Brand: GESTRA

GESTRA MPA 46 Rapid-Action Boiler Blowdown Valve PN 40

Name: GESTRA MPA 46 Boiler Blowdown Valve PN 40
Brand: GESTRA
SKU: MPA 46

Description

A rapid-action blowdown valve for automatic sludge discharge from steam boilers

The GESTRA MPA 46 is a rapid-action intermittent (bottom) blowdown valve with a diaphragm actuator for automatic operation. It is installed in the blowdown pipe of a steam boiler to discharge boiler water carrying non-metallic solids. When it opens, the large cross-section of the orifice creates a suction effect that discharges the precipitated sludge, and when it closes the spring-loaded valve cone is forced back into the seat rapidly. The diaphragm actuator is driven by compressed air or pressurised water as control fluid and performs a brief, repeatable blowdown.

The data sheet covers manual PA valves and automatic MPA valves in three pressure classes: 46 (PN 40, Class 150 and 300, DN 20 to 50), 47 (PN 63, Class 400, DN 25, 40, 50) and 48 (PN 100, Class 600, DN 25, 40, 50). A PA valve is opened by hand with its lever for two to three seconds.

Technical specifications

Parameter	Specification
Types	MPA 46 / MPA 47 / MPA 48 (automatic); PA 46 / PA 47 / PA 48 (manual)
MPA 46 sizes; rating	DN 20, 25, 32, 40, 50 (3/4 to 2 inch); PN 40, Class 150 and Class 300
MPA 47 / MPA 48	DN 25, 40, 50; PN 63 / Class 400 and PN 100 / Class 600
MPA 46, PN 40 flanged (EN 1092-1)	40.0 barg at 20 C, 37.1 barg at 100 C, 33.3 barg at 200 C, 27.6 barg at 300 C; operating data: max. 31 bar at boiling temperature 237.5 C
MPA 46, Class 150 / Class 300	19.6 to 10.2 barg (38 to 300 C) / 51.1 to 39.8 barg (38 to 300 C); Class 300 operating data: max. 41.5 bar at 254 C
Fluids	Group 2 fluids under the Pressure Equipment Directive
Control fluid and pressure	Compressed air or pressurised water; control pressure must not exceed 8 bar; minimum pressure from a diagram against differential pressure
Materials	Body, union nut 1.0460 / SA 105; sealing plug 1.7225 / SA 193 B7; gasket 1.4301 (2.4068 for 48); seat 1.4034 and cone 1.4122 hardened; PTFE yarn packing; EPDM control diaphragm; galvanised steel actuator (1.0334)
Connections, 46	Flange EN 1092-1 B1 PN 40; ASME B16.5 Class 150 RF/RFS, Class 300 RF; socket-weld DIN EN 12760 / ASME B16.11 Class 3000; butt-weld EN 12627 or ASME B16.25
Dimensions	Actuator diameter 235 mm; H2 55 mm (DN 20-32) or 80 mm (DN 40/50); H3 350 mm (DN 20-32) or 360 mm (DN 40/50); H4 350 mm; min. 150 mm free space for actuator removal
PN 40 flanged, H1 / L	DN 20: 105 / 150 mm; DN 25: 115 / 160; DN 32: 140 / 180; DN 40: 150 / 200; DN 50: 165 / 230
Classification	Ex II 2G Ex h IIA T6…T1 Gb; II 2D Ex h IIIA T20 C…T374 C Db for (M)PA 46/47/48

Opening can be triggered by the GESTRA TA program controller, by a continuous blowdown controller such as LRR 1-40, LRR 1-52, LRR 1-53 or LRR 1-60, or by SPECTORcontrol with CAN bus. Optional extras include proximity switch retrofit kits and an emergency lever.

Sizing and installation notes

Select the pressure class from the boiler design pressure and take the control pressure from the diagram for your differential pressure; DN 20 to 32 and DN 40 to 50 have different curves. A PA valve needs an actuating force on the lever of 300 N (DN 20-32) or 490 N (DN 40/50) for PN 40 butt-weld versions, rising with pressure class, so the automatic MPA is the practical choice for frequent blowdown. If exhaust air from a pneumatic actuator can swirl dust in a hazardous area, the plant owner must account for it in zoning, and static charge between valve and pipework is the plant operator responsibility.

