Multi-layer defense for cleaner air and longer life

Introduction

In a regenerative road sweeper, airflow isn’t just about suction—it’s the backbone of performance. That airflow doesn’t just pick up debris; it also carries grit, silt, moisture, and fine dust through the entire system. Effective sweepers don’t rely on just one filter to handle it all. Instead, they must separate different contaminants at different stages—from large debris at the curbside to PM10 particles before exhaust. Just as critical is managing how air flows between those stages: keeping the pressure balanced, the path smooth, and the system breathing cleanly from start to finish.

Most machines simplify this path. They use one or two separation steps and leave the rest to basic filters. That might work briefly on dry roads, but in real-world conditions, fine particles slip through early barriers, moisture clings to dust, and suction pressure fluctuates. With poor routing and unbalanced airflow, debris overloads the wrong components, filters clog too soon, and performance fades long before the job is done. A few missed design steps at the start become serious reliability problems in the field.

To maintain stable suction, clean airflow, and long filter life, a sweeper needs more than just a filter—it needs a strategy. That means combining multiple separation methods, each staged for a specific contaminant and designed to relieve the next one in line. Grit should drop out before it reaches the blower. Moisture should be stripped out before it hits the filters. And fine dust should be captured before it escapes. When air is cleaned in layers, pressure stays stable, parts stay protected, and sweeping performance stays consistent

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Filtration challenges in standard sweeper designs

Conventional street sweepers typically rely on a two-stage or, at best, three-stage separation system. This usually includes

Gravity separation (where larger debris drops out due to reduced velocity),

Basic screening or grilles to catch oversized items,

A single-stage centrifugal separator or cyclone that removes medium to coarse particles using swirling airflow.

These systems are simple, cost-effective, and require minimal energy input or space, making them attractive for budget-conscious builds.

Challenges:

This simplified setup often misses ultrafine particles, moisture-laden silt, or sticky contaminants that don’t separate easily with just cyclonic force or gravity. The result is a high burden on the filter media. In humid environments, sticky fine matter bypasses separation entirely and lodges directly in the filters. This causes premature clogging, poor suction, and erratic airflow performance mid-shift.

To protect internal systems like the blower or impeller, most machines rely on a single primary filter stage placed before the blower. Exhaust air is often recirculated internally to conserve suction pressure or expelled with limited treatment, especially in non-regulated markets. Few sweepers offer multi-stage polishing or PM10-level final filtration unless specified for industrial or urban dust-control applications.

Challenges:

This minimal protection approach means impellers and ducts wear down faster, due to residual fine dust and grit. On the environmental front, exhaust air may still carry PM2.5/PM10 particles, posing a threat to public health and making compliance with dust-control regulations difficult. Additionally, the lack of robust filtering and protective stages compromises the durability of internal parts, which accelerates component degradation and compromises operator safety.

In standard sweepers, airflow is usually direct, unbalanced, and unregulated. Air is pulled straight from the pickup head into the separator and filter box with little control over velocity, pressure, or turbulence. Thermal management is typically nonexistent, filters are placed far from heat sources to avoid warping or fire risk, and no active moisture conditioning is applied.

Challenges:

Without airflow control or thermal conditioning, air enters the filter chamber unevenly, creating “hotspots”, areas where dust overloads the filter while other sections stay underused. These spots clog quickly, reducing efficiency. In humid or monsoon conditions, cold filters trigger condensation, turning dust into sticky sludge. The result is frequent caking, unstable suction, and increased fuel use as the system strains to maintain airflow.

How CycloShield filters better and lasts longer

In the Stratus road sweeper, CycloShieldTM delivers true multi-stage separation, tackling debris, silt, and fine dust through a progressively layered approach. Each stage in the airflow journey uses a different separation method gravity, misting, impact, centrifugal force, and filtration. This approach makes sure that there is no single point of failure, and every type of particle has multiple chances to be intercepted before reaching the final filter.

The multiple steps in the separation solution are:

Gravity-assisted drop and misting slow the airflow and knock out coarse grit early on.

Roof-mounted debris grill catches oversized trash, like plastic, cloth, or bottles, that bypasses the pickup head.

Primary cyclone removes silt and mid-size particles using centrifugal force.

Linear inertial separator shears out ultrafines and moisture by forcing sharp airflow direction changes.

Secondary micro-cyclone polishes the airstream, catching finer residual dust.

Engine-warmed cartridge filters capture PM10 particles while avoiding condensation buildup.

Benifits

Beyond filter protection, multi-stage separation also benefits internal component life. It keeps impellers, ducts, and filter housings cleaner by stopping abrasive grit and wet silt farther upstream. And because the airstream is cleaner, the exhaust to the atmosphere at the end is clean and safe, making CycloShieldTM not just a filter strategy, but a system-wide defense against performance degradation, premature wear, and environmental leakage.

Unlike most sweepers that rely on a single-stage filter to protect their internal systems, Stratus uses CycloShield—a six-stage filtration stack that removes harmful material before it ever reaches sensitive components. By the time air reaches the blower zone, it’s already filtered and polished. And instead of recirculating this air back into the system, risking pressure spikes and dust blowback, Stratus safely vents the clean air out to the atmosphere. This preserves the negative pressure needed to keep the pickup head sealed and dust-tight.

Benifits

With fewer abrasive particles and less moisture reaching internal parts, impellers, ducts, and filter housings face dramatically less wear. Components last longer, airflow stays stable, and the system operates with far less stress. On the environmental side, the final stage of CycloShield includes PM10-grade filtration, meaning the air released back into the environment is already cleaned. The result is a system that not only protects itself, but also the operator, the street, and the environment it works in.
Stratus improves airflow stability much earlier in the system, well before filtration begins. By integrating cyclone-based air routing and inertial separators, it helps straighten and stabilize airflow after pickup. This smooth, laminar airflow reduces turbulence and equalizes pressure before air reaches the Pulse Clean filters downstream. Additionally, not recycling the air back to the impeller helps preserve the negative pressure inside the sweeping head. While thermal conditioning of the filter bay is handled in the Pulse Clean stage by removing moisture and smoothing airflow.

Benifits

By conditioning airflow early, CycloShield prevents the chaotic, high-velocity surges that can overload filters in uneven patterns. This means no hotspots, no sudden pressure spikes, and no shock loads on the filters. It also maintains more consistent suction pressure at the pickup head, improving debris capture. The clean atmospheric exhaust and stable airflow preserve system efficiency, reduce fuel consumption, and extend the service life of downstream filtration components. Pulse Clean then builds on this foundation with thermal protection and automatic filter cleaning, making the full Stratus system more resilient, balanced, and efficient across all environments.

CycloShield isn’t just a filtration system—it’s a design philosophy built around layered defense, stable airflow, and component longevity. By managing contaminants early, conditioning the airstream intelligently, and relieving stress on every downstream part, it transforms how a sweeper performs over time. The result isn’t just cleaner streets—it’s a machine that runs smoother, lasts longer, and delivers consistent results in every environment, every shift.