BURKERT 307901 (Type 6281) is a servo-assisted 2/2-way diaphragm solenoid valve configured with a cast stainless steel body 1.4408 (CF8M), FKM fluor rubber sealing, and an internal NPT 3/4 fluid connection. Operating under circuit function A, the valve remains closed in its de-energized rest state (normally closed, inlet port 1 P/NC). It controls neutral and aggressive liquids or gases compatible with stainless steel and FKM, delivering a water flow coefficient Kv of 8.5 m³/h and a gas nominal flow rate QNn of 9,100 l/min across an operating differential pressure range of 0.2 to 16 bar.

Actuation is powered by a 24 V DC solenoid coil using a central screw mounting design for vibration resistance. With Class H epoxy encapsulation, the valve operates at medium temperatures from 0 °C to +120 °C and ambient temperatures up to +55 °C. The unit is recognized under cURus (UL 429 and UL 429A) for industrial electrically operated valves and fire protection service, conforming to IP65 ingress protection when paired with a DIN EN 175301-803 Form A cable plug.

Technical Data and Operating Parameters

BURKERT 307901 requires a permanent differential pressure of at least 0.2 bar between inlet and outlet to actuate the main diaphragm. When the solenoid is energized, pilot flow opens the pilot seat (1.3 mm orifice), venting the chamber above the diaphragm and allowing line pressure to raise the diaphragm off the DN20 main orifice.

Specification Parameter	Value / Characteristic
Valve Type / Family	Type 6281 EV (Generation EV)
Article Number	307901
Circuit Function	A (2/2-way, normally closed, inlet port 1 P/NC)
Main Valve Orifice (DN)	20 mm (3/4")
Pilot Control Orifice	1.3 mm
Port Connection	Internal thread NPT 3/4
Nominal Pressure Rating	PN 16 (0.2 bar to 16 bar)
Flow Value Kv (Water, +20 °C, 1 bar Δp)	8.5 m³/h
Flow Value QNn (Gas, air at +20 °C, 6 bar)	9,100 l/min
Minimum Pressure Difference for Full Cross-Section	0.5 bar
Operating Voltage / Current Type	24 V DC (voltage tolerance ±10%)
Solenoid Coil Power Consumption	Cold power: 9.5 W; Warm power: 8 W
Solenoid Thermal Insulation Class	Class H (epoxy coil encapsulation)
Operating Duty Cycle	100% ED continuous operation
Switching Time (Opening)	0.1 to 1.5 s (measured per standard test conditions)
Switching Time (Closing)	0.2 to 4 s (measured per standard test conditions)
Medium Temperature Range	0 °C to +120 °C (FKM seal with epoxy coil)
Ambient Temperature Range	0 °C to +55 °C
Maximum Permissible Viscosity	21 mm²/s
Weight	Approximately 0.86 kg
Overall Installation Length	80 mm

INFO

A differential pressure of at least 0.2 bar is required for reliable valve opening and closing. A differential pressure of 0.5 bar is necessary to clear the entire DN20 flow cross-section.

Circuit Function

The valve operates under Circuit Function A (CF A). In the unpowered condition, the pilot orifice is sealed by the spring-loaded magnetic armature, and fluid pressure builds up above the diaphragm to keep it firmly closed against the valve seat. Energizing the 24 V DC coil lifts the armature, relieving pressure above the diaphragm to the outlet side, which forces the main diaphragm upward.

Circuit Function Symbol	Description
2/2-way valve, normally closed (NC)	Circuit function A (CF A): 2/2-way solenoid valve, servo-controlled, normally closed. Inlet port 1 (P) to outlet port 2 (A).

Materials and Construction

All wetted parts are selected for durability and compatibility with aggressive non-corrosive media. The body is cast stainless steel 1.4408, with magnetic components machined from corrosion-resistant ferritic stainless steel 1.4113.

Item No.	Valve Component	Material
1	Solenoid Coil	Epoxy (Class H encapsulation for FKM configurations)
2	Stopper	Stainless steel 1.4113
3	Shading Ring	Silver (Ag) for stainless steel body variants
4	Magnetic Core (Armature)	Stainless steel 1.4113
5	O-Ring	FKM (Fluor rubber)
6	Core Seal	FKM (Fluor rubber)
7	Return Spring	Stainless steel 1.4310
8	O-Ring	FKM (Fluor rubber)
9	Diaphragm	FKM (Fluor rubber)
10	Diaphragm Holder	Polyphenylene sulfide glass-fiber reinforced (PPS GF40)
11	Valve Body	Stainless steel 1.4408 (CF8M)

Per the manufacturer media compatibility guide, FKM seals are suitable for peroxide solutions, hot oils without additives, diesel and heating oil without additives, and washing lye.

Dimensions

The dimensional values below specify the standard threaded variant for DN20 stainless steel bodies with NPT 3/4 process ports and size 5 / size 6 solenoids:

Port Size	DN [mm]	A [mm]	B [mm]	C [mm]	D [mm]	E [mm]	F2 (NPT depth) [mm]	G2 [inch]	L [mm]	SW [mm]	N [mm]
NPT 3/4	20	99.6	115.6	60	74	37	14	NPT 3/4	80	32	10
NPT 1	20	102.1	122.6	60	74	37.5	16.8	NPT 1	80	41	10

Solenoid Coil Size	Width H [mm]	J [mm]	K [mm]	M [mm]	O [mm]
Coil Size 5 (32 mm width)	32	20.5	45	41	3.4
Coil Size 6 (40 mm width)	40	23.5	51	41.4	3.8

All dimensions in mm unless otherwise indicated. For NPT threads, depth F2 and thread code G2 apply.

