Industrial Safety Valves and Systems LESER / LESER GmbH & Co. KG

High Performance spring-loaded safety valves, API 526 standardized relief valves, Compact Performance threaded units, Clean Service aseptic valves, and POSV pilot systems from LESER / LESER GmbH & Co. KG. International technical selection.

High Performance Spring-Loaded Safety Valves (Types 441, 442, 444, 458)

High Performance spring-loaded safety valves safeguard chemical and process installations against critical overpressure events. The full lift architecture delivers maximum discharge capacity within compact installation envelopes. Stellited seating surfaces resist high-velocity erosion.

Flanged process connections from DN 20 to DN 400 per DIN EN 1092 and ASME B16.5 ratings
Set pressure envelope spanning 0.1 to 40 barg for steam, gases, and liquid process media
Body materials available in ductile iron, carbon steel 1.0619, and stainless alloy 1.4408
Optional balanced metal bellows in stainless steel or Inconel for high backpressure

Standardized Flanged Safety Relief Valves API 526 (Type 526)

Type 526 flanged safety relief valves comply fully with API 526 and ASME Section VIII standards for refineries, petrochemical plants, and offshore platforms. Nanotightness lapping provides seat sealing superior to API 527. Standardized dimensions ensure seamless pipeline interchangeability.

Full API orifice coverage from D through T with effective discharge areas up to 16774 mm²
Nominal inlet sizes from NPS 1 to NPS 8 across pressure classes ASME 150 up to 2500
Set pressure capabilities from 0.12 to 400 barg for elevated temperature process media
LESER Single Trim geometry standardized for steam, process vapors, and liquid media

Compact Performance Threaded Safety Valves (Types 437, 438, 439)

Compact Performance threaded safety valves provide reliable overpressure protection for autoclaves, industrial compressors, pumps, and mobile skids. Options include metal-to-metal seating, elastomeric O-rings, and vulcanized soft discs. Units maintain set points under structural plant vibrations.

Threaded process ports G 3/8 to 1 inch and NPT 1/2 to 1 inch plus compact flange options
Broad set pressure spectrum from 0.1 to 365 barg within standard manufacturing series
Type 438 execution with integrated sealing O-ring disk for tight bubbleless shutoff
Type 439 with vulcanized soft sealing disk optimized for lower pressures up to 16 barg

Aseptic Sanitary Safety Valves Clean Service (Types 483, 488)

Clean Service aseptic safety valves are engineered for biopharmaceutical, food processing, cosmetics, and beverage facilities. Gap-free internal geometry with minimal dead space prevents product stagnation. Electropolished wetted stainless surfaces deliver surface finishes down to Ra 0.375 um.

Hygienic Tri-Clamp unions, DIN 11864 aseptic threaded ferrules, and aseptic flanges
Internal surface quality up to Ra max 0.375 um compliant with ASME BPE standards
Complete cleanability under Clean-in-Place CIP and Steam-in-Place SIP washdown cycles
Wetted polymer components compliant with strict international FDA and USP Class VI rules

Pilot-Operated Safety Valves LESER POSV (Types 811, 821)

Pilot-Operated Safety Valves POSV series 810 and 820 protect high-pressure pipelines, LNG transport vessels, and polymer reactors. Non-flowing pilot designs prevent fugitive emissions. Operating pressure can safely approach up to 96 percent of set pressure without risking seat leakage.

Type 811 Pop Action providing instantaneous full lift within 1 percent overpressure
Type 821 Modulate Action providing proportional discharge to minimize product release
Extended set pressure threshold up to 650 barg across extreme cryogenic temperatures
Cryogenic construction tested on liquefied natural gas LNG skids and cryogenic tanks

Change-Over Valves and Maintenance Spares LESER

LESER three-way change-over valves types 310, 320 Flow, and 330 Compact enable continuous plant operation by switching between duplex safety valves without shutting down pipeline media flows. Factory spare components include balanced metal bellows, precision nozzles, discs, and spring kits.

Flow-optimized internal passage design with minimal fluid dynamic inlet pressure losses
Balanced multi-ply metal bellows manufactured in stainless steel 1.4571 and Hastelloy
Precision hardened replacement nozzles and stellited shutoff discs for long service life
Factory plant overhaul kits containing calibrated load springs and standard seal rings

Bench Testing and Set Pressure Calibration of Spring-Loaded Safety Valves

Bench calibration procedures for High Performance and API 526 safety valves involve step-wise pressure ramping using nitrogen or clean instrument air to record opening set points with decimal-bar repeatability.

