Power Required For Adjusting The Height Of Yard Ramps

Several people have enquired about the comparative power required to adjust the height of different designs of yard ramp.

The power required is a simple function of the mass of the ramp, the height it is lifted through, the time taken and the mechanical efficiency of the adjustment system. For any meaningful comparison between different designs of yard ramp, the first 3 of these factors would be the same. Therefore the difference comes down to the overall efficiency of the adjustment system itself. Generally this means a comparison between mechanical adjustment done through landing legs and a small gearbox similar to most HGV trailers and a hydraulic system operated through by a hand pump.

In a mechanical system the losses are those occurring in the actual gear unit and those to overcome friction in the landing leg mechanism. For hydraulic systems there are substantial losses to overcome seal friction in both the pump and operating cylinders, losses in valves and hoses and also due to the geometry of the operating cylinder in relation to the arm movement.

The hydraulic system will therefore normally require a greater power input from the operator in order to raise the ramp. However this system has some benefits when lowering the ramp, because the mass of the ramp and gravity are normally sufficient to do the job, whereas a mechanical system still requires at least a reduced input from the operator. Overall the total power input required for the complete cycle is thus going to be fairly similar, and so the choice really comes down to individual preference and reliability considerations etc. The main point is that whichever system is employed, the power required is well within the capability of a normal healthy adult worker and so this should not be an issue.

Very occasionally yard ramps are fitted with motorised adjustment, but the connection of an external power source by a cable or hose compromises their mobility and generally trailing cables or hoses are not considered the best thing for safety. However where motors are fitted, their power has to be determined by the manufacturer on a case by case basis and will vary according to their specific ramp models.

Selecting The Capacity Of Yard Ramps

When selecting the capacity of a mobile container loading ramp (yard ramp) it is necessary to consider the combined weight of the heaviest forklift and the heaviest weight of the loads it will carry, plus a safety factor. Where nominal loads may be exceeded ( i.e. due to water absorption in the paper recycling industry etc.) it is important to fully allow for this when calculating the ramp capacity.

As a rough rule of thumb, some manufacturers suggest to start by considering a yard ramp with at least three times the rated capacity of your largest forklift truck.

Where ramps are used on a multiple shift basis, or with specialised equipment, advice should always be sought from the original manufacturer.

Yard Ramp Spares

Like any piece of machinery, container loading ramps will eventually require some spare parts, whether due to damage or just wearing out. Because of the nature of the device, virtually every part is safety critical. It is therefore essential that only approved parts are used for repair or maintenance. In most cases these should be obtained directly from the original ramp manufacturer, or their approved agents. Substituting generic or self-made parts could lead to unforeseen failure and liability under safety legislation.

Yard Ramps – Rent or Buy?

There are many factors affecting the decision whether to buy or rent a yard ramp. Obviously the primary consideration is whether the requirement to use the device is a permanent or a temporary one.

If the requirement to use a yard ramp is only a temporary one, then the decision to rent is a clear cut one. Several of the largest yard ramp manufacturers will provide their ramps on a short fixed term rental arrangement.

It should though be remembered that delivery of a ramp to the required location, and its return after the rental has finished, is an expensive operation. This cost will reflect disproportionately on very short term rental periods. However, even then the benefits that using a yard ramp provides still make even very short term rentals effective compared to the alternatives of not using a yard ramp.

If the requirement for a yard ramp is a long term one, then the decision of whether to rent or buy is more complex, and depends to a large extent upon the corporate policy of the buyer and their accounting criteria. Many businesses prefer to avoid outright capital expenditure purchases, and instead they take out renewable 12 month rental contracts which are rolled over each time a renewal period comes around.

Yard Ramp Features

Features of yard ramps:

  • Aids the loading or unloading of a standard ISO container, or rear loaded truck, quickly, safely and efficiently without the need for permanent docking bays. 
  • Allows loading or unloading to be achieved by a single forklift operator.
  • Sorts out a container in a fraction of the time it takes with a pallet truck.
  • Mobile – can be used either inside or outside of buildings.
  • Avoids the necessity for expensive permanent concrete docking bays integrated into buildings.
  • Ideal for short term use in peak periods, or on temporary sites etc.
  • Allows more flexible operations for overflow conditions when all regular docking bays are already in use, or are unavailable due to an unexpected breakdown situation. 
  • Promotes safer working practices than having to manually move cargo with a pallet trucks within a container.

Yard Ramp Reliability

Assuming good design and proper manufacture, coupled with proper use by the operator, then yard ramps should last almost indefinitely without needing much attention. However, in the real world this ideal situation very rarely happens.

