BURKERT 20082538 (Type 2973) is a manually operated 2/2-way diaphragm valve engineered for high-purity, hygienic, sterile, and chemically aggressive fluid control. The valve integrates a zero-deadleg forged stainless steel body in 316L / 1.4435 BN2 with an autoclavable manual actuator and a high-temperature EPDM diaphragm (size 15). Manufactured with welded pipe ends conforming to ASME BPE and DIN 11866 Series C (12.7 x 1.65 mm outer diameter and wall thickness), the valve maintains a nominal operating pressure from 0 to 10 bar (Class 150 / PN 10) across media temperatures spanning -10 °C to +143 °C, with steam sterilization capability up to +150 °C for 60 minutes.

The PPS handwheel assembly provides mechanical stroke limitation in both closing and opening directions, visual position feedback through an optical scale indicator with 50 graduation increments per revolution, and an integrated padlock-compatible locking pin mechanism. With a tested flow value of Kv = 3.1 m³/h (water at +20 °C under 1 bar pressure drop) and compliance with FDA 21 CFR, Regulation (EC) 1935/2004, and USP Class VI standards, article 20082538 serves pharmaceutical processing, biotechnology, food and beverage production, and pure steam utility systems.

Component Materials and Mechanical Construction

The Type 2973 FullFunction manual actuator is constructed from chemically resistant materials suited for aggressive washdown and autoclaving environments. The manual bonnet structure features a PPS handwheel and a stainless steel 1.4308 diaphragm socket. Internal components isolate mechanical actuation from the wetted chamber through the elastomer diaphragm seal.

Item	Component	Material
1	Lock pin	Stainless steel 1.4305
2	Fastening screw	Stainless steel A2
3	Handwheel cover	Polyamide (PA)
4	Handwheel	Polyphenylene sulphide (PPS)
5	Visual position indicator	Polyamide (PA)
6	Valve spindle	Stainless steel 1.4305
7	Diaphragm socket	Stainless steel 1.4308
8	Diaphragm	EPDM high-temperature (AD)
9	Valve body	Forged stainless steel 316L / 1.4435 BN2

Surface Quality Standard

Wetted internal surfaces of the forged stainless steel body (VS) feature mechanical polishing to Ra ≤ 0.5 µm (product code NO14, ASME BPE SF1) or optional electro-polishing down to Ra ≤ 0.38 µm (product code NO17, ASME BPE SF4 / DIN HE4).

Technical Dimensions and Operating Specifications

Article 20082538 corresponds to diaphragm size 15 and port code SA92 (DN 15 welded connection according to ASME BPE / DIN 11866 Series C). Dimensions in the table below apply directly to this execution.

Specification Parameter	Value
Article number (SKU)	20082538
Diaphragm size	15
Pipe connection standard	ASME BPE / DIN 11866 Series C
Nominal diameter (DN)	DN 15 (NPS 1/2")
Outer pipe diameter (∅D1)	12.7 mm
Pipe wall thickness (s)	1.65 mm
Face-to-face body length (L)	108 mm
Body weir height dimension (h)	8.15 mm
Centerline-to-body base dimension (H)	19.85 mm
Product key connection code	SA92
Actuator height open (H1 / H2)	127 mm / 133 mm
Actuator height closed (H3 / H4)	121 mm / 127 mm
Handwheel diameter (∅ B)	45 mm (Size S, spindle slope 1.75 mm/rev)
Water flow coefficient (Kv)	3.1 m³/h (Cv = 3.6 gpm)

Stroke Limitation and Actuator Locking Function

Type 2973 actuators include adjustable minimum and maximum stroke limiters via an internal adjusting sleeve, ensuring precise repeatable flow control and preventing diaphragm overtightening.

Setting Stroke Limitations

1. Rotate the handwheel clockwise until the valve is completely closed.
2. Loosen the handwheel screw using a 2 mm hexagon socket wrench and remove the handwheel.
3. Turn the adjusting sleeve clockwise until mechanical resistance is reached to define the minimum stroke limit.
4. Re-install the handwheel, ensuring the spindle square and sleeve hexagon align accurately.
5. Turn the handwheel counterclockwise to the required maximum open position.
6. Remove the handwheel, pull the adjusting sleeve upward, and turn it counterclockwise to its stop to fix the maximum stroke limit.
7. Re-mount the handwheel and secure the handwheel screw to a torque of 0.9 Nm.

