BURKERT 20136039 (Type 2973) is a manually operated 2/2-way diaphragm valve built for hygienic, sterile, and demanding process applications. Configured with FullFunction manual actuation, article 20136039 incorporates a zero-deadleg forged stainless steel 316L / 1.4435 BN2 body (VS), DN 25 welded spigots conforming to SMS 3008 (tube diameter 25.0 x 1.2 mm), and an Advanced PTFE diaphragm backed by EPDM. The valve provides tight isolation from 0 to 10 bar over a medium temperature span of -5 °C to +143 °C, with steam sterilisation capability up to +150 °C for 60 minutes.

The Type 2973 manual actuator combines a polyphenylene sulphide (PPS) handwheel with an investment-cast stainless steel 1.4308 bonnet. It is autoclavable and resistant to harsh washdowns, aggressive process media, and corrosive plant environments. The internal fluid contact geometry is free from dead zones, delivering a water flow coefficient of Kv = 14.8 m³/h (Cv = 17.2 gpm). The assembly complies with EC Regulation 1935/2004, FDA 21 CFR, and USP Class VI, and satisfies ATEX / IECEx mechanical explosion protection standards for equipment category 2 in Gas Zone 1 and Dust Zone 21.

Component Materials and Mechanical Construction

Every structural part in contact with either the fluid or external cleanroom ambient conditions is selected for chemical inertness and mechanical stability:

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 bonnet / socket	Stainless steel 1.4308
8	Diaphragm	Advanced PTFE with EPDM backing (material code EU / P06)
9	Valve body	Forged stainless steel 316L / 1.4435 BN2 (VS)

Surface Quality

The forged steel body (VS) features an internal surface electropolished to Ra ≤ 0.38 µm (Bürkert code NO17, conforming to ASME BPE SF4 and DIN HE4). The exterior forged surface is mechanically and electropolished. The valve includes an EN 10204 3.1 inspection certificate for the body and a 2.1 certificate for the diaphragm.

Technical Data and Operating Limits

Parameter	Specification
Valve Type	2973 FullFunction
Order Code (Article)	20136039
Nominal Diameter	DN 25 (NPS 1)
Process Connection	Welded spigots, SMS 3008, 25.0 mm OD x 1.2 mm wall thickness
Diaphragm Size	Size 25
Nominal Pressure Class	PN 10 (DIN EN 1333) / Class 150 (DIN EN 1759)
Permissible Medium Pressure	0 to 10 bar (static overpressure)
Medium Temperature Range	-5 °C to +143 °C
Steam Sterilisation Limit	Up to +150 °C for 60 minutes
Ambient Operating Temperature	-10 °C to +130 °C (autoclavable; short-term up to +150 °C)
Flow Rate (Kv Value Water)	14.8 m³/h (measured at +20 °C, 4 bar inlet, 3 bar outlet)
Flow Rate (Cv Value)	17.2 gpm
Handwheel Diameter	45 mm (Actuator Size S)
Spindle Stroke Pitch	1.75 mm per complete handwheel revolution
Position Feedback	Visual stroke scale; optional M5 x 0.5 sensor bores

Dimensions

Actuator Dimensions

The manual actuator for diaphragm size 25 belongs to size group S (handwheel diameter ∅ B = 45 mm):

Diaphragm Size	H1 (Open) [mm]	H2 (Open with Stroke Limiter) [mm]	H3 (Closed) [mm]	H4 (Closed with Stroke Limiter) [mm]	∅ B [mm]
15	127	133	121	127	45
20	138	144	129	135	45
25	143	149	133	139	45

Forged Body (VS) Dimensions — Welded Ports

Article 20136039 utilizes SMS 3008 welded port connections in diaphragm size 25 (product code SA60):

Diaphragm Size	Standard	DN	Pipe ∅D1 [mm]	Wall Thickness s [mm]	Length L [mm]	Port Height h [mm]	Total Height H [mm]	Product Key
25	SMS 3008	25	25.0	1.20	129	19.0	37.0	SA60
40	SMS 3008	40	38.0	1.20	161	27.6	52.4	SA62
50	SMS 3008	50	51.0	1.20	192	35.5	68.3	SA63
25	ISO 1127 / 11866 B	25	33.7	2.00	129	19.0	37.0	SA44
25	DIN 11850-2 / 11866 A	25	29.0	1.50	129	19.0	37.0	SD44
25	ASME BPE / 11866 C	1"	25.4	1.65	127	19.0	37.0	SODF

Position Indication, Stroke Limitation, and Locking Mechanism

The FullFunction manual actuator incorporates a yellow visual position indicator positioned below the handwheel. When turning the handwheel counterclockwise to open the valve, the indicator and its graduation scale become visible. The handwheel rim carries 50 discrete rotary division marks. Combining the handwheel scale with the stationary stroke scale allows precise and repeatable throttle settings.

Operating Closure Torque

Always close the handwheel manually without wrenches or levers. Stop turning once tight shut-off is achieved. For diaphragm size 25 with an Advanced PTFE diaphragm, static isolation at 10 bar requires a closing torque of 3.5 Nm (+10% tolerance), while closing against full dynamic flow requires 5.0 Nm. Excessive manual force degrades the PTFE sealing lip and shortens diaphragm working life.

