Ingersoll Rand 99273906 Air Filter Element for M37 Air Compressor

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1. Product Overview

99273906 is the inlet air filter element for the Ingersoll Rand M37 screw air compressor.

It is installed inside the air filter housing at the compressor intake, upstream of the inlet valve, and serves as the first filtration barrier in the entire compressed air system. As the unit draws in outside air, dust, sand, fibers, water mist and oil mist are captured by the filter media before reaching the airend — surface filtration intercepts larger particles while depth filtration retains finer ones. Only clean air is permitted to enter the rotor meshing zone.

The condition of this element directly affects airend service life. Once unfiltered air enters the screw airend, hard particles accelerate wear on the rotors and bearings while contaminating the downstream separator element, oil filter and lubricant, shortening all three in parallel. When the element becomes severely clogged, intake volume drops, discharge volume falls and energy consumption rises; in extreme cases oil carryover can cause the airend to seize. Replacing the air filter on schedule is therefore the lowest-cost protection measure for the airend.

Key specifications at a glance

Item	Value
Part number	99273906
Description	Air filter element
Applicable model	Ingersoll Rand M37 screw air compressor
Unit discharge volume	6 m³/min @ 0.7 MPa
Element outer diameter	270 mm
Element height	120 mm
Effective filtration area	Approx. 1.3 m²
Filtration rating	2–10 µm
Filtration efficiency	≥98% for particles ≥5 µm
Initial pressure drop	Approx. 0.5–1.0 kPa
Alarm resistance	6.0–6.5 kPa
Recommended replacement interval	Approx. 2,000 hours (adjust to operating conditions)

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2. Basic Parameters

Parameter	Details
Part number	99273906
Brand	Ingersoll Rand
Product name	Air filter element
Product category	Inlet filtration (air filter)
Applicable model	M37 screw air compressor (see Section 6)
Unit discharge volume	6 m³/min @ 0.7 MPa
Installation position	Inside air filter assembly at intake, upstream of inlet valve
Replacement interval	Approx. 2,000 hours

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3. Technical Specifications

3.1 Filtration Performance (Core Indicators)

Parameter	Value / Notes	Data nature
Filtration rating	2–10 µm	Industry value (sources cite 2–10, 3–12, 5–10, 10–15 µm; mainstream overlap range taken)
Filtration efficiency	≥98% for particles ≥5 µm	Industry value
Filter class	HVAC filter classification (EN 779 G/M/F) does not apply; air filters are characterized per ISO 5011 by efficiency + intake resistance + dust holding capacity	Technical note
Dust holding capacity	Approx. 380 g	Estimated (effective area 1.3 m² × typical wood pulp filter paper capacity 300 g/m²)
Beta ratio (β value)	Not applicable to air filters	Not applicable; see note below

About the beta ratio: The β value is a hydraulic and lubricating oil filter indicator determined per ISO 16889 multi-pass testing, characterizing the filtration ratio at different particle sizes. Air filters are not characterized by β value but evaluated per ISO 5011 using filtration efficiency + intake resistance + dust holding capacity. If a beta ratio appears in an air filter specification, it has typically been copied by mistake from a hydraulic filter data sheet.

3.2 Flow and Resistance Parameters

Parameter	Value / Notes	Data nature
Rated air flow	Matches M37 unit discharge 6 m³/min @ 0.7 MPa	Multi-source (unit parameter)
Filtration face velocity	Approx. 0.077 m/s	Estimated (6 m³/min ÷ 1.3 m², within the normal 0.05–0.15 m/s range for air filters)
Initial pressure drop	Approx. 0.5–1.0 kPa	Estimated (based on face velocity and wood pulp filter paper resistance characteristics)
Operating differential pressure range	Approx. 1.0–6.0 kPa	Estimated (full range from new element initial resistance to alarm resistance)
Alarm / final resistance	6.0–6.5 kPa	Estimated (per unit air filter differential pressure indicator alarm setting; refer to the machine for specifics)
Pressure drop vs. energy	Each 1 kPa rise in intake resistance increases unit energy consumption by approx. 1%	Estimated; calculation below

Quantitative relationship between pressure drop and energy (estimated)

Based on M37 discharge pressure of 0.7 MPa (gauge) and atmospheric pressure of 101.3 kPa, intake resistance raises the compression ratio:

Intake resistance	Compression ratio	Relative energy increase vs. baseline
0 kPa (new element)	7.91	Baseline
2 kPa	8.07	+2.0%
4 kPa	8.24	+4.1%
6 kPa (near alarm)	8.41	+6.3%

Engineering implication: As an element goes from new to alarm condition (0 → 6 kPa), unit energy consumption rises by approximately 6% over the interval. For a 37 kW unit running 6,000 hours per year, this represents sustained excess power draw during the latter part of the element's life. The money saved by continuing to run a clogged element is far less than the extra electricity paid — this is the engineering rationale behind the factory differential pressure alarm.

