BURKERT 20139986 Type 6518 is a servo-assisted 3/2-way pneumatic solenoid valve configured in circuit function C (normally closed), designed for controlling single-acting pneumatic actuators and industrial process systems. Engineered with an 8.0 mm nominal orifice and a 32 mm body width, this valve delivers an air flow rate of 1300 l/min across an operating pressure range of 2.0 to 10.0 bar. The unit operates on 24 V UC (AC/DC) power with a 3 W power rating and comes equipped with an integrated 10,000 mm (10 m) moulded electrical connection cable.

Certified under ATEX and IECEx standards for explosion protection class Ex mb (encapsulation), article 20139986 is rated II 2 G mb IIC T6 Gb for gases and II 2 D mb IIIC T80 °C Db for dust in single mounting setups. The valve body is moulded from glass-fibre reinforced polyamide (PA) with brass threaded inserts for G 1/4 port connections, combined with wear-resistant polyurethane (PUR) and nitrile butadiene rubber (NBR) seals. Depending on safety loop architecture, the valve can achieve safety integrity level SIL 2 in accordance with IEC 61508.

Technical Specifications

Specification Parameter	Technical Data Value
Valve Type	Type 6518 servo-assisted pneumatic solenoid valve
Circuit Function	Circuit function C (3/2-way, normally closed)
Fluidic Ports	Port 1 (P/NC), Port 2 (A/OUT), Port 3 (R/NO)
Main Valve Orifice	DN 8.0 mm
Pilot Orifice	1.2 mm
Flow Capacity QNn (Air)	1300 l/min (measured at +20 °C, 6 bar inlet, 1 bar Δp)
Operating Pressure Range	2.0 to 10.0 bar (minimum differential pressure 2.0 bar)
Operating Medium	Neutral media (dry compressed air, lubricated or non-lubricated)
Compressed Air Quality	ISO 8573-1:2010, Class 7.4.4 / Class 7.2.4
Medium Temperature	-10 °C to +55 °C
Ambient Temperature	-25 °C to +55 °C
Operating Voltage	24 V UC (universal current: AC 50/60 Hz and DC, ±10%)
Nominal Power Consumption	3 W
Duty Cycle	100% ED continuous operation
Switching Time Opening	20 ms (pressure build-up 0 to 10%)
Switching Time Closing	50 ms (pressure reduction 100 to 90%)
Electrical Connection	Moulded wire cable, 10,000 mm (10 m) length, non-detachable
Process Connection Ports	G 1/4 internal thread (Ports 1, 2, 3); M5 auxiliary pilot port
Valve Body Material	Glass-fibre reinforced polyamide (PA)
Threaded Bushing Material	Brass (FM03 interface)
Seal Material	PUR (Polyurethane) and NBR
Return Mechanism	Pneumatic spring + mechanical spring
Manual Override	Standard integrated, push and 90° turn detent
Protection Rating	IP65
Safety Integrity	SIL 2 capable according to IEC 61508

Circuit Function & Operation

Burkert Type 6518 operates as a pilot-controlled servo valve utilizing a diaphragm seat mechanism. In de-energized condition (circuit function C), supply port 1 (P) remains closed while working port 2 (A) vents directly through exhaust port 3 (R). When energized with 24 V UC, the pilot stage opens, switching line pressure to actuate the main seat and connect port 1 to working port 2 while isolating exhaust port 3.

De-energized State (Normally Closed - CF C): Port 1 (P/NC) ----[ CLOSED ] Port 2 (A/OUT) <===============> Port 3 (R/NO) [Exhaust]

Energized State: Port 1 (P/NC) <===============> Port 2 (A/OUT) Port 3 (R/NO) ----[ CLOSED ]

The internal valve return mechanism combines a mechanical spring with an internal pneumatic spring, ensuring reliable seat closure even after extended standstill periods. A manual override is incorporated on the valve body for commissioning and emergency cycling. The manual operator must be depressed and turned 90° clockwise until it latches into the locked position.

WARNING

Actuate the manual override only when the electrical power is disconnected. Prior to re-energizing the system, return the manual override to its initial disengaged position.

Explosion Protection & Safety Conditions

Article 20139986 achieves explosion protection through type of protection "mb" (encapsulation). The solenoid coil winding, internal electronics, bridge rectifier, and electrical cable are permanently moulded in solid epoxy resin.

