Cmaa specification 74 pdf free download

The final revised specification is then returned to the various sub groups for review and notification of errata before going to final printing and distribution. A new Summary of Changes from the previous edition has also been added to provide a quick convenient way of checking exceptional changes. This specification contains information which should be helpful to the purchasers and users of cranes and to the engineering and architectural professions.

While much of this information must be of a general nature, the items listed may be checked with individual manufacturers and comparisons made which can lead to optimum selection of equipment. This book promotes standardization and provides a basis for uniform quality and performance. It contains information which can be helpful for purchasers and users of cranes, as well as engineers and architects. Text consists of seven sections: general specifications, crane service classifications, structural design, mechanical design, electrical equipment, crane inquiry data sheet and glossary.

With the introduction of Specification 78, CMAA intends to set higher performance standards and raise customer expectations related to the service of overhead traveling cranes and associated hoisting equipment. Operation of an overhead or gantry crane involved more than operating the controls of the crane.

The operator must consider and anticipate the motions and actions that will occur as a result of operating the controls. Operation of a lifting device involves more than operating the controls of the crane. The operator must consider and anticipate the motions and actions that will occur when operating a lifting device. All under running bridge truck wheels shall be designed to suit the surface on which they run.

Drive wheels shall be the same diameter within a tolerance of. The recommended wheel load shown on Table 4. It should be noted that impact is not considered in these figures and for unusual conditions consideration should be given to other factors which are not included in the simple formula on which Table 4.

It is also important to note that a reduction in the allowable wheel load may be necessary to satisfy the runway lower flange stress requirements. Note I : Charted values are based on wheels with Brinell hardness of Larger wheel loads are obtainable with suitable material and with greater Brinell hardness. Bumpers and their mountings shall be of sufficient length that no other parts of either crane shall come in contact when the two cranes come together.

Runway stops are normally designed and provided by owner or specifier and are located at the limits of the bridge travel. Runway stops shall be attached to resist the force applied when contacted. If it is necessary to partially disassemble the crane for shipment, all conduit and wiring affected shall be cut to length and identified to facilitate reassembly.

Bridge conductors, runway collectors and other accessory equipment may be removed for shipment. Designs not in accordance with these standards may be specified. I AC induction motors may be wound rotor slip ring or squirrel cage single speed or multispeed types. The motor's duty rating should be based on the service class and on the speed range required for the application. TABLE 5. Motors D. C 85 Deg. C, the permissible winding temperature rise must be decreased by the same amount, or may be decreased per the applicable NEMA Standards.

Motors shall be provided with anti-friction bearings. Voltage Motor rated voltage and corresponding nominal system voltage shall be in accordance with Table 5. For nominal system voltages other than shown above, the motor rated voltage should be either the same as the nominal system voltage or related to the nominal system voltage by the approximate ratio of to Certain kinds of equipment have a maximum voltage limit of volts; the manufacturer andlor power supplier should be consulted to assure proper application.

Performance will not necessarily equal rated performance when appreciable ripple is present. AlSE Std. Motor rated voltage may be volts for large frame motors hp and larger. Maximum motor input voltage. I Variations - AC 5.

I Variation from Rated Voltage All AC induction motors with rated frequency and balanced voltage applied shall be capable of accelerating and running with rated hook load at plus or minus 10 percent of rated motor volt- age, but not necessarily at rated voltage performance values. Performance will not necessarily be the same as when the motor is operating with a balanced voltage at the motor 44 terminals.

With rectified power supplies successful operation shall result when AC line voltage variation is plus or minus 10 percent of rated voltage. Performance will not necessarily be in accordance with the standards for operation at rated voltage.

Operation with voltage variations beyond those shown in Sections 5. Opera- tion at reduced voltage may result in unsatisfactory drive performance with rated hook load such as reduced speed, slower acceleration, increased motor current, noise, and heating. Protective devices may operate stopping the drive in order to protect the equipment.

Operation at elevated voltages may result in unsatisfactory operation, such as, excessive torques. Prompt corrective action is recommended; the urgency for such action depends upon many factors such as the location and nature of the load and circuits involved and the magnitude and duration of the deviation of the voltage. These conditions should be reviewed based on the type of drive used.

Motor Time Ratings Single speed motors shall be rated on no less than a 30 minute basis with temperature rise in accordance with the latest NEMA standards for the class of insulation and enclosure used, unless otherwise specified. Multispeed motors may be rated less than 30 minutes on the low speed winding so long as the crane builder data sheets so indicate. Under unusual conditions, such as long lifts at reduced speeds, abnormal inching or jogging requirements, short repeated travel drive movements, altitudes over 3, feet above sea level, abnormal ambient temperatures, etc.

