Public Review Draft 1573

8/6/2019 Public Review Draft 1573

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ASME BTH-1-20XX

(Revision of ASME BTH-1-2008)

Design ofBelow-the-Hook

Lifting Devices

TentativeSubject to Revision or Withdrawal

Specific authorization requiredfor reproduction or quotation

ASME Codes and Standards

2011 The American Society of Mechanical Engineers


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ASME BTH-1-200X

Summary of Changes

Following approval by the ASME BTH Standards Committee and after public review, ASMEBTH-1-200x was approved by the American National Standards Institute on .

Revisions introduced within the 200X edition of ASME BTH-1 are identified by a margin note,(0x).

Page Location Change

X 1-2 New paragraphs added

X 1-4.8 Removed

X 1-5.1 Revised in its entirety

X 1-5.2 Revised in its entiretyX 1-5.3 Revised in its entirety

X 1-5.4 Revised in its entiretyX 1-6.1 Revised in its entiretyX 1-7 References updated

X 3-2.3.2 Revised in its entirety

X 3-2.3.6 Editorially revisedX 3-3.3.1 Formulas revised

X 4-5.4 References updated

X 4-9 Minor revisions

X 4-10.2 Revised in its entiretyX 4-10.3 Editorially revised

X 4-11 Added

X 5-1.3 New wording addedX 5-3 Title revised

X 5-3.8 Added

X 5-4.6 Revised in its entirety

X 5-6.3 Revised in its entiretyX 5-7.3 Revised in its entirety


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Revisions / Additions January 16, 2011 1

Chapter 1

Scope, and Definitions, and References

1-2 SCOPE

This Standard provides minimum structural andmechanical design and electrical component selectioncriteria for ASME B30.20 below-the-hook liftingdevices.

The provisions in this Standard apply to thedesign or modification of below-the-hook liftingdevices. Compliance with requirements and criteriathat may be unique to specialized industries andenvironments is outside of the scope of this Standard.

Lifting devices designed to this Standard shallcomply with ASME B30.20, Below-the-Hook Lifting

Devices. ASME B30.20 includes provisions that applyto the marking, construction, installation, inspection,testing, maintenance, and operation of below-the-hooklifting devices.

The provisions defined in this standard addressthe most common and broadly applicable aspects ofthe design of below-the-hook lifting devices. Thequalified person shall determine the appropriatemethods to be used to address design issues that arenot explicitly covered in the standard so as to providedesign factors and/or performance consistent with theintent of this standard.

Commentary: ASME BTH-1 addresses onlydesign requirements. As such, this Standard should be

used in conjunction with ASME B30.20, which

addresses safety requirements. ASME BTH-1 does

not replace ASME B30.20. The design criteria set forth

are minimum requirements that may be increased at

the discretion of the lifting device manufacturer or a

qualified person.

The design of lifting attachments may be

addressed by existing industry design standards. In

the absence of such design standards, a qualified

person should determine if the provisions of BTH-1 are

applicable.

[unchanged sections skipped]

1-4.8 Pressurized Fluid Systems

Pressurized fluid systems are not covered by thisStandard.

1-5.1 Definitions General

ambient temperature: the temperature of the atmospheresurrounding the lifting device (para. 1-4.7).

below-the-hook lifting device (lifting device, lifter): adevice, other than slings, hooks, rigging hardware,and lifting attachments, used for attaching loads to ahoist used for attaching a load to a hoist. The devicemay contain components such as slings, hooks, andrigging hardware that are addressed by ASME B30volumes or other standards (section 1-1).

cycle, load: one sequence of two load reversals thatdefine a range between maximum and minimum load(para. 1-5.1) ).

[unchanged definitions skipped]

hoist: a machinery unit that is used for lifting andlowering (para. 1-5.1).

lifting attachment: a load supporting device that is bolted or permanently attached to the lifted loadobject being lifted, such as lifting lugs, padeyes,trunnions, and similar appurtenances (para. 1-2 1-5.1).

limit state: a condition in which a structure orcomponent becomes unfit for service, such as brittlefracture, plastic collapse, excessive deformation,durability, fatigue, instability, and is judged either to be no longer useful for its intended function(serviceability limit state) or to be unsafe (strength limitstate) (para. 1-5.1).

load(s), applied: external force(s) acting on a structuralmember or machine element due to the rated load,dead load, and other forces created by the operationand geometry of the lifting device (para. 1-5.2).


