BURKERT 377555 (Type 2100) is a pneumatically operated 2/2-way angle seat valve from the ELEMENT series, configured for decentralized process automation. The valve features a DN25 orifice, ASME BPE weld ends (outer diameter 25.4 mm x wall thickness 1.65 mm), an actuator size of Ø 50 mm (Size D), and control function A (normally closed by spring force). Fluid enters below the valve seat, allowing reliable shut-off for liquids, steam, and gases without water hammer. Designed with a cast CF3M stainless steel body and PTFE seat sealing, the unit provides tight shut-off up to 9 bar(g) operating pressure, with medium temperatures up to +185 °C and full CIP/SIP capability.

Functional Principle and Flow Direction

BURKERT 377555 utilizes control function A (CFA). In its rest position, the valve is held closed by spring force acting on the piston and spindle assembly. Applying pilot air pressure to pilot port 1 lifts the piston against the spring stack, raising the swivel plate off the valve seat into the open position. When pilot air is vented, the springs return the spindle and swivel plate to the closed position.

The flow direction is configured below the seat (flow-to-open). Because the operating medium acts on the underside of the swivel plate, process pressure aids in opening the valve. This flow configuration is required for liquid applications to prevent dangerous pressure surges.

Operating Restriction on Liquid Media

Valves with flow direction above the seat must not be used for liquid media. Rapid closure against flowing liquid produces severe water hammer that can burst pipelines and equipment. BURKERT 377555 is configured with flow direction below the seat, making it fully rated for liquids, steam, and gases.

Materials of Construction

BURKERT 377555 incorporates corrosion-resistant materials throughout its wetted and external structural parts. The stem seal utilizes a self-adjusting PTFE V-ring packing gland with integrated spring compensation, ensuring zero maintenance and long cycle life. Lubricants used in the packing gland and pneumatic actuator are certified according to NSF H1.

Item No.	Component	Material
1	Ground terminal	Stainless steel 1.4301 / 1.4305 (ATEX variants)
2	Optical position indicator	Polysulfone (PSU)
3	Pilot air port	G 1/8" internal thread (Standard: PP push-in connector)
4	Actuator cover	Polyphenylene sulphide (PPS)
5	Actuator casing	Stainless steel 1.4561 (316Ti)
6	Piston seal	FKM
7	Spring	Stainless steel 1.4310
8	Pipe	Stainless steel 1.4401 (316) / 1.4404 (316L)
9	Packing gland	Filled PTFE V-rings with spring compensation
10	Spindle	Stainless steel 1.4401 (316) / 1.4404 (316L)
11	Spindle guide	PEEK
12	Body seal	Graphite (Option: PTFE)
13	Swivel plate	Stainless steel 1.4401 (316) / 1.4404 (316L)
14	Seat seal	PTFE (Option: PEEK)
15	Valve body	Cast stainless steel CF3M

Technical Data and Operating Limits

BURKERT 377555 is rated for continuous operating pressures up to 9 bar(g) with a minimum pilot pressure requirement of 5.2 bar(g). The water flow coefficient (Kv) is 13 m³/h, measured at +20 °C with 1 bar differential pressure.

Technical Parameter	Specification Value
Operating medium	Steam, water, alcohols, oils, fuels, hydraulic fluids, saline solutions, lyes, organic solvents, neutral gases
Medium temperature range	-10 °C to +185 °C
Ambient temperature range	-10 °C to +100 °C (with threaded pilot air bushing)
Viscosity limit	Max. 600 mm²/s
Control medium	Clean dry air or neutral gases
Minimum pilot pressure	5.2 bar(g)
Maximum pilot pressure	10.0 bar(g)
Maximum operating pressure	9.0 bar(g)
Flow coefficient (Kv water)	13 m³/h
Seat leakage	Leakage rate A according to DIN EN 12266-1
Protection rating	IP65 / IP67 according to EN 60529, NEMA Type 4X

Pressure Derating with Medium Temperature

The maximum permissible working pressure reduces at elevated process temperatures according to ASME B16.34 Class 150 and DIN EN 12516-1 PN25 standards:

Medium Temperature [°C]	Max. Permissible Pressure PN25 [bar]	Max. Permissible Pressure Cl.150 [bar]
-10 to +38 / +50	25.0	19.0
100	24.5	16.2
150	22.4	14.8
185	20.9	14.0
200	20.3	13.7
230	19.0	12.7

Dimensions and Mechanical Specifications

BURKERT 377555 combines an actuator size of Ø 50 mm (Size D) with a DN25 welded body conforming to ASME BPE / DIN 11866 Series C.

