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About LESER
LESER GmbH and Co. KG is Europe’s largest manufacturer of safety valves and one of the leading suppliers worldwide. Founded in Hamburg in 1818, the family-owned company has more than 200 years of engineering heritage focused exclusively on one mission: overpressure protection for life, property and the environment. From its production facilities in Hohenwestedt and Hamburg, Germany, LESER builds approximately 160,000 safety valves per year and offers more than two million possible configurations – all delivered under short, predictable lead times.
Every LESER safety valve is engineered as a last line of defence. It is not a process valve and is not a pressure regulator – it has exactly one job: to open and relieve excess pressure from vessels and equipment, then reclose tightly once the system returns to normal. This single-purpose discipline is why LESER is the chosen supplier for BP, Shell, BASF, Linde, Petrobras, Dow Chemical, Atlas Copco, Tetra Pak, Krones, Procter and Gamble, Burckhardt Compression, Saipem, Solvay, Bayer CropScience, Arkema and hundreds of EPC contractors worldwide.
Founded 1818 in Hamburg, Germany. 160,000 valves produced annually. 2,000,000 possible configurations. Standardized delivery times.
Why Engineers Choose LESER
LESER Nanotightness
Proprietary sealing-surface finish with 100 nm flatness and roughness. Exceeds API 527 tightness requirements by 50% on metal-to-metal seats – no soft seal needed in the wetted area.
Global Approval Concept
PED, ASME UV, VdTUV, UKCA, CRN, EAC, TS China, KOSHA – plus marine class (DNV, Lloyd’s Register, ABS, Bureau Veritas, RINA, ClassNK, KR, CCS, US Coast Guard). One specification works worldwide.
Two-Week Standardized Delivery
Standardized inlet and outlet geometries plus a modular bonnet design mean LESER can deliver two million configurations in roughly two weeks – planning security for EPC schedules.
VALVESTAR Sizing Software
LESER’s in-house sizing program (free of charge) handles gas, vapour, liquid and two-phase calculations per ISO 4126, API 520 and AD 2000. We deliver fully documented sizing sheets with every quotation.
Cryogenic to High-Temperature
Service envelope from -273 degC (liquid helium) to +550 degC. Tightness proven at media temperatures below -146 degC on LESER’s in-house cryo test rig per DIN EN 13648-1.
LESER ID Link
Every LESER valve carries a digital nameplate that gives instant smartphone access to its data sheet, sizing calculation, set pressure record, maintenance manual and spare-parts list – no paperwork hunt during turnaround.
Main Valve Types
LESER’s portfolio is organized around three loading principles. Spring-loaded valves cover the vast majority of industrial overpressure scenarios. Pilot-operated valves are the right answer when operating pressure runs close to set pressure. Change-over valves keep continuously running plants protected during maintenance.
Spring-loaded Safety Valves
The standard loading principle. Used across chemical, petrochemical, energy and general industrial overpressure protection.
Pilot-Operated Safety Valves
For high plant efficiency. Operating pressure up to 97% of set pressure, back pressure up to 95%, minimal media loss.
Change-over Valves
Twin-valve manifold for continuous plant availability. Swap one safety valve for service without shutting down the process.
Full Product Portfolio
Below is the complete LESER product catalogue available through Nhan Viet ICS JSC in Vietnam, grouped by product franchise. Click any model card to open the manufacturer’s data sheet on leser.com.
API – Safety Valves to API 526
Standardized capacities, installation dimensions and materials per API 526 and API 520. Wide range of high-alloy materials in standard delivery time. Longer service life through hardened discs, stellited seats and shielded bellows. Set pressure 0.2 to 400 barg, temperature -273 to +550 degC, orifices D to T, DN 25 to DN 200 / NPS 1 to NPS 8.
High Performance – The European Chemical Standard
The standard safety valve for chemical plants in Europe. Easy maintenance, high performance relative to nominal size, DN 20 / 3/4 inch to DN 400 / 16 inch. Set pressure 0.1 to 300 barg, temperature -270 to +550 degC, orifices F- to X. Includes the new Type 441 DN 250 to DN 400 in cast design.
Type 441 / 442 DIN
Full lift valve with rolled-in seat, DIN flange. DN 20 to DN 400. 0.1 to 40 bar. The European chemical-plant standard.
