Franklin Miller vs Smith & Loveless Grit Removal Equipment
Franklin Miller vs Smith & Loveless Grit Removal Equipment
Introduction
Inorganic solids cause expensive damage downstream of the headworks. Eroded impellers, reduced digester capacity and abrasive wear on dewatering equipment cost utilities significant money in preventable maintenance. Yet headworks design frequently suffers from copy-paste specifications that ignore the hydraulic profile and grit characteristics of the actual influent. A common decision point involves comparing Franklin Miller vs Smith & Loveless Grit Removal Equipment.
The comparison involves two different roles in the preliminary treatment train, and clarity about that matters. Smith & Loveless is a grit removal manufacturer, widely known for the PISTA line of forced vortex grit systems. Franklin Miller builds solids reduction and screening equipment — TASKMASTER grinders, SCREENMASTER screens and the SPIRALIFT screw screen series, which screens, washes, conveys and dewaters screenings. Grit separation does not appear in their published product range.
Improper specification at this stage is costly. A grit system capturing only a fraction of the abrasive material allows the rest into secondary treatment, where it accumulates in digesters, reduces volatile solids reduction capacity and forces expensive tank cleanouts. This article analyzes both manufacturers’ equipment in terms of what each actually does in the headworks.
Broader supplier positioning is covered in our overview of the top OEMs for grit removal systems.
How to Select / Specify
Duty Conditions & Operating Envelope
The primary driver is the ratio between minimum daily flow and peak wet weather flow. Forced vortex systems maintain efficiency across a broader hydraulic range because paddle-driven rotation provides separation force independent of influent velocity. Systems relying on gravity settling must be sized for peak hydraulic load to prevent washout, which means oversizing for average conditions.
Characterize the grit itself. Is the target 95 percent removal of 150-micron particles at specific gravity 2.65? Or does the influent carry shell material and lighter organic-coated grit at markedly lower effective density? Forced vortex systems capture fine, high-density particles effectively through induced rotational force. Screening equipment operates on an entirely different principle — physical capture on a perforated barrier — and removes screenings rather than settled grit.
Materials & Compatibility
Grit is abrasive and longevity depends on material hardness and corrosion resistance.
- Vortex internals: Specify stainless steel internals; the floor and lower cone are high-wear zones. Some designs use concrete structures with embedded wear plates, others prefabricated steel vessels.
- Auger and screw components: In screw-based equipment, flighting is the critical wear point. Specify abrasion-resistant alloys or replaceable wear shoes. Shaftless spirals eliminate the submerged bottom bearing — a notorious failure point — but require robust liners to prevent trough wear.
- Corrosion: Headworks carry high hydrogen sulfide. Stainless is the baseline; coated carbon steel eventually fails under combined abrasion and corrosion.
Hydraulics & Process Performance
The core performance metric for grit removal is the cut point — the particle size at which the system achieves its specified removal efficiency.
Analyze headloss curves. Vortex systems introduce headloss to generate rotational velocity; that headloss is parasitic energy but essential to the process. Where the plant has a limited hydraulic grade line, this becomes a deciding constraint. Screening equipment introduces its own headloss profile and draws electrical energy for the drives.
Installation Environment & Constructability
Vortex units are frequently installed as packaged steel systems on concrete pads or integrated into civil works, with a relatively compact footprint for the volume treated.
Screw screens are linear and elongated. They suit retrofits into existing channels where linear space is available but depth is constrained. Constructability review should include crane access for removing heavy screw assemblies or drive motors during overhauls.
Reliability & Failure Modes
- Vortex systems: Failure is rarely in the chamber itself. The failure points are ancillary — the top-mounted drive, the priming system for the grit pump, or the grit pump. If the grit pump clogs, the chamber fills and the process blinds.
- Screw-based screening: Primary failure modes involve the screw — flight wear, liner wear, or jams from large debris. Redundancy strategy focuses on spare drive assemblies and modular liner sections.
Maintainability, Safety & Access
Grit systems sit in headworks buildings with potential hydrogen sulfide exposure. Systems requiring channel entry for routine maintenance are less desirable.
Vortex designs generally prioritize top-side access — elevated drive, top-mounted or dry-pit pump. Screening equipment also prioritizes accessibility through pivot-out designs and accessible covers, though checking a bottom liner on a screw conveyor usually requires draining the unit and confined space entry.
