Type 526

Flanged Steel Pressure Relief Valves

Safety valves from the API product group meet all the requirements of API 526 such as standardized capacity, nominal diameter, and center to face dimensions which offers 100% compatibility. Because of their robust construction, they are especially suitable for being constructed from special materials such as Duplex, Monel, and Hastelloy.

API 526 is a purchase specification in which the nominal diameters, flange pressure ratings, center to face dimensions, flow areas, body and spring materials and their service limits are stipulated for "API safety valves" API safety valves are used worldwide in the petrochemical industry, both on- and off-shore. These applications are characterised by standardised plants, blow-down systems and long pipework sections. The LESER type 526 combines the requirements of the API standards and the ASME Code with the tried and tested service reliability of the LESER range.

Orifice Letter Flow Area According to API 526 Flow Diameter
Orifice mm² sq. in. mm in
D 71.0 0.110 9.5 0.4
E 126 0.196 12.7 .5
F 198 0.307 15.9 0.6
G 325 0.503 20.3 0.8
H 506 0.785 25.4 1.0
J 830 1.287 32.5 1.3
K 1186 1.838 38.9 1.5
L 1841 2.853 48.4 1.9
M 2323 3.600 54.4 2.1
N 2800 4.340 59.7 2.4
P 4116 6.380 72.4 2.8
Q 7129 11.05 95.3 3.8
R 10323 16.00 114.6 4.5
T 16774 26.008 146.1 5.8

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Type 483 484 485 488

Safety Valves for Sanitary/Clean Service

Safety valves from the Clean Service product group were specially developed for the food, beverage, and pharmaceutical industries and meet all the relevant standards and regulations such as DIN 11866 or ASME BPE. With a low deadspace inlet area, the unique LESER HyTight assembly, and the optional pneumatic lifting device you have very good cleanability (CIP, SIP). With a large selection of aseptic connections (threaded, flanged, or clamped) the valve can be optimally fitted to different requirements.

The properties common to the “48x series” are:
- Low Dead Space
- High Surface Quality
- Free of Crevices
- CIP, SIP and COP Capability

The four types differ in capacities and opening characteristics:
TYPE 483: Safety relief valve for small and medium mass flows.
Applications: Pipelines, Stainless steel reactors/vessels.
TYPE 484: Safety relief valve with connection direct to vessel.
Applications: Fermenters Bio-reactors
Type 488: Full lift safety valve for medium and large mass flows.
Applications: Autoclaves Laboratory facilities Beverage industry (bottling plants (mixers) and storage tanks)
Type 485: Safety relief valve with integrated pipe work connection.
Applications: Pipe work protection when direct vessel protection is impossible or not desired.

The safety valves of the 48x series can be fitted with manually lockable lifting devices H4 to hold open at a small lift, and with pneumatic lifting devices H8 for automated systems (CIP process).

Type DN NPS Set Pressure Range Output Aseptic Properties
(bar) (psig) Inlet Outlet
483 25, 40 1", 1-1/2" 0.2....16 3.0....232 medium
Low dead space
Crevice Free
Free Discharge
Crevice Free
No Dome
488 25...100 1"...4" 0.2...16 3.0...232 very high
Reduced dead space
Crevice Free
Free Discharge
Crevice Free
No Dome
484 25, 40 1"...1-1/2" 0.2....16 3.0....232 medium
Dead Space Free
Crevice Free
Free Discharge
Crevice Free
No Dome
485 15, 25, 40, 50
1/5", 1", 1-1/2", 2"
0.2....16 3.0....232 medium
Dead Space Free
Crevice Free
Free Discharge
Crevice Free
No Dome

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Type 441 442

Full Flanged Safety Valves with Flanged Connections

Safety valves from the High Performance product group offer especially high capacity for their size. With a large quantity of nominal diameters (DN), pressure ranges and product options, they have proven themselves as a universal safety valve for many applications.

Full Flanged Safety Valves with Flanged Connections open rapidly to the full design lift.They are used in particular for vapours and gases, in applications where the maximum mass flow has to be discharged rapidly. LESER type 441 is suitable for almost any industrial application, and are worldwide one of the best selling spring-loaded flange type safety valves.

