LESER Change-Over Valve Series (Type 320/330)

Overview

The LESER Change-Over Valve series is a family of manually or gear-operated selector valves that let a plant switch a pressure vessel or pipeline’s protection between two parallel-mounted safety valves without ever leaving the system unprotected and without interrupting production. The current LESER lineup markets this family as the Best Availability range, built around Type 320 Flow and Type 330 Compact, which together replace LESER’s earlier Type 310/311 change-over valve generation referenced in older catalogs; Seven Star LLC uses the current Type 320/330 designation as the primary reference for this series, since that is what LESER’s live product catalog now presents.

Working closely with plant engineers in the region, Seven Star LLC supplies the Change-Over Valve series with full manufacturer traceability and technical guidance on selecting the correct rotor-design change-over valve for a given isolation and maintenance strategy. Refineries and chemical plants across the region rely on this authorized channel to keep safety valve maintenance work from ever forcing an unplanned shutdown.

Operating Principle

A change-over valve is installed between a protected vessel or line and two parallel safety valves, with an internal rotor, disc, or shuttle mechanism that always keeps one flow path fully open to an active safety valve while the other path is fully closed to the safety valve being taken offline for inspection, testing, or overhaul. Critically, the mechanism is designed so that it is mechanically impossible for both paths to be closed simultaneously – the vessel or line always has an active, unobstructed relief path through one of the two safety valves at every point during the change-over motion.

Both Type 320 and Type 330 use this rotor-style flow-path design, in which rotating an internal element progressively opens one port while closing the other, giving a smooth transition with minimal pressure loss compared to shuttle or pendulum-style change-over mechanisms used elsewhere in the industry. The practical result is that safety valve proof-testing, recalibration, or repair can be carried out on a live, running process unit at full pressure and temperature, without a plant shutdown and without exposing the vessel to a period of zero overpressure protection.

Engineering Design of the LESER Change-Over Valve Series

Type 320 Flow is the higher-pressure-capable model, cast in carbon steel (1.0619 / SA 216 WCB) or stainless steel (1.4408 / SA 351 CF8M) bodies sized from DN 25 to DN 300 with flange classes from PN 10 up to PN 250 per DIN EN 1092, giving it the reach for high-pressure chemical, oil and gas, and petrochemical duty up to 250 bar and a temperature range of -273°C to +450°C. Its flow-optimized rotor geometry is designed specifically to minimize pressure losses across the change-over path during normal operation.

Type 330 Compact uses the same carbon steel or stainless steel casting materials and metallic seat gasket design but is built for a larger size range of DN 25 to DN 400 within a more compact envelope, targeting installations where space around the vessel or pipeline is constrained. Its pressure class range of PN 10 to PN 40 (Class 150 to Class 300 per ASME B16.5) is lower than Type 320’s, reflecting its focus on high-availability service in larger, lower-pressure lines such as compressor discharge and process gas headers rather than the highest-pressure chemical reactor duty Type 320 is built for.

Key Features

The LESER Change-Over Valve series delivers consistent safety-without-shutdown advantages across both types:

• Rotor-style flow-path design makes it mechanically impossible for both parallel safety valves to be isolated at once.
• Enables live safety valve testing, calibration, and overhaul without a process shutdown.
• Type 320 Flow reaches pressure classes up to PN 250 for high-pressure chemical and petrochemical service.
• Type 330 Compact extends to DN 400 in a space-saving envelope for larger, lower-pressure lines.
• Carbon steel and stainless steel casting options cover both standard and corrosive-service applications.
• Wide temperature range of -273°C to +450°C suits cryogenic through high-temperature process duty.
• Metallic seat gasket design is engineered to minimize pressure losses through the change-over path.
• DIN EN 1092 and ASME B16.5 flange compatibility simplifies integration into existing piping systems.

Industrial Applications

The LESER Change-Over Valve series is specified in any continuous process where taking a safety valve offline for statutory testing or maintenance cannot be allowed to interrupt production: refinery distillation and cracking units, ethylene and petrochemical crackers, ammonia and fertilizer plants, and compressor stations on gas transmission pipelines. In the Sultanate of Oman and across the wider GCC, this includes the refining and petrochemical complexes at the Sohar and Salalah economic zones, where continuous-operation units cannot tolerate a shutdown simply to recertify a safety valve, making dual-valve change-over protection a standard design requirement.

With fast quotation turnaround and technical support, Seven Star LLC distributes the Change-Over Valve series to refineries, EPC contractors, and plant reliability teams throughout Oman and the GCC, backing every supply with genuine manufacturer documentation and guidance on matching Type 320 or Type 330 to the pressure class and space envelope of the installation. Facility engineers planning a dual-safety-valve protection scheme for a new or retrofit unit can rely on this authorized channel for both models without compromising on traceability.

Technical Specifications

The table below compares the two current Change-Over Valve models, which supersede the older Type 310/311 designation still referenced in some legacy documentation.

Call To Action

Seven Star LLC invites refinery engineers, EPC contractors, and plant reliability teams across Oman and the GCC to submit a formal RFQ for the LESER Change-Over Valve series, Type 320 Flow or Type 330 Compact. Regional warehouse stock and fast-track procurement are available for standard sizes, and a technical datasheet download can be provided on request alongside sizing support from our instrumentation and valve engineering division. With regional stock and engineering support in Muscat, Seven Star LLC guarantees genuine manufacturer hardware, full certification, and dedicated aftersales support for every Change-Over Valve supplied.

Also available: LESER Clean Service Series – Hygienic Safety Valves for Food and Pharma