Lifecycle Cost Drivers
Vortex systems typically command higher capital cost owing to the fluid mechanics design and proprietary internals, but deliver lower operating cost through better capture efficiency and drier grit, reducing downstream and disposal costs. Screw-based equipment may carry lower initial cost with higher maintenance burden related to physical wear over two decades.
Energy analysis must include the grit pump and classifier, not just the drive motors. And the lifecycle model must include hauling cost for wet versus dry material, which is frequently the largest single operating difference.
Comparison Tables
Table 1: Technology & Maintenance Profile
| Criteria | Smith & Loveless (PISTA forced vortex) | Franklin Miller (grinders, screens, screw screens) |
|---|---|---|
| Primary technology | Forced hydraulic vortex using rotating paddles to enhance separation | Solids reduction and screening with screw conveyance, washing and dewatering |
| What it removes | Settled inorganic grit, separated from organics | Rags, plastics, debris and other screenings captured on a perforated barrier |
| Capture mechanism | Induced rotational force directs solids to a center hopper; lighter organics are carried out | Physical capture on the screen basket, with brush conveyance and spray washing |
| Typical headloss | Moderate to high, required to induce vortex action | Low to moderate, primarily channel flow friction |
| Organic separation | High efficiency through the flow path separating organics from grit | Spray washing returns organics to the flow while retaining screenings |
| Maintenance hotspots | Priming systems, grit pumps, drive gearboxes | Screw flights, trough liners, brushes, drives |
| Wear components | Pump impellers and volutes, vortex paddle blades | Screw flighting, wear shoes, brushes, trough liners |
Table 2: Application Fit Matrix
| Application | Appropriate Equipment | Engineering Rationale |
|---|---|---|
| High flow variability | Smith & Loveless forced vortex | Paddle-driven rotation maintains separation force across a wider flow range than gravity settling |
| Restricted footprint, new build | Smith & Loveless vortex | Vertical orientation and high-rate loading deliver more treatment per square foot |
| Rag and debris removal | Franklin Miller screens or screw screens | Grit systems do not remove rags; screening is a distinct and necessary duty |
| Pump protection in a wet well | Franklin Miller grinder or vertical screw screen | Conditioning or removing fibrous material where grit equipment is impractical |
| High rag content ahead of grit removal | Both, in sequence | Vortex chambers require robust upstream screening; ragging fouls ports and pumps |
| Screenings volume reduction | Franklin Miller washer compactor | Washing and compacting cuts disposal weight substantially |
Engineer & Operator Field Notes
Commissioning & Acceptance Testing
The most common oversight in commissioning grit systems is the absence of valid performance testing. Many specifications call for a removal percentage at a defined mesh, but few projects budget for the sand seeding test required to verify it.
During factory testing, focus on control logic. For vortex systems, verify the priming sequence — a common nuisance alarm source. For screw-based equipment, verify torque overload settings stop the drive before mechanical damage occurs during a jam.
Common Specification Mistakes
A frequent error with vortex systems is neglecting the grit pump piping run. If the suction line is too long or carries air pockets, the priming system struggles, producing intermittent removal and hopper compaction. Locate the pump as close to the grit hopper as possible.
For screw-based equipment, engineers routinely under-specify liner material. Standard steel liners corrode and wear quickly. Demand wear bars or UHMW polyethylene liners with visual wear indicators. Failing to specify a spray wash system leaves putrescible organics discharging with the captured material, producing odor complaints at the dumpster.
A third error is expecting screening equipment to remove grit. It does not. Where the treatment train needs grit separation, specify grit separation equipment.
O&M Burden & Strategy
- Daily: Check for abnormal noise in gear reducers. Inspect the dumpster visually — gray or black indicates organics, tan indicates clean grit.
- Monthly: Check belt tension on drives. Grease bearings; automatic greasers are worthwhile for hard-to-reach points.
- Annually: Measure wear on screw flights or vortex paddles. Check gearbox oil quality.
Vortex systems require less daily operator interaction but higher skilled labor for pump and priming troubleshooting. Screw-based systems are mechanically simpler to understand but require more physical cleaning and liner monitoring.
