MTL 8920-PS-DC PAC8000 12VDC System Supply

Description

Product Introduction

The MTL 8920-PS-DC is a specialized DC power supply module built for the MTL8000 and Emerson PAC8000 intrinsically safe (IS) I/O systems. Mounting directly onto the 8724-CA-PS carrier, it takes a nominal 24 VDC plant bus input and converts it into isolated, safety-clamped power to feed up to eight 2/1 IS I/O modules. It provides crucial power distribution in hazardous areas without compromising intrinsic safety loop integrity.

Unlike off-the-shelf DIN-rail supplies, this unit incorporates active load-sharing logic and triplicated crowbar overvoltage protection. You can run two 8920-PS-DC modules on a single carrier for full N+1 redundancy, guaranteeing that a single supply failure won’t drop your field instrumentation loops.

Key Technical Specifications

Application Scenarios & The “Trench” Experience

It’s 3 AM during a winter turnaround at an offshore platform. The distributed process control system throws an unexpected Railbus fault, taking down sixteen critical flow transmitters in a Zone 2 area. The diagnostics point straight to a tripped internal fuse on a failing legacy IS power supply. Without those flow loops live, the safety instrumented system prevents unit restart, burning $45,000 an hour in delayed production. Swapping in a pre-tested, verified replacement module from surplus stock gets the bus powered, clears the fault, and brings the plant back online before morning shift handover.

Target Applications:

• Offshore Oil & Gas: Powers intrinsically safe pressure and temperature transmitters on production platforms.
• Petrochemical Plants: Feeds NAMUR digital inputs and 4-20mA smart positioners mounted in Class I, Div 2 classified locations.
• Chemical Batch Processing: Provides fault-tolerant, N+1 redundant DC bus power to prevent unexpected shutdown of hazardous reaction vessels.

8920-PS-DC

8920-PS-DC

Transparency SOP: Quality Assurance & Testing

We do not just pull a dusty box off a shelf and ship it out. Every 8920-PS-DC goes through a strict functional validation protocol:

1. Inbound Physical Inspection: Verification of casing structural integrity, backplane connector pin alignment, terminal screw integrity, and OEM seal validation.
2. Live Rig Bench Test: The unit is installed on an authentic 8724-CA-PS carrier rack populated with simulated MTL8000 loads.
3. Full Load & Thermal Soak: Powered up at 24VDC input and pulled to a continuous 5.0A load for 4 hours while thermal imaging monitors component temperatures.
4. Redundancy Line Validation: Voltage verification on the P-Share line and triggering simulated primary failure to verify P-Fail relay contact closure.
5. ESD-Safe Packaging: Cleaned, sealed in moisture-barrier anti-static bags, and packed in custom foam inserts designed for heavy industrial shipments.

The Veteran’s Tech Trap Guide

• ⚠️ Don’t treat this like a standard 12V field supply! The 12 VDC output is internal Railbus system power designed strictly for powering the 2/1 IS module electronics through the carrier. Connecting field instruments directly to this output will compromise intrinsic safety ratings and likely fry the internal safety crowbar.
• ❗ Verify the Carrier Model before installation. The 8920-PS-DC requires the 8724-CA-PS carrier. Non-IS 8000 series power supplies use different keyed backplanes. Forcing it onto a standard carrier will bend the high-current interface pins.
• ⚠️ Calculate total bus current when adding I/O modules. A single 8920-PS-DC provides 5A. While one supply typically handles eight IS I/O modules, high-density analog output cards pull significantly more current. If total load exceeds 5A without a second load-sharing unit, the primary supply will thermally shut down.
• ❗ Check line drop on incoming 24VDC. The module input range is 18.5 to 36 VDC. If your bulk 24V supply is situated far from the remote I/O enclosure, voltage drops below 18.5 VDC under heavy load will trigger low-voltage cutouts on the module. Measure voltage directly at the carrier screw terminals under load.

Frequently Asked Questions

Q: Can I hot-swap the 8920-PS-DC while the system is running?

A: Yes, provided you have a dual-supply redundant setup on an 8724-CA-PS carrier. If running a single non-redundant supply, pulling it live will instantly drop power to the attached I/O modules and trip your field loops.

Q: Is the MTL 8920-PS-DC still actively manufactured by Eaton MTL?

A: No. This unit is officially discontinued/obsolete by the OEM. New units are no longer produced, making tested surplus or refurbished stock the primary option for maintaining existing plant installations.

Q: How does the load-sharing feature work between two modules?

A: When two 8920-PS-DC modules are installed on the same carrier, internal control circuitry balances the 5A load evenly between them via the P-Share line. If one fails, the other seamlessly assumes the full load without dropping Railbus voltage.

Q: What is the difference between New Surplus and Refurbished stock?

A: New Surplus units are unused original OEM inventory in factory packaging. Refurbished units are pre-owned modules that have undergone component level checks, internal cleaning, stress testing, and hardware reconditioning. Both ship with a full 12-month warranty.

Q: Why buy surplus instead of upgrading the entire I/O rack to current product lines?

A: Ripping out a legacy MTL8000 or PAC8000 node requires complete loop re-engineering, cabinet rewiring, safety re-certification, and extensive downtime. Replacing a failed power supply module takes less than five minutes and costs a fraction of a system migration.