Paper360 - November/December 2017 - 39

Fig. 2: A 10 in. diameter vacuum line
with failed rubber boot. Leak caused
5 in. Hg of vacuum reduction. Duct
tape indicates previous attempt to fix.

Fig. 3: An example of good labeling.

and processes are modified, proper labeling is
often not completed with the project.
There are a few basic best practices related to
equipment labeling and documents:
* Labeling vacuum pumps, motors and
auxiliary equipment
* Labeling valves and blanks within
the vacuum piping network and
accompanying this with information about
valve/blank positions (normally closed or
normally open)
* Process drawings must be current to show
accurate information
* DCS displays that accurately
show processes
* Use of bar charts in DCS displays
besides just raw data can provide quick
identification of issues
VACUUM PUMP
MAINTENANCE AND REPAIRS
Many people are involved in this effort,
including lubrication and vibration techs, maintenance superintendents, maintenance planners,
and purchasing managers. Essential in-house
maintenance includes routine bearing lubrication and vibration measurement and trending.
Vacuum pump condition/performance can be
determined by several methods, including: performance testing (easiest with smaller pumps),
fiberscope inspections of pump internals, and
measurement and trending of system vacuum
levels and operating horsepower.
This last item, trending operating data, is
seldom done. Many mills will spend between
US$50,000 - $100,000 for removal, rebuilding,
shipping, and reinstalling large vacuum pumps
that were in good condition. Errors can exist in
performance test results and analysis of fiberscope inspections. Meanwhile, no one in the
mill has questioned why a pump reported at
50-60 percent of new performance had little
or no change in vacuum or horsepower before
or after the repair.
Some mills experience frequent bearing
failures and are comfortable with bearing life

Fig. 4: Two fabricated stainless steel rotors for the same pump model. The
right is OEM; the left side tested at 65 percent of new performance.

of 5-10 years. They may not realize most liquid
ring pumps are equipped with robust bearing
designs that often have a design life of 15 to 20
years. Repetitive and high frequency bearing
failures are often due to inaccurate machining and repair issues. Other causes of bearing
failures are due to poor lubrication practices
(lack of, or excessive), misalignment, incorrect
coupling selection, and corrosion and deterioration of bases and foundations.
As mentioned, vacuum pump bearings have
long design lives. Where seal water quality is
very good it is not surprising to find every pump
on one paper machine to be in almost new condition after 25 years. At that point it is wise to
begin a bearing replacement effort.
Vacuum pump manufacturers have OEM
repair facilities or authorized service centers.
There are several other machine shops that
repair vacuum pumps only, and many more
offering to rebuild whatever has recently broken. The OEM facilities will use original and
remanufactured parts and have manufacturing
drawings. Similar to rebuilds of fans and centrifugal pumps, other shops will be reverse engineering components and may have acquired
some original drawings. It is worthwhile to visit
any of these facilities before choosing where a
vacuum pump is to be rebuilt. Request a disassembly report, including photos. Visiting the
shop during disassembly is a good choice to
get a better understanding of wear and failure
issues. Consider testing the pump for capacity
and horsepower following the rebuild (Fig. 4.)
Once the pump is reinstalled, determine if
the bearings were adequately lubricated during
the rebuild; if so, don't add more grease. A few
mills are still relying on oil lubrication, and this
is easier to determine. After installation, alignment, and startup, pay attention to adjusting
packing during the first few weeks. Sometimes
this is ignored and finally gets attention when
the shaft seals are seriously leaking water, which
can get into the bearings.
Maintenance and repair of vacuum pumps
should include these best practices:

1. Understand long bearing design lives,
and investigate repeated failures of
specific pump bearings or random
failures as frequently as within five years
of replacement.
2. Develop good procedures for bearing
lubrication amounts and frequency.
Resist excessive lubrication.
3. Develop good procedures for monitoring
bearing vibration and temperature.
4. Review procedures for pump alignment.
5. Inspect pump bases and foundations for
deterioration. These can be more than
50 years old.
6. Consider performance testing
rebuilt pumps.
7. Either performance test or fiberscope
vacuum pumps at least every two years.
Frequency can be longer depending
on specific mill experiences. Compare
motor loads and vacuum levels to
performance data when evaluating if a
pump needs to be overhauled.
8. Analyze time between failures and
compare entire repair cost (overhaul,
removal, reinstallation, shipping) when
evaluating pump repair choices.
9. Choose repair facilities after some
research, comparison and even
site visits.
Considering the importance of the vacuum
system, there are several items impacting performance besides piping, valves, and motors.
Examining training, housekeeping, equipment
labeling and identification, and maintenance
procedures will have positive effects on troubleshooting, machine efficiency, and maintenance
costs. Application of these best practices will
usually require little cost. Benefits will be measurable and can be significant.
Doug Sweet, P.E. is principal of Doug Sweet &
Associates, Inc., and has more than 40 years
experience with vacuum system optimization
in mills around the world. Contact him at dougsweet@cs.com and visit www.dougsweet.net

Paper360ยบ NOVEMBER/DECEMBER 2017

39


http://www.dougsweet.net

Table of Contents for the Digital Edition of Paper360 - November/December 2017

Setpoint
Over the Wire
Rebuilds and Conversions
Proud to be a Papermaker
The New Cascades
Operational Data Helps Mills Meet Challenges
Papermaking Best Practices with Vacuum-Dewatering Systems: Part 2
TAPPI Library is an Industry Resource
Managing the Decline of Graphic Paper Demand
TAPPI Journal Summaries
2017 PPI Awards Finalists
TAPPI News
ASPI News
Index of Advertisers
Paper360 - November/December 2017 - Intro
Paper360 - November/December 2017 - cover1
Paper360 - November/December 2017 - cover2
Paper360 - November/December 2017 - 3
Paper360 - November/December 2017 - 4
Paper360 - November/December 2017 - 5
Paper360 - November/December 2017 - Setpoint
Paper360 - November/December 2017 - 7
Paper360 - November/December 2017 - Over the Wire
Paper360 - November/December 2017 - 9
Paper360 - November/December 2017 - 10
Paper360 - November/December 2017 - 11
Paper360 - November/December 2017 - Rebuilds and Conversions
Paper360 - November/December 2017 - 13
Paper360 - November/December 2017 - 14
Paper360 - November/December 2017 - 15
Paper360 - November/December 2017 - 16
Paper360 - November/December 2017 - 17
Paper360 - November/December 2017 - 18
Paper360 - November/December 2017 - 19
Paper360 - November/December 2017 - 20
Paper360 - November/December 2017 - 21
Paper360 - November/December 2017 - 22
Paper360 - November/December 2017 - 23
Paper360 - November/December 2017 - Proud to be a Papermaker
Paper360 - November/December 2017 - 25
Paper360 - November/December 2017 - 26
Paper360 - November/December 2017 - 27
Paper360 - November/December 2017 - 28
Paper360 - November/December 2017 - 29
Paper360 - November/December 2017 - The New Cascades
Paper360 - November/December 2017 - 31
Paper360 - November/December 2017 - 32
Paper360 - November/December 2017 - 33
Paper360 - November/December 2017 - Operational Data Helps Mills Meet Challenges
Paper360 - November/December 2017 - 35
Paper360 - November/December 2017 - 36
Paper360 - November/December 2017 - 37
Paper360 - November/December 2017 - Papermaking Best Practices with Vacuum-Dewatering Systems: Part 2
Paper360 - November/December 2017 - 39
Paper360 - November/December 2017 - Managing the Decline of Graphic Paper Demand
Paper360 - November/December 2017 - 41
Paper360 - November/December 2017 - TAPPI Journal Summaries
Paper360 - November/December 2017 - 43
Paper360 - November/December 2017 - 44
Paper360 - November/December 2017 - 45
Paper360 - November/December 2017 - 2017 PPI Awards Finalists
Paper360 - November/December 2017 - 47
Paper360 - November/December 2017 - TAPPI News
Paper360 - November/December 2017 - ASPI News
Paper360 - November/December 2017 - Index of Advertisers
Paper360 - November/December 2017 - cover3
Paper360 - November/December 2017 - cover4
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