The bridge motor rating using either AC or DC power, is basically the mechanical horsepower with considerations for the effect of control, and ambient temperature. Indoor bridge motor required horsepower Required Motor Horsepower: The bridge motor shall be selected so that the horsepower rating is not less than that given by the following formula:. For other types of control consult control manfacturer.

Table 5. For guidance, see Table 5. I-A and Table 5. For guid- ance see Table 5. See Table 5. I -C for typical values of Kt.

O 4. O 5. The acceleration rates shall not exceed the values shown in table 5. To avoid wheel skidding the acceleration rate should not exceed the values shown in Table 5. This would be in the range of 50 to 80 percent of the free running speed N,. Percent of Driven Wheels I00 50 The values in the above table are based upon the peak acceleration torque being equal to 1.

Type of Motor Type of Control Kt'. Cage Ballast Resistor 1. Wheel Dia. Note 1 - For cranes equipped with sleeve bearings of normal proportions, a friction factor of 24 pounds per ton may be used. Note 2 - The above friction factors may require modifications for other variables such as low efficiency worm gearing, non-metallic wheels, special bearings, and unusual rail conditions.

In either case, consideration must be given to proper performance of the drive. Proper speed control, acceleration and braking without wind. Ability of control to reach full speed mode of operation against wind c. Bridge speed, on any control point, when traveling with the wind not to exceed the amount resulting in the maximum safe speed of the bridge drive machinery.

Avoidance of wheel skidding which could likely occur under no load, low percent driven wheels and wind conditions. Sufficient braking means to maintain the bridge braking requirements. The value of Nr is established from the motor-control speed-torque curves at free running horsepower HPFR. The actual full load drive speed may vary a maximum of 5 10 percent of the specified full load speed. Other control requirements such as protection and master switches are covered in other sections.

This section also covers the requirements for hoist and trolley travel controls if not supplied as an integral part of the monorail hoist. On floor operated cranes where the pendant master is also used in a "skeleton" cab, the applicable Specifications for floor con- trolled cranes shall apply. Typical mechanical means include mechanical load brakes or self-locking worm drives. Typical power means include dynamic lowering, eddy-current braking, counter-torque, regenerative braking.

Typical plugging protection includes a magnetic plugging contactor, ballast resistors, slip couplings, motor characteristics, or static controlled torque. I Each magnetic control shall have contactors of a size and quantity for starting, accelerating, reversing, and stopping, and for the specified CMAA crane service class.

All reversing contactors shall be mechanically and electrically interlocked. Definite purpose contactors specifically rated for crane and hoist duty service may be used for CMAA crane service classes A, B, and C provided the application does not exceed the contactor manufacturer's published ratings.

IEC Contactors may be used for Crane and Hoist duty service provided the application does not exceed the contactor manufacturer's published ratings. Wound rotor secondary contactors shall be selected to be not less than the motor full load secondary current, using contactor intermittent rating.

The ampere intermittent rating of a three pole secondary contactor with poles in delta shall be 1'1, times its wound rotor intermittent rating. For adjustable voltage DC drives at voltage other than volts, the contactor horsepower ratings will be directly proportional to the voltage up to a maximum of volts.

OF MIN. For hoists, a minimum of two 2 time delay devices are required in the hoisting direction. Note 1: One 1 contactor of the number shown may be used for plugging on bridge or trolley controls or low torque on hoist controls.

If more than one 1 plugging step is used, additional contactors may be required. Note 2: Plugging detection means shall be added to prevent closure of the plugging contactors until the bridge or trolley drive has reached approximately zero speed. Note 3: A speed point may be manual hand controlled, or automatic, as required. The minimum number of operator station hand controlled speed points shall be three 3 in each direction except as follows: a Class C and D cab operated hoist controllers with four 4 or more resistor stepping contactors shall have a minimum of five 5 hand controlled speed points in each direction.

On multi-motor drives, the contactor requirements of this section apply to each motor individu- ally, except if one set of line reversing contactors is used for all motors in parallel, then the line contactors shall be sized for the sum of the individual horsepowers.

The resistor stepping contactors may be common multipole devices, if desired. An individual set of acceleration resis- tors for each motor shall be provided unless otherwise specified. Timing shall be done with one 1 set of time delay devices.

