The -28 tag means ambient test chamber at -28°C (dry, no condensation). We usually run from 0°C to +50°C, but a client asked for cold-soak behavior down to -35°C. So we obliged.
MPD-055 -28 -OL appears to be a model/part identifier. I’ll assume you want a complete technical and user guide covering identification, specifications, installation, operation, maintenance, troubleshooting, parts, and safety. If this identifier refers to a different product type (electronics, mechanical actuator, PCB module, or optical unit), say so and I will adapt. MPD-055 -28 -OL
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Another strong possibility: MPD stands for Manufacturing Process Directive for a swivel nut or tube fitting used in high-pressure systems (3,000–6,000 psi). The “-28” would match a common UNF thread size: 9/16-18 UNF (where 28 is the TPI sometimes encoded inversely). But more logically, “28” here could mean size 28 in a manufacturer’s series (e.g., Parker, Eaton, Aeroquip). The -28 tag means ambient test chamber at
The OL suffix in fluid systems often means: Signal:
Search procurement notes from Boeing BAC, Airbus ABS, or Lockheed Martin LAC standards. Many OEMs adopted MPD internal codes before transitioning to AS (Aerospace Standard) numbers.