Kaeser SK Series

Name: Kaeser SK Series
Brand: Kaeser

Direct-drive oil-flooded rotary screw in the 15–25 hp class. Sigma Profile airend, air-cooled, targeted at machine shops and small manufacturing.

Type

Oil-flooded rotary screw

Power

15–25 hp (11–18.5 kW)

Flow

40–130 cfm @ 110 psig (depending on frame & pressure)

Pressure

110–217 psig (8–15 bar)

Cooling

air

Drive

direct

Lubrication

oil-flooded

Models

SK 15, SK 20, SK 25, SK 26T

Years produced

~2013 – present. Replaces SM 15/17/22 in the small-frame slot.

Sound level

~63–66 dB(A) @ 1 m (enclosed).

Dimensions

SK: ~30" W × 35" D × 47" H (frame); SK 26T: ~57" L × 30" W × 66" H with tank & dryer.

Weight

~570–900 lb (259–408 kg) depending on frame / package.

Ambient range

40–115 °F (4–46 °C).

Motor efficiency

IE3 / NEMA Premium TEFC standard.

Starter

Wye-Delta on 20/25 hp; DOL on 15 hp; Y-Δ standard.

Integrated dryer

SK 26T ships with integrated Kaeser refrigerated dryer & receiver.

Warranty

5-year airend limited / 2-year package (typical; verify at purchase).

Replaces

Kaeser SM 15 / SM 17 / SM 22

Control modes

Dual
Quadro
Vario
Continuous
Dynamic
Automatic

Typical applications

Machine shops
Small OEM assembly lines
Auto body / paint booths (with proper filtration)

Specs & intervals below are from publicly published OEM literature and long-standing field practice. Torque values, exact revision-dated part numbers, and safety-critical settings vary by serial number — always cross-check the unit’s OEM manual and nameplate before ordering parts or performing service.

Fluid

Spec: Kaeser Sigma Fluid S-460 (or approved semi-synth per OEM chart)

Capacity: ~5–8 gal depending on frame

Change interval: 8,000 hr / 2 yr with S-460

Do not blend fluids. Cold-climate installs may require lower-viscosity spec.

Approved alternatives

Sigma Fluid SR (food-grade H1)
Sigma Fluid FG-460 for stringent food applications

Torque guidance

Head / manifold torque: see OEM manual per frame. Motor lugs: 45–120 in-lb depending on AWG. Never torque cast-iron manifold blind.

Always verify torque values against the OEM service manual for the specific serial number.

Wear parts

Category	Interval	Source
Air filter element	2,000 hr or ΔP alarm
Oil filter (spin-on)	2,000 hr
Separator element	4,000 hr
Sigma Fluid S-460	8,000 hr
Drive belts (SK15/20 belt-driven variants)	Inspect annually, replace at cracking
Inlet valve service kit	8,000 hr
Thermostatic valve element	As needed / on high-temp fault
Cabinet fan filter mat	Quarterly clean, annual replace

Consumable part numbers change by revision and region — pull the current number from the OEM portal.

Parts cross-reference

OEM part numbers with commonly-cited aftermarket equivalents. Verify against the nameplate and OEM parts portal before ordering — dimensionally similar filters can still be wrong for the application.

Air filter

Intake air filter element

OEM

6.2085.0, 6.2085.1

Aftermarket

P822858— Donaldson
PA2848— Baldwin
SA 16430— Hifi
C 15 300— Mann-Filter

VerifiedConfirmed against a public OEM or aftermarket catalog / cross-reference tool at time of entry.LikelyCommonly cited in the vendor's cross tool or long-standing field usage; not independently re-verified against the current OEM parts list.UnverifiedDimensional lookalike or user-reported.

P822858— DonaldsonLikely
source
PA2848— BaldwinLikely
source
SA 16430— HifiLikely
source
C 15 300— Mann-FilterLikely
source

Cartridge style; verify end-cap OD before ordering.

Oil / fluid filter

Fluid filter (spin-on)

OEM

6.3462.0

Aftermarket

P550425— Donaldson
B7577— Baldwin
SO 6119— Hifi
LF3325— Fleetguard

P550425— DonaldsonLikely
source
B7577— BaldwinLikely
source
SO 6119— HifiLikely
source
LF3325— FleetguardLikely
source

3/4-16 thread, 25 psi bypass. Confirm on nameplate.

Air-oil separator

Air-oil separator element

OEM

6.3563.0, 6.3563.1

Aftermarket

P532473— Donaldson
OS 5223— Hifi
OAS30015— Baldwin

P532473— DonaldsonLikely
source
OS 5223— HifiLikely
source
OAS30015— BaldwinLikely
source

Lubricant

Kaeser Sigma S-460 (semi-synthetic)

OEM

9.3419.0 (20 L), 9.3419.00030 (208 L)

Aftermarket

Cetus PAO 46— Chevron
Rarus SHC 1024— Mobil
Supra 46— Summit

Cetus PAO 46— ChevronUnverified
PAO cross — verify seal compatibility.
Rarus SHC 1024— MobilUnverified
Supra 46— SummitUnverified

Never mix ester and PAO fluids. Drain, flush, and refill on switch.

Need to look up a number across all models? Use the parts cross-reference search.

Preventive maintenance

Daily

Check fluid level in sight glass at running temp
Listen for unusual noise / vibration
Check discharge pressure & temperature vs baseline
Verify condensate drain function
Log package amps if metered

Weekly

Blow down receiver and drain traps
Check for oil carryover at first drop leg
Inspect for fluid or air leaks around airend and separator tank
Verify safety valve is not weeping

Every 2,000 hr / 6 mo

Change fluid filter
Change air filter (or sooner per ΔP)
Sample fluid for TAN / metals / water
Clean cooler exterior with low-pressure air (never > 30 psi against fins)

Every 4,000 hr / 12 mo

Change separator element
Change fluid
Inspect scavenge line & orifice for coking
Check coupling / belt alignment & wear
Torque electrical lugs to spec (typ. 45–75 in-lb #4–2/0 AWG)

Every 8,000 hr

Rebuild inlet valve
Rebuild minimum-pressure check valve
Regrease or replace motor bearings per OEM interval
Verify safety valve setpoint against gauge

Common faults & first checks

High airend discharge temp on hot days — cooler pluggage + weak thermal valve
Separator ΔP alarm at 4k hours (change kit as full set)
Belt slap on belt-driven variants after 3–5 years
Sigma Control 2 SD card write errors — reformat FAT32, avoid pulling live

Known issues & field notes

Ambient recirculation in tight closet installs — undersized ventilation is #1 killer
SR (food-grade) fluid viscosity higher at cold start — allow warmup before load

Controller(s)

Sigma Control 2 — 2-line 20-character alphanumeric backlit LCD (STN), 4 discrete status LEDs (Power, Running, Communication, Alarm), 12-key membrane keypad with soft menu keys.

Strengths

Compact footprint
Sigma Profile airend is efficient
Serviceable in tight rooms
Sigma Control 2 has strong onboard logging

Weaknesses

Requires OEM Sigma Fluid for warranty-length change intervals
Sigma Control 2 service PIN gated behind dealer

Field notes

The SK line is Kaeser's small-frame direct-drive screw. SK 26T is the tank-mount / dryer package variant. All ship with Sigma Control 2 as standard.