BURKERT 311678 (Type 2104) is a pneumatically operated 3/2-way stainless steel T-diaphragm valve designed for hygienic processing, sampling, and distribution in decentralised automation systems. The assembly consists of an externally controlled pneumatic piston actuator, an advanced PTFE/EPDM diaphragm, and a zero-deadleg T-valve body machined from solid 1.4435 / 316L block material. Operating under Control Function A (normally closed by spring force), the valve shuts off the branch weir at media pressures up to 10 bar (PN 16 / Class 150) using a 5.5 to 7.0 bar pneumatic pilot pressure signal.

Designed for integration into the Bürkert ELEMENT architecture, the valve features internal pilot air routing and a 360° continuously rotatable interface. The wetted process body features ASME BPE / DIN 11866 Series C butt-weld ends with a main line nominal diameter of DN 65 (2 1/2", 63.5 mm OD) and a branch nominal diameter of DN 40 (1 1/2", 38.1 mm OD), delivering high flow capacity while fully supporting CIP and SIP cycles at temperatures up to 143 °C (and short-term steam sterilisation at 150 °C for 60 minutes).

Technical Specifications

Parameter	Specification Details
Product Type	Type 2104 ELEMENT T-Diaphragm Valve
Article Number	311678
Circuit Function	3/2-way, Control Function A (NC, normally closed by spring force)
Main Port Connection (Port 1)	Butt weld end DN 65 (2 1/2", 63.5 mm outer diameter, 60.2 mm inner diameter, 1.65 mm wall thickness)
Branch Port Connection (Port 2)	Butt weld end DN 40 (1 1/2", 38.10 mm outer diameter, 34.80 mm inner diameter, 1.65 mm wall thickness)
Applicable Pipe Standards	ASME BPE / DIN 11866 Series C
Diaphragm Size	Size 40 (40 mm body weir orifice)
Operating Pressure Range	0.00 bar to 10.00 bar (PN 16 / ASME Class 150)
Pilot Pressure Range	5.5 bar to 7.0 bar (push-in ∅ 6 mm ELEMENT interface)
Medium Temperature Range	-5 °C to +143 °C (steam sterilisation max. +150 °C for 60 min)
Ambient Temperature Range	-5 °C to +55 °C (-10 °C to +60 °C series range)
Pilot Air Fluid	Neutral gases, filtered instrument air
Enclosure Rating	IP65 / IP67, NEMA Type 4X
Documentation Included	EN 10204 3.1 inspection certificate, EN 10204 2.1 diaphragm certificate

Material Specifications and Architecture

The Type 2104 ELEMENT valve pairs a block-machined stainless steel valve body with an autoclaved, chemical-resistant pneumatic actuator casing designed without external air tubing lines:

Pos.	Component Part	Material Specification
1	Ground Terminal	Stainless steel 1.4301 / 1.4305 (for ATEX / IECEx variants)
2	Transparent Position Cap	Polysulfone (PSU)
3	Pilot Air Ports	Push-in connector Polypropylene (PP) ∅ 6 mm, G 1/8 stainless steel 1.4305
4	Internal Actuator Housing	Polyphenylene sulphide (PPS)
5	Actuator Cover Envelope	Stainless steel 1.4561 (316Ti)
6	Piston Seal	Fluoroelastomer (FKM)
7	Diaphragm	Advanced PTFE with EPDM backing cushion (Code EU)
8	T-Valve Body	Stainless steel 1.4435 (DIN EN 10088) / 316L (ASME BPE Table MM-2.1.1)

Wetted surfaces are finished to sanitary process standards: electropolished to Ra ≤ 0.38 µm (ASME BPE SF4 / DIN HE4) or mechanically polished to Ra ≤ 0.5 µm (ASME BPE SF1), with external surfaces finished to Ra ≤ 1.6 µm.

ASME BPE Welded Connection Dimensions

Dimensional layout for Type 2104 welded block T-bodies complies with ASME BPE and DIN 11866 Series C pipe geometry. Article 311678 features Diaphragm Size 40 with a DN 65 main line and DN 40 branch line (product combination key SODJ-SODH):

Diaphragm Size	Port 1–Port 2 DN	∅D1 [mm]	s1 [mm]	∅D2 [mm]	s2 [mm]	A [mm]	B [mm]	C [mm]	E [mm]	F [mm]	G [mm]	H [mm]	I [mm]	Product Key
40	40...40	38.10	1.65	38.10	1.65	152.0	25.0	99.6	25.0	121.0	58.0	35.0	6.4	SODH-SODH
40	50...40	50.80	1.65	38.10	1.65	162.0	30.0	101.6	30.0	131.0	72.0	43.0	14.4	SODI-SODH
40 (311678)	65...40	63.50	1.65	38.10	1.65	162.0	30.0	107.9	30.0	143.0	85.0	50.0	21.4	SODJ-SODH
40	80...40	76.20	1.65	38.10	1.65	162.0	30.0	114.3	30.0	156.0	98.0	56.0	27.4	SODK-SODH

All dimensions are stated in millimetres. Port 1 outer diameter is 63.50 mm (2 1/2") with 1.65 mm wall thickness, while Port 2 outer diameter is 38.10 mm (1 1/2") with 1.65 mm wall thickness.

