The food manufacturing sector is embracing a novel blend of industrial wastewater technologies designed for the efficient removal of solids. This innovative approach minimizes extensive manual labor, reduces worker exposure to messy or potentially hazardous substances, and decreases the need for constant maintenance.
This solution employs a powerful combination of a macerator, which breaks down large solids into smaller fragments, and an automated scraper strainer. This flexible system efficiently filters out larger debris while also capturing tiny particles, all while accommodating high solids loading without clogging.
The fusion of these two established technologies is already being put to the test in some of the toughest and dirtiest straining applications faced by food processors.
Food manufacturing relies heavily on industrial strainers to effectively separate unwanted suspended solids from liquids and slurries. Yet, conventional strainer methods can be unreliable and often lead to extensive maintenance challenges, especially when dealing with substantial debris and significant amounts of suspended solids.
Duplex strainers are typically employed in continuous flow processes that cannot afford downtime for cleaning. These strainers consist of two distinct chambers that operate independently.
When one chamber requires cleaning, the flow seamlessly diverts to the alternate chamber, allowing for the removal and cleaning of the first basket without interrupting the process.
However, cleaning remains a messy and labor-intensive task. It requires equalizing pressure between the baskets, diverting flow to the off-line chamber, opening the cover, manually removing the clogged basket, and cleaning it before refitting and ensuring proper seals.
If an operator neglects to adequately clean the basket strainers, both strainers could clog simultaneously, dramatically compromising the filtration process. This situation can result in quality issues or unexpected downtime until the problem is resolved. Such interruptions can occur simply due to insufficient personnel available to maintain clean basket strainers amidst their other duties.
“As an alternative, a combination of established complementary technologies such as a macerator and an automated scraper strainer can essentially ‘knock out’ even the toughest problems related to large solids and high solids loading in an automated way,” says Robert Presser, vice president of Acme Engineering Prod., Inc., a North American manufacturer of industrial self-cleaning strainers. This company is an ISO 9001:2015 certified manufacturer of environmental controls and systems with integrated mechanical, electrical, and electronic capabilities.
In this innovative configuration, a macerator is installed upstream to reduce large solids to a manageable size. The automated strainer’s capabilities are also crucial to the process, asserts Presser.
“Although the macerator cuts up the largest solids, the strainer must still be able to separate both relatively large pieces and tiny particles while managing high solids loading without becoming obstructed,” explains Presser.
For Acme, the OEM’s automated scraper strainer is engineered to continually remove both very large and very small suspended solids from liquids and slurries. This cleaning process is accomplished via a spring-loaded blade and brush system managed by a fully automatic control system.
Four scraper brushes rotate at 8 RPM, delivering a cleaning rate of 32 strokes per minute. The scraper brushes penetrate wedge-wire slots and dislodge stubborn particulates and solids. Consequently, this approach greatly reduces the likelihood of clogging and fouling when facing large solids and elevated solids concentration.
Typically, blowdown occurs only at the end of the intermittent scraping cycle when a valve opens for a few seconds to flush solids from the collector area. Notably, liquid loss is kept well below 1% of total flow.
If additional pressure is necessary for cleaning the screen, Acme Engineering can introduce an inexpensive trash pump to the blowdown line to assist in solid removal from the strainer sump.
“Since the solids are small, a little trash pump can pressurize the blowdown line to evacuate solids from the strainer. This combination provides a quick ROI because operators no longer need to monitor and clean heavily loaded basket strainers, resulting in significantly reduced labor and downtime,” states Presser.
Alternatively, the sump can be substituted with a cylinder bracketed by two gate valves. These valves open and close as needed to facilitate solid waste removal.
“When you are ready to empty the cylinder, close the top gate valve momentarily, and open the bottom one by pressing a button to dump the accumulated solids into a receptacle like a dump truck or a conveyor bucket, eliminating the need for manual handling,” adds Presser.
Acme has already collaborated with plant operators and managers to implement a variety of specialized straining systems for challenging applications involving exceptionally large solids or very high solids loading.
According to Presser, adapting strainers for the specialized filtration of unique liquids and slurries requires not only expertise but also collaboration with processors and several design iterations.
“For unusual applications, it may take a few attempts to get it right. You may need to adjust the timing and frequency of cleaning and modify the screen slot size—there are many variables at play,” concludes Presser.
Food manufacturers rely on efficient filtration of liquids and slurries to meet quality and regulatory standards. When the removal of large solids or management of excessive solids loading exceeds the practicality of manual basket strainer cleaning, integrating a combination of highly effective technologies may represent the optimal choice.
