High pressure water is a powerful tool used throughout heavy industry by the Ted Berry Company to help maintain the efficiency, production, and capacity of process equipment. Used in various arrangements, high pressure washing equipment and processes replace many of the manual cleaning methods of old. High pressure washing systems use a high-velocity stream of water to blast through materials, such as residue that collects inside pipes or vessels. The term “high pressure washing†refers to a high pressure washing system capable of generating a pressure of 5,000 pounds per square inch (psi) or more. This includes high pressure washing systems used at lower pressures and high volume. There are two levels of high pressure washing, based on the water pressure used:
- High pressure waterblasting–5,000 to 30,000 psi
- Ultra high pressure jetting – greater than 30,000 psi
The term “pressure washing†typically refers to a washing system not capable of generating at least 5,000 psi. Such systems can be found at a car wash or in the form of portable equipment designed for light commercial or home use.
When planning high pressure washing activities at your site, meet with project team to review each task. Identify opportunities to maximize efficiency and safety by providing good access to process equipment.
- Identify the process and chemical hazards related to the hydroblast activities.
- Plan work activities to avoid multiple types of maintenance activities in one area at a time. Consider the logical flow of high pressure washing activities
- When cleaning piping systems, provide open access at least every 100 feet when possible and remove flanged elbows or spool sections of pipe.
- Where piping systems consist of many welded-in elbows and corners, consider replacing them with spool sections to improve access and reduce the time required for cleaning.
- Where possible, remove vessel components and clean them at a designated wash pad location away from other personnel.
Understanding the basic principles of high pressure washing equipment and hydraulics will help you to conduct meaningful risk assessments and effectively apply safe work procedures.
Pressure and flow
The pressure created in a high pressure washing system is a function of the water flow and the size of the discharge orifice.It is important to consider the relationship of pressure and flow when assessing hazards and risk.The amount of back thrust, or “reaction force†(lb-thrust), possible from a high pressure pump can be determined by using the following equation as a measure of power and efficiency:
0.052 × gpm × √psi = lb-thrust
For example, an operator working with a jetting gun at 10,000 psi and 12 gpm will experience a back thrust equal to:
0.052 × 12 × √10,000 = 0.052 × 12 × 100 = 62 lb-thrust
It is not recommended that any one person be required to withstand a back thrust [lb-thrust] of more than one third (3) of his/her body weight for an extended period of time. For the above example, this means that the operator should weigh at least 186 pounds in order to operate the nozzle. In poor conditions (such as uneven or slippery footing, low light, confined spaces, and so on), lower back thrust should be used.
Our teams have a great deal of experience in hydroblasting of pipes, tanks, structures, and vessels of various shapes and sizes however risk is still present at every jobsite. Work as a team and keep each other safe, any employee with a question regarding hydroblasting safety should consult with their project supervisor of the WJTA safety manual which is available in the Ted Berry Compnay Employee Training Center.
Matt Timberlake Vice President