Stroke Limitation Adjustment

On Type 297x actuators, minimum and maximum stroke limits can be set using an internal adjusting sleeve:

1. Rotate the handwheel clockwise to the fully closed position.
2. Loosen the handwheel fastening screw (AF 2 mm hexagon socket) and lift off the handwheel.
3. Thread the adjusting sleeve clockwise until it stops to set the minimum stroke limiter.
4. Replace the handwheel, ensuring the spindle square aligns with the adjusting sleeve geometry.
5. Open the valve to the desired maximum travel position, remove the handwheel again, and pull the adjusting sleeve upward while rotating counterclockwise until seated to fix the maximum opening limit.
6. Refit the handwheel and retighten the set screw with 0.9 Nm torque.

Handwheel Lockout

The FullFunction actuator accepts an integrated lockout mechanism. For diaphragm size 25, the locking device offers 12 locking positions per complete handwheel revolution (every 30° rotation, corresponding to 0.15 mm axial stroke increment). Pushing down the locking pin and rotating it 180° engages the spindle. The exposed 3.8 mm cross-bore accommodates a safety padlock to prevent unauthorized repositioning.

Installation and Self-Draining Alignment

The preferred valve orientation is upright with the actuator positioned vertically upward. Self-draining installation requires setting the pipeline and valve body to the specific drainage angle α permanently marked on the forged body.

Dismantle Before Welding

Thermal conduction from orbital or manual tube welding will destroy the Advanced PTFE/EPDM diaphragm and spindle mechanics. Open the handwheel fully, loosen the body screws crosswise, and detach the actuator and diaphragm subassembly from the forged body prior to welding the SMS 3008 pipe connections.

Assembly and Body Screw Tightening

After orbital or manual welding of the body spigots:

1. De-burr, polish, and thoroughly flush the interior of the pipeline and body seat.
2. Position the actuator with the Advanced PTFE/EPDM diaphragm on the body. Align the diaphragm tab at 90° to the fluid flow line.
3. Orient one of the bonnet relief bores at the lowest position to ensure immediate visual indication of diaphragm leakage.
4. Hand-tighten the four body screws crosswise until the diaphragm is clamped uniformly.
5. Cycle the handwheel open and closed twice to seat the elastomer convolution correctly, then reopen to approximately 20% travel.
6. Tighten the fastening screws crosswise in three gradual steps (1/3, 2/3, 3/3 of final torque) to the specified value:

Diaphragm Size	Body Material	Elastomer Diaphragm (EPDM / FKM)	PTFE / Advanced PTFE (EU) / GYLON®
15	VS, VG, Plastics	3.5 Nm	4.0 Nm
20	VS, VG, Plastics	4.0 Nm	4.5 Nm
25	Forged Steel (VS)	5.0 Nm	6.0 Nm
32	VS, VG, Plastics	6.0 Nm	8.0 Nm
40	VS, VG, Plastics	8.0 Nm	10.0 Nm
50	VS, VG, Plastics	12.0 Nm	15.0 Nm

A tolerance of +10% applies to all tightening torques. Retighten the body screws crosswise following the first complete steam SIP cycle.

Diaphragm Replacement Procedure

Diaphragm size 25 uses a bayonet catch mechanism for Advanced PTFE diaphragms (Bürkert spare part article 20093082, material designation EPDM E04 / PTFE P06):

1. Relieve line pressure completely, drain remaining liquid, and turn the handwheel counterclockwise into the OPEN position.
2. Undo the four body bolts crosswise and lift the actuator clear of the valve body.
3. Turn the handwheel clockwise to the CLOSED position so the compressor protrudes from the bonnet.
4. Rotate the worn Advanced PTFE diaphragm by 90° to disengage the bayonet catch from the compressor slot, and discard the diaphragm.
5. Insert the bayonet pin of the replacement Advanced PTFE diaphragm (article 20093082) into the compressor and rotate 90° until firmly locked.
6. Retract the actuator by turning the handwheel to the OPEN position.
7. Place the subassembly onto the forged body, ensuring the identification tab stands perpendicular to the pipeline direction.
8. Fasten the body bolts in three torque steps up to 6.0 Nm as described above.

Diaphragm Compatibility

If replacing an EPDM diaphragm (threaded connection) with an Advanced PTFE diaphragm on size 25, the threaded compressor insert must be removed before mounting the bayonet pin. Failure to remove the threaded insert will cause severe mechanical damage to the compressor and diaphragm.

Explosion Protection and Hazardous Area Instructions

Under variable code PX51, Type 2973 is certified as mechanical equipment Category 2G/2D for zones 1/21 and 2/22 pursuant to EPS 18 ATEX 2 008 X and IECEx EPS 18.0007X (Ex h IIC T4...T2 Gb / Ex h IIIC T135°C...T300°C Db).

Temperature Class	Maximum Surface Temperature	Permissible Ambient Temperature	Maximum Permissible Medium Temperature
T4	+135 °C	-40 °C to +100 °C	+125 °C
T3	+200 °C	-40 °C to +130 °C	+185 °C
T2	+300 °C	-40 °C to +130 °C	+285 °C

Electrostatic Discharge Hazard in Ex Zones

Electrostatic charging can create an ignition hazard in potentially explosive atmospheres:

• Electrically bond the forged steel valve body to the plant piping system to maintain equipotential bonding.
• If insulating gaskets or plastic line sections are present, connect an auxiliary ground lead directly to the valve body and actuator grounding lug.
• Clean actuator and handwheel surfaces exclusively using a damp or antistatic cloth.
• For media with low electrical conductivity (≤ 100 pS/m), restrict fluid velocities to ≤ 1 m/s to prevent dangerous charge accumulation.