Static power components such as rectifiers, reactors, resistors, etc. Static control systems may be regulated or non-regulated, providing stepped or stepless control using AC or DC motors, as specified. Travel drives systems may be speed andlor torque regulated, as specified. If a speed regulated system is selected the method of deceleration to a slower speed may be by drive friction or drive torque reversal, as specified.

Hoist drives are assumed to be inherently speed regulated and due consideration shall be given to the available speed range, the degree of speed regulation, and optional load float.

Primary reversing of AC motor drives shall be accomplished with magnetic contactors or static components as specified. When static components are used, a line contactor shall be furnished for the drive. Current and torque limiting provisions shall be included not to exceed the motor design limita- tions, and with consideration for desired acceleration. Permanent slip resistance may be included providing due consideration is given to the actual motor speeds under rated conditions.

The crane Specifications shall state whether the hoist motor horsepower used with static con- trol is on the basis of average hoisting and lowering speed with rated load or on the basis of actual hoisting speed to raise rated load. Control panels should be enclosed and shall be suitable for the environment and type of control.

The type of enclosure shall be determined by agreement between the purchaser and the crane manufacturer. General purpose - Indoor - Gasketed. Type 3 - Dust-tight, rain-tight and sleet-resistant, ice-resistant - Outdoor. Type 3R - Rain-proof and sleet-resistant, ice-resistant - Outdoor.

Type 3s - Dust-tight, rain-tight and sleet ice -proof - Outdoor. Type 4 - Water-tight and dust-tight - Indoor and Outdoor. Type 12 - Industrial Use - Dust-tight and drip-tight - Indoor. Type 13 - Oil-tight and dust-tight - Indoor. These enclosures shall be equipped with the necessary ventilation such as louvers or forced cooling.

Air filters or similar devices may be necessary depending on the environment. Since the original definition of the enclosure per its specified type may be somewhat altered by the nature of the ventilation means, the final design shall meet the functional intent. Resistor covers for outdoor cranes shall be adequately ventilated. Brakes, for indoor cranes, may be supplied without covers.

Brakes, for outdoor cranes, shall be supplied with covers. The disconnecting means in Section 5. The user shall state the available fault current or the crane manufacturer shall state in the Specification the interrupting rating being furnished.

Magnetic Mainline contactors, when used, shall be as shown in Tables 5. The size shall not be less than the rating of the largest primary contactor used on any one motion. Contactor Amperes and and Amperes Volts Volts Volts Volts 0 20 20 6 6 3 5 1 30 30 10 20 7 'I2 10 2 50 67 30 60 20 40 3 63 40 The horizontal distance from the surface of the enclosure door to the nearest metallic or other obstruction shall be a minimum of 30 inches.

In addition, the work space in front of the enclosure shall be at least as wide as the enclosure and shall not be less than 30 inches wide.

Bridge Girder. Hoist -- Bridge. Trolley -b- ca-, M. Center Cab 4 Motor Crane. Bridge Girder 3. Iw8 wI3 t. Lowering of the block shall automatically reset the limit switch unless otherwise specified. The manufacturer's proposal shall state which type is being furnished. In the absence of such stan- dardization, suggested arrangement is shown in Figure 5.

Two 2 sets of current collectors shall be furnished for all contact conductors that supply current to a lifting magnet. The collector rating shall be sized for the crane ampacity as computed by Article of the National Electrical Code. A minimum of two 2 collectors for each runway conductor shall be furnished when the crane is used with a lifting magnet.

Refer to section 5. Inverter continuous current must be equal to or greater than full load motor current. The dynamic braking and inverter duty shall meet the requirements of the drives service class.

Mechanical load brake may be considered as overspeed protection for hoisting motion. Dynamic braking resistors may be considered as overspeed protection for horizontal drives.

The control station may consist of pushbuttons, masterswitches, computer keyboards or combination thereof. Electrical interlock is defined as effective isolation of the control circuits with the use of rotary switch contacts, relay contacts or with the use of a programmable logic controller and its inputloutput modules.

This includes physical and electrical separation, shielding, etc. Transmitter arrangements other than as shown belly box style may be used. Bridge Trdley Hoist Hoist. Markings on the crane, visible from the floor, shall indicate the direction of bridge and trolley travel corresponding to the W, X, Y and Z designations on the transmitter.

Designations should be selected as appropriate to each installation. Required Hook Lift Max. Movement Ft. Furnish complete information regarding special conditions such as acid fumes, steam, high tempera- tures, high altitudes, excessive dust or moisture, very sever duty, special or fine load handling.