Decentralised Automation and Control Units

The ELEMENT design allows mounting of intelligent control modules directly onto the actuator interface without external air supply pipes:

• Control Heads Type 8691 / 8695: Contactless inductive position sensor, coloured high-visibility status LEDs, teach-in functionality, AS-Interface, IO-Link, and büS integration.
• Pneumatic Feedback Units Type 8690 / 8697: Compact optical mechanical/inductive limit switch detection with integrated manual override.
• Positioners TopControl Type 8692 / 8694: Electropneumatic continuous positioning modules with graphic backlit display or DIP switches, supporting PROFIBUS DPV1, PROFINET, EtherNet/IP, Modbus TCP, and IO-Link.
• Process Controllers Type 8693: Integrated PID process control with automated TUNE tuning functions and comprehensive diagnostics.

Pipeline Installation and Welding Guidelines

Type 2104 can be installed in any orientation, preferably with the actuator upright. When fitted into circular loop pipelines, specific drain angles should be maintained according to ASME BPE standards to guarantee complete gravity self-drainage.

Damage to Diaphragm or Actuator During Welding

Welding temperatures will degrade elastomer seals and actuator internals. Always unbolt and remove the actuator and diaphragm assembly from the body before orbital or manual welding of the block into the pipeline.

Leakage Detection Relief Bores

The diaphragm bonnet contains radial relief bores that vent fluid in the event of diaphragm rupture. Rotate the valve so that at least one relief bore points towards the lowest position to ensure immediate visual detection of seal leakage.

Actuator Mounting and Body Bolt Torques

When reinstalling the actuator on Control Function A valves, follow the exact pressure sequence:

1. Ensure the compressor is positioned correctly on the spindle.
2. Apply pilot pressure (5.5 to 7.0 bar) to pilot port 1 to retract the actuator spring and open the valve.
3. Position the actuator and diaphragm onto the body.
4. Lightly tighten the body bolts crosswise until the diaphragm sits evenly between the body and bonnet.
5. Cycle the valve twice using pilot air to seat the diaphragm central to the weir.
6. Exhaust the pilot air pressure so the valve returns to the closed position.
7. Tighten the body bolts in three progressive stages (approx. 1/3, 2/3, then 100% of final tightening torque) crosswise without pressure.

Diaphragm Size	Tightening Torque for EPDM / FKM [Nm]	Tightening Torque for PTFE / Advanced PTFE / GYLON® [Nm]
8	2.0	2.5
15	3.5	4.0
20	4.0	4.5
25	5.0	6.0
40 (311678)	8.0	10.0
50	12.0	15.0
65	20.0	30.0
80	30.0	40.0
100	40.0	50.0

Torque tolerance is +10%. For Diaphragm Size 40 with advanced PTFE (EU), tighten bolts to exactly 10.0 Nm.

Diaphragm Replacement and Maintenance

Diaphragms represent consumable components requiring routine inspection. For Diaphragm Size 40, the advanced PTFE diaphragm connects to the actuator compressor via an integrated bayonet catch. Rotate the diaphragm 90° to detach it from the compressor guide slot.

Switching Between Diaphragm Materials

When converting from a bayonet PTFE diaphragm to a threaded EPDM diaphragm on sizes ≥25, an adapter insert must be placed into the compressor. Conversely, remove this insert before mounting a bayonet PTFE diaphragm to prevent damage to the compressor assembly.

Inspection Intervals and Troubleshooting

• Re-torque body bolts crosswise after the first steam sterilisation cycle.
• Check diaphragm wear at 100,000 switching cycles or earlier when operating with abrasive media.

Symptom	Probable Cause	Corrective Action
Actuator fails to switch	Pilot air connected to wrong port	Connect control pressure to pilot port 1 (CF A)
Actuator fails to switch	Pilot air pressure below 5.5 bar	Increase pilot pressure to 5.5–7.0 bar range
Valve seat leakage	Medium operating pressure exceeds 10 bar	Verify system operating pressure complies with specification
Valve seat leakage	Particulate entrapment or diaphragm wear	Disassemble, clean weir surface, or replace diaphragm
Reduced fluid flow rate	Diaphragm bulging due to thermal overstress	Replace diaphragm kit with genuine Bürkert spare part