3.3 Dimensions and Installation Parameters

Parameter	Value / Notes	Data nature
Overall dimensions	270 mm OD × 120 mm height	Multi-source consistent
Construction	Pleated (folded filter paper wound)	Industry value
Effective filtration area	Approx. 1.3 m²	Estimated (based on 270 mm OD / 200 mm ID / 35 mm pleat depth / approx. 154 pleats; approx. 1.7 m² if ID is 165 mm)
Number of pleats	Approx. 150	Estimated
Pleat spacing	Approx. 4.8 mm	Estimated (average circumference 738 mm ÷ 150 pleats)
Mounting interface	End cap located, matched to M37 air filter assembly	Based on model compatibility
Sealing method	Face seal (axial compression)	Estimated (common form for this air filter construction; refer to actual part)

Procurement tip: When cross-checking a replacement, 270 mm outer diameter and 120 mm height are the two most direct comparison dimensions. The same-series ML37 / MU37 models use 39588777 (130 mm OD × 250 mm height) — the size difference is substantial and the two are not interchangeable.

3.4 Material Composition

Parameter	Value / Notes	Data nature
Filter media	Imported wood pulp filter paper (industry commonly uses US HV or Korean Ahlstrom paper)	Industry value
Media grammage	Approx. 130 g/m²	Estimated (midpoint of the typical 100–150 g/m² range for air filter paper)
Inner and outer support	Galvanized steel perforated support, approx. 0.6 mm thickness, open area ≥45%	Estimated (common practice for comparable products)
End caps	Metal end caps (galvanized steel sheet) + polyurethane adhesive	Estimated (no plastic end cap specified for this series)
Seal	Nitrile rubber (NBR) seal ring	Estimated (common material for compressor intake parts, oil and temperature resistant −30 to +100 °C)
Bonding layer	Polyurethane (PU) hot-melt adhesive	Estimated (common process for bonding media to end caps/support)

3.5 Operating Condition Tolerance

Parameter	Value / Notes	Data nature
Operating temperature	−10 to +100 °C	Industry value
Relative humidity	≤80% RH, no condensation	Estimated (wood pulp filter paper loses strength and efficiency when damp; condensation conditions require upstream water removal)
Bursting strength	Filter paper bursting strength approx. 200–400 kPa (per ISO 2758 paper bursting strength test)	Estimated (typical range for air filter paper)
Collapse resistance	Element designed for differential pressure ≥10 kPa	Estimated (approx. 50% safety margin over the 6.5 kPa alarm value)
Special functions	No flame-retardant, anti-static or moisture-proof specification noted for this model	—

3.6 Service Life and Maintenance Parameters

Parameter	Value / Notes	Data nature
Service life	Approx. 2,000 hours	Industry value (multi-source consistent)
Actual replacement interval	Shorten to under 1,000 hours in dusty, sandy or humid environments; follow the differential pressure alarm	Engineering recommendation
Storage shelf life	Approx. 2–3 years (unopened, dry and ventilated conditions)	Estimated (typical validity for filter paper and adhesives under controlled storage; moisture or direct sunlight significantly shortens it)

3.7 Applicable Standards

Item	Details
Applicable product standard	ISO 5011 (inlet air cleaning equipment for internal combustion engines and compressors — performance testing), evaluated by filtration efficiency, intake resistance and dust holding capacity
Commonly cited test standards	ISO 2941 / 2942 / 2943 / 3723 / 3724 / 3968
Standard applicability note	The above ISO 29xx / 37xx series are in fact general test methods for hydraulic transmission filter elements (collapse/burst resistance, structural integrity, material compatibility, axial load, flow fatigue, pressure drop vs. flow characteristics). If a supplier can only provide hydraulic filter standards, request ISO 5011 or the original specification sheet as a supplement.

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4. Standard Maintenance and Installation Steps

Manpower: single-person operation, approximately 20–30 minutes.