Occasionally some yard ramp manufacturers do come up with design modifications which have not been well engineered, or they skimp on areas of the construction to save costs. Unfortunately in the long term it is the user that usually picks up the bill for this, as it just reflects in a shorter working life and a greater maintenance cost and downtime for the user. In contrast there are many examples of ramps of traditional proven design from established manufacturers being in service for very long periods without requiring any attention at all.

Given the very high return on investment that using yard ramps for container unloading provides, then it probably makes little sense to make a purchase decision based merely on the lowest initial price, without considering if the lower price is the result of skimped design or manufacture. The economics of using container ramps is such that the consequential cost of not having a ramp available for use due to reliability issues can be more expensive than the initial cost of buying the ramp in the first place. 

The hydraulically operated height adjustment systems used in some yard ramps introduce reliability issues of their own. In some cases this may not be a significant issue at all, but in others it is well known to be a major and costly problem.

Without a doubt the greatest impact on yard ramp reliability is the manner in which they are used. No matter how well designed on manufactured they are, an operator who is determined to test a ramp to destruction can usually do so. Operators should be educated not to see it as a personal challenge to see how fast they can tow a yard ramp over rough ground and how deep a pothole, or how high a kerb it can be bounced over at speed.

Yard ramps are built to a specified design capacity and it is important to always work well within the stated capacity. The shock impact loads resulting from an over enthusiastic forklift driver mounting a ramp at too high a speed can be much greater than expected. Equally it is necessary to consider that some porous loads can be a lot heavier than expected if they have been left outside in the rain for some time. For maximum reliability it is probably better to choose a standard 10T. capacity ramp rather than a light duty 7T. model, even if the expected loads are always expected to be within 7T. The cost difference between the ramps is very small, and yet the effect on improved reliability is very significant.

With ramps that experience a lot of heavy use there can be some deterioration in the decking surface after a long period of use. After a few years it cam sometimes be necessary to have the decking surface replaced, but fortunately this is a quick and easy job to do. 

Depending upon the yard surface and how frequently or roughly a ramp is towed, there can eventually be some deterioration in the tyres used on the wheels. In Europe most use solid tyres, although in North America, some makers provide inflatable pneumatic tyres. Again these are easy an inexpensive to replace, should it even become necessary. 

Yard Ramp Design

Every manufacturer of mobile yard ramps (container ramps) naturally has their own unique design solutions, but what they all have in common is a need for robust and rigid construction.

The basic layout of all mobile yard ramps is an inclined section of about 9m. length and 2.25m width followed by a flat approach section of about 2.6m length at the top, with a lip to enter into the container or truck being unloaded. Both sides of the ramp are provided with safety raves to prevent forklifts from accidentally driving over the edges. The elevated end of the ramp is supported on adjustable legs with wheels which are used to transport the ramps around. The front end of the ramp is normally provided with some kind of towing hook, or other attachment device, to allow the ramp to be towed by a forklift. The legs are normally adjustable so that the height of the ramp can be raised whilst the truck is put into position and then the ramp is lowered so that the front lip supports the weight of the ramp on the container or truck floor.

The height adjustment mechanism can be hand operated jacks, hydraulic via a hand pump, or occasionally motorised if a suitable electrical or compressed air power source is available for convenient connection.

Some light duty yard ramps have been constructed from aluminium, but although this has weight advantages, aluminium is often not well suited to the rough operating environment and abuse that yard ramps have to withstand. Most yard ramps are therefore constructed from welded steel. Every manufacturer has its own views on the best combination of standard sections and custom manufacture.

There are a variety of choices for the decking material, but as it required to be both tough and non-slip, most makers utilise some form of open grill sheeting supported on a rugged base structure. Non-slip paint finishes on the decking have been tried, but with limited success as they are unable to withstand the conditions of usage for very long.

Advantages of Yard Ramps

The traditional way to unload an ISO shipping container, or a truck which has been loaded with palletised cargo from the rear, is to reverse the vehicle against an elevated concrete docking bay. The docking bay is designed to approx. match the height of the vehicle and an levelling device built into the dock accommodates and slight variations.

Where it is not practical to use a building with built in loading docks, or where the unloading requirement is only temporary, then the answer is use a mobile yard ramp. These are also sometimes known as container ramps or forklift ramps.

Even larger companies that have multiple banks of fixed docking bays in their buildings will also often ensure that they have a mobile yard ramp available, as this gives them extra flexibility to their logistic operations. It also provides an insurance in the case of breakdowns of their fixed docks. This means that they can opt for a cheaper  9 to 5 breakdown cover over 5 days a week, rather than the much more costly full 24 / 7 cover otherwise required.

