Spmt load calculation

Spmt load calculation


  • Effective use of SPMTs for transportation and load-out of a module, Sweden
  • CRITICAL LIFT & TRANSPORTATION
  • Loadout Ramps – design and analysis of the simplest flat plate ramp
  • Hydraulic Modular Trailer
  • Positioning of SPMT’s under the load.
  • A better way calculates stability of hydraulic trailers and improve safety
  • Effective use of SPMTs for transportation and load-out of a module, Sweden

    January 25, 6 Minutes A modular trailer is a series of special vehicles that is used to transport large cargos that are difficult to disassemble. The trailer is also used transport over-length goods. The major applications of modular trailers include power stations, chemical industry, iron and steel industry and the construction industry.

    Modular trailers are used for mining operations because of their excellent lateral stability. A self-propelled modular transporter without the power pack unit is similar to the hydraulic modular trailer. The modular trailer uses a mechanical steering system. Another difference is that the modular trailer can be combined using a gooseneck and a drawbar. The vehicle loading platform of a modular trailer is kept at balance when transporting goods on bumpy or rough roads in a way that the damping property is excellent.

    The brace kit of the vehicle can achieve three or four brace points to ensure that the load of each point is uniform. The four points also ensure that there is no partial set. The steering system of the modular trailer has a hydraulic planar pitman driver. The vehicle can achieve minimum turning diameter and normal drive by adjusting the hydraulic steering system and using different reasonable pitman layouts.

    The supporting assemblies for the trailer part have a solid box beam structure. High performance welding steel is used to make the main frame longitudinal girder, bogie frame, steering arm, and the platform. This form of combination is in different series include the 2-file, 3-file, and 4- file combination with drawbar.

    The main difference on these combinations is the type of accessories used. Each of these combinations is outlined below. It identifies every hydraulic suspension valve and hydraulic line on the transporter and an easy to understand diagram visualizes the oil flow and the effect on the operation. Furthermore, this panel offers definitions and principle working and highlights terminology.

    All other panels refer back to this panel 1 for terminology and abbreviations. It illustrates the possible movements of such axles with their respective minimum and maximum height to negotiate uneven terrain.

    A picture clarifies the various components of a pendulum axle assembly. This panel also offers a sample calculation of how to determine the minimum required number of axle lines to carry a certain load.

    This calculation can be easily applied to your situation. Similarly it shows how to figure out how many drive axles an SPMT would need to transport the same load and what the capacity kW or hp of the power pack PPU needs to be to handle the demand.

    In case the transport is climbing a gradient it is obvious that the required power increases, the panel provides this as well. The hydraulic stability angle is a measure of how close the combined center of gravity CoG is to the tipping lines of the stability area.

    This gives the crew a better level of comfort when changes in the field take place. The structural stability angle is a measure of how close the transporter is to being structurally overloaded. In addition, this panel provides information on the limiting factors on 3-point and 4-point suspension and on the recommended Safe Stability Angles. It also calculates the minimum number of requires axle lines given a certain load and the required pull force while going up hill.

    This panel gives an outline that can be easily adopted to your load. The spine beam offers resistance against torsion, bending and shear forces. It is important not to exceed the maximum values of these forces. Specifically with concentrated loads there is a significant risk of spine beam overload if not correctly analyzed. This panel shows how to determine the spine beam bending moment and how many axles may extend beyond the load given the type and approximate age of the transporter model.

    This panel offers two easy methods of calculating ground pressure underneath a transporter. Both methods are an approach with acceptable outcomes and avoid that a full soil analysis by geophysicists has to be carried out. The centripetal forces cause the transporter and load to have the tendency to move away from the center of the curve. The faster the transporter moves higher speed , the higher these centripetal forces become. Centripetal forces can get out of control rather rapidly as they quadruple when the velocity doubles.

    These forces are determined in a similar way although they act differently on the load. The deceleration forces, when applying the brakes or when making an emergency stop, are the most significant and therefore have the largest impact on transport stability. Still, the other forces cannot be neglected.

    It shows how each lashing contributes in each direction given the angle it is applied at. This panel shows how much lashing is required to secure against the external forces from the preceding panels. The dunnage placed between the load and the transporter deck increases the friction which is taken into account as well. An added benefit is that correctly and sufficiently applied lashing reduces the combined Center of Gravity.

