This report documents the results of a dust hazard analysis (DHA) of the cold spray process at the Corpus Christi Army Depot (CCAD) Building 8 facility located in Corpus Christi, Texas. CCAD plans on using their Booth 7 for the cold spray technology. This facility has existing thermal spray booths that are located in Building 8 and have suppression within the spray booths and dust collection systems.
The dust hazard analysis included an evaluation of combustible dust handling operations associated with the cold spray process in accordance with the 2019 Edition of NFPA 652, Standard on the Fundamentals of Combustible Dust. The purpose of conducting a DHA is to develop a “road map” of combustible dust hazards in the facility and to ensure such hazards, where present, are being managed in accordance with the industry standard of care. To this end, relevant requirements outlined in the 2019 Edition of NFPA 484, Standard for Combustible Metals, were also evaluated. Other standards (e.g. NFPA 70, National Electrical Code) referenced
by NFPA 484 and 652 were also evaluated as applicable.
The objectives of the DHA were to:
Observe and document current plant conditions related to combustible dust hazards;
Identify and document combustible dust fire, deflagration (flash fire), and explosion hazards;
Evaluate existing measures employed to mitigate these hazards; and
Provide prioritized recommendations to close gaps between existing safeguards and industry best practice.
The DHA consisted of four evaluation categories: material hazards, equipment hazards, building hazards, and management systems.
MATERIAL HAZARD EVALUATIONS
Solvus Global provided combustible dust data for the metals to be used in their cold spray process. Pure metals such as tantalum were found to be combustible. The site also has plans to use other metal powders such as titanium which is also known to be combustible. Furthermore, these metals have displayed tendencies to be pyrophoric1 once they reach nano particle sizes that can occur from the collision of powders in the cold spray application.
Not all powders used in this process are combustible (e.g, wear impact powder (WIP)); however, fine metal powders such as tantalum will support a deflagration. As such, it is important that combustible metal powder accumulations are managed to prevent the development of hazardous conditions.
SUMMARY OF BUILDING AND EQUIPMENT HAZARDS
The findings of the hazard analysis for combustible dust handling equipment and building areas associated with the cold spray process are summarized as follows:
Although most of the combustible powders are processed in enclosed inert conditions or deposited onto the material to be coated, potential deflagration hazards may be present in the baghouse.
A combustible dust cloud will be present inside the baghouse during pulsing of the filters. The dust collector will need to be isolated to prevent propagation of fire and explosion to other equipment throughout the facility.
SYNOPSIS OF RECOMMENDATIONS FOR BUILDING AND EQUIPMENT HAZARDS
The hazard summary and full list of recommendations for each area that handles or produces combustible dust within the facility is provided in Section 6 of this Report. A synopsis of these recommendations is as follows:
+ The effective deposition rate of the cold spray was tested to be 50-92%. Dusts aspiration is likely to capture most of the fugitive dust generated; however, it is expected for some combustible metal dust to accumulate in the surrounding surfaces. It is important to limit significant accumulations of dust while using appropriate tools and procedures to limit ignition sources.
SYNOPSIS OF RECOMMENDATIONS PERTAINING TO MANAGEMENT SYSTEMS
While a detailed assessment of management systems and full list of recommendations is provided in Section 5 of this report, a synopsis of these recommendations is as follows:
+ A written housekeeping program should be developed that outlines cleaning intervals, cleaning methods, and requirements for fugitive dust monitoring and auditing.
+ Procedures should be developed to ensure safe work practices are in place for tasks that may expose workers to suspended combustible dust.
+ The facility inspection, testing, and maintenance should include applicable measures for ignition source control (e.g. bearing monitoring) as recommended throughout this report. Bonding and grounding should also be included in the inspection, testing, and maintenance program.
+ Initial and annual refresher training on combustible dust hazard awareness should be provided to employees. It should also be verified that contractors have received appropriate combustible dust hazard awareness training.
+ A Management of Change program should be in place and should take into account combustible dust hazards.
Provided that the recommendations made in this DHA are implemented, Jensen Hughes finds that potential combustible dust hazards will be managed in accordance with the applicable provisions of NFPA 484 and 652. Credible hazards should not exist during normal operation and potential hazards associated with upset conditions will be managed in accordance with the industry standard of care.
1. Pyrophoricity of nano-sized aluminum particles. Article in Journal of Nanoparticle Research – February 2012
To view the Corpus Christi Army Depot (CCAD) Cold Spray Dust Hazard Analysis document in its entirety, please download the RPT_Corpus Christi Cold Spray DHA pdf file. For more information on the Corpus Christi Army Depot go to https://www.ccad.army.mil/ or to learn more about Jensen Hughes, visit their website: https://www.jensenhughes.com/