Ratholes, Bridges and Blockages in Bulk Storage Vessels

Published: February 20th 2013

All of these conditions are the result of material buildup in your bulk storage vessels. The restricted or blocked flow caused by these conditions can lead to less productivity, lost inventory and possibly unplanned outages for your facility.

So, What Exactly Are These Conditions?

Ratholes occur when material clings or builds up on the sides of the vessel, creating a narrow flow channel from top to bottom of the vessel. Vessels that have ratholes generally maintain material flow but will require more frequent fill cycles due to the reduced live capacity.

Bridges occur when the material arches over the discharge. Material below the bridge will discharge from the vessel creating a void, while material above the bridge is not able to discharge.  Bridges ultimately create a no flow condition.

Blockages occur when the material hardens together and obstructs material flow at the discharge point of the vessel. Blockages will create intermittent or no-flow condition.

What Are Some Signs of Buildup In A Storage Vessel?

There could be many signs but some of the most common are:

  • Fill cycles take less time but needs to be done more often (day bins don’t last a day/shift without needing to be filled).
  • Discharge pattern of the vessel has changed, is inconsistent or is off center.
  • Chunks of material come out or occasionally obstruct the discharge.
  • Hot spots or bunker/silo fires occur.

What Should I Do I About These Conditions?

Depending on the severity of the buildup it may be necessary to use a professional cleaning service such as MartinPLUS® Silo Cleaning.  Our silo cleaning service can safely and efficiently remove buildup from the outside of the vessel, reducing the risks associated with confined space entry.

Once the vessel is cleaned, implementing best practices (i.e. lowering levels frequently, avoiding frequent spot filling, etc) may be enough to keep buildup to a minimum.  However, if the vessel is not designed properly for the material being stored, you may benefit from installation of a flow aid system or purchase of a cleaning system.

Flow aids systems are designed to stimulate material flow and will include products such as Martin® Vibrators and or Martin® Air Cannons.  Flow aid systems should be sized specifically for vessel size/configuration and material being stored.