    An easy to understand matrix indicates how much lashing is required in each direction under the given conditions. Used by many, understood by few. This panel explains the difference between the two types of goose necks in existence. The goose neck transfers part of the load weight to the 5th wheel of the truck via a hydraulic hinge system, herewith eliminating the need for counterweight and resulting in a lower gross vehicle weight GVW.

    This transfer of load results in a reduced axle load. It highlights the pros and cons of both the 3-point as well as the 4-point suspension configuration and recommends when to use which one. These recommendations are determined by the center of gravity CoG and the potential to overload the transporter.

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    CRITICAL LIFT & TRANSPORTATION

    They come in various sizes and shapes and cover a wide variety of topics. From rigging applications to hand signals and from basic math to safety tips. You name it and there is a reference card for it. Except for hydraulic platform transporters… until now. It has a handy size of 12 cm x 9 cm 4. It is laminated and weather proof and very suitable to be used in the field.

    Last but not least, it is in both metric as well as imperial units. The ITI website will open in a new window, but this window will remain open as well. Once you complete the transaction you can simply close the ITI window and return to The Works international website. Panel 1 gives an overview of the standard 3-point and 4-point suspension settings.

    It identifies every hydraulic suspension valve and hydraulic line on the transporter and an easy to understand diagram visualizes the oil flow and the effect on the operation. Furthermore, this panel offers definitions and principle working and highlights terminology. All other panels refer back to this panel 1 for terminology and abbreviations. Panel 2 explains the difference between an axle and an axle line. It illustrates the possible movements of such axles with their respective minimum and maximum height to negotiate uneven terrain.

    A picture clarifies the various components of a pendulum axle assembly. Panel 3 highlights the difference between pull type and self propelled transporters, in terms of steering capabilities, steering angles, tires per axle, payload per axle line, self weight and dimensions.

    This panel also offers a sample calculation of how to determine the minimum required number of axle lines to carry a certain load. This calculation can be easily applied to your situation. Panel 4 offers an overview of rolling resistance of vehicles and how you can quickly determine the required truck capacity to pull a certain load. Similarly it shows how to figure out how many drive axles an SPMT would need to transport the same load and what the capacity kW or hp of the power pack PPU needs to be to handle the demand.

    In case the transport is climbing a gradient it is obvious that the required power increases, the panel provides this as well. Panel 5 shows a quick and easy calculation on how to determine the hydraulic stability angle of a transport, in a 3-point as well as in a 4-point suspension configuration, with a single formula.

    The hydraulic stability angle is a measure of how close the combined center of gravity CoG is to the tipping lines of the stability area. This gives the crew a better level of comfort when changes in the field take place. Panel 6 is similar to panel 5 but with the focus on calculating the structural stability angle of a transport, in a 3-point as well as in a 4-point suspension configuration, with a single formula.

    The structural stability angle is a measure of how close the transporter is to being structurally overloaded. In addition, this panel provides information on the limiting factors on 3-point and 4-point suspension and on the recommended Safe Stability Angles. Panel 7 shows a complete hydraulic and structural stability sample calculation based on the information and formulas from the preceding panels.

    It also calculates the minimum number of requires axle lines given a certain load and the required pull force while going up hill. This panel gives an outline that can be easily adopted to your load. Panel 8 is about the spine beam. The spine beam offers resistance against torsion, bending and shear forces. It is important not to exceed the maximum values of these forces. Specifically with concentrated loads there is a significant risk of spine beam overload if not correctly analyzed.

    This panel shows how to determine the spine beam bending moment and how many axles may extend beyond the load given the type and approximate age of the transporter model. Panel 9 deals with ground pressure, arguably the most controversial topic in the Heavy Transport industry. This panel offers two easy methods of calculating ground pressure underneath a transporter. Both methods are an approach with acceptable outcomes and avoid that a full soil analysis by geophysicists has to be carried out.

    Panel 10 handles the first of 3 types of external forces, the curve or centripetal forces. The centripetal forces cause the transporter and load to have the tendency to move away from the center of the curve. The faster the transporter moves higher speed , the higher these centripetal forces become.

