Emerson 38B Series Pneumatic Relays – 38B5786X132

Technical Dossier

Product Details And Specifications

Emerson 38B Series Technical Notes

The Emerson 38B Series single-acting direct pneumatic relays are precision signal-conditioning devices deployed across the full spectrum of global heavy industry. Installed in petrochemical complexes, offshore platforms, nuclear power stations, and crude oil refineries, these relays serve as the pneumatic interface between electronic control systems and final control elements. Their role in distributed control system (DCS) architectures — particularly within Fisher and Rosemount instrument loops — makes them a critical spare parts category for any facility operating continuous-process equipment. The 38B Series is characterized by its direct-acting, single-acting output configuration, compact manifold-mount form factor, and compatibility with 3–15 psi and 6–30 psi instrument air signal ranges. Facilities running legacy Emerson DeltaV, Fisher PROVOX, and RS3 control platforms maintain standing inventories of 38B Series relays as insurance against unplanned shutdowns.

The Evolution of 38B Series Architecture

The 38B Series traces its design lineage to Fisher Controls' mid-20th-century pneumatic instrumentation portfolio, predating the widespread adoption of electronic field devices. Early variants operated exclusively on 3–15 psi signal ranges and were designed for direct panel or manifold mounting in pneumatic control rooms. As the industry transitioned through the 1980s and 1990s toward hybrid electro-pneumatic architectures, the 38B Series was re-engineered to accommodate 6–30 psi ranges and higher-flow output demands, reflected in the X-suffix variant codes (e.g., X012, X022, X032, X132). The introduction of stainless steel body options addressed corrosion requirements in offshore and chemical service environments. By the 2000s, the 38B Series entered a mature/sustaining lifecycle phase: Emerson continued to manufacture select variants for installed-base support while positioning the Fisher 67 Series and Rosemount 3490 Series as forward-design replacements for new projects. Today, the 38B Series is classified as a long-term maintenance (LTM) product line. New installations are rare; however, the global installed base in operating refineries and power stations ensures sustained demand for OEM and reconditioned spare units through at least 2035.

38B Series Full Catalog & Functionalities (SKU List)

The following SKUs represent verified, commonly stocked variants within the Emerson 38B Series pneumatic relay family, organized by output range and body configuration:

Single-Acting Direct Relays — 3–15 psi Output Range

• 38B5786X012: Single-acting direct relay, 3–15 psi output, aluminum body, standard flow capacity
• 38B5786X022: Single-acting direct relay, 3–15 psi output, aluminum body, high-flow capacity orifice
• 38B5786X032: Single-acting direct relay, 3–15 psi output, stainless steel body, corrosion-resistant service
• 38B5786X042: Single-acting direct relay, 3–15 psi output, aluminum body, reverse-acting configuration
• 38B5786X052: Single-acting direct relay, 3–15 psi output, stainless steel body, reverse-acting, high-flow

Single-Acting Direct Relays — 6–30 psi Output Range

• 38B5786X112: Single-acting direct relay, 6–30 psi output, aluminum body, standard flow
• 38B5786X122: Single-acting direct relay, 6–30 psi output, aluminum body, high-flow orifice
• 38B5786X132: Single-acting direct relay, 6–30 psi output, stainless steel body, corrosion-resistant service
• 38B5786X142: Single-acting direct relay, 6–30 psi output, aluminum body, reverse-acting configuration
• 38B5786X152: Single-acting direct relay, 6–30 psi output, stainless steel body, reverse-acting, high-flow

Booster & High-Capacity Variants

• 38B5786X212: Volume booster relay, 3–15 psi, aluminum body, 1:1 ratio, high-flow actuator service
• 38B5786X222: Volume booster relay, 6–30 psi, aluminum body, 1:1 ratio, high-flow actuator service
• 38B5786X312: Ratio relay, 3–15 psi input, adjustable output ratio, aluminum body
• 38B5786X322: Ratio relay, 6–30 psi input, adjustable output ratio, stainless steel body
• 38B5786X412: Bias relay, 3–15 psi, aluminum body, fixed bias spring, panel-mount configuration
• 38B5786X422: Bias relay, 6–30 psi, stainless steel body, adjustable bias, manifold-mount
• 38B5786X512: Reversing relay, 3–15 psi, aluminum body, inverts pneumatic signal polarity
• 38B5786X522: Reversing relay, 6–30 psi, stainless steel body, inverts pneumatic signal polarity