BURKERT 20051938 (Type 8640) is a 7-bank modular pneumatic valve block engineered for piloting pneumatic process valves and actuating pneumatic control circuits. Built with a 33 mm width per station configuration, this assembly integrates seven valve stations operating with 3/2-way valve functionality. The supply connection features a G 1/2 port, and all G 1/4 pneumatic working ports are arranged on the side opposite the supply feed. Operating across a nominal pressure envelope of 2.0 bar to 8.0 bar, the unit handles compressed dry air and neutral gases at medium temperatures from 0 °C to +50 °C within ambient operating limits of 0 °C to +55 °C.

Designed for standalone electrical architectures, article 20051938 operates via individual single wiring rather than internal backplane bus communications. The modular valve unit uses polyamide (PA) bodies and modules with NBR seals, mounted directly to standard DIN rail EN 50022 profiles (35 x 7.5 mm or 35 x 15 mm). It carries an ingress protection rating of IP20 as an open assembly, reaching IP65 protection when installed inside a sealed control cabinet or when each station is fitted with an approved cable plug such as Type 2516.

Technical Specifications

Specification Parameter	Value / Execution
Article Number	20051938
Product Type	Type 8640
Assembly Description	Valve block 8640 33mm 7-bank
Number of Valve Stations	7-bank (7 valve slots)
Width per Station	33 mm
Valve Circuit Function	3/2-way valve function
Operating Pressure Range	2.0 bar to 8.0 bar
Minimum Pressure Difference (Ports 1 to 3)	2.0 bar
Medium Temperature Range	0 °C to +50 °C
Ambient Operating Temperature	0 °C to +55 °C
Storage Temperature	-40 °C to +55 °C (dry, dust-free)
Compressed Air Quality	ISO 8573-1:2010, Class 7.4.4 (5 µm filtration recommended)
Supply Port 1 (P) / Exhaust Port 3 (R)	G 1/2
Working Ports 2 (A) / 4 (B)	G 1/4 (opposite of supply side)
Intermediate Supply Ports	0 PCE
Digital Input Modules	0 PCE
Modular Bus Variant	Without (due to single wiring)
Internal Bus Communication	Without (due to single wiring)
Operating Voltage	24 V DC (±10% tolerance, 1 Vss residual ripple)
Operating Mode	Continuous operation (100% duty cycle)
Degree of Protection	IP20 (IP65 in closed cabinet or with Type 2516 plug)
Installation Type	Standard DIN rail EN 50022 (35 x 7.5 or 35 x 15) or direct wall mounting

Modular Block Construction and Assembly

The Type 8640 modular block architecture consists of interconnected pneumatic modules locked mechanically by built-in latch hooks and tabs, eliminating intermediate external tubing between adjacent stations.

Assembly Sequence

1. Position the left pneumatic supply module as the starting station.
2. Verify that two clean O-rings are seated in the inter-module sealing grooves of each consecutive sub-base.
3. Lightly grease or oil all O-rings prior to engagement.
4. Align the lower latch hooks of the adjacent base module with the receiving latch grooves of the preceding unit.
5. Pivot and press the module upwards slightly until the upper latch hook snaps securely into place.
6. Fit three O-rings into the recesses on the mounting interface of each valve station.
7. Secure each valve to its pneumatic base plate using two fastening screws tightened to a recommended torque of 0.6 ±0.1 Nm.

Sealing Integrity Warning

Crushed, dislodged, or unlubricated O-rings between sub-bases or beneath valve mounting interfaces cause immediate internal cross-channel leakage or external atmospheric leakage. Inspect all profile seals before snapping modules together.

Mechanical and DIN-Rail Installation

Article 20051938 supports rapid mounting on EN 50022 symmetrical DIN rails (35 x 7.5 mm or 35 x 15 mm) or direct flat-surface installation using M4 machine screws.

Standard Rail Installation Steps

• Hook the upper mounting groove of the valve block over the top edge of the DIN rail.
• Press the lower section of the block downward and snap the lower clamping pieces over the bottom rail edge.
• Fasten the clamping piece fixing screws to lock the assembly against lateral movement along the rail.
• For wall or backplate installation, secure through the dedicated lateral mounting brackets directly with M4 screws.

