BURKERT 354721 (Type 0330) is a direct-acting, media-separated 3/2-way pivoted armature solenoid valve engineered for controlling neutral and aggressive fluids, including oxidizing acids, salt solutions, and exhaust gases. Built in circuit function D (normally open), the valve establishes a flow path from inlet port 1 to outlet port 2 while exhaust port 3 remains closed in the de-energized position. The design utilizes a high-grade 1.4401 stainless steel body, FKM seals, a DN 4.0 mm orifice, and G 1/4 threaded ports. Operating on 24 V DC across a gauge pressure range of 0.00 to 5.00 bar, it delivers a water flow coefficient Kv of 0.17 m³/h (QNn 180 l/min for air/gas) and features an integrated manual override for commissioning and functional verification.

Operating Principle and Pivoted Armature Technology

Type 0330 utilizes pivoted armature architecture where the magnetic actuator remains fully isolated from the fluid flow by a flexible separating diaphragm. This media separation prevents corrosive media, solids, and temperature extremes from contacting the coil assembly or internal metallic moving parts.

• Media separation via FKM diaphragm prevents fluid ingress into the actuator chamber.
• Epoxy-encapsulated coil system provides vibration resistance and class H thermal insulation.
• Direct-acting switching operates reliably from 0 bar differential pressure up to the rated maximum.
• Manual operation lever is integrated directly onto the valve body for manual override and testing without electrical excitation.

Technical Data

Specification Parameter	Value
Manufacturer Article (Ident Code)	354721
Valve Type Family	Type 0330
Circuit Function	D (WW D: 3/2-way, direct-acting, normally open)
Nominal Diameter (DN)	4.0 mm (5/32")
Port Connection Size	G 1/4 internal thread
Body & Valve Seat Material	Stainless steel 1.4401
Sealing Material	FKM (Fluor rubber, 70 Shore A)
Operating Pressure Range	0.00 to 5.00 bar
Vacuum Pressure Capability	-0.98 to 3.00 bar
Kv Value (Water)	0.17 m³/h
Flow Value QNn (Gas)	180 l/min
Electrical Supply Voltage	24 V DC (±10% voltage tolerance)
Power Consumption	11 W (cold pull-in), 8 W (warm holding)
Operating Duty Cycle	100% ED continuous rating
Switching Time Opening	10 to 20 ms
Switching Time Closing	10 to 20 ms
Fluid Temperature Range	0 °C to +90 °C
Maximum Ambient Temperature	+55 °C
Maximum Fluid Viscosity	37 mm²/s
Electrical Connection Standard	Form A connector acc. to DIN EN 175301-803
Protection Rating	IP65 (with properly fitted cable socket)
Installation Length	46 mm
Valve Weight	0.45 kg

Circuit Function and Port Allocation

Under circuit function D, the direct-acting valve operates as a normally open 3/2-way valve. The external ports 1, 2, and 3 are allocated according to the manufacturer standard connection assignment:

Port Number	Circuit Function D Allocation	Line Designation
Port 1	R	Exhaust / Return line
Port 2	B	Working outlet line
Port 3	P	Pressure supply inlet line

Port Markings and Fluid Routing

When de-energized, the internal path between inlet port P (3) and outlet port B (2) is open, while exhaust port R (1) remains closed. When energized, the solenoid pulls the pivot armature, shutting off pressure supply port P (3) and venting service line B (2) through exhaust port R (1).

Pressure Limits Across Circuit Functions

The internal return spring within Type 0330 is factory-adapted for each specific circuit configuration. If a valve manufactured for circuit function D is redirected to execute other circuit functions, the permissible maximum operating pressure changes according to the manufacturer specification:

Reassigned Circuit Function	Maximum Working Pressure (DN 4, Metal Body, 8 W DC)
Applied as Circuit Function A	2.0 bar
Applied as Circuit Function B	5.0 bar
Applied as Circuit Function C	2.0 bar
Applied as Circuit Function D (Factory Spec)	5.0 bar
Applied as Circuit Function E	2.0 bar
Applied as Circuit Function F	2.0 bar

Reassignment Restrictions

When operating a circuit function D unit in reassigned function A or B, the fluid piping must strictly follow the port allocation table of the corresponding 3/2-way configuration.

Dimensions and Mechanical Installation

• Connection threads: G 1/4 parallel female thread (D1 = G 1/4, thread engagement length L1 = 9 mm).
• Body installation length: 46 mm.
• Minimum thread depth for the center connection is 7.5 mm.
• Mounting pattern: Two bottom mounting holes arranged in a 38 mm x 24 mm pattern for M4 mounting fasteners.
• Mounting attitude: Any mounting position is permitted, but upright orientation with the coil actuator positioned vertically upward is recommended.

Electrical Connection and Accessories

Unit 354721 is equipped with terminal contact pins for DIN EN 175301-803 Form A cable plugs. A suitable standard Type 2518 cable plug is enclosed in delivery.

Accessory Item	Ordering Code	Technical Specification
Type 2518 Cable Plug (Form A)	314802	0–250 V AC/DC, unshielded standard socket
Type 2518 Cable Plug (Form A)	314812	12–24 V AC/DC with integrated LED indicator
Type 2518 Cable Plug (Form A)	314820	12–24 V AC/DC with LED and varistor surge protection
DIN Rail Mounting Bracket Kit	013253	Complete mounting plate set for DIN rail installation
Manual Override Lockout Snap Ring	013372	External retaining ring to prevent accidental manual operation