Certification Entity	Approval Identification & Marking
ATEX Certificate	EPS 18 ATEX 1 232 X
ATEX Marking	II 2 G Ex mb IIC T6 Gb II 2 D Ex mb IIIC T80 °C Db
IECEx Certificate	IECEx EPS 18.0110X
IECEx Marking	Ex mb IIC T6 Gb Ex mb IIIC T80 °C Db
Permitted Installation	Single mounting configuration for T6/T80 °C rating

Operating Temperature Restrictions

To maintain the temperature class, medium temperature must never exceed the permitted class rating minus 5 K. For temperature class T6 (+85 °C), the maximum allowable medium temperature is +80 °C; for article 20139986, the operating medium limits remain specified at -10 °C to +55 °C.

Static Hazard Precautions

Prevent electrostatic charge accumulation on plastic surfaces. Clean the device only using a damp or antistatic cloth. Do not install the unit in environments exposed to pneumatic powder transport or electrostatic coating processes.

Dimensions & Installation Guidelines

Type 6518 valves can be mounted in any orientation, although Burkert recommends positioning the valve with the solenoid actuator upright. Direct surface mounting is executed using M4 fasteners through the body holes.

Mechanical Connection	Fastener / Thread	Recommended Torque	Maximum Torque
Direct Wall Mounting	M4 screws	2.0 to 5.0 Nm	5.0 Nm
Main Process Ports (1, 2, 3)	G 1/4 internal thread	4.0 to 7.0 Nm	20.0 Nm
Auxiliary Pilot Port	M5 internal thread	1.0 to 1.2 Nm	3.0 Nm
Coil Fastening Nut	Hex nut (AC10 size)	—	5.0 Nm

Pneumatic lines should be inspected for particulate contamination prior to fitting. Upstream installation of a filter or dirt trap (≤ 500 μm) within 500 mm of port 1 prevents seat degradation. The non-detachable 10 m connection cable features three conductors:

• Green-Yellow: Protective conductor (PE)
• Black: Neutral conductor / Cathode (-)
• Black: Phase / Anode (+)

TIP

The solenoid unit can be turned by 4 × 90° on the core guide tube by loosening the top hex nut with an open-end wrench. After positioning, re-tighten the nut to a maximum torque of 5.0 Nm.

Manifold Assembly with MP07 Base Modules

Type 6518 valves can be configured as individual units or mounted onto modular pneumatic base rails using Burkert Type MP07 modules. The modules snap onto standard 35 mm DIN rails (DIN EN 50022 / 50023) or mount directly to flat surfaces, accommodating blocks of up to 12 valves.

Item	Module Element	Function Description
1	Connection module left	Common supply G 1/2 connection block
2	Base module 3-fold	Pneumatic base supporting 3 valve positions
3	Intermediate / Right module	Isolator module for dual-pressure supply or rail end
4	Base module 2-fold	Pneumatic base supporting 2 valve positions
5	Connection module right	Common exhaust G 1/2 connection block
6, 7, 8	Supply connections 3(R), 1(P), 5(S)	Common rail distribution galleries
9	Cover plate	Blanks unused valve stations on MP07 base

Manifold Operating Limit

While standard Type 6518 valves support dense block assembly, valves with Ex mb coils operated in dense manifolds require derating: if different power levels share a manifold, ambient temperature must not exceed +40 °C. Article 20139986 is specified for T6 under single mounting conditions.

Ordering Information & Selection

Article No.	Model / Circuit Function	Orifice	Flow Rate QNn	Voltage / Power	Pressure Range	Connection / Cable
20139986	Type 6518 CF C (NC)	DN 8.0 mm	1300 l/min	24 V UC / 3 W	2.0 to 10.0 bar	G 1/4, 10 m moulded cable (Ex mb T6)
350443	Type 6518 CF C (NC)	DN 8.0 mm	1300 l/min	24 V UC / 3 W	2.0 to 10.0 bar	G 1/4, 3 m moulded cable (Ex mb T5)
350449	Type 6518 CF C (NC)	DN 8.0 mm	1300 l/min	110 V UC / 3 W	2.0 to 10.0 bar	G 1/4, 3 m moulded cable (Ex mb T5)
350451	Type 6518 CF C (NC)	DN 8.0 mm	1300 l/min	230 V UC / 3 W	2.0 to 10.0 bar	G 1/4, 3 m moulded cable (Ex mb T5)
350452	Type 6518 CF D (NO)	DN 8.0 mm	1300 l/min	24 V UC / 3 W	2.0 to 10.0 bar	G 1/4, 3 m moulded cable (Ex mb T5)