There are various series available:
Type 441 ANSI: Cast steel construction with ANSI flanges. Two body materials: stainless steel and cast steel. Center to face length in accordance with API 526, greater discharge capacity than standard API valves.
Type 441/442 DIN:Cast construction with DIN flanges. Two body materials: stainless steel and carbon steel.
Type 441/442 "XXL":Robust welded construction with DIN or ANSI flanges. Welding procedures to EN and ASME standards. Two body materials: stainless steel and carbon steel.

Type Bonnet Flange ANSI B 16.5 Flange DIN 2501 Main Characteristic
441 ANSI Closed #150... #300 1"...8" - - Cast Construction, semi nozzle
442 ANSI Open
441 DIN Closed - - 16...40 20...200
442 DIN Open
441 "XXL" Closed #150... #300 8"-16" 10...25 200...400 Welded Construction, full nozzle
442 "XXL" Open

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Type 447


PTFE-lined safety valves from the Critical Service product group are utilized for highly corrosive media such as chlorine, acids, and lyes. With their highly resistant lining they offer a safe solution for corrosive media.

Product Features
- Valve Sizes 1" - 4"
- Body: WCB, PTFE-lined
- Isostatic lining in virgin PTFE
- Smooth PTFE surfaces, no adherence
- Nozzel: PTFE/glass sintered
- Single trim for gas and liquid

- Corrosive or aggressive chemicals
- Chemical equipment and piping
- Chlorine manufacture and processing
- Reducing acids
- Alkalis or caustic service

Type Set Pressure Range Flange ANSI B 16.5 Flange DIN 2501
(bar) (psig) PR NPS PN DN
447 0.1...16 1.5...235 #150 1"...4" 16 25...100

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Type 437 459 462

Safety Valves with Threaded Connections

The product group Compact Performance includes threaded and flanged safety valves with compact dimensions for economical protection of small and midsized capacites. Due to its many orifice diameters, seals, and connections this product group offers a very wide area of application.

There are two series available
Type 437:Safety relief valve spring loaded for small mass flows (e.g. thermal expansion and overflow). Body material: stainless steel, 430 chrome steel.
Type 459/462Full lift safety valve spring loaded for the medium mass flow range (e.g. small scale or pilot plant). Two body materials: stainless steel or steel.

Type Inlet-Male NPT
437 1/2"
459 3/4"...1"
462 3/4"...1"

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Type 310

Change-Over Valves

Change-over valves from the Best Availability product group increase plant availability.Change-over Valves are used when a plant shutdown is impossible or undesirable for process engineering or commercial reasons. With change-over valves, it is possible to switch over between parallel safety valves without interrupting operation, so as, for example, to perform maintenance work. The design of the change-over valves ensures: low pressure losses on discharge flow (3% criterion) adequate open passage in any position during the change-over process stable operation of the downstream safety valves The combination of LESER change-over and safety valves has been comprehensively tested on full flow test labs.

There are two series available:
Type 310: Cast construction DN 25...50/ NPS 1"...2"
Type 311: Welded construction DN 80...400/ NPS 3"...16"

Continuously Functioning Plant
- Bitumen refineries
- Oilfields
- Ethylene plants

Non-Drainable Systems
- Natural gas caverns
- Large storage facilities
- Storage tanks for technical gases (e.g. ehtylene reservoirs)

Application Required by National Standards:
- TRB 801 Nr. 14 for refrigeration systems
- TRB 801 Nr. 26 for technical gases below -10°C (14°F)
- TRB 801 Nr. 27 for liquid gas systems

Type Flange ANSI B 16.5 Flange DIN 2501 Main Characteristics
310 #150...#600 1"...2" 40...160 25...50 Cast Construction
311 #150...#600 3"...16" 10...160 80...400 Welded Construction

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Type 431 433

Relief and Safety Relief Valves with Flanged Connections

Safety valves from the Modulate Action product group feature a standard or proportional opening characteristic. They minimize medium loss when opening and are used for protection from pressure peaks, thermal relief, and liquids.

Relief and Safety Relief Valves with Flanged Connections are ideal relief valves for medium mass flows. Their large proportional range leads to consistent functioning and relief of pressure peaks, particularly with liquids. Both proportional and safety relief valves are characterized by particularly stable operation.

Type Bonnet Flange ANSI B 16.5 Flange DIN 2501 Form Opening Characteristic
431 Open #150 1/2"...6" 16...40 15...150 Angle Type Safety Relief
433 Closed

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