The water-treatment industry in Latin America depends on industrial strainers to separate unwanted suspended solids from liquids and slurries. However, conventional strainer methods can be unreliable and lead to extensive maintenance, particularly when the debris or solids are of substantial size and there is a significant amount of suspended solids present.

Fortunately, the utilization of a novel blend of industrial wastewater technologies now allows for the efficient removal of solids without the need for extensive manual labor, worker exposure to messy or potentially hazardous substances, or constant maintenance. Specifically, the design involves a one-two punch combination of a macerator, which breaks down large solids into smaller fragments, and an automated scraper strainer that is flexible enough to efficiently filter out larger debris along with tiny particles. This innovative solution can even accommodate high solids loading without clogging.

The combination of these two established technologies is already being applied to some of the toughest, dirtiest straining applications in the water-treatment industry.

Overcoming Traditional Limitations
Duplex strainers are often used in continuous-flow processes that cannot be shut down for cleaning purposes. Duplex basket strainers employ two distinct chambers that function independently. When one chamber needs cleaning, the flow is seamlessly diverted to the alternate chamber, enabling the removal and cleaning of the first basket.

A novel blend of industrial wastewater technologies now allows for the efficient removal of solids without the need for extensive labor, worker exposure, or constant maintenance.

Cleaning is a messy, laborious process that involves 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 it, ensuring the seal, and tightening the fasteners. If an operator fails to adequately clean the basket strainers, both strainers can become clogged at the same time. This compromises the filtration process, resulting in quality issues or unexpected downtime until the problem is resolved. For many water-treatment plants, this can occur simply due to having insufficient personnel to keep basket strainers clean.

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. In this configuration, a macerator would be installed upstream to reduce large solids down to a manageable size. The capabilities of the automated strainer are crucial to the process, as well.

An automated scraper strainer is designed to continually remove both very large and very small suspended solids from liquids and slurries.

Although the macerator cuts up the biggest solids, the strainer must still be able to separate both relatively large pieces and tiny particles while handling high solids loading without becoming obstructed.

One original equipment manufacturer in Latin America designs the automated scraper strainer to continually remove both very large and very small suspended solids from liquids and slurries. Cleaning is accomplished by a blade-and-brush system that is spring-loaded and managed by a fully automatic control system.

Four scraper brushes rotate at 8 rpm, resulting in a cleaning rate of 32 strokes per minute. The scraper brushes get into wedge-wire slots and dislodge resistant particulates and solids. This approach enables the scraper strainers to resist clogging and fouling when faced with large solids and high solids concentration.

Adapting strainers for the specialized filtration of uncommon liquids and slurries requires not only expertise but also collaboration with the processor, as well as some design iterations.

Blowdown typically occurs only at the end of the intermittent scraping cycle when a valve is opened for a few seconds to remove solids from the collector area. Liquid loss is well below 1 percent of total flow. If additional pressure is required to clean the screen, an inexpensive trash pump can be added to the blowdown line to assist in removing the solids from the strainer sump.

Since the solids are small, a little trash pump can pressurize the blowdown line to evacuate solids from the strainer. The combination provides quick return on investment because operators no longer have to monitor and clean out heavily loaded basket strainers, resulting in substantially less labor and downtime.

Alternatively, the sump can be replaced by a cylinder bracketed by two gate valves that open and close as needed to remove the solids waste.

When you are ready to empty the cylinder, close the top gate valve momentarily and open the bottom one by depressing a button to dump the accumulated solids into a receptacle, such as a dump truck or conveyor bucket, so there is no manual handling required.

Automated scraper strainers paired with macerators eliminate high volumes of large, suspended solids from slurries for a “set it and forget it” approach.

Adapting strainers for the specialized filtration of uncommon liquids and slurries requires not only expertise but also collaboration with the processor, as well as some design iterations.

With unusual applications, getting it right may take a few attempts. You may have to adjust the timing and frequency of cleaning, as well as the screen slot size. There are quite a few variables involved.

When it comes to water treatment, industry professionals depend on the filtration of liquids or slurries to meet quality and regulatory standards. When the removal of large solids or the management of excessive solids loading exceeds the feasibility of manual basket-strainer cleaning, integrating a combination of highly effective technologies may be the best decision.

About the author
Robert Presser is vice president of Acme Engineering Products, Inc. He can be reached by phone at (518) 236-5659.

About the company
Acme Engineering is a manufacturer of industrial self-cleaning strainers. The company is an ISO 9001:2015 certified manufacturer of environmental controls and systems with integrated mechanical, electrical, and electronic capabilities. For more info, visit acmeprod.com.

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