BURKERT 349748 (Type 6281) is a servo-assisted 2/2-way diaphragm valve with an explosion-proof terminal box connection, designed for shut-off, dosing, and control of neutral fluids and gases. Built with a cast stainless steel 1.4408 (CF8M) valve body and FKM (fluororubber) seals, this valve configuration operates across a pressure span of 0.2 bar to 16 bar. The primary connection is an internal thread G 1 1/4 with an orifice size of DN 25 mm, delivering a water flow coefficient (Kv) of 12 m³/h and a gas flow rate (QNn) of 13,000 l/min.

The valve utilizes a damped diaphragm assembly to achieve quiet closing under process pressures. Actuation is driven by a centrally screwed, vibration-resistant solenoid actuator rated for 24 V AC/DC (50/60 Hz). With certified explosion protection according to ATEX and IECEx standards (Ex eb mb IIC T4 Gb and Ex mb tb IIIC T130 °C Db), article 349748 fulfills European and international safety requirements for potentially explosive gas and dust environments.

Differential Pressure Requirement

Type 6281 is a servo-assisted valve and requires a permanent minimum differential pressure of 0.2 bar between the inlet and outlet to actuate reliably. A differential pressure of 0.5 bar is required to fully open the valve cross-section.

Technical Specifications

Specification Parameter	Technical Value
Circuit function	A (2/2-way valve, servo-assisted, normally closed)
Nominal diameter (DN)	25 mm (1")
Pilot orifice	1.4 mm
Port connection	G 1 1/4 internal thread
Installation length	95 mm
Flow coefficient Kv (water, +20 °C)	12 m³/h
Flow rate QNn (gas)	13,000 l/min
Operating pressure range	0.2 bar to 16 bar (gauge pressure)
Nominal pressure	PN 16 (DIN EN 1333)
Fluid media	Neutral liquids and gases compatible with housing and seal materials
Fluid viscosity	Maximum 21 mm²/s
Medium temperature (ATEX)	0 °C to +90 °C (maximum medium temp must not exceed T4 limit minus 5 K)
Ambient operating temperature	-30 °C to +55 °C
Storage temperature	-40 °C to +80 °C
Operating voltage	24 V AC/DC (50/60 Hz)
Voltage tolerance	±10%
Duty cycle	100% continuous operation (ED)
Degree of protection	IP65 according to DIN EN 60529 / IEC 60529 (with terminal box mounted)
Valve weight	1.7 kg

Materials of Construction

Item	Component	Material
1	Coil body	Epoxy (H class insulation, rated for FKM execution)
2	Stopper	Stainless steel 1.4113
3	Shading ring	Silver (Ag, fitted in stainless steel valve variants)
4	Magnetic core	Stainless steel 1.4113
5	O-ring	FKM (fluororubber)
6	Core seal	FKM (fluororubber)
7	Core spring	Stainless steel 1.4310
8	O-ring	FKM (fluororubber)
9	Diaphragm	FKM (fluororubber)
10	Diaphragm holder	PPS GF40
11	Valve body	Stainless steel 1.4408 (CF8M)

Dimensions and Mounting Data

All dimensions are provided in millimeters (mm). For article 349748 (DN 25, G 1 1/4 connection, terminal box variant, coil size 6 / 40 mm):

Dimension Code	Description	Value (mm)
A	Total valve height to actuator top	111.6
B	Total valve height to cable gland center	136.6
C	Solenoid body length	70
D	Solenoid depth including terminal cover	85
E	Centerline to port face distance	46
F1	Thread engagement depth (G 1 1/4)	20
G1	Thread connection	G 1 1/4
L	Face-to-face body installation length	95
SW	Body hex width across flats	50
N	Clearance below valve body centerline	15
H	Solenoid width (coil size 6)	40
J	Centerline to side edge	23.5
K	Coil body height	52
P	Terminal box clearance offset	74.8
R	Actuator reach dimension	103
S	Total clearance height for disassembly	177.7

