BURKERT 347794 (Type 2031) is an externally controlled 2/2-way diaphragm valve with a pneumatic piston actuator and a flow-optimised stainless steel body. Configured in Control Function A, the valve is normally closed by spring force in the rest position and opens bidirectionally when pilot pressure is supplied to the lower pilot port. The process connection consists of butt-weld ends sized to DN 100 according to ISO 4200, DIN 11866 Series B, and DIN EN ISO 1127 (pipe dimensions 114.3 mm outer diameter and 2.3 mm wall thickness, connection code SA39).

Built for high-purity, hygienic, and aggressive media, this complete valve assembly combines a size 225 (Size code L) polyamide (PA) actuator housing with a forged stainless steel 1.4435 (316L) body and a PTFE/EPDM diaphragm (diaphragm size 100). The valve operates across an operating pressure range of 0.00 to 7.00 bar with a flow coefficient ($K_v$) of 235 m³/h for water. The internal construction is CIP and SIP cleanable, and the unit comes factory certified with an EN 10204 3.1 inspection certificate and a 2.1 diaphragm certificate.

Construction and Components

The Type 2031 construction provides isolation between the process media and the actuator mechanism. Fluid contact is limited exclusively to the internal surface of the forged body and the media face of the PTFE diaphragm.

Item	Component	Description / Function
1	Transparent cap	Integrated optical position indicator
2	Actuator cover	Polyamide (PA) upper housing cover
3	Upper pilot air port	Used for pilot air release in Control Function A (or active feed in CF B / CF I)
4	Lower pilot air port	G 1/4 pilot air intake to open the valve against spring force
5	Diaphragm bonnet	Cast stainless steel 1.4308 intermediate bonnet interface
6	Diaphragm	Size 100 two-piece PTFE shield with EPDM backing membrane
7	Body screws	Fasteners securing actuator to forged body
8	Port connection	DN 100 butt-weld ends (114.3 x 2.3 mm)
9	Valve body	Forged stainless steel 1.4435 (316L) body with internal weir

Materials of Construction

Actuator size 225 (L) uses high-strength polymer and stainless steel elements rated for demanding process operating conditions:

No.	Element	Material
1	Cover	Polyamide PA
2	Pilot air ports	Stainless steel 1.4305
3	Diaphragm bonnet	Stainless steel 1.4308
4	Diaphragm	PTFE with EPDM backing membrane (EA code)
5	Valve body	Forged stainless steel 1.4435 BN2 (316L)
-	Piston seal	NBR (Nitrile rubber)

Traceability and Compliance

The PTFE/EPDM diaphragm material complies with FDA Code of Federal Regulations, EC Regulation 1935/2004, and USP Class VI biological tests. The metallic valve body and diaphragm are fully traceable with included EN 10204 3.1 and 2.1 certificates.

Dimensional Specifications

Actuator Dimensions (Size 225 / L)

Diaphragm Size	Actuator Size Ø	Ø A [mm]	C [mm]	Pilot Air Port (K)	Height H [mm]
100	225 (L)	261	155	G 1/4	345

Forged Body Dimensions (SA39)

Body dimensions for connection DIN EN ISO 1127 / ISO 4200 / DIN 11866 Series B, Product Code SA39:

Diaphragm Size	Port Connection DN	Ø D1 [mm]	Wall Thickness s [mm]	Face-to-Face Length L [mm]	Body Center Height h [mm]	Total Body Height H [mm]	Product Key
100	100	114.3	2.3	295	63.5	127.0	SA39

Technical & Performance Parameters

Parameter	Value
Operating medium	Neutral gases and liquids, ultra-pure, sterile, aggressive, or abrasive media
Control medium	Neutral gases, compressed air
Maximum permissible operating pressure	7.00 bar (Static) / 4.00 bar (Dynamic) for PTFE/EPDM on DS 100
Pilot pressure range	5.0 to 6.0 bar
Flow coefficient ($K_v$ value)	235 m³/h (water at +20 °C, inlet 4 bar, outlet 3 bar)
Medium temperature range	-10 °C to +130 °C (Steam sterilisation up to +140 °C for 60 min)
Ambient temperature range	-10 °C to +50 °C (PA actuator size 225)
Nominal pressure rating	PN 16 (DIN EN 1333) / Class 150 (DIN EN 1759)
Manual override	No

Temperature Restrictions

Per technical guidelines, the component with the lowest maximum permissible temperature determines the limit of the complete assembly. With a PA actuator size 225, maximum ambient operating temperature is limited to +50 °C.

Installation and Self-Draining Guidelines

The valve may be installed in any orientation, preferably with the actuator facing upwards. When monitoring leakages, one of the relief bores in the intermediate diaphragm bonnet must point downwards at the lowest position.

To ensure complete self-draining without media holdup:

1. Maintain pipeline inclination according to ASME BPE recommendations.
2. Position the valve body at the specified self-draining angle $\alpha$.
3. The self-draining indicator marking on the port connection must point upwards.

Connection Code	Pipe Standard	DN	Diaphragm Size	Pipe Dimensions [mm]	Self-Draining Angle ($\alpha$)
SA39	DIN EN ISO 1127 / ISO 4200 / DIN 11866 Series B	100	100	114.3 x 2.3	14°

Welding Body into Pipeline

1. Disassemble the actuator and diaphragm before welding to avoid thermal destruction of seals and plastic components.
2. Pressurise the lower pilot air port with compressed air (5 to 6 bar) to lift the diaphragm off the body seat before loosening screws.
3. Loosen body screws crosswise and detach the actuator assembly.
4. Weld the forged body into the pipe system, ensuring proper alignment without stress.
5. Thoroughly clean the body cavity and sand surfaces smooth before reassembly.

Fastener Tightening Torques

When reinstalling the actuator onto the valve body, tighten the body screws crosswise in three gradual stages (approx. 1/3, 2/3, and full torque) without applying medium pressure:

Diaphragm Size	Tightening Torque (EPDM, FKM)	Tightening Torque (PTFE, advanced PTFE, GYLON®)	Tolerance
100	40 Nm	50 Nm	+10%

Diaphragm Mounting on Diaphragm Size 100

For diaphragm sizes 25 and larger, PTFE diaphragms feature a bayonet mount. Engage the bayonet into the compressor recess and lock it into place by rotating the diaphragm by 90°. The identification tab must align perpendicular to the flow direction.

Automation and Service Accessories

Burkert 347794 can be automated by retrofitting external sensor heads or control units:

• Electrical Position Feedback Type 8697: Compact feedback unit equipped with mechanical or inductive limit switches and LED position display, fitting actuator size 225 via adapter MT85.
• Pneumatic Control Unit Type 8690: Integrated automation system for discrete process valve actuation.
• Seal Kit for PA Actuator Size 225 / DS 100: Article number 186775.
• Replacement PTFE/EPDM Diaphragm (DS 100): Article number 20093077 (Material Code EPDM E04 / PTFE P05).