Type 441 / 442 ANSI
Full lift valve with rolled-in seat, ASME flange. DN 25 to DN 100 / NPS 1 to NPS 4. 0.1 to 51 bar.
Type 441 / 442 Full Nozzle DIN
Full lift valve with full nozzle, DIN flange. DN 25 to DN 50. 0.1 to 40 bar. For aggressive media in chemical service.
Type 441 / 442 Full Nozzle ANSI
Full lift valve with full nozzle, ASME flange. DN 25 to DN 100. 0.1 to 51 bar. ASME UV stamped.
Type 444 DIN
Deep-drawn stainless steel body, DIN flange. DN 25 to DN 80. 0.1 to 16 bar. Cost-effective stainless option.
Type 444 ANSI
Deep-drawn stainless steel body, ASME flange. DN 25 to DN 80. 0.1 to 16 bar. Light, lower cost.
Type 455 / 456
High-pressure full lift valve with rolled-in seat. DN 25 to DN 100. 2.5 to 100 bar.
Type 457 / 458
High-pressure full lift valve with nozzle. DN 25 to DN 150. 2.5 to 300 bar. For high-pressure chemical and refinery service.
Compact Performance – Threaded and Small-Flange Safety Valves
Flanged and threaded valves with a flexible range of options. Bellows version available. Set pressures up to 1,000 bar / 14,504 psig. For securing small and medium capacities in process equipment, compressors, tubing skids and instrumentation lines.
Type 437
Small-capacity threaded valve. G 3/8 to G 1 / NPT 1/2 to 1. 0.1 to 365 bar. The compact workhorse.
Type 438
O-ring disc for increased tightness. G 3/8 to G 1. 5 to 180 bar. Soft-seat tightness in compact form.
Type 439
Vulcanized soft seal for very low set pressures. G 3/8 to G 1. 0.1 to 16 bar. Drum and tank protection.
Type 459
Medium-capacity valve. NPT 1/2 to NPT 2. 0.2 to 250 bar. Workhorse for instrument and skid duty.
Type 459 HDD
High set pressure variant. NPT 1/2 to NPT 1. 250 to 850 bar. For very high pressure duty.
Type 462
O-ring disc for increased tightness. NPT 1/2 to NPT 2. 0.5 to 250 bar.
Type 462 HDD
O-ring disc for very high set pressures. NPT 1/2 to NPT 1. 250 to 350 bar.
High Efficiency – Pilot-Operated Safety Valves (POSV)
For plants that want to run close to the set pressure without blow-off losses. Operating pressures up to 97% of set pressure, back pressures up to 95%. Used in LNG / LPG liquefaction (Linde), hydrogen, compressor and high-purity gas applications. Set pressure 1.0 to 650 barg, temperature -162 to +300 degC.
Type 811 – Pop Action POSV
Pilot-operated per API 526, pop action. DN 25 to DN 200. 2.5 to 255 bar. For gas and vapour service.
Type 821 – Modulate Action POSV
Pilot-operated per API 526, modulate action. DN 25 to DN 200. 1.0 to 650 bar. Minimal media loss.
Type 814 – Dual Outlet Pop Action
Two opposite outlets, pop action. DN 100 to DN 200. 2.5 to 102 bar. For balanced reaction-force installations.
Type 824 – Dual Outlet Modulate
Two opposite outlets, modulate action. DN 100 to DN 200. 2.5 to 102 bar. Lower media loss in large lines.
Modulate Action – For Liquid and Thermal-Expansion Service
Primarily for liquid applications. Identical inlet and outlet connections, low loss of medium when opening, ideal for thermal expansion duty. Back-pressure resistant up to 40 bar / 580 psig. Set pressure 0.2 to 160 barg, DN 15 to DN 150.
Type 431 / 433
Standard modulate-action valve, rolled-in seat, DIN and ASME flanges. DN 15 to DN 150. 0.2 to 40 bar.
Type 431 / 433 PN 160
High-pressure modulate with screwed seat. DN 15. 0.3 to 160 bar. For high-pressure liquid lines.