Dimension Code	Description	Dimension [mm]
DN / NPS	Nominal size	DN 25 / NPS 1"
Actuator Size Ø	Actuator casing external size	50 mm (Size D)
Ø A	Actuator casing outside diameter	64.5 mm
B	Max. total height to top of actuator	175 mm
H	Height to center of pilot air port	173 mm
K / M	Port center to body connection lower edge	156 mm
LS	Face-to-face body installation length	152 mm
ES	Weld end insertion length	30 mm
CS	Port center to pipe end offset	51 mm
Ø DS	Outer pipe diameter	25.4 mm (1.00")
WS	Pipe wall thickness	1.65 mm (0.065")
Inner Ø	Inner pipe diameter	22.1 mm

Installation and Actuator Alignment

BURKERT 377555 can be installed in any physical position, preferably with the actuator upright.

Disassemble Actuator Before Welding

To protect the internal seals, spindle guides, and PPS actuator housing from thermal damage during pipeline welding, remove the actuator assembly from the valve body before welding. Apply 5.0 bar pneumatic pilot pressure to pilot port 1 to lift the swivel plate into the open position, hold the body hex flat with a wrench, and unscrew the actuator from the body.

Assembly Tightening Torques

When reinstalling the actuator onto the valve body, inspect the body seal, grease threads with Klüber paste UH1 96-402, and pressurize pilot port 1 with 5 bar air to keep the swivel plate lifted off the seat. Tighten according to the nominal diameter:

Nominal Diameter DN	Actuator Size	Tightening Torque [Nm]	Tolerance [Nm]
DN 15	40 (C), 50 (D), 63 (E)	45	+10 / -5
DN 20	40 (C), 50 (D), 63 (E), 80 (F)	50	+10 / -5
DN 25	50 (D)	60	+10 / -5
DN 32	63 (E), 80 (F), 100 (G)	65	+10 / -5
DN 40	63 (E), 80 (F), 100 (G), 125 (H)	65	+10 / -5
DN 50	63 (E), 70 (M), 80 (F), 90 (N)	70	+10 / -5

Actuator 360° Position Adjustment

The pilot air connections can be rotated through 360° to simplify pneumatic tubing routing.

Rotation Direction Restriction

Pressurize pilot air port 1 with 5 bar air to open the valve before turning the actuator. Turn the actuator nut only in the direction shown on the housing mark while counter-holding the body hex. Turning in the opposite direction will loosen the body connection and compromise valve sealing.

Pneumatic Connection and Commissioning

BURKERT 377555 features a G 1/8" female pilot air port (Port 1). Connect compressed air supplied with a minimum pilot pressure of 5.2 bar(g) and maximum 10 bar(g). Clean dry instrument air conforming to ISO 8573-1 is recommended. In aggressive operating environments, route exhaust air from open pneumatic vents to a neutral atmosphere using tubing.

Food Contact Conformity

Wetted materials comply with EC Regulation 1935/2004 based on the manufacturer's declaration. The unit is fully compatible with CIP (Clean-in-Place) and SIP (Steam-in-Place) cleaning cycles up to +185 °C.

Maintenance and Troubleshooting

Perform regular visual inspections during planned maintenance intervals:

Inspection Area	Check Item	Corrective Action
1	Process pipe weld connections	Inspect welds and re-weld/repair if leakage is observed
2	Relief bore on actuator neck	Check for medium discharge; replace packing gland or actuator assembly
3	Swivel plate and valve seat	Check for internal pass-through leakage; replace swivel plate / seat seal set

Troubleshooting Guide

Fault Symptom	Probable Cause	Corrective Action
Actuator fails to switch	Pilot air connected to incorrect port	Connect pilot supply to pilot port 1
	Pilot pressure below 5.2 bar	Increase pilot air pressure to specified minimum
	Operating medium pressure exceeds 9 bar	Reduce process line pressure to rated limit
	Pipeline flow direction reversed	Verify body flow arrow points in the flow direction
Seat passes fluid when closed	Pilot pressure insufficient or line pressure exceeds limit	Restore correct operating and pilot pressure limits
	Debris lodged between seal and valve seat	Flush system or dismantle valve body to remove debris
	Swivel plate PTFE seal worn or damaged	Install replacement swivel plate kit
Medium escapes from relief bore	Packing gland V-rings worn	Replace packing gland using socket tool (Part no. 683221, A/F 19 mm)

Automation and Modular Combinations

BURKERT 377555 can be integrated directly with ELEMENT modular automation accessories to form automated valve systems (Type 8801-YE):

• Type 8695 Control Head: Optimized for actuator size Ø 50 mm, featuring non-contact inductive position sensing, integrated pilot valve, automatic teach-in end position detection, and AS-Interface / IO-Link / büS communications.
• Type 8697 Pneumatic Control Unit: Compact limit switch and pneumatic control unit with optical position indicator, designed for actuator size Ø 50 mm, available with mechanical or inductive switches and ATEX / IECEx intrinsically safe options.