machinery reliability-heinz bloch
TRANSCRIPT
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Second levelThird level
Fourth level
Fifth level
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(1) Start with cost estimates and budgets
Why Best-of-Class companies budget towards mostrel iable machinery and not towards their least
expensive initial outlay options
They start by having only the most capablevendors on their bidders (vendors) lists
Their budgets for machinery include 5% of thecost of this machinery to perform MQA
Have a contingency budget to pay forupgrades or things overlooked in the specs
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of Webinar 9, (6/20/ 2013)
Several recent texts
include descriptionsof MQA
The smartest budgets
include 5% or more forperforming MachineryQuality Assessment(MQA);often a one-year payback
Next slide: Pre-invest!
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MQA Example: Nozzle size increases for
D$ ~ 4 to 6 k--low gas velocity The benefits of soundly
done pre-investment in
contingency upgrades(as successfully done by
Dakota Gasification;
briefly discuss example)
Examples of large gearbox and compressor
nozzle sizing upgrades
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(2) Decisions with Reliability Impact for
Reciprocating Compressors: Or,
small matters add up
Suction valves were not automatically opened whenpower was interrupted--bearing bores then contact their
pins or journals Grout support under compressor frame had been allowed
to degrade over time--generally no issue, but crankshaftis then slightly curved
Bearing bores then experienced edge loading With no power to compressor driver, there was no lube
oil supply to bearings, hence no cooling; some melting
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Edge loading means reduced areas of
contact;pressure = force per unit area (psi) Crank pin
Crosshead pin
Main journal______________
The loads (arrows) actonly on a smallarea, psi. Now the
pressure becomestoo high; no oilfilm; high temperat.,softening of alloy(babbitt) takes
place; bearing fails
1
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Edge-loading of bowed crankshaft wrecks a bearing Theowner plant allowed four deviations to become new normal: curvature
of crankshaft, high force on bearing, no cooling oil
2
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Real pros always look at the entire system: Example ofKing Tool
conventional horizontal filter-coalescer vs. self-cleaning models
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Why reciprocating compressor moisture
disengagement strategies are often flawed
Example of a reciprocating machine having an
inlet capacity of 1000 volume units (cubic feet per
minute, or cubic meters per hour)
Volume = Area times velocity [cfm=sq ft x ft/min]
Volume = Area times velocity [m^3/hr = m^2 x m/hr]
1000=10 x 100----- small area x high velocity ($)
1000=100 x 10----- large area x low velocity ($$$)
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of Webinar 9, (6/20/ 2013)
(3)The merits of superior machinery storagepreservation (cost justification is not difficult)
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Cost justification for OM storage protection
System cost: ~$300,000 Without oil mist outdoor storage protection, must
dismantle and inspect/clean 120 process pumps($10,000 each) = $1,200,000 and electricmotors ($3,000 ea) = $ 360,000
Total cost avoidance is $1,560,000-$300,000 =
$1,260,000. Operating cost of the OM storagesetup is offset by credits for future use as unit-wide oil mist lubrication system
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(4+5) Examples of knowledge requirements:
Lube and bearingenvironment (synonymous) Specify the correct lube viscosity: Enlist vendors
Select film strength formulations, know about
viscosity improvers and other additives
What does this imply? Mineral oils versus
synthesized hydrocarbons---synthetics
When are the latter justified? For an experts
answer, view the next slide
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Liquids always tend to wash off lubricants
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(4) Where only synthetics will do:
(1) In bearings operating at (or developing) hightemperature, synthetics slow down oxidation and filmthickness degradation
(2) When increased vibration alerts you to an incipient
defect, synthetics fill micro-cracks(3) After deleting cooling water (which best-of-class
companies have done for the past 40 years), synthetics
greatly expand range of allowable operating temps
(4) In gear units of all sizes (except if common w/comp.(5) In reciprocating process gas compressor cylinders
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(5) Superior bearings
are available
Double-row bearingswith two inner rings (top)
Ceramic bearings best inwet screw compressors
API 610 is only a guide
PumPacbrgs preventsliding and heat-related
bearing degradation Buy only from mfrs that
can provide applicationengineering expertise
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Notice the REs expanding horizons
Its not machine fail; must be machines fault
Its not fix only what is broken. Underlyingcauses must be found and addressed
Always an early warning; API-stds are only min.
Rarely only one deviation; several deviationswill combine and cause a failure
When someone says weve always done it thatway---they may have always done it wrong
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(5a)--Sliding pipe support details
Note that 2 polymer(Teflon) plates areneeded
Consider whathappens if money issaved using onlya single poly plate:Rust forms on thesteel surfaces andnothing moves!
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(5b) Effect of pulling pipe into place: Distress
Bearing is designedto make contourcontact
Pipes pulled into
place to matchcasing nozzles willcause casings todistort
Bearings are point-loaded and the oilfilm is no longeradequate
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(6) Rotary valve stuffing boxes and pump bearing housings
need protection against intrusion of debris
Remember: Modernbearing housing seals
for pumps are designed
as rotating labyrinths
Advanced seals do not
have an O-ring that
contacts a sharp edge or
O-ring groove Unless specified, youll
always get the cheapest
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(7) Spare parts management: New 3D
printer methods make patterns for
castings; contour measuring machines
Getting primed for implementing modern 3D PrinterMethods of pattern production for certain spare parts(buying very few spare parts). A good project decision!
