtbooks/gulfpub/hp_202109
https://www.nxtbook.com/nxtbooks/gulfpub/hp_202108
https://www.nxtbook.com/nxtbooks/gulfpub/petrochemical_processes_handbook_2021_v2
https://www.nxtbook.com/nxtbooks/gulfpub/petrochemical_processes_handbook_2021
https://www.nxtbook.com/nxtbooks/gulfpub/hp_202107
https://www.nxtbook.com/nxtbooks/gulfpub/hp_202106
https://www.nxtbook.com/nxtbooks/gulfpub/hp_202105
https://www.nxtbook.com/nxtbooks/gulfpub/hp_202104
https://www.nxtbook.com/nxtbooks/gulfpub/hp_ebooks
https://www.nxtbook.com/nxtbooks/gulfpub/hp_202103
https://www.nxtbook.com/nxtbooks/gulfpub/hp_202102
https://www.nxtbook.com/nxtbooks/gulfpub/hp_202101
https://www.nxtbook.com/nxtbooks/gulfpub/catalyst_handbook_2020_v2
https://www.nxtbook.com/nxtbooks/gulfpub/catalyst_handbook_2020
https://www.nxtbook.com/nxtbooks/gulfpub/hp_202012
https://www.nxtbook.com/nxtbooks/gulfpub/hp_202011
https://www.nxtbook.com/nxtbooks/gulfpub/hp_202010
https://www.nxtbook.com/nxtbooks/gulfpub/hpimarket_2021
https://www.nxtbook.com/nxtbooks/gulfpub/hp_202009
https://www.nxtbook.com/nxtbooks/gulfpub/hp_202008
https://www.nxtbook.com/nxtbooks/gulfpub/refining_processes_handbook_2020
https://www.nxtbook.com/nxtbooks/gulfpub/refining_processes_handbook_2020_v2
https://www.nxtbook.com/nxtbooks/gulfpub/hp_202007
https://www.nxtbook.com/nxtbooks/gulfpub/hp_202006
https://www.nxtbook.com/nxtbooks/gulfpub/hp_202005
https://www.nxtbook.com/nxtbooks/gulfpub/hp_202004
https://www.nxtbook.com/nxtbooks/gulfpub/hp_202003
https://www.nxtbook.com/nxtbooks/gulfpub/hp_202002
https://www.nxtbook.com/nxtbooks/gulfpub/hp_202001
https://www.nxtbook.com/nxtbooks/gulfpub/hp_201912
https://www.nxtbook.com/nxtbooks/gulfpub/hp_201911
https://www.nxtbook.com/nxtbooks/gulfpub/hpimarket_2020_v2
https://www.nxtbook.com/nxtbooks/gulfpub/hpimarket_2020
https://www.nxtbook.com/nxtbooks/gulfpub/hp_201910
https://www.nxtbook.com/nxtbooks/gulfpub/hp_201909
https://www.nxtbook.com/nxtbooks/gulfpub/hp_201908
https://www.nxtbook.com/nxtbooks/gulfpub/hp_201907
https://www.nxtbook.com/nxtbooks/gulfpub/hp_201906
https://www.nxtbook.com/nxtbooks/gulfpub/hp_201905
https://www.nxtbook.com/nxtbooks/gulfpub/hp_201904
https://www.nxtbook.com/nxtbooks/gulfpub/hp_201903
https://www.nxtbook.com/nxtbooks/gulfpub/hp_201902
https://www.nxtbook.com/nxtbooks/gulfpub/hp_201901
https://www.nxtbook.com/nxtbooks/gulfpub/petrochemical_2018_v2
https://www.nxtbook.com/nxtbooks/gulfpub/petrochemical_2018
https://www.nxtbook.com/nxtbooks/gulfpub/hp_201812
https://www.nxtbook.com/nxtbooks/gulfpub/hpimarket_2019_v2
https://www.nxtbook.com/nxtbooks/gulfpub/hpimarket_2019
https://www.nxtbook.com/nxtbooks/gulfpub/hp_201811
https://www.nxtbook.com/nxtbooks/gulfpub/hp_201810
https://www.nxtbook.com/nxtbooks/gulfpub/hp_201809
https://www.nxtbook.com/nxtbooks/gulfpub/hp_201808
https://www.nxtbook.com/nxtbooks/gulfpub/hp_201807
https://www.nxtbook.com/nxtbooks/gulfpub/hp_201806
https://www.nxtbook.com/nxtbooks/gulfpub/hp_201805
https://www.nxtbook.com/nxtbooks/gulfpub/hp_201804
https://www.nxtbook.com/nxtbooks/gulfpub/hp_201803
https://www.nxtbook.com/nxtbooks/gulfpub/hp_201802
