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How to buy a Truck Scale
Click:1767 Date:2012-6-16 4:26:10

How to buy a Truck Scale

You've decided to buy a truck scale. Good. The purchase of a truck scale is a wise investment but, like any investment, it requires some research and thought to ensure that you get the most for your investment dollar. But where do you start? The information that follows will help you decide what type of scale is best for your needs, explain some of the jargon associated with truck scales and make you aware of potential pitfalls in purchasing and installing your new scale.

 

First,make sure  What Kind of Scale Do you Need。

You don't have to look at too many truck scale brochures to become thoroughly confused about what's available and what is and isn't important to you. Generally, there are two basic types of scales used to weigh trucks; axle load scales which are used to weigh one or two axles at a time and full-length truck scales which weigh the entire truck at one time. While axle load scales are less expensive they are also subject to error. The approaches to the axle load scale must be perfectly level and at the same elevation to minimize the error. Unless you simply don't have room for a full-length scale or your budget won't allow for one, the axle load scale is not a good choice for accurate truck scales. For that reason, we will limit our discussion to full-length truck scales.

 

Full-length truck scales may be of either portable or permanent installation. Portable truck scales include a lower framework that is placed on a prepared surface (either a concrete slab, wooden beams, or even dirt) and ramps are placed at either end for access. Portable scales are generally more expensive because of the lower framework but are much easier to move from site to site and are ideal for contractors or road builders. Scales that are permanently mounted may be mounted either in a pit (like the basement of a home) or of an above-ground low profile design where the scale is mounted on a concrete slab with ramps at either end. The advantages of a pit type scale include easier access to the bottom of the scale, the capability of adding a dump chute in the middle of the scale for unloading of bulk commodities like grain, no requirement for entry and exit ramps and no problems with snow accumulation beneath the platform. Generally, the cost of a pit type scale is greater because of the increased cost of excavation and pit construction. Low profile truck scale designs are less expensive yet require construction of access ramps at either end of the scale.

 

Both pit type and low profile scales offer a choice in platform material. Platforms may be constructed from concrete or steel plate or, in some cases, wood. The material you choose will depend somewhat on personal preference as well as the way you use your scale. The initial price of a concrete scale will be a little less than an equivalent scale with a steel platform yet when you add in the cost of the concrete and finishing labor, it will exceed the cost of its steel decked cousin. Concrete also requires a curing time which will delay the use of the scale but concrete is less slippery in wet weather, is not affected by most chemicals, doesn't rust, requires little or no maintenance and provides years of service. Steel decks are usually constructed from checkered plate which gives extra traction in wet weather. In general, if your application calls for heavy loads and lots of them, concrete is the preferred material for the scale deck.

 

Scales are available in either full electronic or electromechanical models as well. Full electronic scales are directly supported by multiple load cells typically numbering 6 to 12 cells or more depending on the length of the scale. Electromechanical scales are supported by a series of bearings attached to ends of levers mechanically summing the forces applied to the scale platform. A summed force is applied to a single load cell. Most truck scales today are of the full electronic type simply because they are easier and less expensive to construct. Electromechanical scales are still available from some manufacturers (including keda scales) and offer some unique advantages. The use of a single load cell makes the scale less susceptible to damage from lightning and they require less power to operate which means a simple battery operated weight indicator can be used when power is not available. Disadvantages of the electromechanical scale include the need for periodic maintenance or repair due to the wear in the bearings of the mechanical lever structure and higher initial cost. The full electronic truck scale has a lower initial price and is easier to work on since there is no complex lever system. The individual load cell signals of a full electronic truck scale must be summed to provide the total weight signal to the weight indicator. Summing of the load cell signals normally takes place within one or more junction boxes typically located at or near the scale. Because the outputs normally differ from load cell to load cell, it is necessary to make compensating adjustments which may become lengthy depending on the method used.

 

Finally, when choosing a truck scale, consideration should be given to the method of weighbridge restraint used. The weighbridge or scale platform must be constrained so that it does not slide off the supporting structure as a truck enters of leaves the scale. Although there are a number of ways of accomplishing this, the two most common are check rods and bumper bolts. Bumper bolt systems consist of an adjustable rod or bolt or similar device attached to the weighbridge and positioned such that it strikes the adjacent foundation or lower structure preventing further movement of the scale weighbridge. This is an effective and simple means of restraining the weighbridge but, to work properly, it must be periodically adjusted to maintain the proper clearance between the adjacent lower structure or scale foundation and bolt head. As the scale is used, this gap changes and must be adjusted to keep the restraint system operating properly. The check rod type of restraint system is a long thin rod that attaches the weighbridge to the surrounding structure preventing lateral movement of the weighbridge. The ratio between the length of the rod and its diameter is quite large allowing the rod to flex without affecting the accuracy of the scale. Unlike bumper bolts, check rods do not wear and therefore require little or no maintenance.

 

The table below summarizes the advantages and disadvantages of different types of truck scales offered. Remember that each selection of a truck scale requires that you evaluate the various alternatives and choose those which offer the greatest advantages in your specific application. Perhaps the best way of accomplishing this is to contact one of our KEDA scales sales associates for an evaluation of your needs and a site survey or you can send email to us。

 
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