Handwheel Locking Procedure

The manual actuator for diaphragm size 15 incorporates 12 discrete locking positions per handwheel revolution (every 30° of rotation, equivalent to 0.15 mm of spindle stroke). To secure the setting, depress the locking pin and rotate it 180° until fully engaged. The integrated 3.8 mm diameter transverse bore allows attachment of a padlock to safeguard against unauthorized operation.

Installation and Assembly Guidelines

Dismantle Before Welding

To prevent thermal damage to internal elastomers and moving mechanisms, dismantle the actuator assembly and diaphragm from the valve body before executing orbital or manual line welding.

1. Rotate the handwheel counterclockwise into the fully OPEN position.
2. Loosen body fastening bolts crosswise and detach the actuator bonnet and diaphragm from the forged body.
3. Weld the 316L / 1.4435 BN2 body into the piping system, maintaining pipe alignment in compliance with ASME BPE self-draining inclination rules.
4. Clean the internal cavity thoroughly following pipe weld cool-down.
5. Re-seat the actuator and diaphragm onto the body, ensuring the diaphragm tab is oriented at a 90° angle relative to the pipeline axis.
6. Tighten the body fastening screws crosswise in three progressive torque steps (approx. 1/3, 2/3, and 100% of the final value).

Tightening Torques for Diaphragm Size 15 Body Screws

Valve Body Material Group	Diaphragm Material	Final Torque Value (Tolerance +10%)
Forged Steel (VS), Cast (VG), Plastics	EPDM (AD) / FKM (FF)	3.5 Nm
Forged Steel (VS), Cast (VG), Plastics	PTFE / Advanced PTFE / GYLON®	4.0 Nm
Tube Valve Body (VP)	EPDM (AD) / FKM (FF)	3.5 Nm
Tube Valve Body (VP)	PTFE / Advanced PTFE / GYLON®	4.0 Nm

Handwheel Closing Torques

For diaphragm size 15 with EPDM elastomer, apply a static handwheel closing torque of 0.8 Nm (dynamic closing torque 1.5 Nm) to seal against 10 bar media pressure. Excessive closing force must be avoided to preserve diaphragm lifecycle.

Maintenance and Diaphragm Replacement

The Type 2973 actuator mechanism is maintenance-free under normal operating conditions. The diaphragm bonnet contains an external relief bore positioned at the lowest point during installation to ensure immediate visual leak detection if diaphragm integrity is compromised.

Component	Maintenance Inspection Procedure
Relief Bore	Check periodically for process fluid weepage; replace diaphragm immediately if medium is detected
Body Screws	Re-tighten body screws crosswise after the first operational steam sterilization cycle
Switching Cycles	Inspect elastomer diaphragm condition after a maximum of 100,000 switching operations

For diaphragm size 15, the EPDM membrane connects to the actuator compressor via a bayonet catch mechanism. Replacement involves turning the handwheel to the OPEN position, releasing body screws, driving the actuator to the CLOSED position, and rotating the old diaphragm 90° to disengage the bayonet. Insert the replacement diaphragm (original Bürkert replacement article 693 163, material code EPDM E04), rotate 90° until locked, and reassemble as specified.

Approvals and Regulatory Conformity

• Food Contact Regulations: FDA 21 CFR compliance and European Regulation (EC) 1935/2004 compliance declaration.
• Pharmaceutical Standards: USP Class VI certified elastomer composition.
• Inspection Documentation: DIN EN 10204 3.1 inspection certificate for body material and 2.1 manufacturer conformity declaration for diaphragm material.
• Explosion Protection (Optional PX51): Certified under EPS 18 ATEX 2 008 X and IECEx EPS 18.0007X (II 2G Ex h IIC T4…T2 Gb / II 2D Ex h IIIC T135 °C…T300 °C Db) for use in Zones 1, 21, 2, and 22.
• Fugitive Emissions: TA-Luft compliant under variable code PM01.