Ambient Temperature in Building: Max. Speeds Required: Hoist fpm. Bridge fpm. Trolley fpm. Crane to Operate: l ndoors Outdoors Both. Type of Control: Give complete information including No. Full Magnetic Static Other. Specify when double hook cranes, double trolley cranes or special cranes are required giving detailed information on hook spacing, etc.

Complete attached building clearance drawing, making special note of any obstructions which may interfere with the crane, including special clearance conditions underneath the girders or cab. Low point of roof truss, lights, sprinklers or other obstructions. Center lo. The tremities of the crane and the centerline of the hook. KIP: A unit of force equivalent to pounds. An auxiliary girder may be provided to re- capacity positioned on the bridge to give maximum duce the torsional stresses on the main girder.

SPAN: The horizontal distance center-to-center of run- way rails or beams. STOP: A device to limit travel of a trolley or crane bridge. This device normally is attached to a fixed struc- ture and normally does not have energy absorbing ability. These beams make up the crane runway. Acceleration Torque Factors Table 5. I -A Enclosure - Control 5. I-B Enclosure - Resistor 5.

I Allowable Stress - Structural 3. I 3 Assembly 4. I-A Girder - Welding - Figure I 4 Collision Loads 3. Motors 5. I Runway Conductor Table 2. I-B Wind Loads 3. Open navigation menu. Close suggestions Search Search. User Settings. Skip carousel. Carousel Previous. Carousel Next. What is Scribd? Cmaa Uploaded by Alejandro Saco Herrera. Did you find this document useful? Is this content inappropriate? Report this Document. Flag for inappropriate content.

Download now. Related titles. Carousel Previous Carousel Next. Jump to Page. Search inside document. TABLE 2. Additional Loads 3. The kinetic energy released on the collision of two cranes with the moving masses of M,, M2, and a 40 percent maximum traveling speed of V, and V , shall be determined from the following equa- tion: The bumper forces shall be distributed in accordance with the bumper characteristics and the freedom of the motion of the structure with the trolley in its worst position.

See paragraph 3. It shall have a moment of inertia no less than: If Gcis greater than CJT a distance equal to twice the distance from the inner surface of the compression flange to the neutral axis shall be substituted in place of "h" in equation for I,. They shall each have a moment of inertia no less than: If Gc is greater than 5 a distance equal to twice the distance from the inner surface of the compression flange to the neutral axis shall be substituted in place of "h" in equation for I,.

Box Section Girder Built of Two Beams Box section girder built up of two beams, either with or without reinforcing flange plates, shall be designed according to the same design data as for box section girder cranes for stress and deflection values only. Crane Class Sfs A. I The type of bearing shall be specified by the crane manufacturer.

The allowable stresses are as follows: a. Direct axial and bending: b. Torsional and transverse shear: c. For combined stresses when all of the direct axial and bending stresses are combined with the torsional stresses and all are fluctuating: d. I Top Running Bridge Wheels 4. These factors are obtained from the following formulas: for RPM 5 The size and location of the bridge bumpers shall be specified by the crane manufacturer.

Runway stops engaging top running wheels are not recommended. C 'If ambient temperatures exceed 40 Deg. Bridge Motor Size Selection The bridge motor rating using either AC or DC power, is basically the mechanical horsepower with considerations for the effect of control, and ambient temperature. Static Control Static power components such as rectifiers, reactors, resistors, etc. Magnetic contactors, if used shall be rated in accordance with Section 5. Control torque plugging provisions shall be included for bridge or trolley drives.

Enclosures Control panels should be enclosed and shall be suitable for the environment and type of control. Warning Devices 5. Hoist -- Bridge Trolley -b- ca-, M. The letters used are only intended for the purpose of illustration. Date Number of Cranes Required 2.

Capacity: Hoist s Tons. Approximate Length of Runway: Ft. Number of Cranes on Runway: 6. Material Handled Crane to Operate: l ndoors Outdoors Both Other List of Special Equipment if Accessories Desired Anonymous sqFTF5tu.

Mock Khang Hi. Narayan Prasad. CWen Teow. Angel De Los Santos. Rishabh Verma. Arun Venkat. Mohammed Rizwan Ahmed. Guillaume Boivin. Erc Nunez V. Bv Rao. Marlon Arq. Maey Akim. Mohammed Atef. Cesar Augusto Vera Jaimes. Toni Renedo. Gaddipati Mohankrishna.

Jonathan Soto Olaya. Luis Maria Arrien. More From Alejandro Saco Herrera. Alejandro Saco Herrera. Popular in Mechanical Engineering.