At a glance
- Type
- Compressed-air filtration
- Grades
- Three grades (C, T, A) in one series
- Flow range
- 1.6 – 410 m³/min
- Housings issued
- 66 models (22 flow steps × 3 grades)
- Elements issued
- 30 models (10 flow steps × 3 grades)
- Envelope
- Common across grades at a given flow step
Overview
PUREPART PF is the SIND compressed-air filter range. It is one series carrying three grade letters — C, T and A — not three separate products. Housings combine a flow figure and a grade letter — for example PF-6C, where the flow figure is rated throughput in m³/min and the grade letter sets the removal duty. Replacement elements carry an -E suffix, for example PF-6C-E. The issued list holds 96 entries: 66 housings and 30 elements, covering 22 flow steps from 1.6 to 410 m³/min.
Model range
PUREPART PF covers 22 flow steps from 1.6 to 410 m³/min in three grades (C, T, A). The issued list holds 66 housings and 30 elements.
C-grade
Coalescing filter
- Removes
- Oil aerosol and liquid water
- Position
- First stage
- Housings
- 22 models (1.6 – 410 m³/min)
T-grade
High-efficiency particulate
- Removes
- Dry particulate, rust, desiccant fines
- Position
- Second stage or standalone
- Housings
- 22 models (1.6 – 410 m³/min)
A-grade
Carbon adsorption
- Removes
- Oil vapour
- Position
- Third stage (behind coalescing)
- Housings
- 22 models (1.6 – 410 m³/min)
Technology
Technology Platform
PurePart PF uses coalescing and particulate filtration to remove contaminants from compressed air. Compressed air flows through a filter element; contaminants are captured by the filter media. The three grades remove different contaminants:
Three Grades, One Series
PurePart PF is one series with three grade letters — not three separate product families. The housing envelope is common across the three grades at a given flow step. For example, PF-17C, PF-17T and PF-17A share the same housing dimensions and pipework connections.
Multi-Stage Filtration
Compressed air filtration is typically multi-stage. One filter cannot do all three jobs (coalescing, particulate, carbon adsorption) — three duties means three stages in series. The correct arrangement is:
More technical detail
Technology Platform
- C-grade — coalescing filter. Removes oil aerosol and liquid water. The filter media coalesces small oil droplets into larger droplets, which then drain away. C-grade is the first stage of filtration, installed upstream of the dryer or as the first stage in a multi-stage filtration system.
- T-grade — high-efficiency particulate filter. Removes dry particulate (dust, rust, desiccant fines) and residual oil aerosol. T-grade is installed downstream of C-grade or as a standalone particulate filter for general plant air.
- A-grade — carbon adsorption filter. Removes oil vapour by adsorption onto activated carbon. A-grade is installed downstream of a coalescing stage — carbon must sit behind a coalescing filter, because liquid oil saturates the carbon bed rapidly. A-grade is specified for oil-sensitive applications (food, pharmaceutical, electronics).
Three Grades, One Series
This architecture simplifies installation and maintenance. The housing is a permanent installation; the element is the consumable. When the duty changes, the housing stays and the element is swapped.
Multi-Stage Filtration
The finest stage must not be placed first. A-grade placed upstream of C-grade would be saturated by oil aerosol and liquid water, rendering it ineffective within hours.
- First stage: C-grade (coalescing) — removes oil aerosol and liquid water. Protects the downstream stages from bulk liquid and oil.
- Second stage: T-grade (particulate) — removes dry particulate and residual oil aerosol. Protects the carbon stage from particulate loading.
- Third stage: A-grade (carbon) — removes oil vapour. Only required for oil-sensitive applications. Must sit behind a coalescing stage — liquid oil saturates the carbon bed rapidly.
Element Replacement and Differential Pressure
Filter elements are consumables. They load up with contaminants over time and must be replaced. Element replacement is based on differential pressure, not the calendar. As the element loads, the pressure drop across it increases. When the differential pressure reaches the maximum allowable value, the element is replaced.
Differential-pressure indication is strongly recommended on every stage. Without it, you cannot tell when the element is loaded — and a loaded element increases energy cost (pressure drop) and may fail catastrophically (element collapse, contaminant release).
Exception: carbon (A-grade) elements are changed on a schedule set from the duty, because a saturated carbon bed shows no rising differential pressure. Carbon adsorption does not increase pressure drop — the carbon simply stops removing oil vapour when saturated.