    Centripetal forces can get out of control rather rapidly as they quadruple when the velocity doubles. These forces are determined in a similar way although they act differently on the load. The deceleration forces, when applying the brakes or when making an emergency stop, are the most significant and therefore have the largest impact on transport stability. Still, the other forces cannot be neglected.

    Panel 13 is about lashing and securing. It shows how each lashing contributes in each direction given the angle it is applied at. This panel shows how much lashing is required to secure against the external forces from the preceding panels.

    The dunnage placed between the load and the transporter deck increases the friction which is taken into account as well. An added benefit is that correctly and sufficiently applied lashing reduces the combined Center of Gravity. Panel 14 shows a complete lashing calculation using the information from the preceding panels.

    An easy to understand matrix indicates how much lashing is required in each direction under the given conditions. Panel 15 is about the application of a goose neck. Used by many, understood by few. This panel explains the difference between the two types of goose necks in existence. The goose neck transfers part of the load weight to the 5th wheel of the truck via a hydraulic hinge system, herewith eliminating the need for counterweight and resulting in a lower gross vehicle weight GVW.

    This transfer of load results in a reduced axle load. Panel 16 provides you with a Beaufort wind scale and a number of recommendation when deciding on a suspension configuration. It highlights the pros and cons of both the 3-point as well as the 4-point suspension configuration and recommends when to use which one. These recommendations are determined by the center of gravity CoG and the potential to overload the transporter.

    Reference cards are not meant to replace back office or home office engineering or detailed calculations. Reference cards are mainly for a relatively quick decision in the field when there is a need for such a decision. Often a deviation from the planned work sequence has taken place and a verification is required to check if the new situation is still within the norm or margin.

    If the reference card indicates that this is indeed the case, the work can continue without any loss of time. If the reference card indicates that the new situation is too close for comfort, the engineering department needs to get involved. In such cases the field crew has at least explored the options before any down time is experienced.

    Loadout Ramps – design and analysis of the simplest flat plate ramp

    In some cases, Dynamic Stability will also contribute towards more efficient ways of using hydraulic trailers. Dynamic Stability was developed in-house and has been verified and approved by classification society DNV. Mammoet will be using Dynamic Stability for all hydraulic transport projects from now on. These rules stipulate that the center of gravity of the load must stay within a seven-degree tipping limit and that it can tilt up to two degrees before a hydraulic group is overloaded.

    However, when implemented almost 40 years ago, they were based on static trailers. Since then, loads have significantly increased in size and weight. At the same time, the axle load capacity of trailers has increased, making margins smaller and exact calculations more relevant.

    Hydraulic Modular Trailer

    With this in mind, Mammoet concluded that it is time to reassess industry standards and develop a verified calculation method that incorporates the effects of multiple dynamic forces such as the acceleration and deceleration of the trailer, the forces exerted by the wind, the slope and camber of the road, and the surface on which the load is transported.

    This is ensured by a carefully monitored ballasting operation which keeps the vessel on even keel and level with the quay even during tidal variations. The picture below depicts a loadout operation using a SPMT trailer.

    We can see the ramps at the left-hand bottom corner of the picture.

    Positioning of SPMT’s under the load.

    A loadout using a SPMT trailer source: www. We can also notice that there are four files of SPMT trailers and there is one ramp placed for each file only two ramps are fully visible, while the third is partially visible. Looking at these ramps and imagining the SPMT going over the ramp, we can gauge the kind and distribution of forces the Ramp will be undertaking during the operation.

    As the wheels of the SPMT leave the quay side and get on to the ramp, load starts getting transferred to the ramp. When the first wheel moves in, the ramp will experience the quantum of load which the first wheel of the SPMT carries.

    A better way calculates stability of hydraulic trailers and improve safety

    The Ramp should be analyzed for all such scenarios in which different configuration of wheels can be conceived. The simplest ramp — the flat plate The simplest form of ramp can be just a rectangular flat plate over which the SMPT trailer passes. The figure below depicts the scenario in which an axle of the SPMT is at the center of the ramp. The ramp will have to be analyzed for its strength for this load case.


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