Recommended Tightening Torques for Threaded Ports

Connection Size	Port Marking / Function	Recommended Torque	Maximum Permissible Torque
G 1/2	Supply Port 1 (P), Exhaust Port 3 (R)	6.0 to 10.0 Nm	20.0 Nm
G 1/4	Working Ports 2 (A), 4 (B) / Supply Options	4.0 to 7.0 Nm	20.0 Nm
G 1/8	Working Ports / Single Outlets	3.0 to 6.0 Nm	7.0 Nm

Piping Installation Precaution

Never use the solenoid coil or pilot actuator housing as a lever arm when tightening pneumatic fittings into the port threads. Support the polyamide block body directly with an open-end wrench.

Pneumatic and Electrical Installation

Pneumatic Line Connection

Pneumatic supply lines must provide clean, dry compressed air compliant with ISO 8573-1:2010 Class 7.4.4. A filtration degree of 5 µm is recommended (maximum particle size 10 µm). A minimum differential pressure of 2.0 bar between supply port 1 (P) and exhaust port 3 (R) must be maintained at all times.

Hose lines attached to push-in connectors or threaded adapters must fulfill the following mechanical criteria:

• Minimum material hardness: 40 Shore D (pursuant to DIN 53505 / ISO 868).
• Outside diameter tolerances per DIN 73378.
• Right-angle, burr-free cuts with undamaged outer sealing surfaces.

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

Single Wiring Electrical Connection

Article 20051938 uses single wiring connections directly to the coil contacts. Electrical control is established per station using cable plugs conforming to DIN EN 175301-803 Form C (such as Bürkert Type 2516).

• Connect the 24 V DC supply leads to the designated plug pins, maintaining rated polarity.
• Seat the flat elastomeric seal evenly between the cable plug and the coil mating surface to achieve IP65 sealing.
• Tighten the center fixing screw of the cable plug to a torque of 0.3 Nm (maximum 1.0 Nm on the coil contact base).
• Verify protective conductor ground continuity: measured electrical resistance between the protective conductor contact and the valve housing must not exceed 0.1 Ω (tested at 12 V, 1 A test current).

Continuous Operation Reliability

When valves remain energized or unswitched during extended operational standbys, Bürkert recommends scheduling 1 to 2 test switching cycles per day to maintain pilot mechanical responsiveness.

Commissioning and Troubleshooting

Before applying operating pressure, verify that all pneumatic lines are correctly routed and that the electrical manual override on each station is turned counterclockwise into its disengaged zero position.

Operational Faults and Remedial Actions

Fault Observed	Possible Cause	Corrective Action
Valve fails to switch	Insufficient or absent electrical operating voltage	Check supply wiring; ensure 24 V DC ±10% voltage is present at the coil plug terminals.
Valve fails to switch	Manual override engaged in locked position	Rotate manual override counterclockwise 90° back to the zero position.
Valve fails to switch	Supply pressure below operating threshold	Restore system pressure; maintain supply pressure between 2.0 bar and 8.0 bar.
Delayed switching or blow-off at exhaust	Insufficient air volume or restrictive upstream regulators	Install large-volume air lines and upstream regulators sized for peak consumption; maintain minimum 2 bar delta.
Delayed switching or blow-off at exhaust	Valve block not pressurized in de-energized home state	Apply pneumatic supply pressure to port 1 before actuating solenoid control signals.
Delayed switching or blow-off at exhaust	Exhaust silencers clogged, generating excessive back pressure	Clean or replace contaminated silencers; verify exhaust ducting diameter is unobstructed.
Delayed switching or blow-off at exhaust	Particulate contamination inside pilot or main seat	Purge exhaust ports with pulsed air or replace the affected valve seat insert.
External leakage between sub-bases	Missing, pinched, or damaged O-rings	Disassemble sub-block, replace defective inter-module O-rings, and re-engage latch hooks.
Leakage under valve base	Defective or misaligned flat gasket seal	Remove valve mounting screws, inspect flat gasket, replace if damaged, and retorque to 0.6 ±0.1 Nm.