Clean Service – Food, Beverage and Pharmaceutical
Low dead space, gap-free internal parts, surface qualities up to Ra max = 0.375 micron. CIP and SIP compatible. Compliant with FDA, USP VI and EU directives. Aseptic clamp, tri-clamp, threaded and flange connections. Used by Tetra Pak, Krones and Procter and Gamble.
Type 481
Small capacity for secondary hygienic processes. DN 15 to DN 25. 0.1 to 68 bar. Compact, aseptic.
Type 483
Standardized aseptic connections. DN 25 to DN 40. 0.1 to 16 bar. The default hygienic valve.
Type 484
Container-integrated valve. Container flange. 0.1 to 16 bar. For tank-top high-purity duty.
Type 485
Pipeline-integrated valve. DN 25 to DN 50. 0.1 to 16 bar. For ultra-pure inline duty.
Type 488
For high capacities in hygienic plants. DN 25 to DN 100. 0.1 to 16 bar. Large fermenters and storage tanks.
Critical Service – PTFE-Lined for Corrosive Media
Wetted areas in corrosion-resistant PTFE. Cost-effective alternative to nickel-based alloys for highly corrosive media. Optional ATEX-compliant conductive lining prevents electrostatic charge. Set pressure 0.1 to 16 barg, temperature -85 to +200 degC, DN 25 to DN 100.
Type 447
Full PTFE lining in inlet and outlet. DN 25 to DN 100. 0.1 to 16 bar. For highly corrosive chemical service.
Type 447B
Conductive PTFE lining for ATEX explosive atmospheres. DN 25 to DN 100. 0.1 to 16 bar.
S and R – Heating and HVAC Safety Valves
Safety valves for heating technology per DIN EN ISO 4126-1, DIN 4751 part 2, TRD 721. Suitable for steam generators up to 1 bar overpressure and water heating systems up to 120 degC. DN 15 to DN 150.
Type 424
For steam generators up to 1 bar overpressure. DN 25 to DN 150. 0.5 to 1 bar. TRD 721 compliant.
Type 440
Flanged valve for water heating to 120 degC. DN 20 to DN 150. 1 to 10 bar. DIN 4751 part 2.
Type 460
Threaded valve for water heating to 120 degC. DN 15 to DN 20. 1 to 10 bar. Compact heating duty.
High Efficiency – Supplementary Loading System (SLS)
Pneumatic auxiliary load on a spring-loaded valve, giving tight-to-set-pressure performance and operating pressure up to 97% of set pressure. Proven at DESY for liquid helium at -273 degC. Set pressure 0.1 to 250 barg, DN 25 to DN 400.
Type 712 – Pneumatic SLS
Pneumatic supplementary loading. DN 25 to DN 400. 0.1 to 250 barg. Operating pressure up to 97% of set.
Type 714 – Electric-Pneumatic SLS
Electric-pneumatic SLS. DN 25 to DN 400. 0.1 to 200 barg. Active monitoring and remote release.
Best Availability – Change-over Valves
Twin-valve manifold installed below or beside a pair of safety valves to keep one valve in service while the other is serviced. Pressure rating PN16 to PN250 / Class 150 to 1500. Flow-optimized designs for minimum inlet pressure drop. DN 25 to DN 400.
Type 320 Flow
Flow-optimized for minimum pressure loss. DN 25 to DN 300. PN 16 to PN 250.
Type 330 Compact
Compact dimensions. DN 25 to DN 400. PN 16 to PN 40. Lightweight twin manifold.
Best Availability – Bursting Disc Combinations
Part-tested safety valve / bursting disc combinations. Bursting disc protects the safety valve seat from corrosion or polymerizing media; the valve recloses after a relief event. Set pressure 0.2 to 200 barg, DN 25 to DN 400. Materials include Stainless Steel, Hastelloy and Inconel.
Real-World Applications
Where LESER valves protect plants today – many of these installation contexts are exactly the projects Nhan Viet supports in Vietnam.
Hydrogen Production and Storage
Electrolyzers, fuel-cell stations, ammonia plants. LESER POSV plus standard spring-loaded for the full H2 recycling chain.
ATEX Explosive Atmospheres
LESER valves are suitable for potentially explosive atmospheres even without dedicated ATEX certification – confirmed in the LESER ATEX statement.
Breweries and Beverage Lines
Clean Service Type 483 / 484 / 488 for fermentation, storage, filtration and filling. CIP and SIP ready.