rigging hardware: a detachable load supporting devicesuch as a shackle, link, eyebolt, ring, swivel, or clevis

(para. 1-5.1).serviceability limit state: limiting condition affecting theability of a structure to preserve its maintainability,durability, or function of machinery under normalusage (para. 1-5.12).

shall: indicates that the rule is mandatory and must befollowed (section 1-2).

should: indicates that the rule is a recommendation, the

Attachment 1 - BTH-1-2011 Revisions - 1-16-11


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advisability of which depends on the facts in eachsituation (para. 2-2.1).

sling: an assembly to be used for lifting whenconnected to a hoist or lifting device at the slingsupper end and when supporting a load at the slingslower end (para. 1-5.1).

strength limit state: limiting condition affecting thesafety of the structure, in which the ultimate loadcarrying capacity is reached (para. 1-5.1).

stress concentration: localized stress considerably higherthan average (even in uniformly loaded cross sectionsof uniform thickness) due to abrupt changes ingeometry or localized loading (para. 3-4.1).


1-5.2 Definitions for Chapter 3


gross area: full cross-sectional area of the member(para. 3-2.1).

limit state: a condition in which a structure orcomponent becomes unfit for service, such as brittlefracture, plastic collapse, excessive deformation,durability, fatigue, instability, and is judged either to be no longer useful for its intended function(serviceability limit state) or to be unsafe (strength limitstate) (para. 1-5.2).

local buckling: the buckling of a compression element

that may precipitate the failure of the whole memberat a stress level below the yield stress of the material(para. 1-5.2).


slip-critical: a type of bolted connection in which shearis transmitted by means of the friction producedbetween the faying surfaces by the clamping action ofthe bolts (para. 1-6.1).

strength limit state: limiting condition affecting thesafety of the structure, in which the ultimate loadcarrying capacity is reached (para. 1-5.2).

unbraced length: the distance between braced points ofa member, measured between the centers of gravity ofthe bracing members; for beams not braced againsttwist or lateral displacement, maximum span betweensupports or points of applied load (para. 1-5.2).



back-driving: a condition where the load impartsmotion to the drive system (para. 4-5.5).

coefficient of static friction: the nondimensional numberobtained by dividing the friction force resisting initialmotion between two bodies by the normal forcepressing the bodies together (para. 4-9.1).

drive system: an assembly of components that governsthe starting, stopping, force, speed, and directionimparted to a moving apparatus (para. 1-5.3).

fluid power: energy transmitted and controlled bymeans of a pressurized fluid, either liquid or gas. Theterm applies to both hydraulics, which uses apressurized liquid such as oil or water, andpneumatics, which uses compressed air or other gases(section 4-11).

grip ratio: the ratio of the sum of the horizontal forceson one side of the load to the live weight of the load.

For example, if the total horizontal force on one side ofthe load is 100,000 lb and the live load is 50,000 lb, thegrip ratio is 2. For purposes of this calculation, theweight of the load does not include the weight of thelifter (section 4-9.


vacuum: pressure less than ambient atmosphericpressure (para. 1-5.3).

vacuum lifter lifting device: a below-the-hook liftingdevice for lifting and transporting loads using aholding force by means of vacuum (section 4-10).

vacuum pad: a device that applies a holding force onthe load by means of vacuum (para. 4-10.1).

vacuum reservoir: the evacuated portion of a vacuumsystem which functions to compensate for leakage inthe vacuum system or to provide a vacuum reserve inthe event of vacuum generator failure (para. 4-10.2).



control system: an assembly or group of devices that

govern or regulate the operation of an apparatus(para. 5-3.1).

duty cycle:

duty cycle =time on

time on + time offx 100

and is expressed as a percentage (para. 5-2.1).

EXAMPLE: 1/2 3 min on, 2 min off = equals



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1/2 / (1/2 + 2) x 100 = 20%

3

3+ 2x 100 = 60%

electromagnet, externally powered: a lifting magnet,

suspended from a crane, that requires power from asource external to the crane (para. 5-6.3).

ground (grounded): electrically connected to earth or tosome conducting body that serves in place of the earth(section 5-5).


1-6.1 Symbols for Chapter 3

[unchanged symbols skipped]

beff = effective width to each side of the pin-

hole, in. (mm) (para. 3-3.3.1)bf = width of the compression flange, in.

(mm) (para. 3-2.3.2)Cb = bending coefficient dependent upon

moment gradient (para. 3-2.3.2)Cc = column slenderness ratio separating

elastic and inelastic buckling (para. 3-2.2)

Cf = stress category constant for fatigueanalysis (para. 3-4.5)

CLTB = lateral-torsional buckling strengthcoefficient (para. 3-2.3.2)

Cm = coefficient applied to bending term in

interaction equation for prismaticmember and dependent upon columncurvature caused by applied moments(para. 3-2.4)


J = torsional constant, in.4 (mm4) (para. 3-2.3.1)

K = effective length factor based on thedegree of fixity at each end of themember (para. 3-2.2)

l = (para. 3-2.2)

l = the actual unbraced length of the mem-ber, in. (mm) (para. 3-2.2)Lb = distance between cross sections braced

against twist or lateral displacement ofthe compression flange; for beams not braced against twist or lateraldisplacement, maximum span betweensupports or points of applied load, in.(mm) (para. 3-2.3.2)

Lp = maximum laterally unbraced length of a

bending member for which the full plas-tic bending capacity can be realized,uniform moment case (Cb = 1.0), in.(mm) (para. 3-2.3.2)


Pv = allowable double plane shear strength beyond the pinhole, kips (N) (para. 3-3.3.1)

R = distance from the center of the hole tothe edge of the plate in the direction ofthe applied load, in. (mm) (para. 3-3.3.1); variable used in the cumulativefatigue analysis (para. 3-4.6); radius ofedge of plate (Table 3-5)

r = radius of gyration about the axis underconsideration, in. (mm) (para. 3-2.2),radius of curvature of the edge of the

plate, in. (mm) (Commentary for para.3-3.3.1)


1-7 REFERENCES

The following is a list of publications referenced inthis Standard.

ANSI/AGMA 2001-C95, Fundamental Rating Factorsand Calculation Methods for Involute Spur andHelical Gear Teeth1

Publisher: American Gear Manufacturers Association

(AGMA), 500 Montgomery Street, Alexandria, VA22314-1581

ANSI/AWS D14.1-1997 2005, Specification forWelding of Industrial and Mill Cranes and OtherMaterial Handling Equipment1

Publisher: American Welding Society (AWS), 550N.W. LeJeune Road, Miami, FL 33126

ANSI/NFPA 70-2005 2008, National Electrical Code1

Publisher: National Fire Protection Association(NFPA), 1 Batterymarch Park, Quincy, MA 02269-9101

ASME B17.1-1967 (Reaffirmed 1998 2008), Keys andKeyseats

ASME B30.20-2003 2010, Below-the-Hook LiftingDevices1

1 May also be obtained from the American National

Standards Institute (ANSI), 25 West 43rd Street, New York,NY 10036.



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Publisher: The American Society of MechanicalEngineers (ASME), Three Park Avenue, New York,NY 10016-5990; Order Department: 22 Law Drive,Box 2300, Fairfield, NJ 07007-2300

ASTM A 325, Standard Specification for StructuralBolts, Steel, Heat Treated, 120/105 ksi MinimumTensile Strength

ASTM A 490, Standard Specification for StructuralBolts, Alloy Steel, Heat Treated, 150 ksi MinimumTensile Strength

Publisher: American Society for Testing and Materials(ASTM), 100 Barr Harbor Drive, WestConshohocken, PA 19428-2959

DIN 6885-1, Drive Type Fastenings Without TaperAction; Parallel Keys, Keyways, Deep Pattern

Publisher: Deutsches Institut fr Normung e.V. (DIN),10772 Berlin, Germany

ICS 2-2000 (R2005), Industrial Control and Systems:Controllers, Contactors, and Overload Relays Rated600 Volts

ICS 6-1993 (R2001, R2006), Industrial Control andSystems: Enclosures

MG 1-2003, Revision 1-2004 2006 Rev 1-2007, Motorsand Generators

Publisher: National Electrical ManufacturersAssociation (NEMA), 1300 North 17th Street, Suite1847 1752, Rosslyn, VA 22209

Pilkey, W.D., 1997 2008, Petersons StressConcentration Factors, 2nd 3rd edition

Publisher: John Wiley & Sons, Inc., 111 River Street,Hoboken, NJ 07030-5774

[unchanged references skipped]

Bjorhovde, R., Galambos, T.V., and Ravindra, M.K.,1978, LRFD Criteria for Steel Beam-Columns,Journal of the Structural Division, Vol. 104, No. ST9

Duerr, D., 2006, Pinned Connection Strength andBehavior, Journal of Structural Engineering , Vol. 132,No. 2

Dux, P.F., and Kitipornchai, S. (1990). Buckling of

Suspended I-Beams. Journal of StructuralEngineering , 116(7), 18771891, American Society ofCivil Engineers, Reston, VA.

Fisher, J.W., Galambos, T.V., Kulak, G.L., andRavindra, M.K., 1978, Load and Resistance DesignCriteria for Connectors, Journal of the StructuralDivision, Vol. 104, No. ST9



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Chapter 2

Lifter Classifications

[No changes for Chapter 2.]



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Chapter 3

Structural Design

3-2.3.2 Strong Axis and Weak Axis Bending

of Compact Sections with Unbraced Length

Greater than Lp and Noncompact Sections. The allowable bending stress for members withcompact or noncompact sections, as defined by Table3-1, loaded through the shear center, bent about eitherthe major or minor axis, and laterally braced at intervals not exceeding Lr for major axis bending asdefined by eq. (3-10) for I-shape members and by eq.(3-11) for box members is given by eq. (3-9). For channels bent about the strong axis, the allowablebendingstress is given by eq. (3-16) (3-17).

[unchanged paragraphs skipped]

When

Lb

rT>

17.59ECb

Fy(3-15)

Fb =!2ECb

Nd Lb rT( )2"

Fy

Nd

Fb = CLTB!2ECb

Nd Lb rT( )2"Fy

Nd(3-16)

For any value of Lb rT

Fb =0.66ECb

Nd Lbd Af( )!

Fy

Nd

Fb = CLTB0.66ECb

Nd Lbd Af( )!

Fy

Nd(3-17)

where

CLTB = 1.00 for beams braced against twist or lateraldisplacement of the compression flange at the

ends of the unbraced length

CLTB =3.00 Ix J

Lb bf! 1.00 for beams not braced

against twist or lateral displacement of thecompression flange at the ends of the unbracedlength

Lb= distance between cross sections braced againsttwist or lateral displacement of thecompression flange; for beams not braced

against twist or lateral displacement, maximum

span between supports or points of appliedload

rT= radius of gyration of a section comprising thecompression flange plus 13 of the compressionweb area, taken about an axis in the plane ofthe web

bf= width of the compression flange

The allowable major axis moment M for tees anddouble-angle members loaded in the plane ofsymmetry is

M =!

Nd

EIyGJ

LbB + 1+ B

2

( )"FyaSx

Nd

M = CLTB!

Nd

EIyGJ

LbB + 1+ B

2( ) "FyaSx

Nd(3-18)

wherea = 1.0 if the stem is in compression

= 1.25 if the stem is in tension

B = 2.3 d Lb( ) Iy J CLTB = 1.00 for beams braced against twist or lateral

displacement of the compression element at theends of the unbraced length

CLTB=

0.80 Ix J

Lb bf+ 0.25 ! 1.00

for beams not braced

against twist or lateral displacement of thecompression flange at the ends of the unbracedlength if the stem is in tension

CLTB =1.75 Ix J

Lb bf+ 0.20 !1.00 for beams not braced

against twist or lateral displacement of thecompression flange at the ends of the unbracedlength if the stem is in compression

G = shear modulus of elasticityIy= minor axis moment of inertia

The value B is positive when the stem is in tensionand negative when the stem is in compressionanywhere along the unbraced length.

Commentary: Noncompact shapes that are bracedat intervals not exceeding the spacing defined by eqs.(3-10) or (3-11) have a limit state moment that equatesto outer fiber yield. The allowable bending stress formembers with noncompact sections provides a design



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factor ofNdwith respect to outer fiber yielding.I-shape members and channels bent about the

strong axis may fail in lateral torsional buckling.Equations (3-13) through (3-17) define allowablebending compression stresses that provide a designfactor ofNdwith respect to this limit state.

The allowable moment expression for tees anddouble angle members eq. (3-18) defines theallowable moment based on the lesser limit state oflateral torsional buckling (Kitipornchai and Trahair,1980) or yield (Ellifritt, et al, 1992). The value of a =1.25 is based on the discussion in Commentary forpara. 3-2.3.4.

Eqs. 3-10 through 3-18 are based on the behavior of

beams that are restrained against twist or lateral

displacement at the ends of the unbraced length Lb.

Suspended beams exhibit different behavior with

respect to lateral torsional buckling (Dux, P.F., and

Kitipornchai, S., 1990). I-shape beams show a

buckling strength less than that predicted by the

standard elastic buckling equations at proportions

where Lb bf( ) Ix J is greater than about 3. Tee

shape beams show reduced buckling strength at all

proportions. The coefficient CLTB in eqs. 3-16, 3-17,

and 3-18 accounts for this reduced buckling strength.


3-2.3.6 Shear on Bars, Pins, andUnstiffened Plates. The average shear stress Fv on bars, pins, and unstiffened plates for which

h t! 2.45

E Fy shall not exceed

Fv =Fy

Nd 3(3-28)

whereh = clear depth of the plate parallel to the applied

shear force at the section under investigation.For rolled shapes, this value may be taken asthe clear distance between flanges less the filletor corner radius.

t = thickness of the plate

Methods used to determine the strength of platessubjected to shear forces for which h t! 2.45 E Fy

shall provide a design factor with respect to the limitstate of buckling not less than the applicable valuegiven in para. 3-1.3.

Commentary: The allowable shear stressexpression is based on CMAA #70, which specifies theallowable shear stress as a function of the shear yield

stress. The shear yield stress is based on the Energyof Distortion Theory (Shigley and Mischke, 2001). Thelimiting slenderness ratio of plates in shear is takenfrom AISC (2000).

Experience has shown that the members of below-the-hook lifting devices are not generally composed ofslender shear elements. Therefore, provisions for thedesign of slender shear elements are not included inthe Standard.


3-3.3.1 Static Strength of the Plates. Thestrength of a pin-connected plate in the region of thepinhole shall be taken as the least value of the tensilestrength of the effective area on a plane through thecenter of the pinhole perpendicular to the line ofaction of the applied load, the fracture strength beyond the pinhole on a single plane parallel to theline of action of the applied load, and the double plane

shear strength beyond the pinhole parallel to the lineof action of the applied load.


The effective width shall be taken as the smaller of thevalues calculated as follows:

beff ! 4t! be

beff = 4t! be (3-47)

beff ! be0.6 FuFy

Dhbe

! be

beff = be0.6Fu

Fy

Dh

be! be (3-48)

wherebe = actual width of a pin-connected plate between

the edge of the hole and the edge of the plateon a line perpendicular to the line of action ofthe applied load

The width limit of eq. (3-47) does not apply to plates

that are stiffened or otherwise prevented frombuckling out of plane.



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Chapter 4

Mechanical Design

4-5.4 Relation to Other Standards

As an alternative to the Lewis formula in eq. (4-1),spur and helical gears may be based uponANSI/AGMA 2001-C95, Fundamental Rating Factorsand Calculation Methods for Involute Spur andHelical Gear Teeth.

Commentary: The Committee decided to provide

the Lewis formula to the qualified person as a simpler

method to size gearing. Based on a review of a large

number of gear designs, the Lewis Equation coupled

with the design factorNdprovides conservative results.

As an alternative, the qualified person can use

ANSI/AGMA 2001-C95 to provide a more refinedanalytical approach where the design parameters of

the lifter are more constrained.


4-9 GRIP RATIO

This section sets forth requirements for the gripratio, as defined in ASME B30.20, for pressure-gripping lifters (friction-type). Factors such as typeand condition of gripping surfaces, environmentalconditions, coefficients of friction, dynamic loads, and

product temperature can affect the required grip ratioand should be considered during the design by aqualified person. In addition, lifters such as bar tongsand vertical axis coil grabs have other special loadhandling conditions (e.g., opening force) that shouldbe considered.

Commentary: Design of other types of lifting

devices, such as indentation-type lifters, is not covered

in this section.


4-10 VACUUM LIFTING DEVICE DESIGN


4-1 0.2 Vacuum Preservation Reservoir

System

The vacuum lifter lifting device shall incorporate amethod vacuum reservoir system of sufficient size to

prevent the vacuum level under the pads pad(s) fromdecreasing more than 25% 10% (starting from ratedvacuum level) in 5 4 minutes with without primarypower off and the vacuum pad(s) attached to on aclean, dry, and nonporous surface at the rated load.Consideration should be given to conditions such assurface temperatures, contamination, torsion andbending loads of the vacuum pad, tested vacuum padperformance, and surface conditions of interfacingmaterials. Unintended loss of power shall notdisconnect the pads pad(s) from the vacuumpreservation method reservoir system.