For continuous (top) blowdown control see the GESTRA LRGT 16-1 conductivity transmitter and the controller range under control valves and regulators.

Documents and quotation

The attached GESTRA data sheet 818424 lists ratings, materials, dimensions and actuating forces for PA and MPA 46, 47 and 48. Send the boiler design pressure, nominal size, connection standard, control fluid and trigger method for a quotation, and confirm the exact model and certificates before ordering.

Datasheets & Documents

Datasheet GESTRA PA 46-48 and MPA 46-48 blowdown valve data sheet 818424-07 (08-2026) Download

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About brand

GESTRA is the German steam and condensate specialist behind the UNA ball float steam traps, the MPA blowdown valves and a long line of boiler level and conductivity controls. It was founded in Bremen in 1902 by Gustav F. Gerdts, and has been part of Spirax Sarco since 2017.

Seven Star LLC is an independent supplier in Muscat. We list GESTRA steam traps, blowdown valves and boiler control equipment, and supply GESTRA parts and spares to boiler houses and process plants in Oman and the GCC.

GESTRA company profile

Established	29 October 1902, Bremen, Germany, by Gustav Friedrich Gerdts; renamed Gustav F. Gerdts KG in 1907
Ownership history	Became a stock corporation (GESTRA AG) in 1987, was taken over by Flowserve in 2002, and has been part of the Spirax Sarco group since 2017
Product families	Steam traps, non-return and check valves, boiler blowdown valves, control valves, and boiler control electronics for level, conductivity and temperature
Applications	Steam boilers, steam distribution and condensate return in process plants, power stations, hospitals, food and textile plants

Milestones

1902: Gustav Friedrich Gerdts founds the company in Bremen on 29 October.
1907: The company is renamed Gustav F. Gerdts KG.
1987: It becomes a stock corporation, GESTRA AG.
2002: Flowserve takes over GESTRA.
2017: GESTRA becomes part of the Spirax Sarco group.

GESTRA products we list

Series	Type	What it does
UNA 45, UNA 16, UNA 38	Ball float steam traps	Continuous condensate discharge from heat exchangers and process equipment; the UNA 38 is the high-pressure version (PN 100)
BK 45	Bimetallic steam trap	Robust trap for steam main drainage and tracing, resistant to water hammer
MK 45, TK 23, SMK 22-81	Thermostatic steam traps	Air venting and condensate discharge; the SMK 22-81 is the sanitary version for clean steam
MPA 46	Rapid-action blowdown valve	Short, intermittent bottom blowdown that removes sludge from the boiler
NRS 1-54, NRR 2-50, NRR 2-60, NRGT 26-2	Boiler level controls	Water level limiting, feedwater control and continuous level measurement
LRGT 16-1, LRR 1-50	Conductivity measurement and control	Keeps boiler water conductivity in range through continuous blowdown
TRS 5-50	Safety temperature limiter	SIL 3 temperature limiting for boilers and hot water systems

The type of steam trap follows the duty. Ball float traps discharge condensate as soon as it forms, which suits heat exchangers with changing loads. Thermostatic and bimetallic traps hold condensate back slightly and suit steam mains, tracing and air venting. On the boiler itself, GESTRA level and conductivity electronics work as a system: electrodes or transmitters in the boiler, controllers in the panel, and the feedwater and blowdown valves they drive.

Where GESTRA products are used

In Oman and the GCC, GESTRA equipment is used in boiler houses of refineries, petrochemical and fertiliser plants, power and desalination stations, food and beverage plants, laundries, hotels and hospitals.

Ordering GESTRA parts: what we need

Send the type designation, pressure rating (PN) and connection size (DN), the end connection (flanged, screwed or socket weld), the operating pressure and condensate load for steam traps, and the supply voltage and bus type (CAN bus, 4-20 mA) for control equipment. For electrodes, add the insertion length.

Facts checked against GESTRA company history and Bremen city records, October 2026.

Browse GESTRA products by category: Liquid Analysis Sensors.