BURKERT 20128594 is a Type 8640 modular pneumatic valve island configured with eight valve slots operating in 3/2-way Circuit Function C (normally closed) on an 11 mm station pitch. Operating within a pressure range of 2.5 bar to 10.0 bar, the unit features G 1/4 central supply ports for supply channel 1 (P) and exhaust channels 3 (R) and 5 (S), alongside bottom-oriented D6 mm push-in working ports. Built to generation Revision 3 (REV3) architecture, this valve block integrates pneumatic HotSwap (integrated P-shut-off) to allow pilot valve replacement under line pressure, along with integrated non-return check valves in exhaust ports 3 and 5 to suppress backpressure surges.

Electrical actuation is established through a parallel collective socket module utilizing screw-type terminals and looped-through ground potential. Designed for standard DIN-rail mounting inside control cabinets, the assembly carries an IP20 ingress protection rating and consumes 0.8 W per pilot valve at 24 V DC.

Technical Specifications

Parameter	Specification
Product Type	Modular pneumatic valve island Type 8640
Ident Code / SKU	20128594
Hardware Generation	Revision 3 (REV3)
Station Width	11 mm per valve position
Number of Valve Slots	8 stations
Valve Circuit Function	Circuit Function C (3/2-way, servo-controlled, normally closed)
Nominal Orifice	DN 4.0 mm
Standard Air Flow Rate ($Q_{Nn}$)	300 l/min (measured at +20 °C, 6 bar inlet pressure, 1 bar $\Delta p$)
Effective Flow Rate ($Q_{Nn}$) with HotSwap	Reduced by approx. 20% (approx. 240 l/min)
Operating Pressure Range	2.5 bar to 10.0 bar (overpressure to atmosphere)
Switching Time (ISO 12238)	Opening: 15 ms; Closing: 28 ms
Operating Voltage	24 V DC (tolerance ±10%, residual ripple 1 Vss)
Power Consumption per Valve	0.8 W
Total Current Capacity	Max. 3 A (collective connection)
Operating Duty Cycle	100% continuous operation (100% ED)
Degree of Protection	IP20 (according to DIN EN 60529)
Electrical Protection Class	Class III according to VDE 0580
Operating Medium	Compressed air (oil-free or lubricated, Class 7.4.4 to ISO 8573-1:2010), neutral gases (5 µm filtration recommended)
Medium Temperature	0 °C to +50 °C
Ambient Temperature	0 °C to +55 °C
Storage Temperature	-20 °C to +60 °C
Primary Port Sizes	Supply 1 (P), Exhaust 3 (R), Exhaust 5 (S): G 1/4
Working Ports 2 (A)	Push-in connector for D6 mm tubing (bottom outlet)
Materials	Body: Polyamide (PA); Seals: FKM, NBR, PUR
Installation Method	Standard rail EN 50022 (35 x 7.5 mm or 35 x 15 mm)

Pilot Solenoid Valves and Circuit Function

BURKERT 20128594 uses Type 6524 pilot valves consisting of a Type 6144 pilot flipper solenoid valve acting on a pneumatic seat valve body. In Circuit Function C, pressure port 1 (P) is closed and working port 2 (A) vents through exhaust port 3 (R) when de-energized. Energizing the coil directs pilot pressure onto the seat mechanism, closing port 3 and routing line pressure from port 1 to working port 2.

Each Type 6524 pilot valve is fitted with a mechanical manual override as standard. To actuate manually, press the override element and rotate it 90° clockwise until it locks. Manual overrides must be returned to zero position and unlocked prior to initiating electrical control.

Operating Precaution

Manual overrides must only be operated when electrical power is switched off. Engaging the manual override during electrical sequencing can cause uncoordinated machine motion.

Revision 3 (REV3) Modular Features and Safety Functions

The Revision 3 (REV3) execution incorporates standardized pneumatic flange interfaces (FM20 / FM24) and optimized channel geometry:

• Pneumatic HotSwap (P-Shut-off): An integrated mechanical check seal in supply port 1 (P) isolates the pressure supply when a pilot valve is removed from its station. Valves can be replaced during live plant operation without depressurizing the main air header. Flow reduction caused by the REV3 HotSwap mechanism is limited to a maximum of 20%, compared to up to 50% in REV1 and REV2 designs.
• Integrated Check Valves (RSV): Built-in non-return valves in exhaust ducts 3 (R) and 5 (S) prevent backpressure from interfering with unactuated stations when adjacent valves exhaust simultaneously.
• Visual Distinguishing Features: REV3 modules feature a wavy staggered channel arrangement for working connections, blue hose release rings on push-in connectors, and standardized FM24 valve mounting screws (M2 x 20 mm).

