BURKERT 20090698 (Type 2961) is a manually operated 2-way globe control valve engineered for continuous flow regulation of neutral gases, water, steam, alcohols, oils, fuels, hydraulic fluids, saline solutions, lyes, and organic solvents. Built for process installations requiring reproducible manual flow setting, this article features a nominal connection size of DN 50 (NPS 2) with welded pipe ends conforming to DIN 11850 Series 2 / DIN 11866 Series A / DIN EN 10357 Series A (outer tube diameter 53.0 mm, wall thickness 1.5 mm). The valve configuration combines a 316L/CF3M stainless steel globe body, an exchangeable 50 mm orifice seat, a PTFE soft seat seal providing DIN EN 60534-4 Leakage Class VI shut-off, and a high-performance PPS manual actuator with an optical stroke scale.

Equipped with an equal percentage parabolic control cone providing a theoretical rangeability of 50:1, the valve reaches a nominal flow coefficient Kvs of 37 m³/h (Cv 43.1 gpm) across a 26 mm stroke. Flow passes below the seat (flow-to-open), preventing water hammer during closure. The self-adjusting PTFE V-ring gland packing includes integrated spring compensation, maintaining stem sealing without manual adjustment.

Design and Operating Principle

BURKERT Type 2961 operates by manually rotating the polyphenylene sulphide (PPS) handwheel. Counterclockwise rotation drives the stem upward, lifting the parabolic control cone away from the replaceable valve seat to establish medium flow. Clockwise rotation forces the cone downward against the flow until the PTFE seat seal contacts the stainless steel seat ring, achieving bubble-tight shut-off. A precision spindle guide in 1.4404 (316L) stainless steel with PTFE filling supports the spindle to maintain accurate flow characteristics under demanding line vibrations.

The manual actuator incorporates a multi-turn optical position indicator. Handwheel size M (Ø 110 mm) provides an axial spindle slope of 1.75 mm per complete 360° turn. The handwheel rim carries a 50-division radial scale, while the actuator neck reveals a reproducible stroke scale as the handwheel lifts. This dual-scale arrangement permits repeatable positioning across 50 increments per revolution.

Visual Indicator Setting Notice

The visibility of the stroke scale does not directly correlate with the fully closed position across all body types. Depending on the valve design, the repeatable stroke scale may not be visible when open, or may remain partly visible when closed. Always reference the flow curve table and calibrate the zero position against the seat touch point.

Materials of Construction

Item	Component	Material
1	Cover	Polyamide (PA)
2	Screw	Stainless steel 1.4301
3	Locking device	Stainless steel 1.4305
4	Handwheel	Polyphenylene sulphide (PPS)
5	Visual position indicator with scale	Polyamide (PA)
6	Packing gland	PTFE V-rings (filled), with spring compensation
7	Stem	Stainless steel 1.4401 or 1.4404
8	Spindle guide	Stainless steel 1.4404 (316L), PTFE filled
9	Housing seal	Graphite
10	Control cone	Stainless steel 1.4571
11	Seat seal	PTFE (Polytetrafluoroethylene)
12	Valve seat with O-ring	Stainless steel 1.4571, EPDM
13	Valve body	Stainless steel 316L / CF3M

Fluidic Data and Flow Characteristics

Flow characteristics conform to DIN EN 60534-2-4. For seat sizes greater than DN 10, the turn-down ratio KvR threshold is defined at 5% of valve stroke. The theoretical rangeability (Kvs / Kv0) is 50:1. The table below lists the intermediate Kv values measured with water at incremental stroke percentages for article 20090698 (DN 50, seat size 50 mm), along with smaller exchangeable seat trims available for the DN 50 globe valve body.

Port Size DN	Seat Size [mm]	Handwheel Size	Max. Pressure [bar(g)]	Leakage Class	5%	10%	20%	30%	40%	50%	60%	70%	80%	90%	100% (Kvs)
50	50 (20090698)	110 (M)	25 (20)¹	VI (PTFE)	0.90	1.1	1.9	2.9	4.5	6.8	10.5	15.5	22.0	29.5	37.0 m³/h
50	40	110 (M)	25 (20)¹	VI (PTFE)	0.60	0.70	1.0	1.7	2.6	4.0	5.9	9.2	14.0	18.9	24.5 m³/h
50	32	110 (M)	25 (20)¹	VI (PTFE)	0.48	0.60	0.90	1.3	2.1	3.2	4.6	6.9	11.6	16.0	21.0 m³/h
50	20	110 (M)	25 (20)¹	II (Steel)	—	0.14	0.25	0.38	0.57	0.85	1.3	1.9	2.8	4.1	6.3 m³/h

¹ Pressure derating in parentheses (20 bar) applies to compressible fluids of Group 1 (hazardous gases and vapors according to Pressure Equipment Directive 2014/68/EU).

Operating Limits and Pressure-Temperature Derating

The maximum permissible working pressure of BURKERT process valves is governed jointly by the body pressure rating (PN 25 / Class 150), connection standards, and medium temperature.

