Working with Weights
Weight Definitions: What the Numbers Mean
- Gross Weight: Total weight of the load plus the car. This is what the typical track scale will display to the nearest 100 lbs.
- Light Weight: Weight of the empty rail car. This is also called "tare" or "tare weight". Light Weight is stenciled on the side of the rail car.
- Net Weight: Weight of the load. This is the Gross Weight (displayed by track scale) minus the stenciled Light Weight (empty car weight). Net Weight is calculated by railroad clerks or computers, depending on the era, and is the weight billed to the shipper.
- Capacity: Normal maximum Net Weight for a rail car, stenciled on the car side. For example, a 50 ton hopper has a Capacity of 100,000 lbs. Commodity-specific cars, coal hoppers for example, are often loaded at or even above Capacity.
- Load Limit: Absolute maximum Net Weight permitted based on axle and journal limits, stenciled on the car side. If Gross Weight minus Light Weight (equals Net Weight) is greater than the Load Limit, the rail car is overloaded and unsafe.
Load Weight & Safety
For safety, a rail car should be loaded so that Gross Weight is less than the sum of its stenciled Load Limit + Light Weight. Train crews should spot cars exceeding that Gross Weight limit where the load can be lightened. This means leaving the car on an industry or yard track, depending on where the car was weighed. The car would then be reweighed the following day (operating session).
Crew Challenge: Is it Safe?
As an extra challenge for the operating crew, the WeighStation™ Track Scale's Display Ranges can be set so that some rail cars will be over their Load Limit. Simply set the maximum weight limit for a Display Range above the sum of Load Limit + Light Weight of some or all rail cars.
For example, if a set of grain hoppers have stenciled Load Limits + Light Weights that add to 265,000 lbs., setting the maximum weight limit on the Display Range used for grain hoppers to 270,000 lbs. will produce an occasional "over the limit" car.
How occasional? If the minimum weight limit for the Display Range is set to 240,000 lbs., there is a 25,000 lbs. weight range that is safe (240,000-265,000 lbs.) and a 5,000 lbs. weight range that is unsafe (265,000-270,000 lbs.). Thus you can expect the Track Scale to display 1 unsafe over Load Limit weight for every 5 safe weights for your grain hoppers.