https://www.nxtbook.com/nxtbooks/gulfpub/hp_201801
https://www.nxtbook.com/nxtbooks/gulfpub/hp_201712
https://www.nxtbook.com/nxtbooks/gulfpub/hp_201711
https://www.nxtbook.com/nxtbooks/gulfpub/hp_201710
https://www.nxtbook.com/nxtbooks/gulfpub/hp_201709
https://www.nxtbook.com/nxtbooks/gulfpub/hp_201708
https://www.nxtbook.com/nxtbooks/gulfpub/hp_201707
https://www.nxtbook.com/nxtbooks/gulfpub/hp_201706
https://www.nxtbook.com/nxtbooks/gulfpub/hp_201705
https://www.nxtbook.com/nxtbooks/gulfpub/hp_201704
https://www.nxtbook.com/nxtbooks/gulfpub/hp_201703
https://www.nxtbook.com/nxtbooks/gulfpub/hp_201702
https://www.nxtbook.com/nxtbooks/gulfpub/hp_201701
https://www.nxtbook.com/nxtbooks/gulfpub/hp_2017mediaplanner
https://www.nxtbook.com/nxtbooks/gulfpub/hp_201612
https://www.nxtbook.com/nxtbooks/gulfpub/hp_201611
https://www.nxtbook.com/nxtbooks/gulfpub/hp_201610
https://www.nxtbook.com/nxtbooks/gulfpub/hp_201609
https://www.nxtbook.com/nxtbooks/gulfpub/hp_201608
https://www.nxtbook.com/nxtbooks/gulfpub/hp_201607
https://www.nxtbook.com/nxtbooks/gulfpub/hp_201606
https://www.nxtbook.com/nxtbooks/gulfpub/hp_201605
https://www.nxtbook.com/nxtbooks/gulfpub/hp_201604
https://www.nxtbook.com/nxtbooks/gulfpub/hp_201603
https://www.nxtbook.com/nxtbooks/gulfpub/hp_201602
https://www.nxtbook.com/nxtbooks/gulfpub/hp_201601
https://www.nxtbook.com/nxtbooks/gulfpub/hp_201512
https://www.nxtbook.com/nxtbooks/gulfpub/hp_201511
https://www.nxtbook.com/nxtbooks/gulfpub/hp_201510
https://www.nxtbook.com/nxtbooks/gulfpub/hp_2016mediaplanner
https://www.nxtbook.com/nxtbooks/gulfpub/hp_201509
https://www.nxtbook.com/nxtbooks/gulfpub/hp_201508
https://www.nxtbook.com/nxtbooks/gulfpub/hp_201507
https://www.nxtbook.com/nxtbooks/gulfpub/hp_2015tmsd
https://www.nxtbook.com/nxtbooks/gulfpub/hp_201506
https://www.nxtbook.com/nxtbooks/gulfpub/hp_201505
https://www.nxtbook.com/nxtbooks/gulfpub/hp_201504
https://www.nxtbook.com/nxtbooks/gulfpub/hp_201503
https://www.nxtbook.com/nxtbooks/gulfpub/hp_201502
https://www.nxtbook.com/nxtbooks/gulfpub/hp_201501
https://www.nxtbook.com/nxtbooks/gulfpub/hp_201412
https://www.nxtbook.com/nxtbooks/gulfpub/hp_201411
https://www.nxtbook.com/nxtbooks/gulfpub/hp_2015mediaplanner
https://www.nxtbook.com/nxtbooks/gulfpub/hp_201410
https://www.nxtbook.com/nxtbooks/gulfpub/hp_201409
https://www.nxtbook.com/nxtbooks/gulfpub/hp_201408
https://www.nxtbook.com/nxtbooks/gulfpub/hp_201407
https://www.nxtbook.com/nxtbooks/gulfpub/hp_2014petrochemicalprocesses_v2
https://www.nxtbook.com/nxtbooks/gulfpub/hp_2014petrochemicalprocesses
https://www.nxtbook.com/nxtbooks/gulfpub/hp_201406
https://www.nxtbook.com/nxtbooks/gulfpub/hp_201405
https://www.nxtbook.com/nxtbooks/gulfpub/hp_201404
https://www.nxtbook.com/nxtbooks/gulfpub/hp_201403
https://www.nxtbook.com/nxtbooks/gulfpub/hp_2014calendar
https://www.nxtbook.com/nxtbooks/gulfpub/hp_201402
https://www.nxtbook.com/nxtbooks/gulfpub/hp_201401
https://www.nxtbook.com/nxtbooks/gulfpub/hp_201312
https://www.nxtbook.com/nxtbooks/gulfpub/hp_2014mediaplanner
https://www.nxtbook.com/nxtbooks/gulfpub/hp_201311
https://www.nxtbook.com/nxtbooks/gulfpub/hp_201310
