In the United States, the Fire Department Bureau uses vacuum trucks for trench rescue operations. This safety device can efficiently reduce the rescue dig time by up to anVacuum_Trucks amazing 80 percent. The Occupational Safety and Health Administration (OSHA) has recorded a shockingly high percentage of deaths attributed to collapsed trenches. Because of the use of vacuum trucks, trench rescue operations are much faster than the traditional method of using shovels to excavate the accident site. With this rapid ability to perform trench cave-in rescues, operating procedures can be done at an increased rate.

Centrifugal Fan Units vs. Positive Displacement Air Pump

One type of vacuum truck utilizes a centrifugal fan unit. The generated vacuum is due to the large fan than creates airflow through a pick-up hose, which transports the debris to the debris chamber and exits through the fan exhaust chamber. The airflow that is generated by the fan unit will be the measure for performance. The centrifugal fan unit can produce a vacuum pressure of 3,000 to 8,000 cubic feet per minute (cfm). This is relatively low since the measurement is in inches of water rather than inches of mercury (Hg).

Another option has been developed for vacuum trucks to obtain a high-speed suctioning performance. This is accomplished through the use of a two-stage compressor process that increases airflow speed. This type of vacuum truck is similar to a fan unit, yet the vacuum pump utilizes positive displacement to produce high pressure. This positive displacement air pump can produce airflow of 2,000 to 3,000 cfm. The airflow that is generated is high compared to the typical fan unit because it is measured by inches of mercury (Hg). Operators should be vigilant when using this high-speed vacuum system because of the potential harm closely associated with it.

Air Knife

The large fan unit vacuum truck sometimes cannot smash large soil debris while performing a rescue, so another instrument is needed to break the soil without additional harm to the victim. An air knife is another tool to assist in removing debris while performing trench cave-in rescues. This type of instrument uses a pressurized air plenum which delivers air velocity to cut large soil. Unlike normal vacuum trucks, the air knife’s nozzle tip is placed stationary next to the victim to speed up the rescue operation.

Trench Cave-in Rescue

Pneumatic soil knives and vacuum trucks are the tools to efficiently rescue any victim from trench collapse incidents. Trench cave-ins are a most time-consuming and labor intensive life saving activity. During the operation, the rescuers are competing with time to save the trapped victim as quickly as possible. The most common problems associated with trench collapse are crush syndrome, internal traumatic injuries and hypothermia. All of these are potentially deadly, so rescuers must act fast.

Phases of Vacuum Truck Trench Rescue

Phase 1: Soil Reduction

The soil is fractured and cut into small chunks using a pneumatic air knife. By fracturing and aerating the soil into small chunks, it enhances the ease of the vacuum truck’s ability to unearth the victim.

Phase 2: Soil Removal

Using vacuum trucks, the soil can rapidly be removed and displaced through suctioning. Pneumatic trucks can easily carry soil, mud, sand and gravel using high speed airflow.

Rescue Operation Procedures

  1. Assess the area and determine if the victim is still viable.
  2. Establish a 50 to 300 foot vibration zone perimeter.
  3. Check if there is a need for special tools (vacuum trucks, air knives and air compressors).
  4. Position the ground pad near the trench lip and take away identified trip hazards.
  5. Locate the victim.
  6. Create a resource area outside the vibration zone perimeter.
  7. Create a safe zone.
  8. Assemble shoring equipment (sheeting, upright timbers, and braces).
  9. After a safe zone is established, the rescuers enter and attempt to remove the soil around the victim, starting from the head down to the chest to facilitate breathing.
  10. Establish a sump area on the side of the victim where the soil can be pulverized using the air knife and sucked up using the vacuum truck.
  11. After the victim is uncovered completely, the rescuers can remove the person using a patient lifting device.

To conveniently extract a partially or totally covered victim from a trench cave-in incident, rescuers are encouraged to utilize pneumatic vacuum trucks to perform soil removal. It is a hazardous operation, both to the victim and to the rescuers; however, it is the quickest way possible to achieve a successful rescue from a trench collapse by using the powerful vacuum truck!