Valve & Fire Protection Industry Glossary

A full-bore gate valve whose wedge is encapsulated in a flexible elastomer (typically EPDM) that seats against a metal body, giving bubble-tight shut-off with low operating torque and no repacking. RSGVs are the dominant isolation valve in water, wastewater and fire mains and are specified under AWWA C515 (US), ISO 5208 and EN 1074.

Devices installed where a potable supply could be contaminated by reverse flow from a cross connection. The most common type is a double check valve assembly of two independent check valves with a testable connection; it is mandatory at hose connections, irrigation and most industrial cross connections.

A valve that automatically reduces a high supply pressure to a constant lower set pressure downstream. Hydraulic self-operated PRVs (such as the 500X) protect fire mains and building risers from overpressure and water-hammer while keeping the downstream set point stable.

A valve bonnet arrangement with the operating stem outside the pipe and a yoke that raises the stem as the valve opens, so its position is visible. OS&Y gate valves are the classic heavy-duty fire and main isolation valve; the stem seal is outside the fluid path.

An underground fire hydrant that stays empty below ground level; the barrel fills with water only when a port is opened, which keeps water out of the barrel in cold climates so it does not freeze. Dry-barrel hydrants are the standard for frost-protected municipal networks and are specified under AWWA C502 (US) and EN 14384 (Europe).

A connection on a building or system that lets the fire department pump water in through its hoses. A siamese FDC typically has two DN65 (2.5") inlets and a DN100 flanged outlet, and is the entry point for deluge and sprinkler systems.

A number describing a sprinkler’s flow rate at a given pressure, expressed as the discharge coefficient. Flow (gpm) equals K multiplied by the square root of pressure (psi); common ratings are K=5.6, K=80 and K=115. The K-factor, together with the hazard classification from NFPA 13, drives head spacing and layout.

A classification of sprinkler head by how quickly its thermal element activates. Quick-response heads (RTI < 51 °C·s^½) detect a developing fire earlier and are generally required in high-hazard and occupant-protected areas; standard-response heads suit most ordinary-hazard commercial systems.

A dry sprinkler system in which the piping is kept dry and two independent signals are required before water enters the lines — typically a fire-alarm trigger plus a separate sprinkler-activation. It protects areas where water damage from an accidental leak is the main risk, such as data centers and archives.

A dry system with open (non-draining) nozzles, supplied through a deluge valve that opens on a detection signal so that all open heads discharge at once. Deluge systems address flash-fire and high-hazard industrial processes, paired with the deluge alarm valve group.

The NFPA standard for the installation of automatic sprinkler systems. It sets hazard classifications, head spacing and K-factor rules, required piping and valves, and the system types (wet, dry, deluge, preaction) for commercial and industrial buildings.

A bayonet-style universal fire coupling sized to the hose diameter (Storz 2, 3, 4, 5) that can be connected without tools and seals automatically when turned. It is the dominant international hose coupling standard, alongside US NIST and British BS336.

The NFPA standard for fire hose. It defines construction (jacket, liner, coupling), the rated working pressure (commonly 150 or 250 psi), and the required factory and periodic testing. A compliant attack hose pairs a high-strength fabric jacket with a vulcanized rubber lining.

The American Water Works Association standard for ductile iron resilient seated gate valves. It defines materials, dimensions, operating torque, pressure and flow requirements and the mandatory shell and seat testing for water and wastewater gate valves in North American specifications.

The AWWA standard for dry-barrel fire hydrants. It specifies the design, materials, operating pressure (typically 125–250 psi), flow capacity and the required pressure and leakage testing for hydrants used in municipal fire and water supply networks across North America.

A safety certification issued by Underwriters Laboratories after a product is tested against a named standard and the factory is assessed. A listed valve or sprinkler may be specified in buildings where the code or insurer requires it; listing applies to a specific product and model, not to a whole company.

An approval from FM Global (now FM Global / FM Approvals) based on performance and durability testing beyond minimum-code requirements. FM approval is frequently specified by large insurers and industrial projects; like UL, it is granted per product and per model.

Two flange-rating systems: PN (Pressure Nominal, metric, e.g. PN10/PN16) follows EN/DIN, while ANSI/ASME class ratings (Class 150/300) follow US and most of the Americas. A valve’s flange face must match the system standard and rating — mixing PN and ANSI faces on the same line is a common specification error.

A size designation that does not equal the pipe’s physical bore. DN (diamètre nominal) is the metric designation (DN80, DN100); NPS (nominal pipe size) is the US designation (3", 4"). DN and NPS sizes map to each other for selection but the flange dimensions differ by standard.

Mexico’s Official Mexican Standards (NOM) and the NR (Norma de Riesgo / fire) regime govern fire-protection products in the Mexican market, with certification through designated authorities. A LatAm tender in Mexico may require NOM conformity for hydrants and fire equipment; compliance is confirmed per model.

Two per-unit tests that verify a valve or hydrant before shipment: a hydrostatic shell test that checks the body against leakage or deformation at an over-pressure, and an air-leakage test that confirms the valve seals bubble-tight in service position. Records per serial number are the primary evidence of a genuine manufacturer.