Pressure Derating for PN 25 Body (DIN EN 12516-1)

Temperature [°C]	Maximum Permissible Operating Pressure [bar(g)]
-10 to +50 °C	25.0 bar
+100 °C	24.5 bar
+130 °C (PTFE limit)	23.0 bar
+150 °C	22.4 bar
+200 °C	20.3 bar
+230 °C	19.0 bar

Seat Seal Temperature Boundaries

Sealing Material	Leakage Class (DIN EN 60534-4)	Medium Temperature Range	Application Notes
PTFE (Article 20090698)	Class VI (Soft seal)	-40 °C to +130 °C	Bubble-tight shut-off; eliminates need for secondary isolation valve below 130 °C.
PEEK (Optional)	Class VI (Soft seal)	-10 °C to +230 °C	Recommended for medium temperatures > 130 °C.
Stainless Steel (Optional)	Class II (Metal-to-metal)	-40 °C to +230 °C	Permissible seat leakage 0.5% of nominal flow; resistant to erosion.

Dimensions

Actuator Dimensions for Type 2961 Globe Body

Nominal Size DN	Nominal Size NPS	Handwheel Size	Handwheel Ø [mm]	Height H1 [mm]	Height H2 (with Lock) [mm]
15	1/2	S	45	217	224
20	3/4	S	45	224	230
25	1	S	45	228	234
32	1 1/4	M	110	296	303
40	1 1/2	M	110	301	307
50 (20090698)	2	M	110	307	313
65	2 1/2	L	160	361	368
80	3	L	160	369	375
100	4	L	160	379	385

Welded Body Dimensions: DIN 11850-2 / DIN 11866 Series A / DIN EN 10357 Series A

Nominal Size DN	Body Length LS [mm]	End Depth ES [mm]	Outer Tube Ø DS [mm]	Wall Thickness WS [mm]
10	90	20	13.0	1.5
15	90	20	19.0	1.5
20	100	20	23.0	1.5
25	130	26	29.0	1.5
32	140	26	35.0	1.5
40	150	26	41.0	1.5
50 (20090698)	175	26	53.0	1.5
65	210	26	70.0	2.0
80	230	26	85.0	2.0
100	260	26	104.0	2.0

Installation and Assembly

Before welding the valve body into the pipeline, the manual actuator must be disassembled from the body to protect the internal seals and PTFE packing from thermal degradation.

1. Rotate the handwheel counterclockwise by approximately two turns to lift the plug away from the seat seal.
2. Apply an open-end wrench to the body connection wrench flats and unscrew the actuator assembly from the valve body.
3. Weld the valve body into the pipe system, ensuring proper pipeline alignment and flushing out weld slag, chips, and debris.
4. Prior to reassembly, inspect the graphite body seal and replace it if damaged.
5. Apply an approved lubricant (such as Klüberpaste UH1 96-402) to the external threads of the body connection.
6. Screw the actuator back into the body. Tighten to the specified torque using a calibrated torque wrench.

Valve Body Nominal Diameter DN	Tightening Torque [Nm]	Tolerance [Nm]
10 / 15	45	±3
20	50	±3
25	60	±3
32	65	±3
40	65	±3
50 (20090698)	70	±3
65	100	±3
80	120	±5
100	150	±5

Body Connection Torque Check

In piping installations subjected to severe mechanical vibration or operating temperatures exceeding 140 °C, the threaded body connection can loosen over time. Check the body connection screw torque before initial startup and at regular maintenance intervals.

Stroke Limitation and Handwheel Locking Options

While article 20090698 is supplied standard without mechanical stroke limitation, the Type 2961 actuator platform supports optional stroke limit adjustment sleeves and handwheel interlocks.

• Stroke Limitation: Adjusting sleeves allow mechanical limitation of minimum and maximum travel. With the handwheel removed, rotating the sleeve clockwise sets minimum opening stroke, while pulling upward and turning counterclockwise locks maximum opening stroke.
• Handwheel Interlock: Handwheel size M accommodates 13 locking points per revolution (one interlock every 27°, corresponding to 0.13 mm of stroke). Pressing down and rotating the locking pin engages the interlock, which features a Ø 3.8 mm hole accepting standard lockout padlocks.

Maintenance and Troubleshooting

Under normal service conditions following manufacturer guidelines, the Type 2961 manual actuator is maintenance-free. Perform an annual visual inspection of the valve body, pipe connections, and relief bore.

Problem	Probable Cause	Corrective Action
Valve seat fails to seal tightly	Particulate debris trapped between plug and seat	Flush line; install upstream strainer
	Seat seal worn or damaged	Replace closure member / seat seal
	Pipeline flow direction reversed	Verify arrow on body; flow must enter below seat
	Operating pressure exceeds limit	Check line pressure against type label specifications
Medium leakage at actuator relief bore	Stem packing gland worn	Replace PTFE V-ring gland packing set

Explosion Protection (ATEX / IECEx)

BURKERT Type 2961 conforms to ATEX / IECEx certification EPS 18 ATEX 2 008 X and IECEx EPS 18.0007X (Category 2 mechanical equipment, suitable for Zone 1/21 and Zone 2/22).

• Marking: II 2G Ex h IIC T4...T2 Gb / II 2D Ex h IIIC T135°C...T300°C Db

Temperature Class	Maximum Surface Temperature	Permissible Ambient Temperature	Maximum 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 Hazardous Areas

Sudden electrostatic discharge from insulated conductive components in explosive atmospheres poses an ignition hazard. Connect the valve body to the pipe grounding system. If conductive non-grounded accessories are installed, provide separate potential equalization straps. Clean outer plastic actuator surfaces only using a damp or antistatic cloth.