Electrical Collective Connection Module

Control signals are routed through a parallel collective connection module equipped with screw-type terminals and looped-through ground potential.

• Individual stranded conductors wire directly to dedicated terminal positions for each valve coil.
• Operating voltage is 24 V DC (±10%).
• Total electrical current across all energized valves must not exceed 3 A.
• Protection against contact corresponds to degree of protection IP20 under closed cabinet conditions.

Pneumatic Assembly and Mechanical Installation

BURKERT 20128594 is composed of modular polyamide sub-bases joined via mechanical snap-fitting hooks and sealed by pre-formed elastomeric seals.

Item	Sub-Assembly Component	Description
1	Pneumatic connection module, left	Houses main G 1/4 pneumatic ports 1 (P), 3 (R), 5 (S)
2	Basic pneumatic modules (2x 4-fold)	11 mm pitch stations with bottom D6 push-in connectors, HotSwap, and RSV
3	Pneumatic connection module, right	Closes the pneumatic gallery; allows secondary feed or zoning if modified
4	Solenoid valves Type 6524	8x 3/2-way CF C pilot valves secured by M2 screws (0.6 ±0.1 Nm torque)

Mounting is accomplished directly on DIN rails conforming to EN 50022 (35 x 7.5 mm or 35 x 15 mm). The valve island is hooked into the upper guide groove, swung downward, snapped onto the lower rail edge, and clamped with integrated mounting screws.

Pneumatic Line Connection Guidelines

Tubing inserted into the D6 push-in fittings must comply with DIN 73378 and ISO 14743:2020:

• Minimum hose hardness: 40 Shore D (DIN 53505 / ISO 868).
• Outside diameter tolerance: PA tubing 6 mm ±0.08 mm; PU tubing 6 mm ±0.1 mm.
• Ends must be cut square, deburred, and pushed firmly into the fitting past the retaining claws until seated against the mechanical stop.

Tubing Outer Diameter	Minimum Tensile Holding Force: Polyamide (PA)	Minimum Tensile Holding Force: Polyurethane (PU)
6 mm	120 N	100 N

Replacement Valves and Compatible Spare Parts

Component Description	Specifications / Revision Compatibility	Article Number
Replacement Valve Type 6524	3/2-way CF C, 2.5...10 bar, 24 V DC, 0.8 W, REV3 (FM24 interface)	20029918
Base Unit 4-Fold (11 mm)	D6 push-in ports, HotSwap, check valves (RSV), REV3	20040335
Supply Connection Unit, Right	11 mm width, G 1/4 port	20040351
Supply Connection Unit, Left	11 mm width, G 1/4 port	20040352
Valve Seal Set FM24	12x replacement seals for Type 6524 on REV3 base	20024336
Module Seal Set MP16	4x inter-module profile seals for Type 8640 REV3	20024339
Unused Station Cover Plate	Covers pneumatic port on base module (requires electrical cover 653670)	661092
Electrical Connection Cover	Protective blind cover for unused electrical base slot	653670

Troubleshooting and Maintenance Guide

Fault	Possible Cause	Corrective Action
Valve fails to switch	Absence of 24 V DC supply voltage or excessive voltage drop	Check collective socket screw terminals; verify 24 V DC ±10% at the coil
	Manual override locked in manual position	Rotate manual override counter-clockwise to zero position
	Pilot supply pressure below 2.5 bar	Restore pressure supply to at least 2.5 bar; verify header capacity
Delayed switching or blow-off at exhaust	Supply volume inadequate (pressure dip during actuation)	Increase upstream pipe diameter; clean upstream filter elements (≤ 5 µm)
	Valves switched before pressure build-up	Apply pressure to supply port 1 (P) before sending electrical control signals
	Silencer blocked on exhaust ports 3 or 5	Clean silencer or install larger expansion vessel to remove backpressure
	Particulate contamination inside seat valve	Blow out exhaust passages with clean compressed air; replace contaminated valve
Air leakage between modules	Damaged or misaligned inter-module O-rings	Disassemble sub-blocks, verify seating of O-rings, lightly grease with compatible lubricant, and re-engage snap tabs
Air leakage at valve base	Crushed or missing flat seal between valve and sub-base	Install replacement FM24 seal set (20024336); torque M2 screws to 0.6 ±0.1 Nm