Troubleshooting
High organic content in the grit dumpster
- Vortex: Paddle speed too slow, or grit pump cycle too short and pumping excess water
- Screw: Spray wash pressure too low, or screw speed too fast to allow drainage
- Fix: Adjust timer and drive settings; optimize the washing cycle
Grit accumulating in upstream channels
- Cause: Channel velocity dropping below the level needed to keep grit in suspension
- Fix: This is a hydraulic profile design error. Aeration or channel narrowing may be required to convey grit to the removal device.
Design Details / Calculations
Sizing Logic
Surface overflow rate governs settling: SOR = flow rate divided by surface area. Conventional settling operates within a modest range; vortex systems achieve higher apparent rates because induced rotation effectively increases the separating force acting on the particle.
Detention time: Vortex systems require sufficient detention at peak flow for the secondary circulation that separates organics from grit to establish. Too short and separation fails; too long and organics settle with the grit.
Specification Checklist
- Motor service factor: Minimum 1.15 to account for heavy starting torque against settled grit
- PLC integration: Non-proprietary code accessible to the plant’s SCADA team; avoid black box controllers
- Material certification: 316L stainless for wetted metal parts in the grit chamber
- Spare parts: Mandate a commissioning spares kit and a multi-year operational spares kit covering wear shoes, pump seals and belts
Standards
Reference AWWA standards for coating systems and Hydraulic Institute standards for the grit pumps. Electrical components should be NEMA 4X, or explosion-proof where installed in classified areas, which is common in headworks buildings.
FAQ Section
Does Franklin Miller make grit removal equipment?
Their published range covers grinders, crushers, shredders, screens, mills and septage receiving systems. The SPIRALIFT series is a screw screen that screens, washes, conveys and dewaters screenings — it is not a grit separation device. Smith & Loveless is the grit removal manufacturer in this pairing. The two lines of equipment are complementary rather than competing.
What is the difference between forced and free vortex grit removal?
A forced vortex uses a mechanical paddle to induce a specific velocity and flow pattern, maintaining separation force regardless of influent flow rate. A free vortex relies solely on the hydraulic energy of the incoming water to create the swirl, and loses efficiency significantly at low flows. Forced vortex systems hold efficiency across a wider operating envelope.
How is shell material handled?
Shells are problematic because they are flat and settle differently from spherical sand. Conservative sizing at a lower surface overflow rate helps. Because shells are lighter than silica, agitation must be tuned carefully to avoid resuspending them while still washing off organics.
What is the typical lifecycle of a grit pump impeller?
In grit service, impellers are sacrificial and replacement is measured in a few years depending on grit load and abrasiveness. Recessed impeller designs common in vortex packages extend that life because grit does not strike the vanes as directly as in a standard centrifugal pump.
Can these systems be retrofitted into existing aerated grit chambers?
Yes. Existing concrete tanks are often reused as the settling zone with new equipment installed to convey settled grit out. Vortex manufacturers also offer retrofit configurations designed to fit existing civil footprints, though these may require concrete modification to create the necessary geometry.
Why is organic capture undesirable?
The goal is removing inorganic solids while leaving organics in the water for biological treatment. A system capturing excessive putrescible matter produces a dumpster that smells, attracts vectors, and costs more in tipping fees for wet waste. Vortex designs scour organics through the induced flow path; screening equipment relies on spray washing to return organics to the stream.
Conclusion
Key Takeaways
- Different duties: Smith & Loveless separates grit; Franklin Miller reduces and screens solids. A complete headworks needs both.
- Test with sand: Never accept a grit system on native grit testing alone. Mandate a sand seeding test.
- Characterize the grit: Lighter, organic-coated grit requires derated sizing.
- Maintenance trade-off: Vortex concentrates maintenance on pumps and priming — higher skill. Screening concentrates it on liners and screws — more physical labor.
- Washing determines cost: Whatever the removal method, the washing stage drives odor and disposal expense.
The decision in Franklin Miller vs Smith & Loveless Grit Removal Equipment is not about finding a better brand but about matching each technology to its proper place in the treatment train. Smith & Loveless has defined the forced vortex grit market, offering high-efficiency capture in a compact footprint suited to variable flows. Franklin Miller brings solids reduction and screening expertise that protects that grit equipment from the rags and debris which would otherwise foul it.
Characterize the influent grit, calculate available hydraulic head, and assess the maintenance team’s capabilities realistically. Related comparisons appear in our analyses of Franklin Miller and Hydro International, Smith & Loveless and Egger Turbo, and JWC Environmental and Franklin Miller.