Urea and Fertilizer Plants
1,800+ LESER valves installed in urea plants worldwide. Steam Flushing System prevents carbamate condensation in the seat.
LNG / LPG Liquefaction
Cryo-POSV qualified at -161 to -164 degC. Used in Linde LIMUM liquefaction units worldwide.
Compressors and OEM Skids
Horizontal and inverted-spindle installation positions tested and approved on Type 526 and 441 for tight OEM packages.
Industries We Serve in Vietnam
LESER’s 11 industry verticals map directly onto Nhan Viet’s customer base in Vietnam – upstream oil and gas, downstream refining and petrochemicals, food and beverage, breweries, pharmaceutical CMOs, marine and shipyards, power generation, district heating and industrial gases.
Chemical Industry
High Performance, Critical Service and Best Availability for diverse chemical processes and corrosive media.
Oil and Gas
API 526 valves for high production rates with the highest safety standards. Used by BP, Shell, Petrobras.
Petrochemical
High-efficiency POSV plus SLS for downstream operations where running close to set pressure saves money.
Energy and Power
Boiler, steam line and turbine protection. Reliability when downtime is unacceptable.
Technical Gases
Air separation, helium, hydrogen. Cryogenic-qualified valves down to -273 degC.
LNG and LPG
Liquefaction trains, regasification, storage. POSV plus standard API for the full LNG and LPG chain.
Pharmaceutical
Clean Service for sterile, high-purity, GMP-grade installations. Used by Novartis, PIA.
Food and Beverage
FDA, USP VI, EU food contact compliant. Used by Tetra Pak, Krones, Procter and Gamble.
Marine and Shipbuilding
DNV, Lloyd’s Register, ABS, Bureau Veritas, RINA, ClassNK, KR, CCS, US Coast Guard certified.
Heating, HVAC and District Heat
S and R valves Type 424, 440 and 460 for hot water and steam-generator service per DIN 4751 and TRD 721.
General Industrial Plants
Process tanks, compressors, OEM packages, water and steam utilities across general manufacturing.
Global Certifications and Standards
LESER carries the full set of pressure-equipment and marine certifications needed for international project work. Vietnamese EPC, MOIT and Vietnam Register requirements are met out of the box.
ASME Section VIII UV
VdTUV (Germany)
UKCA
CRN (Canada)
EAC (Russia)
TS China
KOSHA (Korea)
DNV
Lloyd’s Register
ABS
Bureau Veritas
RINA
ClassNK
Korean Register
CCS China
US Coast Guard
ATEX (statement)
FDA / USP VI (Clean Service)
Why Partner with Nhan Viet ICS JSC
Local Sizing and Selection
Send us your process data sheet, P and ID extract or relief-load calculation; we return a fully documented VALVESTAR sizing report and a quotation referencing your applicable code (API 520 / ISO 4126 / AD 2000).
In-Country Stock and Lead Time Buffer
Nhan Viet holds buffer inventory of the most-used Type 441 / 442, 459 and 483 models in Vietnam. We coordinate with LESER’s Hamburg and Hohenwestedt plants for project lots and rush orders.
Calibration and Set-Pressure Certification
Test-bench services for set-pressure verification, leak test and seat-tightness check. Calibration certificates accepted by Vietnam Register and major EPC contractors.
Trainings and Maintenance Support
LESER maintenance handbook plus on-site training for operators and reliability engineers – covering High Performance, Clean Service, POSV and SLS overhaul procedures.
EPC Project Documentation
EN 10204 3.1 / 3.2 material certificates, witnessed FAT, PMI, NDT reports, dossiers and ITP support for Vietnamese refineries, LNG terminals and chemical clusters.
Spare Parts and Aftermarket
Genuine LESER spares – discs, nozzles, bellows, springs – sourced direct from Hamburg. ID Link lookup for fast spare-part identification at the asset.
Calibration, Lead Times and After-Sales Support
Lead times
LESER’s standardized configuration system delivers approximately two million possible specifications in roughly two weeks ex-works. For project work (witnessed inspection, special material grades, painting specs) typical lead time is 6 to 10 weeks from order. Nhan Viet pre-stocks the most-used Type 441 / 442 DIN, Type 459 NPT and Type 483 aseptic models so that emergency replacements ship within days.
Calibration and set-pressure adjustment
Every LESER valve leaves Hamburg with a CE / VdTUV / ASME UV set-pressure certificate. For re-certification, set-pressure adjustment, seat-tightness verification and overhaul we run our test bench in Vietnam. Calibration reports are signed by accredited technicians and accepted by Vietnam Register and major EPC contractors.
Field service and maintenance
LESER’s modular Durable Design means most overhauls are a disc-and-spring change handled by trained reliability staff. For complex POSV or SLS overhauls we deploy field engineers; LESER’s online Engineering Manual covers every type from 437 to 824. Use the LESER ID Link sticker on the bonnet to pull the exact manual for the asset in front of you.
Frequently Asked Questions
Is Nhan Viet an authorized LESER distributor in Vietnam?
Yes. Nhan Viet ICS JSC supplies the full LESER product portfolio in Vietnam, with factory backing from LESER GmbH and Co. KG, Hamburg. All valves shipped through Nhan Viet are genuine LESER product with original CE / VdTUV / ASME UV documentation.
What is a safety valve actually for?
It protects life, property and the environment. A safety valve opens when system pressure exceeds the set pressure, relieves the excess, then recloses once pressure returns to normal. It is not a process valve and not a pressure regulator – it is a safety device, often the last line of defence.
Which LESER product is right for my application?
For most chemical, energy and general industrial duty the High Performance Type 441 / 442 is the default. For API 520 / API 526 oil and gas projects pick Type 526. If operating pressure is close to set pressure, choose a Pilot-Operated Type 811 (pop) or Type 821 (modulate). For hygienic plants the Clean Service Type 483 is the workhorse. Send us your data sheet and we will recommend the type plus do the sizing calculation in VALVESTAR.
What is LESER Nanotightness?
It is LESER’s proprietary sealing-surface finish, with flatness and roughness in the 100 nm range, that delivers tightness exceeding API 527 requirements by 50% on metal-to-metal seats. It removes the need for a soft seal in the wetted area on most chemical, petrochemical and gas duty.
Is LESER suitable for ATEX explosive atmospheres?
Yes. LESER safety valves are suitable for use in potentially explosive atmospheres even without a dedicated ATEX certificate – confirmed in the official LESER ATEX statement. For applications requiring conductive lining (anti-static) we recommend Critical Service Type 447B.
How cold can LESER valves go – is cryogenic helium possible?
The standard service envelope reaches -273 degC. LESER has supplied liquid helium service to DESY at -273 degC, and LNG service down to -164 degC at Linde plants. Tightness is verified on LESER’s in-house cryo test bench per DIN EN 13648-1.
Can LESER be installed horizontally or upside down?
Yes for selected types. LESER has tested and approved horizontal-spindle and inverted-spindle installation positions on Type 526 and Type 441 – useful for OEM compressor packages where vertical mounting is impossible. Discuss orientation with us during sizing so we apply the correct correction factors.
What is the LESER ID Link?
A digital nameplate on each valve that gives instant smartphone access to that specific valve’s data sheet, sizing calculation, set-pressure record, maintenance manual and spare-parts list. It replaces the paper-hunt during turnaround and means each asset stays linked to its documentation forever.
Do you provide calibration certificates accepted by Vietnam Register?
Yes. Nhan Viet runs a set-pressure and seat-tightness test bench. Calibration certificates are signed by accredited technicians and accepted by Vietnam Register and the major EPC contractors operating in Vietnam (PVN, Petrovietnam Engineering, Lilama, PTSC and others).
What documents can you provide for an EPC project package?
EN 10204 3.1 and 3.2 material certificates, set-pressure certificate (CE, VdTUV or ASME UV), CMTR for body and bonnet, NDT reports (where ordered), painting certificate, witnessed FAT report, PMI report, plus the manufacturer’s installation and operation manual.
Request a Quotation
Send us your LESER specification, P and ID extract or process data sheet. We respond with a fully documented VALVESTAR sizing report, a model selection (Type number, orifice, materials, connections) and pricing within 1 to 3 business days.
Nhan Viet ICS JSC
Authorized distributor of LESER safety valves in Vietnam
Email: sales@nhanvietgroup.vn
Website: nhanvietgroup.vn