Service technicians adjust the spring compression via the threaded adjusting screw beneath the valve cap, achieving crisp disc lift without flutter or chatter. Liquid configurations undergo hydrostatic testing with deaerated water to pinpoint start-to-leak thresholds.

Following initial pressure set adjustments, repeated test pops verify reseating pressures within ASME Section VIII and ISO 4126 allowable limits.

The adjusting screw is locked with its heavy locknut, after which the cap mechanism receives a serialized wire seal accompanied by official calibration documentation.

Precision Seat Lapping and Nanotightness Sealing Surface Restoration

Micro-leakage across Type 441 or 526 valve seats requires disassembly for optical inspection of nozzle and disc contact lands. Fine galling, steam cutting tracks, or pitting necessitate progressive flat lapping on nodular iron plates using diamond pastes graduated from 14 down to 1 micrometer.

The proprietary Nanotightness procedure restores surface finishes into the nanometer roughness domain.

Flatness evaluation of reconditioned discs and nozzles utilizes monochromatic light and optical flats to observe straight interference fringe patterns. Final leakage verification complies strictly with API 527 bubble test protocols, confirming zero-bubble shutoff at 90 percent of set pressure.

Balanced Bellows Overhaul and Variable Backpressure Compensation Testing

In backpressure manifolds, multi-ply metal bellows formed from austenitic steel 1.4571 or Hastelloy isolate valve bonnets and balance superimposed or built-up backpressures.

During scheduled overhauls, the bellows assembly is unbolted for pneumatic submersion testing in an illuminated water bath under positive air pressure. Bubble generation immediately indicates inter-ply metal fatigue or cracking.

Technicians inspect guide sleeve clearances to confirm perpendicular travel without cocking the disc during high-lift discharges. Damaged or work-hardened bellows are replaced as complete assemblies with fresh graphite and PTFE gaskets, torqued according to manufacturer guidelines.

High-Pressure Pilot-Operated Safety Valve Maintenance and Testing

Maintenance protocols for POSV series 810 and 820 require segregated inspection of the control pilot and the main piston valve. Technicians blow out sensing lines, clean internal mesh filters, and replace resilient dynamic lip seals on the main piston.

For Pop Action Type 811 units, blowdown adjustment sleeves are calibrated to ensure snappy closure within prescribed margins.

Pneumatic and cryogenic test rigs confirm zero seat emissions up to 96 percent of set point prior to pop actuation. Modulating Type 821 pilots are tuned for smooth stroke opening relative to upstream overpressure, dampening pressure pulsations and preventing water hammer inside header systems.

Change-Over Three-Way Valve Overhaul and In-Service Switching Operations

Three-way change-over valves Types 310, 320, and 330 facilitate plant protection by allowing online isolation of dual safety valves without interrupting piping flows.

Mechanical servicing evaluates lead screw smoothness, thrust bearing wear, and handwheel operating torques across the full travel stroke from left to right seating positions.

Engineers verify metal shutoff tightness at terminal stops to ensure no process media escapes into the isolated branch while technicians dismount the standby valve. Corroded or eroded internal change-over seats receive replacement parts along with mechanical limit stops alignment.

Hygienic Clean Service Valve Maintenance and ASME BPE Surface Auditing

Sanitary Type 483 and 488 valves require periodic inspection of self-draining angles, Tri-Clamp ferrule gaskets, and electropolished wetted profiles.

Surface roughness testers verify that internal passages maintain finishes below Ra 0.375 um, preventing biofilm adherence in biopharmaceutical vessels. All elastomeric diaphragms are renewed using validated FDA and USP Class VI compounds.

Reassembled hygienic valves undergo Clean-in-Place and Steam-in-Place simulation cycles to verify leak tightness during rapid thermal transients. Spring housings and stem seals are inspected for moisture-free operation, ensuring full compliance with sterile engineering practices.

LESER / LESER GmbH & Co. KG and model names are trademarks of their respective owners and are used only to identify the equipment for which we source parts. SpareX is not an official dealer, distributor or representative of LESER / LESER GmbH & Co. KG and is not affiliated with the trademark owner. Origin, documents and warranty are stated for each item in the quotation.