22 Dec

The pros and cons of using pit scales in northern climates

As we move inexorably toward another winter, I thought I would revisit a topic that comes up frequently, especially at this time of year – Are pit scales appropriate for northern climates?

And the answer is yes – Not only are pit scales appropriate in northern climates, in some cases they are even required. Since a pit scale saves on space because you don’t have to construct an approach ramp, they are the option of choice whenever real estate is very limited. Another place they may be the best choice is if the scale is installed under a load out hopper. Here, the additional height required for an aboveground scale may restrict the ability to drive trucks on the scale and interfere with the loading equipment chutes/gates.

There are some positives and negatives about using pit scales in northern climates. On the plus side, pit scales are enclosed, installed in the ground, and essentially out of the elements. This means it will usually take longer for snow, debris, and ice to accumulate around the load cells or mechanical levers beneath the weighbridge.

Temperature control is another plus. Some applications use heating elements in the pit to moderate temperatures, which is more difficult to do with an above ground truck scale.

One of the biggest negatives is cleanout and debris removal. Though pit scales typically require less frequent cleanout than aboveground scales; the pit is less accessible and cleaning is more time consuming. In most cases you will need to physically remove debris through a manhole cover or side access.

Maintaining scale deck gaps (space between the scale deck and the side and end pit walls) can also be a negative. Snow, ice, or debris can build up in this gap and cause problems. Pit scales typically require gravity drains or sump pumps to allow for water drainage, and freezing drains or sumps can be an issue in northern climates. Finally, there are additional costs for bringing AC power to the pit for lighting or drainage sump pumps.

There are a few other issues to keep in mind when using pit scales – these apply to pit scales in general, and may not be associated with northern climates in particular. First of all, construction costs may be higher, since scale pits require more expensive foundations. Also, clearance requirements and frost line requirements can be an issue and can add to costs. Most northern states require a specific clearance from the bottom of the weighbridge to the top of the pit floor. In most cases the requirement to extend the pit construction below the frost line guarantees that you meet the clearance regulation, because the frost line may be 6-8 feet.

Finally, some companies, states, or other governing agencies may categorize a pit scale as a confined space, making it subject to extensive safety regulations under MSHA or OSHA. These regs may make it more costly to service and repair a pit scale.

Some of the issues can be mitigated simply by regular and proper scale maintenance and cleaning. This is always important, but may be even more critical during the winter months in a northern climate.

Here are a few tips to keep in mind:

  • Clean out snow, ice, and debris under the scale deck to help prevent buildup around the critical weighing elements like load cells or mechanical levers.
  • Make sure to maintain drains during the winter months to ensure proper draining.
  • Install steel or rubber T-belts to cover the gap between the scale deck and the pit side and end walls to prevent buildup around the scale deck. Fasten permanent belting to the pit coping and over the gap between the scale deck and the pit wall to prevent buildup.
  • Shovel the snow off the deck just like any sidewalk or street and use a hand shovel rather than a snow plow. Otherwise, the buildup of snow and ice from the daily thaw/freeze cycle could lock up a scale quickly.
  • Control pit temperatures by using heating elements to moderate temperatures.