Thus: Linking up with a knowledgeable provider will beadvantageous to the owner-purchaser or design firm, andalso for existing plants that need to consolidate spares.
Contour-measuring allows superb reverse-engineering
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(8) Old traditional oil mist lubrication: Some OMescaped before it had an opportunity to reach the bearings
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(8) Oil mist applied per API-610 (2009)
allows flow entirely through bearings
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(9) Grouting and hold-down bolt issues
avoided with epoxy-filled base
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Anchor bolt, on left, must have a free length (non-
encased, allowed to stretch) equal to 10 diameters
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Typical as-installed baseplate cost
comparison:Conventional vs. Pre-Filled
$ 6,259
$ 4,194
$ 2,065
IMMEDIATE
PAYBACK!
Equipment Installation: Baseplates
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(10) Seal-related upgrade opportunities
Enlist an expert to optimize your mechanical sealSpecifications and buy seals from 2 or 3 suppliers
Make a competent vendor your failure reduction
partner, not merely your supplier of inexpensivemechanical seals
Plan to upgrade to dual seals and closed-loopwater management systems wherever possible. Itis sure to decrease repair frequency and will savemuch money
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Sometimes it is advantageous to interrupt the flow
around the seal faces; one could use Vortex Breakers
Option 1: Changing the seal environment
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Option 2: Change to dual sealsbut beware
Some seal designs do not optimize the exchange of fluid.
Parallel slots move little, if any, of the barrier fluid
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Change the environment with a superior dual
seal; add value with better pumping rings
Some dual seal designs truly optimize the exchange of fluid.
This one uses a wide-clearance tapered pumping ring
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Mechanical seal with internal flow baffle(shown here with a flow guide, but w/o tapered pumping ring)
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Bi-directional internal flow device (Buffer Fluid
Impeller) incorporated in mechanical seal
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Bi-directional barrier fluid pumping device---a
highly effective Tapered Barrier Fluid ImpellerTHREE ADVANTAGES
Efficient No cost impact
Moves more
cooling fluid to
critical regionof mechanical seal
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API 682 / ISO 21409Awareness of
Standards and deviations from same
All seals should operate continuously for
25,000 hours without need for replacement
The minimum performance requirements and
permitted leakage detailed in Section
10.3.1.4.1 of the standard specifies an average
leakage rate of less than 5.6 grams / hour perset of seal faces
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Air Testing Protocol outlined in Section10.3.4.2 of the standard
Each sealing section shall be independently
pressurized with clean air to a gauge pressure of0.17 Mpa (1.7 bar) ( 25 psi). The volume of eachtest setup shall be a maximum of 28 liters (1 cu. ft.)
Isolate the test setup from pressurizing source and
maintain the pressure for at least 5 minutes The maximum pressure drop during the test shall be
0.014 Mpa (0.14 bar, or 2 psi)*
API 682 / ISO 21409
T t
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of Webinar 9, (6/20/ 2013)
Test 125 L Vessel plus
1.5 approximate air volumein rig providing total of
26.5 liters, or95% of the
maximum air volume per
10.3.4.2 pressure tested.Result: Pass
Tests
Test 226.5 Liter air
volume fitted with a NPT plug with a 0.008
hold drilled through the
center. Pressure tested.
Result: Pass
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of Webinar 9, (6/20/ 2013)
Test 326.5 L Air volume
connected to mechanicalseal fitted with the NPT
plug with 0.008 hole.
Pressure tested
Result: Pass
Tests
Test 41.5 L Air Volume
connected to Mechanical
seal fitted with the NPTplug with 0.008 hole.
Pressure tested
Result: Fail
T t 6 7 & 8 O ifi d f th l d tt h d
F il
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of Webinar 9, (6/20/ 2013)
Test 6, 7 & 8 Orifice removed from the seal and attached
to nitrogen pressurized water vessel to measure the leakage
at different pressures against the 5.6 grams /hour (g/h)
specification in API 682 / ISO 21409
1,500 g / h270 x allowable test
Fail
3,000 g / h
540 x allowable test
Fail
7,500 g / h
1,300 x allowable test
Fail
of Webinar 9, (6/20/ 2013)
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Summary
1. Decision to deal only with the best vendors;MQA and pre-investment in risk reduction
2. Decisions with impact on reliability of
reciprocating compressors3. Oil mist for superior storage preservation
4. Use synthetics where only synthetics will do
5. Bearings for highest reliability: from vendorswith application engineering know-how!
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Summary
6. The right bearing protection is part of built-inreliability. Specify it in the project
7. Fewer spare parts: Use 3D print pattern library
8. Plant-wide oil mist includes electric motors!Rapid payback is possible (SKF/Colfax Ind., etc)
9. Pre-grouted epoxy-filled base plates make
economic sense and give long trouble-free life10. Better and smarter mechanical seal options exist
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QUESTIONS?