https://www.nxtbook.com/nxtbooks/gulfpub/hp_201309
https://www.nxtbook.com/nxtbooks/gulfpub/hp_201308
https://www.nxtbook.com/nxtbooks/gulfpub/hp_srsguide2013
https://www.nxtbook.com/nxtbooks/gulfpub/hp_201307
https://www.nxtbook.com/nxtbooks/gulfpub/hp_201306
https://www.nxtbook.com/nxtbooks/gulfpub/hp_201305
https://www.nxtbook.com/nxtbooks/gulfpub/hp_201304
https://www.nxtbook.com/nxtbooks/gulfpub/hp_201303
https://www.nxtbook.com/nxtbooks/gulfpub/hp_201302
https://www.nxtbook.com/nxtbooks/gulfpub/hp_201301
https://www.nxtbook.com/nxtbooks/gulfpub/hp_201212
https://www.nxtbook.com/nxtbooks/gulfpub/hp_201211
https://www.nxtbook.com/nxtbooks/gulfpub/hp_201210
https://www.nxtbook.com/nxtbooks/gulfpub/hp_201209
https://www.nxtbook.com/nxtbooks/gulfpub/hp_201208
https://www.nxtbook.com/nxtbooks/gulfpub/hp_201207
https://www.nxtbook.com/nxtbooks/gulfpub/hp_srsguide2012
https://www.nxtbook.com/nxtbooks/gulfpub/hp_201206
https://www.nxtbook.com/nxtbooks/gulfpub/hp_201205
https://www.nxtbook.com/nxtbooks/gulfpub/hp_201204
https://www.nxtbook.com/nxtbooks/gulfpub/hp_201203
https://www.nxtbook.com/nxtbooks/gulfpub/hp_201202
https://www.nxtbook.com/nxtbooks/gulfpub/hp_201201
https://www.nxtbook.com/nxtbooks/gulfpub/hp_201112
https://www.nxtbook.com/nxtbooks/gulfpub/hp_201111
https://www.nxtbook.com/nxtbooks/gulfpub/hp_201110
https://www.nxtbook.com/nxtbooks/gulfpub/hp_201109
https://www.nxtbook.com/nxtbooks/gulfpub/hp_201108
https://www.nxtbook.com/nxtbooks/gulfpub/hp_201107_srsguide
https://www.nxtbook.com/nxtbooks/gulfpub/hp_201107
https://www.nxtbook.com/nxtbooks/gulfpub/hp_201106
https://www.nxtbook.com/nxtbooks/gulfpub/hp_201105
https://www.nxtbook.com/nxtbooks/gulfpub/hp_201104
https://www.nxtbook.com/nxtbooks/gulfpub/hp_201103
https://www.nxtbook.com/nxtbooks/gulfpub/hp_201102
https://www.nxtbook.com/nxtbooks/gulfpub/hp_201101
https://www.nxtbook.com/nxtbooks/gulfpub/hp_201012
https://www.nxtbook.com/nxtbooks/gulfpub/hp_201011
https://www.nxtbook.com/nxtbooks/gulfpub/hp_201010
https://www.nxtbook.com/nxtbooks/gulfpub/hp_201009
https://www.nxtbook.com/nxtbooks/gulfpub/hp_201008
https://www.nxtbook.com/nxtbooks/gulfpub/hp_201007
https://www.nxtbook.com/nxtbooks/gulfpub/hp_201006
https://www.nxtbook.com/nxtbooks/gulfpub/hp_201005
https://www.nxtbook.com/nxtbooks/gulfpub/hp_201004
https://www.nxtbook.com/nxtbooks/gulfpub/hp_201003
https://www.nxtbook.com/nxtbooks/gulfpub/hp_201002
https://www.nxtbook.com/nxtbooks/gulfpub/hp_201001
https://www.nxtbook.com/nxtbooks/gulfpub/hp_200912
https://www.nxtbook.com/nxtbooks/gulfpub/hp_200911
https://www.nxtbook.com/nxtbooks/gulfpub/hp_200910
https://www.nxtbook.com/nxtbooks/gulfpub/hp_200909
https://www.nxtbook.com/nxtbooks/gulfpub/hp_200908
https://www.nxtbook.com/nxtbooks/gulfpub/hp_200907
https://www.nxtbook.com/nxtbooks/gulfpub/hp_200906
https://www.nxtbook.com/nxtbooks/gulfpub/hp_200905
https://www.nxtbook.com/nxtbooks/gulfpub/hp_200904
https://www.nxtbook.com/nxtbooks/gulfpub/hp_200903
https://www.nxtbook.com/nxtbooks/gulfpub/hp_200902
https://www.nxtbook.com/nxtbooks/gulfpub/hp_200901
https://www.nxtbookmedia.com