Electrical Data and Coil Performance

Type 6281 solenoid actuators with explosion-proof terminal boxes utilize molded epoxy coils. Power consumption ratings for the ATEX/IECEx AC/DC execution on DN 13 to DN 50 valves (coil width 40 mm) are standardized:

Execution Type	Orifice (DN)	Coil Size	Nominal Power (AC/DC)
ATEX/IECEx Terminal Box	13 mm to 50 mm	40 mm	9 W

Electrical and Thermal Safeguards

Do not energize the solenoid coil unless it is fully mounted and secured on the core guide tube of the valve body. Connecting the solenoid without a pre-installed valve causes rapid overheating and permanently damages the coil encapsulation. For continuous operation on AC supplies, monitor the core movement; a seized plunger will cause the coil to overheat.

Explosion Protection and Approvals

Article 349748 is specifically certified for use in hazardous areas. The terminal box execution eliminates external plug connectors in favor of an integrated Ex e connection compartment:

Certification Body	Approval Certificate	Identification Marking
ATEX	EPS 18 ATEX 1232 X	II 2 G Ex eb mb IIC T4 Gb II 2 D Ex mb tb IIIC T130 °C Db
IECEx	IECEx EPS 18.0110 X	Ex eb mb IIC T4 Gb Ex mb tb IIIC T130 °C Db
General Conformity	CE, EAC	Directives compliance verified via EU Declaration of Conformity

Temperature Class Limitations

Under explosion protection standards, the process medium temperature must never exceed the permitted temperature class (T4: +135 °C) minus 5 K. For article 349748, the continuous medium temperature is rated from 0 °C to +90 °C in ATEX service.

Installation and Operational Guidelines

Pressure and Voltage Hazard

Before loosening any process piping or servicing the valve, completely isolate system pressure and vent all connected process lines. Switch off all electrical power to the terminal box and secure against accidental re-energization.

Mechanical Installation

• Clean all supply lines thoroughly before inserting the valve into the system pipeline.
• Install a dirt trap or inline strainer with a mesh size ≤ 500 µm upstream of the valve inlet to prevent debris from blocking the pilot control bore.
• Observe the fluid flow direction indicated by the arrow cast into the stainless steel valve body.
• Hold the valve body firmly using an open-end wrench across the body flats (SW 50). Do not use the solenoid housing or terminal box as a lever arm.
• Mounting position is arbitrary, but Burkert recommends orientation with the actuator in the upright vertical position.

Solenoid Mounting and Torque

• Slide the solenoid housing onto the core guide tube over the O-ring and anti-twist device.
• Tighten the top fixing nut using an open-end wrench to 5 Nm (solenoid type AC10, coil width 40 mm). Never overtighten or use improper tools.
• Verify protective earth conductor continuity between the terminal box earth screw and the stainless steel valve body.

Ordering Information and Accessories

Associated ATEX/IECEx Terminal Box Models

Article No.	Circuit Function	Port Connection	DN (mm)	Kv (m³/h)	Pressure (bar)	Body Material	Seal Material	Voltage / Frequency
349748	A (NC)	G 1 1/4	25	12	0.2–16	Stainless steel	FKM	24 V AC/DC
349749	A (NC)	G 1 1/4	25	12	0.2–16	Stainless steel	FKM	230 V AC/DC

Compatible Ex Cable Glands and Service Tools

Accessory Description	Ex Approval / Standards	Clamping Range	Article No.
Ex cable gland, polyamide (included standard)	PTB 13 ATEX 1015 X / IECEx PTB 13.0034X; II 2 G Ex e IIC Gb, II 2 D Ex tb IIIC Db IP68	7 mm to 13 mm	773277
Ex cable gland, nickel-plated brass (optional)	PTB 04 ATEX 1112 X / IECEx PTB 13.0027X; II 2 G Ex e IIC Gb, II 2 D Ex tb IIIC Db IP68	6 mm to 13 mm	773278
SC02-AC10 service set (special SW19 5 Nm tool and manual for turning terminal box)	—	—	293488

Spare Part Sets

Original replacement parts are available in structured sets from Bürkert. Order spare part sets SET 1, SET 3, or SET 7 by quoting the device article number 349748.