Approvals and Standards

BURKERT 307901 complies with European directives, North American safety standards, and global quality requirements:

• cURus / UL Recognized: Certified for the USA and Canada under UL 429 (electrically operated valves) and UL 429A (electrically operated valves for fire protection service).
• CE Conformity: Compliant with applicable EU directives and harmonized standards.
• EAC: Certified for compliance within Eurasian Customs Union member states.
• Degree of Protection: IP65 according to DIN EN 60529 / IEC 60529 when equipped with a matching Type 2518 or Type 2509 cable plug.

Installation Guidelines

DANGER: System Pressure and Electrical Hazard

Before loosening pipes or removing the valve, depressurize the system and vent all lines. Disconnect power supply and secure against unintended restart before servicing.

1. Pipeline Preparation: Flush pipelines thoroughly to remove chips, thread tape, and particulates. Install a dirt trap or strainer upstream of the valve with mesh size ≤ 500 µm.
2. Orientation: Mounting position is arbitrary; mounting with the solenoid coil upright in a vertical orientation is recommended.
3. Flow Direction: Observe the cast arrow on the valve body indicating the forward fluid flow direction (from port 1 to port 2).
4. Wrench Attachment: Do not use the solenoid coil as a lever arm. Fasten piping by applying an open-end wrench (width across flats SW 32) directly onto the body connection bosses.

Operational Reliability

During long periods of system downtime, execute at least 1 to 2 switching cycles per day to maintain diaphragm flexibility and functional reliability.

Electrical Connection

Electrical connection is established via a DIN EN 175301-803 Form A plug pattern.

1. Use a compatible cable socket (such as Bürkert Type 2518 or Type 2509).
2. Ensure the flat sealing gasket is correctly seated between the coil terminal face and plug housing.
3. Connect the protective earth conductor (PE) to terminal earth and verify electrical continuity between the coil grounding contact and the stainless steel body.
4. Tighten the central plug fixing screw to a maximum torque of 1 Nm to maintain the IP65 seal integrity.
5. Verify that operating voltage is 24 V DC ±10% before energizing.

Solenoid Coil Maintenance and Installation

Fire Hazard: Coil Overheating

Never energize the solenoid coil without the valve body and armature guide tube installed. Operating the coil unmounted causes rapid overheating and leads to total coil destruction.

When removing or replacing the solenoid coil:

1. De-energize the coil and isolate pipeline pressure.
2. Loosen the top fastening nut (1) using an open-end wrench. Do not use improper pliers that deform the nut or guide tube.
3. Lift the solenoid housing off the core guide tube (2), taking care not to misplace the O-ring (3) and anti-twist washer (4).
4. Slide the new or serviced coil onto the tube, seat it firmly onto the housing cover, and refit the washer and nut.
5. Tighten the fixing nut to the specified tightening torque:

Solenoid Type	Coil Width	Tightening Torque
AC10	32 mm or 40 mm	5 Nm
AC19	42 mm	10 Nm

Troubleshooting and Diagnostics

If the valve exhibits abnormal behavior during commissioning or operation, conduct the following systematic checks:

Malfunction Symptom	Potential Root Cause	Corrective Action
Valve fails to open / no actuation	Power supply interrupted or incorrect voltage	Verify 24 V DC supply across terminals and check coil winding continuity.
	Operating pressure out of bounds	Verify that fluid differential pressure is within 0.2 to 16 bar.
	Contamination in armature area	Disassemble coil and inspect armature guide tube; clean out particles.
Valve fails to close	Diaphragm control bore clogged	Remove bonnet screws; clean the small pilot orifice in the FKM diaphragm.
	Foreign matter under valve seat	Disassemble body and clean main valve seat and FKM seal surface.
	Valve manual override engaged	Check if optional manual lever (if fitted) is positioned in vertical bypass mode.

Spare Parts and Accessories

Spare parts for Type 6281 EV are ordered by specifying the device identification number 307901 and the required kit designation:

• SET 1: Solenoid fastening nut, coil seal kit, and armature components.
• SET 3: Complete core/armature subassembly and internal spring.
• SET 7: Diaphragm set including pre-assembled FKM diaphragm, holder, and body O-rings.

Recommended Electrical Connectors (Type 2518 Form A)

Cable plugs must be ordered separately. Compatible Type 2518 DIN EN 175301-803 Form A units include:

Cable Plug Variant	Voltage Range	Article Number
Type 2518 without circuitry (standard AC/DC)	0 to 250 V AC/DC	314802
Type 2518 with LED	12 to 24 V AC/DC	314812
Type 2518 with LED and Varistor	12 to 24 V AC/DC	314820
Type 2518 with Rectifier, LED, and Varistor	12 to 24 V AC/DC	314816
Type 2509 without circuitry (standard connector)	0 to 250 V AC/DC	137943