Glossary & FAQ

Glossary — 22 terms

SPDT

Single Pole Double Throw. A micro-switch configuration with one common terminal, one normally open (NO) contact, and one normally closed (NC) contact. The standard micro-switch on PEECO flow switches.

DPDT

Double Pole Double Throw. Two independent SPDT switches operated simultaneously by a single actuator. Used in Multiple Action applications where two separate circuits must be switched at the same time.

NEMA 4X

A National Electrical Manufacturers Association enclosure rating indicating the housing is weatherproof, dust-tight, and corrosion-resistant. Suitable for indoor and outdoor use in non-hazardous locations.

Explosion Proof (XP)

An enclosure design that can contain any explosion originating inside and prevent it from igniting flammable gases or vapors outside. Required in Class I hazardous locations. PEECO E and H Series are UL/CSA listed explosion proof.

Class I, Division 1

A hazardous location classification where flammable gases or vapors are present continuously, intermittently, or periodically under normal operating conditions. Requires explosion-proof equipment.

Class I, Division 2

A hazardous location where flammable gases or vapors are handled, processed, or used but are normally confined within closed containers. Less stringent than Div 1 but still requires appropriate equipment.

Dead Band

The difference between the flow rate at which the switch actuates (trips) and the flow rate at which it resets. PEECO flow switches maintain less than 10% dead band between make and break points.

Bellows

A seamless, flexible metal tube (321 stainless steel on PEECO switches) that transmits fluid force to the actuating mechanism without requiring packing glands or stuffing boxes. Inherently leak-proof by design.

Flexure Tube

Used on the H Series in place of a bellows. A stainless steel tube through which a solid rod extends. Wall thickness is engineered based on pressure requirements, allowing operation at 600+ PSI.

Specific Gravity (SG)

The ratio of a fluid's density to the density of water at a standard temperature. Used to calculate the actual flow force on the paddle. Water = 1.0. Heavier fluids (SG > 1) require less velocity to actuate the switch.

Viscosity

A measure of a fluid's resistance to flow. High-viscosity fluids (like heavy oils) exert more drag on the paddle at a given velocity, which affects the set point. Provided in centipoise (cP) or SSU.

GPM

Gallons Per Minute. A common unit for volumetric flow rate in liquid applications. Used with pipe size and specific gravity to determine fluid velocity at the paddle.

Velocity (ft/sec)

The speed of the fluid past the paddle. PEECO flow switches are velocity-actuated — the paddle deflects based on fluid velocity, not pressure. Velocity is calculated from GPM and pipe cross-sectional area.

Paddle

The sensing element that extends into the flow stream. Deflects in response to fluid velocity and transmits force through the bellows or flexure tube to actuate the micro-switch.

Dash Pot

A hydraulic or pneumatic damping device that slows the response of the switch to prevent false trips caused by turbulent flow, pulsation, or water hammer.

Stem Dampener

A mechanical damping device attached to the paddle stem to reduce sensitivity to turbulent flow conditions. Similar function to a dash pot but simpler in construction.

Wafer Tee (WT)

A connection style where the flow switch body is sandwiched between two pipe flanges. Used on NT-F and ET-F models for 2″ and smaller line sizes.

Top Mount (NP/EP/HP)

A connection style where the flow switch mounts to the top of the pipe via a screwed or flanged fitting. Used for line sizes 2½″ and larger.

Hermetically Sealed

A micro-switch option where the contacts are completely sealed in a gas-tight enclosure. Provides superior protection against moisture, corrosive atmospheres, and contamination.

Teflon (PTFE)

Polytetrafluoroethylene. Used as a lining or solid construction material for flow switch bodies and paddles in corrosive media applications. Resistant to virtually all chemicals.

Sanitary

A construction option for food, beverage, and pharmaceutical applications. Features smooth, crevice-free surfaces, sanitary fittings (Tri-Clamp), and materials that meet FDA/3A standards.

IOM Manual

Installation, Operation, and Maintenance manual. The PEECO IOM covers proper installation orientation, wiring, set point adjustment, and maintenance procedures.