1. Shut down, isolate power and release pressure
   Press the emergency stop or shutdown button, disconnect the main power and apply lockout/tagout. Open the receiver tank drain valve to release system pressure and wait until the pressure gauge on the separator tank reads zero. Criterion: gauge reads 0 and no residual air flow is audible.

2. Locate and open the air filter housing
   The M37 filter assembly is at the intake end of the unit. Loosen the housing clamp or end cap bolts and remove the end cap. Criterion: end cap not deformed, clamp not seized; if the clamp is seized, address it before removal.

3. Remove the old element and inspect its condition
   Pull the old element straight out and observe dust distribution and media condition. Criterion: if the media shows damage, perforation, end cap debonding or a flattened sealing face, replace immediately even if the interval has not been reached; if the outer surface carries black oil sludge, intake oil mist is abnormal and the upstream environment should be checked.

4. Thoroughly clean the housing interior
   Wipe the housing inner wall and base with a lint-free cloth. Do not blow compressed air forcefully into the housing interior (this drives dust into the intake passage). Criterion: no loose dust on the inner wall, sealing face flat and free of debris.

5. Verify the new element
   Compare old and new parts: 270 mm outer diameter, 120 mm height, face seal strip complete without gaps, media undamaged. Criterion: all three dimensions and appearance conform; if any item does not match, do not install — recheck the part number.

6. Install the new element and refit the end cap
   Place the new element vertically into the housing, confirming it seats fully at the bottom and the sealing face contacts without trapped material. Refit the end cap and tighten the clamp or bolts evenly in a diagonal sequence. Criterion: even gap between end cap and housing, no visible skew.

7. Start-up check
   Restore power and run the unit for 5–10 minutes. Criterion: no abnormal whistling or intake air noise at the intake (abnormal noise usually means the seal is not compressed or the element is not seated); the air filter differential pressure indicator is in the green zone.

The single iron rule of installation: Never start the unit before the element is seated. Starting with no element or an uncompressed seal allows completely unfiltered air into the airend, causing irreversible wear in a short time.

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5. Frequently Asked Questions

Are 99273906 and 39588777 interchangeable?
No. 39588777 corresponds to the ML37 / MU37 models, with element outer diameter 130 mm and height 250 mm; 99273906 corresponds to the M37, with outer diameter 270 mm and height 120 mm. The size difference is more than double and they physically will not fit the same housing. When ordering, verify both the model and the part number.

How often should it be replaced?
Approximately 2,000 hours under standard conditions. This figure is not a hard deadline: in high-dust environments (cement, foundry, woodworking, mining sites) shorten it to under 1,000 hours; in clean environments with short running hours it may be extended appropriately. The most reliable approach is to follow the air filter differential pressure indicator and replace when it reaches the alarm position.

What happens if it is not replaced?
Failure propagates through the chain and has a clear economic cost. As dust accumulates, intake resistance rises; based on compression ratio estimates, energy consumption increases by approximately 6.3% as resistance goes from 0 to 6 kPa. Once the media is damaged or the seal fails, unfiltered air enters the airend directly, and dust contaminates the screw rotors, bearings, separator element, oil filter and lubricant simultaneously — escalating repair cost from the price of one filter to the scale of an airend overhaul.

How do I know it is time to replace?
Three signals: first, the differential pressure indicator enters the alarm zone (approximately 6.0–6.5 kPa); second, after shutdown the element shows a media surface fully covered with dust so the original pleat pattern is no longer visible; third, the unit shows reduced discharge volume with rising current/energy consumption. Replace on any one signal.

Can the element be cleaned and reused?
Not recommended. This is a pleated paper element designed as a single-use part. Back-blowing with compressed air from inside out only removes surface dust; fine particles trapped in the depth of the media cannot be cleared, and back-blow pressure can easily fracture fibers or deform pleat spacing, creating invisible channels that let unfiltered air pass through. Reusing a cleaned element is a "looks clean, actually failed" condition — the risk outweighs the benefit.

What else should be checked when replacing the air filter?
Recommended checks: whether the air filter differential pressure indicator still responds correctly (does it return normally after being pressed to reset), whether the intake hose is cracked or loose, whether the housing seal ring is aged, and whether the inlet valve operates correctly. These parts work together with the air filter; replacing only the element without checking the surroundings can quickly lead to intake problems again.

Is this element a genuine part?
The 99273906 described on this page is an Ingersoll Rand original part number. When ordering, verify against the part number itself — the part number is the only identity that cannot be confused. Do not order based solely on "fits M37" or visual similarity.