For those businesses that only have an infrequent unloading requirement, then the significant expense of integrating docking bays into a building cannot be justified. Once again the answer lies in the mobile yard ramp which is inexpensive and does not require any special modifications to buildings.

For smaller businesses without docking bay facilities the alternative option is to manually manoeuvre the cargo to the rear doors of the container, or truck, so that it can be removed from there by forklift. The use of pallet trucks to move cargo within the confined spaces of a container can present safety problems, but mainly it is very inefficient. It is not only costly in terms of the manpower required, but even more so in the amount of time it takes to unload the container or vehicle. Making use of a yard ramp for container unloading means that the whole task can be accomplished by a single forklift operator and in a fraction of the time. The savings are such that even those businesses handling only 1 or 2 loads per month normally find that a yard ramp is very extremely effective with a quick return in investment.

Safety with Yard Ramps

With any device involving elevated working, mobile vehicles, heavy loads, lifting etc. safety considerations must always be paramount. Unloading a vehicle mounted ISO container, or truck directly through the rear doors, raises many safety issues. Utilising mobile yard ramps to permit the loading or unloading operation by forklift truck largely eliminates the risks associated with using pallet trucks and having people on the ground in the very restricted working area. However the use of yard ramps can add some additional safety concerns of their own. 

In particular :

  • The front lip of the yard ramp must be correctly located on the floor of the container or truck body and the safety chains must be correctly attached to the vehicle before the ramp is used.
  • Yard ramps can be used in frost and ice although there may be some reduction in grip. The main problem encountered is compressed paper contamination. Common sense should always prevail on the safe efficient condition of the ramp. If there is noticeable slippage then the ramp should not be operated.
  • Yard ramps should only be used on solid ground and never on a significant slope or tilt.
  • Personnel should not use the yard ramp to enter the unloading area when it is being used by forklifts, or unless handrails are fitted to the sides.
  • Yard ramps should not be overloaded beyond their rated capacity.
    When being towed to new locations sensible care should be observed. Although yard ramps are very rugged and designed to be mobile, if they are towed at excessive speeds serious damage can occur to the legs if the wheels encounter either potholes or solid obstructions.
  • Yard ramps should always be checked for obvious damage by the operator before each use. Damaged wheels or legs, or loose decking etc. must always be repaired before further use.
  • For ramps using hydraulic height adjustment, the integrity of the hydraulic system MUST be regularly checked for leakage as well as the level of the hydraulic fluid etc.

Yard Ramp Height Adjustment

The working height of mobile yard ramps needs to be adjustable to suit varying vehicle bed heights. The working height will also alter slightly as the vehicle is unloaded and rises on its suspension and as the forklift enters and exits. Normally a working range of  1m. to 1.7 m. is considered suitable.

Initially the yard ramp must be in its raised position and then once the vehicle is reversed into position, the ramp is lowered so that the leading lip rests on the floor of the container or truck body. The yard ramp supports are then raised further to ensure sufficient clearance that the weight of both the ramp and the load are taken by the truck under all circumstances.

There are a variety of mechanisms used to provide height adjustment and different manufacturers have varying opinions about the advantages and disadvantages of each.

The simplest and probably most reliable system uses manually adjusted landing legs. The operator quite simply winds a handle which raises or lowers the legs. As it works through a gearbox, the mechanical advantage makes this an easy task to do without much effort. This solution is normally regarded as tough, quick and simple to do and very reliable.

Other makers prefer a hydraulically operated system of height adjustment. Here the user has to operate a small lever activated hand pump which provides high pressure hydraulic fluid to the operating cylinders when required. The main drawback of hydraulically operated yard ramps is often the poor reliability of the components and the additional requirement for regular maintenance. Given the environment in which yard ramps are used, regular maintenance can often be overlooked and eventually unexpected breakdowns as a result if hydraulic system failures can occur. Whilst this may be good for the sales of spare parts by the maker, the consequences can be disastrous for users if a yard ramp suddenly becomes unavailable for use at an inconvenient time. With any hydraulic ramp it is always a wise precaution to keep a full set of system spares in stock on site, so that a competent maintenance crew can quickly get the ramp back into action.

Regulations are getting increasingly more stringent and users of hydraulically adjusted ramps will have to guard against spillage of hydraulic fluids. If it is necessary to build an anti-spillage bund wall, then this will seriously hinder manoeuvrability.

A few yard ramps have been built with motorised height adjustment, but these require the connection of either an electrical or air supply to power the driving motor. In most applications this is highly inconvenient and limits the ability to use the yard ramp as a mobile device. Normally electrical or compressed air powered height adjustment is provide only as a special option and where the user intends to use the yard ramp in a fixed location, rather than as a mobile device.

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