Sizing on Actual Flow
Size the filter on actual delivered flow at the point of installation in m³/min, not the compressor nameplate. Compressor nameplate flow is typically rated at standard conditions (1 bar(a), 20 °C). Actual flow at operating pressure is lower — and the filter must handle the actual flow, not the standard flow.
The 22 flow steps (1.6 to 410 m³/min) are not a uniform increment. Do not interpolate a size — choose the flow step at or above your actual flow.
Selection Logic
PurePart PF selection is based on four parameters:
Pick the flow step at or above your actual flow, then confirm the grade letter against the duty with SIND.
- Actual flow at the point of installation (m³/min): size on actual flow at operating pressure, not the compressor nameplate.
- Operating pressure (bar(g)): affects the actual flow and the housing pressure rating.
- Air-quality duty: determines the grade (C, T or A) and the number of stages required.
- Inlet condition upstream: determines the pre-filtration required (e.g., if oil aerosol is present, C-grade must be first).
Selection & quote checklist
- Actual flow at the point of installation (m³/min): size on actual flow at operating pressure, not…
- Operating pressure (bar(g)): affects the actual flow and the housing pressure rating.
- Air-quality duty : determines the grade (C, T or A) and the number of stages required.
- Inlet condition upstream : determines the pre-filtration required (e.g., if oil aerosol is present, C-grade must…
FAQ
How do I select?
State actual flow at the point of installation in m³/min, operating pressure, the air-quality duty, and the inlet condition upstream. Pick the flow step at or above your actual flow, then confirm the grade letter against the duty with SIND.
Are C, T and A three different series?
No. Three grades inside one series, PurePart PF. The housing envelope is common across the three grades at a given flow step. Changing the duty does not change the pipework footprint — only the element inside the housing changes.
Can one filter do all three jobs?
No. Three duties means three stages in series. Carbon must sit behind a coalescing stage, and the finest stage must not be placed first. The correct arrangement is C-grade (first) → T-grade (second) → A-grade (third, if required).
When is an element changed?
On differential pressure, not the calendar. Change carbon on a schedule set from the duty, because a saturated carbon bed shows no rising differential pressure. Differential-pressure indication is strongly recommended on every stage.
Can I fit another maker’s element?
Interchangeability is unverified and no cross-reference is published. Order against the full SIND element model string (e.g., PurePart PF-17C-E).
More questions
What if I need a size above 23 m³/min?
Housings are issued up to 410 m³/min. Element coverage stops at 23 m³/min. Above that, element availability is available on request. Contact SIND for the current coverage.
Ownership & service
Energy, maintenance and service
Target Industries and Markets
PurePart PF is specified wherever compressed air quality matters:
- General plant air — T-grade particulate filtration for general industrial applications.
- Painting and coating — C-grade + T-grade to prevent oil and particulate from causing surface defects (fish eyes, blushing, inclusions).
- Food and beverage — C-grade + T-grade + A-grade for oil-free air quality.
- Pharmaceutical — C-grade + T-grade + A-grade for oil-free air quality.
- Electronics and semiconductor — C-grade + T-grade + A-grade for oil-free, particle-free air.
- Instrument and control air — T-grade to prevent particulate from damaging valves and actuators.
- Laser cutting assist air — C-grade + T-grade to prevent contamination of the assist air.
- Pneumatic conveying — T-grade to prevent particulate from contaminating the conveyed product.
- Workshop point-of-use filtration — T-grade for general workshop air.
Energy and Total Cost of Ownership
Compressed-air filters are low-cost items, but they have a significant impact on total cost of ownership:
- Energy cost — a loaded filter element increases pressure drop, which increases the compressor’s specific power and energy cost. A filter with 200 mbar pressure drop costs significantly more in energy than one with 50 mbar. Differential-pressure indication ensures elements are replaced before pressure drop becomes excessive.
- Element cost — elements are consumables. Element life depends on inlet condition (contaminant loading) and operating hours. Budget element replacement as a recurring maintenance cost.
- Cost of poor air quality — in painting, food, pharmaceutical and electronics applications, poor air quality causes product rejection, batch loss, surface defects or regulatory non-compliance. The cost of poor air quality typically far exceeds the cost of filtration. Proper filtration removes this risk.
Specifications are typical values. The grade definition is the final authority — confirm the grade letter against your duty before ordering.
