Concrete pumping operations present a number of typical mishaps that can lead to personal injury. Many of these hazards are associated with the forces and energy exerted by the pump and should be controlled through proper planning, training, effective work processes, and proper management.
In this article, Civil Engineer & Construction Expert, Jeffrey Tedder, P.E., discusses some of the hazards relevant to concrete pumping operations and the corresponding safety measures. He also provides potential discovery questions related to these disputes.
THE HAZARDS OF CONCRETE PUMPING OPERATIONS – EXPERT OVERVIEW
Advancements in concrete pumping equipment have led to improvements in quality, reliability, cost, and availability, making their use on modern day construction sites commonplace. The advantages of pumping concrete in lieu of more traditional means are well established throughout the industry. Improvements to production save time leading to labor, cost, and schedule efficiencies making it the preferred option in many cases.
Struck-By Hazard - Hose at Point of Placement (Whipping):
Truck mounted concrete pumps are equipped with an articulating boom which carries the concrete conveyance piping, as demonstrated in Figure 1. The operator manipulates the boom via a remote-control box to extended the boom to the rough location of placement.
The ‘hose-man’ is then responsible for manually controlling the discharge location of the concrete as it is discharged by physically guiding (manipulating) the end hose, as shown in the image below.
The hose-man is typically the most vulnerable member of the concrete placement team as his proximity to the end of the discharge hose exposes him to the greatest risk for potential harm. To effectively perform his job he must remain in the ‘end-hose movement area’ at all times when concrete is being placed (‘end-hose movement area’ per the American Concrete Pumping Association (ACPA) is the area within the radius of the last flexible piece of piping).
End-Hose Movement Area Hazards:
Being in the end-hose movement area poses elevated risk for hazard when air is introduced into the pipeline. The presence of air by itself poses no real hazard, it is only when the air is compressed that a hazard is created. Air can enter the system at the hopper, the tip of the hose, or if there are other points of entry at holes along the length of the pipeline.
Once in the pipeline the air compresses and is pushed by the concrete behind it, the air in turn pushes the concrete in front of it. As the entrapped air travels the distance of the pipeline to the discharge point the pressure required by the pump to push the concrete forward reduces and the air expands (air volume is inversely proportional to pressure). As the air approaches the end of the hose it expands rapidly propelling the concrete in front of it at an accelerated rate. Plugging of the end-hose, a common problem, exacerbates the issue by causing further pressurization in the line prior to release.
The reaction of the air escaping at high velocity causes the end-hose to whip violently creating the potential for injury to those exposed. It is not feasible to know when the hose will whip. It is possible, however, to monitor for conditions that create hose whip hazards and warn personnel in the end-hose movement area to evacuate.
- Struck-By Hazard – Other Than Whipping: Pressures in the pipeline, specifically where line plugging has occurred, can cause failures in the piping, joints, and fittings causing catastrophic failure of the pipeline leading to piping shrapnel and projectile aggregate.
- Fall Hazard – Pumping at Height (Walls & Elevated Decks): End hose whipping and hose movement in general are especially dangerous in these situations as contact with the hose can cause the worker to fall from height.
- Overhead Power Hazard: Pump trucks are commercially available with booms up to 65 meters (approx. 200 ft.) in length. Even if the chassis of the pump truck appears to be a safe distance from overhead power lines a distinct possibility of electrocution from boom contact still exists.
- Pump Truck Tipping Hazard: The magnitude of the forces and moments created by the extension of the boom and the action of pumping the concrete are significant, if the foundation is insufficient to resist these forces the results can be catastrophic.
Discovery Questions for Concrete Pumping Disputes
Contractor (GC & Concrete Subcontractor) operations:
- Did the contractor conduct a pre-construction meeting with all parties to discuss logistics, pump staging, duties and responsibilities, and hazards inherent with the work?
- Was a competent pour supervisor appointed with delegated authority to oversee the pour?
- Did the contractor verify that the concrete mix meets specification requirements and was indeed pumpable?
- Were processes in place to reject concrete that is too dry to pump or that contained deleterious material that might cause the pump to plug?
- Did the contractor monitor the efforts of the pump operator and ready-mix truck drivers?
- Were all parties involved, especially the hose-man, trained?
- Were all un-necessary personnel segregated from the end-hose movement area?
Concrete Pumping Subcontractor operations:
- Was equipment properly maintained? Concrete is abrasive, accelerating system wear. Worn equipment increases the likelihood of failure.
- Was the pump operator competent, qualified, and trained on the specific equipment used?
- Did the subcontractor conduct pre-pour equipment inspection? Improperly cleaned piping, for instance, can restrict flow increasing the likelihood of plugging.
- Were ground conditions verified prior to set-up? If deficiencies were found, did they refuse set-up until remediated?
- Did the subcontractor verify the presence of overhead powerlines? If present, what provisions were made to assure guarding against this hazard?
- Was the pumping system primed with grout to lubricate pipeline prior to concrete pumping?
- Was the pump immediately stopped when the blockage was encountered? The operator must evacuate all personnel from the end-hose area prior to attempting to clear the blockage.
- Did the subcontractor slow pump operation upon introduction of air to the system until the air has been expelled from the end-hose?
Concrete Ready-Mix Supplier operations:
- Was a pumpable mix supplied that meets specification requirements?
- Was the concrete supplied on-time to avoid delays?
- Did the supplier notify the Contractor of any delivery delays? Pumpability is greatly affected by time.
- Did the supplier maintain minimum concrete level in the pump hopper to avoid introduction of air? Did they notify the pump truck operator immediately or activate the pump kill switch upon air introduced?
- Did the supplier add mix water onsite without the authorization of the pour supervisor? Additional water can cause segregation of coarse aggregate leading to plugging.
Investigating Concrete Pumping Incidents
The hazards involved with concrete pumping can be controlled when all parties involved conduct their work in accordance with industry standards and established best practices. The Construction Safety experts at Robson Forensic have worked at every level within the industry, from bricklayer on residential projects to project manager on multi-prime worksites. Our experts have performed the work central to your case and can testify regarding the hazards, risks, and responsibilities in the construction industry.
For more information, submit an inquiry or call us at 800.813.6736.
Civil Engineer & Construction Safety Expert
Jeffrey Tedder is a Civil Engineer with nearly 20 years of professional construction and engineering experience. His experience in complex, industrial construction where all trades are involved has granted Jeff a comprehensive understanding of the construction industry. Jeffrey applies his knowledge of the industry and expertise in standards and best practices to forensic casework involving construction claims and injuries.