RE-140: Alternative Load Handling Equipment - Applications & Engineering

Application & Engineering Telescopic Hydraulic Gantry Systems

Alternative Load Handling Equipment

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InstructorDavid Duerr, P.E.• President, 2DM Associates, Inc.• Vice Chair, ASME BTH Committee• Member, ASME B30.1, B30.20 Subcommittees• Author, Telescopic Hydraulic Gantry Systems

Application & Engineering



TRAINING • FIELD SERVICES • CERTIFICATION • BOOKSTORE • E-LEARNING • WEBINARS • WORKSHOPSA World Leader of Educational and Technical Services for those who use Cranes, Rigging and Load Handling Equipment.

MODULE OUTLINE

• Introduction & Major Considerations• Application & Engineering• Lift Planning & Operations• Strand Jacks on Telescopic Hydraulic Gantries




LESSON OUTLINE

• The Hydraulic System• Loads and Load Combinations• Gantry System Stability




THE HYDRAULIC SYSTEMTHE LIFT CYLINDER




THE HYDRAULIC SYSTEMTHE LIFT CYLINDER




THE HYDRAULIC SYSTEMFLUID FLOW IN THE LIFT CYLINDER




THE HYDRAULIC SYSTEMFLUID FLOW IN THE LIFT CYLINDER




THE HYDRAULIC SYSTEMCALCULATION OF CYLINDER FLUID PRESSURE AREAS




THE HYDRAULIC SYSTEMSYSTEM COMPONENTS – THE CHECK VALVE




THE HYDRAULIC SYSTEMSYSTEM COMPONENTS – THE RELIEF VALVE




THE HYDRAULIC SYSTEMSYSTEM COMPONENTS – THE COUNTERBALANCE VALVE




THE HYDRAULIC SYSTEMSYSTEM COMPONENTS – THE COUNTERBALANCE VALVE




THE HYDRAULIC SYSTEMSYSTEM COMPONENTS – THE COUNTERBALANCE VALVEThe pressure required at the counterbalance valve pilot port is called P and is calculated with this equation...

S = counterbalance value setting (cracking pressure)L = pressure at Port 1 due to the supported loadPR = counterbalance valve pilot ratio = AP / AR

CR = cylinder area ratio = AB / AA




THE HYDRAULIC SYSTEMSYSTEM COMPONENTS – DIRECTIONAL CONTROL VALVE




THE HYDRAULIC SYSTEMCIRCUIT DIAGRAM




THE HYDRAULIC SYSTEMCIRCUIT DIAGRAM – CYLINDER EXTENDING




THE HYDRAULIC SYSTEMCIRCUIT DIAGRAM – CYLINDER RETRACTING




LOADS AND LOAD COMBINATIONS

The loads that act on a hydraulic gantry system can be divided into six categories:

• Gravity loads• Cross cornering• Forces due to misalignments of the system• Dynamic loads due to motion• Racking• Environmental loads





Gravity Loads

The weight of the item being lifted

The weight of rigging and other hardware





Cross Cornering

Cross cornering is the change in distribution of the lifted load from the theoretical distribution due to unequal extension or retraction of the gantry legs.





Cross Cornering









Misalignments of the System

Misalignments of the gantry system include misaligned or out-of-plumb rigging and an out-of-level setup of the gantry system.





Out-of-Plumb Rigging




















Out-of-Level Base





Dynamic (Inertial) Loads

Dynamic loads are forces created due to the motion of the system (lifting, lowering, travel, and side shifting).

When a gantry system is used in conjunction with other types of lifting equipment, standards for that other equipment may require the use of dynamic load factors other than those required for normal gantry use.





DynamicLoads





Dynamic Loads

Using an underhung trolley and hoist suspended from the gantry system header beam introduces the need to comply with applicable provisions of ASME B30.17.

The requirements of CMAA Specification #74 may also apply for the design of the header beam.





DynamicLoads





Racking Loads

Racking is the longitudinal misalignment of a gantry system that occurs when the legs on one track get ahead of the legs on the other track.

The result of racking is a slight twisting of the suspended load and the rigging going out of plumb.





Racking Loads





Racking Loads





Environmental Loads

Environmental loading with respect to gantry system lift planning is generally limited to wind loads.

Seismic loads may be of importance in some situations.

A gantry system can normally resist the magnitudes of wind loads that can be expected during a lift. A seismic event of significance will most likely result in the toppling of the system.





Environmental Loads





Environmental Loads

Wind loads can be calculated using ASCE/SEI 7 Minimum Design Loads for Buildings and Other Structures.

The wind speed used in these calculations should be based on the expected or permissible wind speed during the lift, not the wind speed required for the design of permanent structures.





Load Combinations

The loads discussed here do not all occur at the same time, but they don’t necessarily occur independently, either.

The likelihood of certain loads occurring simultaneously is based on the cause of those loads.








GANTRY SYSYEM STABILITY

What is Gantry System Stability?

Gantry system stability simply refers to the ability of the gantry legs individually or the gantry system as a whole to resist toppling under the effects of horizontal loading.

Unlike a mobile crane, a gantry system does not have stability-limited rated loads.




GANTRY SYSTEM STABILITY












GANTRY SYSTEM STABILITYSIMPLIFIED ANALYSIS

Lateral Stability Longitudinal Stability




GANTRY SYSTEM STABILITYDETAILED ANALYSISThe detailed stability analysis accounts for the major aspects of gantry behavior that reduce stability. These include:

• Telescopic lift boom drift• Boom and lift cylinder deflection• Out-of-level support surface




GANTRY SYSTEM STABILITYDETAILED ANALYSISBoom Drift




GANTRY SYSTEM STABILITYDETAILED ANALYSISOut-of-Level Surface




GANTRY SYSTEM STABILITYDETAILED ANALYSISStability Analysis Model




GANTRY SYSTEM STABILITYDETAILED ANALYSISThe detailed stability analysis, like the simplified analysis, is primarily a geometry calculation. It is more complex since more variables are addressed.

The gantry system user will generally not have to perform these calculations since there isn’t much the user can do to improve stability beyond leveling the track.

Further, details like boom or cylinder deflection are generally not known to the user, but can be estimated using guidelines in Chapter 5 of the text.




GANTRY SYSTEM STABILITYANALYSIS OF A TWO-LEG SYSTEM








GANTRY SYSTEM STABILITYANALYSIS OF A TWO-LEG SYSTEMIf both tracks are perfectly level, then the stability of the system is simply the sum of the stabilities of the two legs.

If both tracks are out of level by the same amount and in the same direction, again the stability of the system is simply the sum of the stabilities of the two legs.

If both tracks are out of level by the same amount but in opposite directions, then the out-of-level effect cancels out and the system stability is the same as on level tracks.








GANTRY SYSTEM STABILITYANALYSIS OF A FOUR-LEG SYSTEM




GANTRY SYSTEM STABILITYANALYSIS OF A FOUR-LEG SYSTEM




WHAT’S NEXT?

• Introduction & Major Considerations• Application & Engineering• Lift Planning & Operations• Strand Jacks on Telescopic Hydraulic Gantries

Date post:	11-Apr-2017
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