Stainless Steel Deluge Valve — SS304/SS316, Explosion-Proof & Air-Controlled (DN50–DN350)

The key difference is molybdenum content. SS316 contains 2–3% molybdenum which significantly increases its resistance to chloride-induced pitting corrosion — the dominant corrosion mechanism in marine and coastal environments. SS316 has a Pitting Resistance Equivalent (PRE) of approximately 26 versus 18 for SS304.

Specify SS316 for: offshore platforms, any installation within 5 km of the coastline with salt spray exposure, seawater-cooled facilities, LNG terminals, and any process environment where chloride concentration in the atmosphere or process water exceeds 200 ppm. Specify SS304 for: onshore chemical plants, food processing, pharmaceutical, wastewater treatment, and general humid industrial environments without significant chloride exposure. When uncertain for a coastal project — specify SS316. The price premium (15–25%) is negligible compared to the cost of premature valve replacement.

Air-controlled (dry pilot) actuation means the detection circuit uses compressed air (0.1–0.3 MPa) instead of water. The valve stays closed until air pressure in the pilot line is released by a detection device. No water ever sits in the pilot line tubing.

This solves two problems simultaneously. For cold climates (-20°C operation): water in pilot lines freezes and blocks the detection circuit — air does not. The valve operates reliably without heat tracing or antifreeze maintenance on the pilot circuit. For Zone 1 hazardous areas: pneumatic actuation means no electrical components are required inside the Zone 1 boundary of the detection zone. Standard electric solenoid actuation requires an Ex-rated solenoid inside the hazardous area — air-controlled actuation eliminates this requirement entirely, which some Zone 1 SIL-classified systems mandate. The electric solenoid on the ZSFM-P-Ex is located on the valve trim outside the hazardous zone boundary, with only the pneumatic pilot tubing running into Zone 1.

The stainless steel body addresses corrosion. The Ex certification addresses ignition — these are independent requirements that frequently co-occur in the same installation. An offshore LNG terminal, for example, requires both: SS316 body because the environment is salt-spray corrosive, and Ex db IIC T6 Gb certification because the Zone 1 methane atmosphere means any electrical spark on the valve could ignite an explosion.

A stainless steel valve without Ex certification is unsuitable for Zone 1/2 because its electrical trim components (solenoid, pressure switch) would present an ignition risk. An Ex-certified valve with a carbon steel body is unsuitable for offshore because the body would corrode rapidly. The ZSFM-P-Ex combines both in a single certified unit — which is the only correct specification when both conditions apply simultaneously, as they routinely do in offshore, coastal petrochemical, and LNG applications.

Yes — the air-controlled dry pilot mechanism is specifically designed for pre-action configurations. In a double-interlock pre-action setup, the valve requires both a fire detection signal (from a smoke, heat, or flame detector connected to the fire alarm panel) and activation of the pilot line (from a dedicated detection sprinkler or pneumatic actuator) before water is released. Neither signal alone opens the valve.

This dual-trigger logic prevents accidental water discharge in sensitive areas such as cold storage warehouses, data halls, and archives where water damage equals or exceeds fire damage. The ZSFM-P-Ex with air-controlled primary actuation is the correct specification when you need both pre-action false-discharge prevention and Zone 1/2 Ex certification in the same valve — a combination not available in standard diaphragm deluge valves with solenoid-only trim.

Yes. The EPDM diaphragm and SS304/SS316 body are fully compatible with foam-water mixture at up to 6% concentrate — AFFF, AR-AFFF, FFFP, and protein foam types. No modification to the valve body or trim is required. The valve connects directly to balanced-pressure proportioner or bladder tank systems upstream without adapters or wetted material compatibility issues.

For offshore and LNG terminal foam-water systems, the ZSFM-P-Ex with SS316 body is the standard specified valve — combining the corrosion resistance required by the marine environment with the Ex certification required by the Zone 1 gas classification and the foam-water compatibility required for flammable liquid suppression. See the foam bladder tank range for compatible upstream proportioning equipment.

Monthly (offshore): Visual inspection of all SS body surfaces and grooved couplings for any signs of crevice corrosion at gasket contact points — more frequent than onshore due to continuous salt-spray environment. Check pilot air pressure against specification. Verify IP65 enclosure integrity on all Ex components — any damage to enclosure seals requires immediate attention in Zone 1/2 service.

Quarterly: Check flange bolt torque — thermal cycling on offshore decks causes greater bolt relaxation than onshore. Inspect all cable gland entries on Ex enclosures. Verify drain valve seating. Check alarm pressure switch function with test drain.

Annually: Full functional test — activate via all three modes, confirm response times against factory baseline, test alarm gong and pressure switch. Inspect pilot air circuit for any moisture accumulation at low points. Review Ex certification documents — confirm all replacement components carry valid Ex certification before installation.

Biennially: Full diaphragm inspection — remove bonnet and inspect EPDM diaphragm for cracking, compression set, or chemical degradation from foam-water service. Replace as a scheduled maintenance item if any deterioration is observed, regardless of visual appearance. Replace all Ex enclosure gaskets. CA-FIRE can supply diaphragm service kits and Ex-certified spare parts — contact sales@ca-fire.com.