Burkert 20122679 Type 8640 is a pre-configured 5-bank modular pneumatic valve block designed for DIN-rail installation in control cabinets and process automation systems. Engineered with an add-on pitch dimension of 33 mm per station, article 20122679 provides a central G 1/2 supply pressure port (P / 1) and dedicated G 1/4 working connection ports positioned directly opposite the supply side. Operating across a nominal pressure span of 3 bar to 10 bar and a medium temperature range of 0 °C to 50 °C, this unit utilizes an individual single-wiring architecture without internal bus communication, rated to IP20 protection.

Technical Attributes and Configuration

Article 20122679 provides a pre-assembled pneumatic base for discrete valve actuation. The mechanical layout groups 5 valve positions on a common manifold rail, routing pressurized air to actuator outlets while segregating pilot exhaust.

Attribute Group	Specification Parameter	Value
Identity	Article Number / SKU	20122679
Identity	Model / Type	8640
Setup	Configuration	33 mm 5-bank (5 valve stations)
Setup	Add-on Dimension 1	33 mm
Process Connection	Pressure Port 1 (P)	G 1/2
Process Connection	Working Ports 2 (B) / 4 (A)	G 1/4
Process Connection	Working Connection Position	Opposite of supply side
Pressure Limits	Nominal Operating Pressure	3.00 bar to 10.00 bar
Temperature Limits	Medium Temperature	0.00 °C to +50.00 °C
Temperature Limits	Ambient Temperature	0.00 °C to +70.00 °C
Electrical Interface	Communication Version	Without (due to single wiring)
Electrical Interface	Internal Bus Communication	Without (due to single wiring)
I/O Capacity	Digital Inputs	0 PCE
Manifold Features	Intermediate Feed Quantity	0 PCE
Manifold Features	Manual/Automatic Switching	No
Manifold Features	Integrated Check Valves in 3 (R) / 5 (S)	No
Manifold Features	Pneumatic HotSwap in 1 (P)	No
Protection & Mounting	Enclosure Rating	IP20 (max. with suitable connector)
Protection & Mounting	Mounting Type	DIN-rail installation

Single Wiring System Design

Article 20122679 is configured for discrete parallel wiring of individual valve coils. It contains no internal communication modules, fieldbus nodes, or digital input feedback cards. Each installed valve is addressed directly via external cabling.

Modular Assembly and Multi-Block Architecture

The Type 8640 system combines polyamide bodies and modular manifold blocks using integrated snap connectors. Multi-block units interlock horizontally via upper and lower latching mechanisms, sealed at each interface by elastomer O-rings.

Item	Designation	Functional Description
1	Left Connection Module	Primary pneumatic entry and exhaust block termination
2	Latch Tab	Upper retention tab for module interlocking
3	Latch Hook	Lower mechanical hook engaging the preceding module groove
4	Base Modules (3-fold)	Triple-station valve mounting sub-base
5	Right Connection Module	End block termination; allows multi-pressure staging or auxiliary feed
6	Base Modules (2-fold)	Dual-station valve mounting sub-base
7	Exhaust Channel 3 (R)	Common vent pathway for discharged pilot and actuator air
8	Supply Channel 1 (P)	Common pressurized header feeding all valve stations
9	O-Ring Seals	Interface boundary seals preventing inter-module leakage

Assembly Sequence

1. Begin module assembly from the left connection module.
2. Confirm every module interface has 2 complete O-rings seated in the sealing recesses.
3. Lightly lubricate all O-rings with grease or oil prior to engagement.
4. Hook the lower latch hooks of the adjacent module into the lower latch grooves of the preceding module.
5. Press the module upward slightly until the upper latch hook snaps securely into place.
6. Insert 3 O-rings into the rear recess of each valve body before bolting to the base.
7. Tighten each valve onto the base module using 2 fastening screws to 0.6 Nm (±0.1 Nm).

Seal Positioning Caution

Crushed, pinched, or missing O-rings and profile seals between module blocks cause immediate internal and external air leakage. Always inspect seal seating before latching modules.

Mechanical and DIN-Rail Installation

Burkert Type 8640 valve blocks support direct panel mounting or installation on standard DIN mounting rails in accordance with EN 50022 (35 x 7.5 mm or 35 x 15 mm).

Mounting Procedures

• Standard Rail Installation: Hook the upper mounting groove of the valve block over the top edge of the DIN rail. Press down and snap the lower clamping brackets into the rail. Tighten the clamping screws to lock the assembly against lateral movement.
• Wall Installation: Align the block against the mounting panel and secure through the designated mounting tabs using M4 fastening screws.