Do M37 and other M-series models use the same air filter?
No. Air filter specifications differ across Ingersoll Rand M-series models: M22 uses 39588470 (130 mm OD), M37 uses 99273906 (270 mm OD), M55 uses 39708466 (278 mm OD), ML37 uses 39588777. Being in the same series does not mean the same element — each model must be verified individually.

What is the most error-prone step during installation?
Two: first, compressing the end cap with material trapped at the sealing face or with the element not fully seated, causing a poor seal and air leakage; second, tightening end cap bolts in a one-sided sequence, causing uneven loading and skew. The correct approach is to confirm seating, then tighten evenly in a diagonal cross pattern in stages.

Are there storage requirements for new elements?
Yes. Filter paper swells and deforms when damp, reducing filtration efficiency, and the metal support corrodes with moisture. Store on indoor shelving in a dry, ventilated area, away from walls and floors, and away from water and oil contamination. Use within 2–3 years in unopened condition. Follow first-in-first-out with unopened packaging; long-term stockpiling is not recommended.

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6. Compatible Machine Models

No.	Model	Unit discharge volume	Air filter part number	Element OD × height
1	M37	6 m³/min @ 0.7 MPa	99273906	270 mm × 120 mm
2	M22	3 m³/min @ 0.7 MPa	39588470	130 mm × 151 mm
3	M55	10 m³/min @ 0.7 MPa	39708466	278 mm × 125 mm
4	ML37 / MU37	6 m³/min @ 0.7 MPa	39588777	130 mm × 250 mm
5	30S	3 m³/min @ 0.7 MPa	42855429	130 mm × 123 mm
6	50S	6 m³/min @ 0.7 MPa	42855411	216 mm × 318 mm
7	75S	10 m³/min @ 0.7 MPa	42855403	278 mm × 251 mm

How to read this table

• The product on this page, 99273906, corresponds to row 1, M37; the other rows are provided as same-series model references to help you avoid mis-purchase.
• Row 4 (ML37 / MU37) and row 1 (M37) both have 6 m³/min discharge volume, but the air filter part numbers and dimensions are completely different — the same discharge volume does not mean a common element. This is the most easily confused point in this series.
• If your unit nameplate model is not listed above, please provide a photo of the unit nameplate and the full model number; we will confirm by reverse part number lookup before ordering.

Note on model generations

Ingersoll Rand M37 units exist in different production generations. The 99273906 described on this page is the inlet filter for early M37 models. Newer M37-75 series units (corresponding to the SL/SM37-75KW operation parts manual) use a different part number system in their parts manual. If your unit is a recent machine, verify against the parts manual supplied with the unit, or contact us to confirm by unit serial number. In practice, the most reliable confirmation is still to read the part number from the old element itself.

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7. Related Components

Seven components in the M37 intake and lubrication system are maintained on the same cycle as the air filter. They are listed below by location, function and inspection points; for specific part numbers, refer to the unit parts manual.

Component	Location	Function	Inspection points
Oil filter element	Main oil circuit, between cooler and airend	Removes wear debris and sludge from lubricant, protecting bearings and rotors	Replace together with the air filter; after replacement check the housing sealing face for oil seepage
Separator element	Inside the separator tank	Separates oil mist from compressed air and returns oil, controlling discharge oil carryover	When replacing, also check whether the oil return line is blocked (poor oil return directly causes excessive discharge oil carryover)
Air filter differential pressure indicator	On the air filter assembly	Indicates element clogging level and signals replacement timing	Should return normally after being pressed to reset; a reading that never moves indicates failure and should be replaced
Coolant filter element	Coolant circuit, between cooler and filter	Keeps coolant clean, preventing scale and wear debris deposits	Replace together with the oil filter element
Thermostatic control valve element	Between cooler and filter	Controls whether coolant passes through the cooler, maintaining airend operating temperature	If the unit runs cold for long periods or triggers a high-temperature alarm, check the thermostatic valve first
Breather filter	On the separator tank	Balances tank pressure and prevents external dust from entering the oil circuit	Inspect on the same cycle as the air filter; shorten the interval in dusty environments
Intake hose and housing seal ring	Between air filter assembly and airend	Ensures the intake path has no leakage or unfiltered air bypass	Check for cracks, aging and loose clamps — bypass leakage is as harmful as running without an element

Recommended group replacement: At sites with heavy dust, we recommend replacing the air filter + oil filter element + separator element as a set to avoid staggered maintenance intervals and repeated downtime. The coolant filter element and thermostatic valve element follow their own separate schedules.