4 Tips for Troubleshooting Central Vacuum Cleaning Systems
Dust and debris are normal byproducts of most industrial processes. However, when not properly removed, they can irritate workers’ eyes and airways, potentially causing lung problems and other long-term health problems. For facilities where combustible or toxic debris is emitted, there is also the potential for explosion. Central vacuum cleaning systems (CVCS) are engineered to remove this hazardous material from job sites and store it safely prior to disposal.
Why do industrial facilities need a central vacuum cleaner?
To put it simply, dirt, dust, and other contaminants get in the way — creating safety and health risks as well as threatening product quality and overall job productivity. Whether you’re decontaminating a clean room, complying with OSHA and NFPA combustible dust standards, or just simply trying to keep things tidy, it’s important that your central vacuum cleaning system do the job thoroughly and efficiently.
Additionally, since the release of the NFPA 652: Standard on the Fundamentals of Combustible Dust (2016), installing a CVCS has become a critical housekeeping requirement for many facilities responsible for handling combustible dust. Furthermore, OSHA’s increased enforcement of the NFPA standards from their 2008 National Emphasis Program (NEP) means it’s more important than ever to ensure your industrial vacuum is running properly.
How does a central vacuum cleaning system (CVCS) work?
Generally speaking, a central vacuum cleaning system is made up of the following components:
- Filter receiver
- Material discharge mechanism
- Vacuum-producing device
- Centrifugal positive-displacement (PD) exhauster
A CVCS is a fixed-pipe vacuum system that removes dust accumulation from surfaces. It uses a variable-volume, negative-pressure airflow from remotely located hose connection stations to convey the collected dust to an air material separator. When properly designed and maintained, a central vacuum cleaning system should work reliably and consistently for many years.
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Common Central Vacuum Cleaning System Design Issues
01. Insufficient Airflow
Oftentimes, in order to win a bid, suppliers will look for ways to reduce the cost of a central vacuum project. One of the most substantial ways to decrease cost on this type of project is by lowering the airflow. However, this shortcut method of winning a bid will often backfire for the user. The effectiveness of a CVCS is reliant upon proper airflow velocity into the hose or tool. For example, if a 1.5-inch diameter hose is designed for 75 scfm (standard cubic feet per minute), the inlet velocity will translate to about 6,100 fpm (feet per minute). This may seem like a positive relationship, however, the inlet velocity for 90 scfm is approximately 7,300 fpm. One would think the 6,100 fpm (75 scfm) hose would perform about 84 percent as well as the 7,300 fpm (90 scfm) hose. However, this isn’t the case.
The efficiency is based on the third power of the ratio. When 6,100 is divided by 7,300 and taken to the third power, the result is an efficiency of only 58 percent. This indicates that the 75 scfm airflow will take about twice as long to clean the same area as the 90 scfm airflow — resulting in a significant decrease in actual performance when compared to the relatively small difference in airflow.
02. Operating Outside of Designated Capacity
Operational problems can also occur when the initial design fails to address the actual usage requirements of the system. If a vacuum system is designed for only the maximum simultaneous operation and ignores all other scenarios, this means the system is often operating with a lower airflow volume which can eventually lead to plugging. For example, if a system is designed for three simultaneous operators, that means the velocity volume will be approximately 8,000 fpm in a 4-inch main line. However, if the central vacuum cleaning system often functions with just two operators, the velocity will drop to approximately 5,800 fpm and create plugging. This is a common problem and is specifically not allowed for combustible dust per the NFPA combustible dust standards.
04. Selecting the Incorrect Blower
Positive-displacement (PD) blowers are often used because of their high performance. However, because a PD vacuum blower inherently has a limited range of airflow, these blowers have a reduced capacity and require fewer simultaneous operators. In instances where a higher number of simultaneous users is necessary, a centrifugal CVCS unit would be the best option. A centrifugal vacuum blower is designed for situations where variable airflow volume occurs and is better equipped to handle a wide range of velocities. Conversely, a PD blower will often attempt to detach a conveying line when vacuum speed and airflow are at the same rate. As with anything, each vacuum blower has an appropriate use and must be applied properly. It’s important to understand how the central vacuum cleaning system will be used on a daily basis to ensure those standards are applied to the initial design and equipment selection.
Industrial Vacuum Systems from Bedson REPS
Designing a CVCS requires careful analysis and planning to ensure that each component meets the needs of your facility. If you’re unsure of where to begin, Bedson REPS can help. We can provide you with ample information to make the right decision for your CVCS needs. Our experts will evaluate your facility, review your dust production, and determine which system will provide the best results for your employees and your equipment.