Connection Port Tightening Torques

When securing fittings into the pneumatic port connections, observe the recommended torque limits to prevent thread damage in the polyamide manifold bodies.

Port Size	Port Marking / Function	Recommended Torque (Nm)	Maximum Torque (Nm)
G 1/4, NPT 1/4	P, R/S Supply and Exhaust	4 to 7	20
G 1/8, NPT 1/8	P, R/S Connection, A/B Outlets	3 to 6	7

Push-In Connector and Piping Guidelines

Pneumatic lines must meet DIN ISO 14743:2020 specifications to ensure holding capacity and pressure tightness under operating conditions from 3 to 10 bar.

• Hose Hardness: Minimum 40 Shore D in accordance with DIN 53505 or ISO 868.
• Outer Diameter Tolerance: According to DIN 73378 (maximum deviation ±0.1 mm from nominal dimension).
• End Preparation: Burr-free, cut square at 90 degrees, with no surface scoring on the outer diameter.

Hose Material	Hose Outside Diameter (mm)	Permitted Deviation (mm)
Polyamide (PA)	3 to 10	±0.08
Polyamide (PA)	12 to 16	±0.10
Polyurethane (PU)	3 to 8	±0.10
Polyurethane (PU)	10 to 16	±0.15

Tensile Force Ratings for Push-in Connections

According to DIN ISO 14743:2020, connected tubing must withstand the minimum holding forces listed below:

Hose OD (mm)	3 (1/8")	4 (5/32")	6 (1/4")	8 (5/16")	10 (3/8")	12 (1/2")	14	16 (5/8")
Min. Tensile Force PA (N)	60	70	120	170	250	300	300	350
Min. Tensile Force PU (N)	25	50	100	150	200	200	250	300

Support Sleeve Usage

When utilizing flexible polyurethane (PU) tubing, install support sleeves (ID 20099400) inside the hose ends to maintain circular profile geometry and optimize grip.

Valve Circuit Functions and Conversions

Manifold stations accommodate various pilot and main valve functions, including 3/2-way, 4/2-way, 5/2-way, and 5/3-way configurations.

Conversion from 4/2-Way to 3/2-Way Operation

A 4/2-way valve installed on the block can be adapted into a 3/2-way function by sealing one of the active working ports with an airtight plug.

Port 2 Status	Port 4 Status	Resulting Circuit Function	Operating State Description
Closed with plug	Open	Function C (Normally Closed)	Rest position: Port 1 closed, Port 4 vented to exhaust 3
Open	Closed with plug	Function D (Normally Open)	Rest position: Port 1 connected to Port 2, exhaust 3 closed

Manual Override Operation

Valves include a mechanical manual override on the pilot stage:

1. Depress the manual override actuator.
2. Turn the actuator 90 degrees clockwise until it stops to lock the valve in energized state.
3. Turn back counter-clockwise to unlock the valve for automatic electrical operation.

Electrical Safety

Operate the manual override only when the electrical supply is switched off. Unlock all manual overrides prior to placing the system into remote electrical service.

Maintenance and Troubleshooting

Pressure and Voltage Hazard

Before opening pneumatic fittings or servicing electrical plugs, depressurize supply channel 1 (P), vent connected working lines, and disconnect control voltage.

Fault Symptom	Probable Cause	Corrective Action
Valves fail to actuate	Operating voltage missing or below tolerance	Verify coil voltage against nameplate; check connector continuity.
Valves fail to actuate	Manual override locked in engaged position	Rotate manual override 90 degrees counter-clockwise to zero position.
Valves fail to actuate	Supply pressure below operating threshold	Restore supply pressure to at least 3 bar (minimum pilot threshold).
Delayed switching or continuous venting at exhaust	Main header pressure volume insufficient	Increase supply line cross-section; inspect upstream filters and regulators.
Delayed switching or continuous venting at exhaust	Exhaust silencers clogged with dirt or undersized	Clean exhaust silencer elements or replace with higher flow silencers.
Delayed switching or continuous venting at exhaust	Particulate contamination inside valve pilot stage	Flush exhaust channels with pulsed air; replace contaminated pilot valve.
Air leaks between block modules	Damaged or missing O-rings at block interface	Disassemble modules and install fresh, lightly greased O-rings.
Air leaks under valve body	Flat seal misplaced or damaged during valve mounting	Inspect valve sub-base seal; torque valve screws to 0.6 Nm.