Design, Codes, and Opportunities Steve Meicke HDR Engineering, Inc. Portland, OR Spillway Gate Hoist Machinery Rehab and Replacement
Design, Codes, and Opportunities
Steve Meicke
HDR Engineering, Inc.
Portland, OR
Spillway Gate Hoist
Machinery Rehab and
Replacement
Purpose and Background 2
• Hoist machinery rehab: opportunity
to increase safety and reliability
• ‘Refresher course’ for project
owners:
– Applicable design codes, recent
changes
– Load cases for design
– Torque limiting techniques
Why are Gates Important?
3
What could happen at your
project if your gate doesn’t
function properly?
Introduction 4
• Dam construction in the NW occurred in
the early to mid-1900’s
• Many spillway gate hoist systems are
nearing or past their designed useful life
• Past designs may not meet present day
design criteria
– Improved understanding of fatigue
– Past design guidance:
• Not well understood
• May be based on internal knowledge
• No widely accepted codes
• Motivated by different factors
Issues Facing Existing Hoists 5
• Primary: Age! Years of fatigue,
exposure to elements, corrosion, wear
• Other possible issues:
– Lack of redundancy
– Overstress due to under-design
– High maintenance requirements and
costs
– Cumulative fatigue damage
– More…
What’s next? Rehab or Replacement?
Primary Design Codes for Design 6
• USACE EM 1110-1-2610:
– Significant update in July 2013
– Provides general design criteria, best
practices for a wide range of gate
components.
• AASHTO LRFD Moveable Highway
Bridge Design Specifications:
– Specific formulas used in design
– Fills in gaps and expands upon criteria
from EM-2610
EM 2610 – Recent Revisions 7
• Overall: doubled in length, added 400
MB reference materials
• Load Cases:
– Normal Case: change from actual hoist
load to 100% motor full load torque
– Overload case: clarification on wire
rope load sharing
• Other revisions:
– Bearings (AFB and composite)
– Wire rope
AASHTO LRFD Specifications 8
• More detail and calculation oriented…
– Design guidance that EM-2610 lacks
• Many of the same formulas and figures
as EM-2610
• Specific formulas for design:
– fatigue theory, contact stresses for
open gearing, stress concentration
factors, etc.
– Much more…
Design Codes - Summary 9
• EM-2610: general guidance on load
cases and allowables, best practices
• AASHTO LRFD: detailed calculation
guidance, fills EM-2610 gaps
• EM-2610 and AASHTO have much in
common, but differences exist
– Design team should be clear which
criteria will be used for each component
– Design criteria memo!
Load Cases for Design (EM-2610) 11
• Normal Operating Case:
– 50 / 50 lifting load split
– Motor at 100% Full Load Torque (FLT)
– Allowable Stress: 20% of Ultimate
– Purchased components: manufacturer
ratings
• Normal operating case often drives
design!
Load Cases for Design (EM-2610) 12
• Overload Case:
– 70 / 30 lifting load split: represents
jammed gate, racked to one side
• Must check worst case of 100 / 0!
– Motor at 280% FLT for NEMA D*
– Allowable Stress: 75% of Yield
• Normal startup torque: is does not
constitute Overload
Torque Limiting Techniques
13
Technique Pros Cons
Passive
Slip Clutch − Reliable
− Instant reaction − Additional maintenance
Current Limiting
Device − Inexpensive
− Prevents extended OL
− Response may not be
quick enough
Acitve Load / Torque Cell
with Feeback Loop
− Real-time feedback
− PM / failure diagnostics
− Fast response and motor
control possible
− Difficult to maintain
− Low reliability?
− Software support may
be an issue
− Most complex option
Effect to load cases mentioned previously?
Treatment of Torque Limiting Devices 14
• Project-by-project basis, based on
consequences of hoist failure
• Best practice is to assume these
devices will not perform when you need
them!
• Design hoist components to withstand
280% FLT and one-sided lifting
– Simple is beautiful
– May be cost prohibitive or not
necessary
Conclusions:
16
• Spillway gate hoists: critical to safety
• Many existing systems nearing / past expected life
• Considerations for gate hoist rehab / replacement:
– Understand issues with your hoist
– Primary design codes, recent changes
– Load cases which drive design
– State of the art: torque limiting and control
Additional Design References:
18
• Machinery Handbook
• Federal Wire Rope Specification RR-W-410
• Wire Rope User’s Manual
• EM-1110-2-3200: Wire Rope Selection Criteria for Gate
Operating Devices
• EM-1110-2-2702: Design of Spillway Tainter Gates
• AASHTO LRFD Moveable Highway Bridge Design
Specifications, revisions 2008
• AASHTO Movable Bridge Inspection, Evaluation and
Maintenance Manual 1998
• Peterson’s Stress Concentration Factors
• Steel Manual ASD
Mechanical / Structural Relationship
19
Structural Mechanical
Load Case 2:
Normal Operating Loads Size prime mover to lift load
Design system – determine
reduction, friction, drum
diameter, etc.
Overload Case Normal Case
70 / 30 lifting split,
locked rotor motor torque
50 / 50 lifting split,
FLT of motor
Check 1-sided lifting loads!
Design… Design…
Load Case 4:
overload 100/0
lifting split
Design…
Load Changed? Loads
Complete
Preliminary Gate Design
No
Yes
Wire Rope Loads
Gate Weight
Trunnion Friction