In choosing a system for safe, clean materials conveyance, it seems that the choices can be remarkably complex. Before choosing, a plant’s conveyor usually has human operators, open conveyor belts and implements such as buckets. While workers might be protected by proper clothing, masks and goggles, materials are exposed to air and dirt, waste is a constant worry, and particulates that endanger expensive equipment can slow or jam it. With constant economic pressures and attention focused on the bottom line, it’s mandatory that plant professionals seek alternatives and improvements such as pneumatic conveying systems. It seems so simple.
Since labor is one of the highest costs in a plant or facility, reducing man-hours becomes a primary target of any executive interested in reducing operating costs. A primary benefit of a pneumatic conveying system should be the reduction of man-hours. Where numerous workers were previously required to manipulate material, there might now be the need for only one to add material at the front end of the process. (VAC-U-MAX)
Why, then, does evaluating the options for pneumatic conveying systems appear to require an engineering degree? Even engineers are going to have a hard time answering questions such as:
- Should the system be dilute phase or dense phase?
- Should the system be vacuum, pressure or combination?
- Given the physical properties of your materials, how exactly will they be best conveyed?
- What’s the friction factor of your solids?
- How do you calculate the expected losses of pressure throughout the system?
- Given that some chemicals are oxygen sensitive, what gas should you use?
It gets worse when you have to figure in factors such as gas densities and solids velocity in horizontal, diagonal and vertical pipe runs.
Okay, hold up
Take a deep breath and a giant step back. Remember the original reasons for wanting to do this in the first place. Those reasons are relatively simple and, fortunately, so are the choices involved. In evaluating a pneumatic conveying system, you want three pieces of information:
Is the system going to truly automate a process? If a particular process now involves five workers, can most or all of those people be assigned to more productive activities elsewhere? Will it be possible to run the process with little to no attention, save perhaps periodic monitoring?
Is the system reliable? Will the system run continuously without babysitting? Will it stand up to the required process; is it robust and seriously proofed against breakdowns? How much maintenance will it require?
What is the system cost? A system’s installed cost is only the beginning of the answer. How quickly would the system pay for itself? How much time and cost will its implementation save?
These questions are interrelated, and each must be answered in detail. Fortunately, if you use reliable expert assistance, you won’t need to answer that first set of horribly niggly engineering-type questions. These important questions can be answered fully by an outside expert and to your satisfaction.
An understanding of material characteristics is essential when designing a vacuum transfer system. Experts often possess data about a particular substance’s behavior and will test it within a proposed configuration to ensure it conveys properly. Sometimes this knowledge must be extensive. For example, often several product grades within the same product group might have completely different characteristics such as free-flowing, sluggish or non-free flowing. One grade of zinc oxide might be dry and free-flowing while another grade might be more cohesive and adhere to the inside of conveying tubes. Pneumatic conveying experts are skilled in designing custom solutions based on application-specific requirements.
Pneumatic systems convey material from closed hoppers through closed lines and require little to no intervention. (VAC-U-MAX)
A pneumatic conveying vendor that routinely designs and builds custom pneumatic conveying systems most likely will know how to tailor a system to meet your present and future needs. There’s a possibility that the design can work properly out of the box. The better vendors of pneumatic equipment have large-scale testing facilities that can confirm material flowability and system capacity using materials specific to your application.
Implementing an appropriate pneumatic conveying system — or correctly expanding an existing system — yields numerous benefits. Switching to a pneumatic conveying system is a simple solution that might yield amazing cost benefits.
The right system means reduced or eliminated cleanup. Because pneumatic conveyor systems are fully enclosed, they eliminate problems with fugitive material, messy accidents, labor-intensive cleanup of floors and surfaces, and unnecessary machinery cleaning. A fully-enclosed system also translates to a healthier work environment because it reduces or eliminates exposure to hazardous substances and dust explosions. Although plant floor engineers protect workers by using extensive exhaust ducting and respiratory protection, they often continue to search for a better solution.
One company eliminated the need to dump 50-pound bags of toxic material into a mixer manually by converting to a monorail-mounted hoist. The device lifts and positions semibulk bags to an unloader, which forms a dust-tight seal against the ring on the discharge opening. Agitator pads and an auger under the storage bin help to deliver material into a weigh hopper on the floor below at a controlled rate. The material is then conveyed to a blender on an upper floor. The entire flow path is enclosed.
An understanding of material characteristics is essential when designing a vacuum transfer system. Experts often already possess data about a particular substance’s behavior and will test within a proposed configuration to ensure it will work properly. (VAC-U-MAX)
In many industries, product reclamation is important for reducing costs. A bucket-elevator type system at a marshmallow manufacturing operation merely threw starch around. In addition to the need for bi-weekly cleaning, the plant was wasting substantial quantities of a raw material.
The revised system uses vibratory pans within a pneumatic conveying system to shake excess starch from the marshmallows as they exit cooling drums. After passing through filter separators, the starch is recycled for reuse. The enclosed system reclaims about 1,000 lbs. of starch a day and reduces product loss by as much as 2%.
Plants often use pneumatic conveyors to improve production because the material moves more quickly and there’s less room for error. This is especially true with open conveying systems and containers that need to be moved, filled and emptied manually. Pneumatic systems convey material from closed hoppers through closed lines and requires little to no human intervention.
Because labor is the highest cost factor in a plant, reducing labor-hours becomes a prime target of any executive interested in reducing operating cost. A pneumatic conveyor’s major benefit is the reduction of labor-hours per unit of output. Where numerous workers were required to manipulate material, there might now be a need for only one to add material at the front end of the process.
One company knew it needed to make dramatic changes to be competitive. Their manual blending process required 20 minutes to blend 1.5 tons of output. With pneumatic conveying, that same output was completed in 20 seconds — a 60-fold improvement. The company invested the cost savings into additional R&D, marketing and sales staff.
Downtime is the worst enemy of productivity and immediately affects revenue when it occurs. Pneumatic conveying systems can reduce or eliminate downtime for maintenance and for cleaning.
Pneumatic conveying systems require virtually no maintenance or cleaning because there are so few moving parts. You simply clean or swap out hoses and check the motor and lubricants twice a year. You can add approximately 30 hours of production per year.
Downtime is one of the worst enemies of a manufacturing facility and immediately impacts revenue. Because pneumatic conveying systems have few moving parts, there is virtually no maintenance necessary. (VAC-U-MAX)
Of course, a system should be tailored to the specific material being processed and — if needed — it should be able to accommodate different materials. Sometimes a single line must be able to process more than one material or be adjustable to accommodate the volume of production necessary.
For example, one plant used a pneumatic conveying dump station to feed ingredients to blenders for smaller and normal size orders. For higher-volume products, it loaded the blenders pneumatically directly from silos at an even greater rate.
Some mobile pneumatic conveying systems can be relocated as needed within a plant. In short, pneumatic conveying systems can handle virtually any material and application.
Keep your eye on the prize. The goal of using a pneumatic conveying system is to automate operations and make them more cost-effective; in effect, to simplify processes. Less complexity equals less downtime, reduced labor-hours and reduced cost. Evaluating and choosing a system shouldn’t be complex. With expert guidance, you should be able to follow the evaluation elements as laid out above.
Doan Pendleton is vice president, sales and marketing, VAC-U-MAX (www.vac-u-max.com).