Okay, this is a challenging environment. Let's break down the issues and explore some options for your fire alarm system in this corrosive grey water treatment plant.

Understanding the Core Problem



Severe Corrosion

The combination of chlorine and moisture (likely high humidity) creates a highly corrosive atmosphere. This attacks metal components, including EMT, enclosures, and electronic devices.

Inadequate Ventilation

While they're "ventilating" with open doors, it's not a controlled or effective ventilation system. It doesn't necessarily remove the corrosive atmosphere effectively.

Device Failure

The fire alarm devices will suffer the same fate as the exhaust fans and previous panel components without proper protection.

Code Compliance

Any solution must, of course, meet applicable fire alarm codes (NFPA 72 in the US, plus any local amendments).

Addressing the EMT Issue: Alternatives to Plastic-Coated RMC

Plastic-coated RMC is the typical go to in this case, it has significant drawbacks, including installation complexity and cost. Here's a breakdown of the various factors and alternatives:1. Rigid Stainless Steel Conduit (RMC Stainless)



Pros

Excellent corrosion resistance, strong and durable, familiar installation methods (threading, couplings). Very long life expectancy.

Cons

Significantly more expensive than plastic-coated RMC. Can be more difficult to cut and thread. Requires specialized tools for cutting and threading, or outsourcing.

Considerations

If the budget allows, this is the best long-term solution. Consider 304 or 316 stainless steel, with 316 providing superior chloride resistance.2.

Aluminum Conduit (RMC Aluminum)



Pros

Naturally corrosion resistant (aluminum forms a protective oxide layer), lighter than steel, easier to work with than stainless steel.

Cons

Aluminum is reactive, and corrosive materials can break down that oxidation layer. Aluminum can react with chlorine, but that depends heavily on the concentration of the chlorine, and any other chemicals. Can be expensive.

Considerations

Check the material compatibility of the conduit and fittings with the specific chemicals present in the greywater treatment process. Look for aluminum alloys specifically designed for corrosion resistance (e.g., marine-grade aluminum).3.

IMC (Intermediate Metal Conduit)



Pros

Less expensive than RMC, lighter weight, similar installation methods to RMC. Can be hot dipped galvanized.

Cons

Not typically recommended for use in corrosive environments. Galvanized coatings may quickly degrade with constant exposure to chlorine.

Considerations



Not Recommended. The galvanization is unlikely to provide adequate long-term protection.4. PVC Conduit (Schedule 80)



Pros

Highly resistant to most chemicals, including chlorine. Easy to cut and install. Less expensive than metal options.

Cons

Not suitable for locations where physical protection is critical. Requires specialized fittings and installation techniques (e.g., solvent welding). Requires grounding conductor in the conduit.

Considerations

While PVC is chemically resistant, it may not be the best choice for a fire alarm system. Subject to temperature limitations.5.

Fiberglass Conduit (RTRC)



Pros

Very corrosion resistant. Lighter than steel.

Cons

More expensive than PVC. Can be brittle and require special installation techniques.

Considerations

A decent option if chemical resistance is paramount and physical protection requirements are moderate.

Key Considerations for ALL Conduit Options



Fittings

The conduit is only as good as its weakest point. Use fittings made of the same material or a compatible, corrosion-resistant material. For example, use stainless steel fittings with stainless steel conduit. Ensure fittings are NEMA 4X rated or better.

Sealing

Properly seal all conduit runs to prevent the corrosive atmosphere from entering the conduit and attacking conductors. Use sealant designed for corrosive environments.

Grounding

Ensure proper grounding according to code. This is critical for safety and to minimize electrical noise. If using non-metallic conduit, run a separate, insulated grounding conductor within the conduit.

Support

Use appropriate hangers and supports that are also corrosion-resistant (e.g., stainless steel).

Addressing the Fire Alarm Devices



Conventional Devices with Monitor Modules

You're on the right track with using addressable monitor modules in the protected environmental enclosure.

Device Selection

Choose devices specifically designed for harsh environments. Look for:

Sealed construction

Devices should be sealed against moisture and dust (NEMA 4X or IP66/67 rating).

Corrosion-resistant materials

Look for devices with housings made of stainless steel, reinforced fiberglass, or durable, chemically resistant plastics.

Wide temperature range

Ensure the devices can operate reliably within the temperature range of the environment.

Mounting

Mount devices using corrosion-resistant hardware (stainless steel).

Consider Heat Detectors

In environments where rapid fire detection is not crucial, heat detectors may be more reliable than smoke detectors due to reduced false alarms from dust and moisture.

Addressing the Enclosure



Location

The breezeway is a better location than inside the treatment building, but ensure it's still a relatively clean and dry area.

Enclosure Rating

Use a NEMA 4X (or better) rated enclosure made of stainless steel or fiberglass. The enclosure needs to be completely sealed and gasketed.

Internal Environment

Consider adding a small heater and dehumidifier inside the enclosure to further control the internal environment and prevent condensation.

Important Recommendations



Consult with Experts

Engage a qualified fire alarm system designer and/or a corrosion specialist to get specific recommendations tailored to the chemicals and conditions present at the site.

Review Material Safety Data Sheets (MSDS)

Review the MSDS for all chemicals used in the grey water treatment process to understand their corrosive properties and material compatibility.

Consider a Preventative Maintenance Plan

Implement a regular inspection and maintenance plan for the fire alarm system. This should include visual inspections for corrosion, testing of devices, and cleaning of enclosures.*

Improve Ventilation (Long-Term)

The open doors are not a long-term solution. Invest in a properly designed and engineered ventilation system that effectively removes the corrosive atmosphere from the building. This will significantly extend the lifespan of all equipment in the area.

In summary, while plastic-coated RMC is a common solution, it may not be the best option in this case. Rigid stainless steel conduit offers the best corrosion resistance but is the most expensive. Thoroughly research the chemical compatibility of aluminum before using it. Carefully consider the environment when selecting devices and enclosures, and implement a preventative maintenance plan. Flag for review