Fisher 38B DVC Relay Modules 38B5786X112

Technical Dossier

Product Details And Specifications

Fisher 38B Series: Comprehensive DVC Relay Module Range and Technical Overview

The Evolution of 38B Series Architecture

The 38B relay architecture was introduced as part of Emerson's transition from analog I/P transducers to fully digital valve positioner platforms in the mid-1990s. Early-generation DVC5000 controllers used a predecessor relay design with a single-acting pneumatic output and limited supply pressure range (up to 2.4 bar / 35 psi). The 38B relay generation introduced a modular, field-replaceable relay cartridge concept, separating the pneumatic relay from the electronics module to simplify maintenance in hazardous area installations.

The 38B relay is available in three functional configurations: single-acting direct (A), single-acting reverse (B), and double-acting (C/D). Each configuration uses a different internal spool and feedback spring arrangement. Compatibility spans DVC6000, DVC6000f, DVC6000 SIS, DVC6200, DVC6200 SIS, and DVC2000 host platforms. Cross-generation compatibility requires verification of supply pressure rating and actuator travel range. Units manufactured before 2008 may require firmware-level recalibration when installed in DVC6200-series controllers running firmware v10 or later.

38B Series Full Catalog & Functionalities (SKU List)

The following SKUs represent verified, commonly stocked configurations within the Fisher 38B DVC Relay series, classified by functional type:

Single-Acting Direct Relay (Type A)

• 38B5786X112: Standard single-acting direct relay assembly, DVC6000/DVC6200 compatible, 1.4–3.8 bar supply range
• 38B5786X122: Single-acting direct relay, high-supply variant, rated to 4.2 bar, for high-pressure actuator service
• 38B5786X132: Single-acting direct relay with stainless steel body, corrosion-resistant, offshore/coastal service
• 38B5786X142: Single-acting direct relay, low-temperature rated, –40°C ambient, arctic/cold climate installations

Single-Acting Reverse Relay (Type B)

• 38B5787X112: Single-acting reverse relay assembly, fail-open actuator service, DVC6000 series
• 38B5787X122: Single-acting reverse relay, high-supply pressure variant, 4.2 bar rated
• 38B5787X132: Single-acting reverse relay, stainless steel body, corrosion-resistant service
• 38B5787X142: Single-acting reverse relay, low-temperature rated, –40°C ambient

Double-Acting Relay (Type C/D)

• 38B5788X112: Double-acting relay assembly, dual output ports, DVC6000/DVC6200 double-acting actuator service
• 38B5788X122: Double-acting relay, high-supply variant, 4.2 bar, large-bore actuator applications
• 38B5788X132: Double-acting relay, stainless steel body, aggressive environment service
• 38B5788X142: Double-acting relay, low-temperature rated, –40°C, cryogenic adjacent service

Relay Repair Kits & Sub-Assemblies

• 38B5789X012: Relay repair kit, includes diaphragm, O-rings, and spring set for 38B5786/87/88 series
• 38B5790X012: Relay seat and ball assembly kit, for single-acting relay refurbishment
• 38B5791X012: Relay feedback spring kit, assorted rates for actuator travel calibration
• 38B5792X012: Complete relay cartridge exchange unit, factory-tested, drop-in replacement for all 38B variants

Sourcing Hard-to-Find & Obsolete 38B Series Parts

Plants operating DVC6000 controllers installed prior to 2010 frequently encounter relay configurations that are no longer listed in current Emerson price books. DriveKNMS cross-references legacy bill-of-materials data to identify the correct 38B relay variant and supply verified replacements with full traceability documentation.

Quality Control for the 38B Series Range

Each 38B relay unit processed by DriveKNMS undergoes a structured inspection and functional test protocol specific to the pneumatic relay sub-assembly: