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!

Motor Loads on Machinery

10

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

What Else Can You Do?

15

Inspect and Maintain!

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

Questions?

17

Thank You!

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