Commentary: This performance-based requirementallows the use of various vacuum preservationmethods (e.g. battery backup, compressed air storage,vacuum reservoir, etc.).

4-10.3 Vacuum Indicator

A vacuum indicator shall be visible to the lifteroperator during use and shall continue to functionduring an unintended loss of power. It shall indicatethe presence of the minimum vacuum required for therated load of the vacuum lifting device.

4-11 FLUID POWER SYSTEMS

4-11. 1 Purpose

This section identifies requirements of fluid powersystems and components for below-the-hook liftingdevices.

4-1 1.2 Fluid Power Components

(a) The lifting device manufacturer or qualifiedperson shall specify system components such ascylinders, pumps, valves, pipes, hoses, and tubes.Fluid power systems should be designed so that lossof the lifter power source(s), fluid loss, or controlsystem failure will not result in uncontrolledmovement of the load.

(b) Each hydraulic fluid power component shallbe selected based on the manufacturers rating and themaximum pressure applied to that component of thesystem, provided that the rating is based on a designfactor equal to or greater than 1.67 Nd.



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(c) Each pneumatic fluid power component shallbe selected based on the maximum pressure applied tothat component of the system and a rating equal to themanufacturer's rating divided by 0.50 Nd. Alternately,pneumatic fluid power components may be selected inaccordance with para. 4-11.2(b).

(d) Components whose failure will not result inuncontrolled movement of the load may be selectedbased on the manufacturers rating.

Commentary: Standard hydraulic components are

designed with a design factor of 4 (burst pressure /

operating pressure). The design factor requirement of

1.67 Nd defined in this section equates to a required

design factor of 5 for Design Category B.

4-11.3 Power Source/Supply

Where the lifter uses an external fluid power source

that is not part of the below-the-hook lifter, the supplyrequirements, which shall include the maximum sumof all fluid power components possible to actuate atone time, shall be detailed in the specifications.

4-1 1.4 F luid Pressure Indication

If a change in fluid pressure could result inuncontrolled movement of the load, an indicatorshould be provided to allow the lifter operator toverify that the fluid pressure is sufficient during allstages of lifter use. Additional indicators may benecessary to allow monitoring of various systems. Thefluid pressure indicator(s) shall be clearly visible oraudible.

4-11.5 System Guarding

Fluid power tubing, piping, components, andindicators should be located or guarded to resistdamage resulting from collision with other objects andwhipping in the event of failure.



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Chapter 5

Electrical Components


5-1.3 Power Requirements

The electrical power supply and control powerrequirements for operating a lifting device shall bedetailed in the specifications. The supply requirementsshall include the maximum full load amperage draw based on the operating conditions that will create thelargest demand on the system.

5-3 OPERATOR INTERFACE LIMIT

SWITCHES, SENSORS, AND PUSH

BUTTONS[unchanged sections skipped]

5-3.8 Indicators

Indication or signal lights should be provided toindicate power is on or off. If used, the lights shallbe located so that they are visible to the lifter operator.Multiple bulbs may be used to avoid confusion due toa burned-out bulb.


5-4 .6 Lifting Magnet Controllers

Controllers for lifting magnets shall be in accordancewith ASME B30.20.

(a) All lifting magnet controllers should havevoltage and amperage indicated.

(b) Provisions shall be made for maintaining thecontrol switch in position per Section 5-3.2 to protect itfrom unintended operation.

(c) If the crane is remote controlled, loss of theremote control signal shall not result in deenergizingthe lifting magnet.


5-6.3Disconnect for Magnet

(a) Hoisting equipment with an externally poweredelectromagnet shall have a separate magnet circuitswitch of the enclosed type with provision for locking,flagging, or tagging in the open (off) position. Means

for discharging the inductive energy of the magnetshall be provided. The magnet disconnect switch shall be connected on the line side (power supply side) ofthe hoisting equipment disconnect switch.

(b) Power supplied to lifting magnets from DCgenerators can be disconnected by disabling theexternal powered source connected to the generator,or by providing a circuit switch that disconnectsexcitation power to the generator and removes allpower to the lifting magnet.

(c) Disconnects are not required on externallypowered electromagnets operating from a 120 V ACsingle phase power source.


5-7 .3 Battery Alarm

Battery backup systems for lifters or lifting magnetsshall have an audible or and visible signal to warn thelifter operator when the primary power to the lifter ormagnet is being supplied by the backup battery(ies).


Documents

Public Review Draft 1573