How Stem Dampeners Work
Flow Pulsates or Surges
Turbulence, pulsations from a positive-displacement pump, or sudden surges cause the paddle to oscillate rapidly — conditions that would trigger false actuation on a standard unit.
Dampener Absorbs Stem Motion
The special built-in dampener acts directly on the stem, resisting rapid back-and-forth movement. Short-duration oscillations are absorbed before they can rotate the stem far enough to trip the switch.
Switch Trips Only on True Flow Change
A sustained, genuine change in flow rate — not a momentary pulse — deflects the stem past the set point and actuates the switch. The dampener is fully adjustable to tune the response time for your specific conditions.
Key Features
Damping on the Stem Itself
Unlike the Dash Pot, which uses a separate external pneumatic assembly, the stem dampener integrates the damping mechanism directly into the stem. The result is a more compact, more rugged assembly with fewer external components to maintain.
Fully Adjustable Response
The built-in dampener is field-adjustable, allowing you to dial in the right balance between responsiveness and stability for your specific flow conditions — from mild pulsation to severe surging.
Eliminates False Actuation
Turbulence, pulsations, and surges that would cause nuisance trips on a standard switch are absorbed by the dampener. The switch only responds to a real, sustained change in flow — reducing downtime and alarm fatigue.
Positive-Displacement Pump Applications
Gear pumps, piston pumps, and diaphragm pumps all produce a characteristic pulsating flow. The stem dampener is specifically suited to these applications, where the Dash Pot may be oversized or impractical.
Typical Applications
Positive-displacement pump discharge lines
Gear pump & piston pump circuits
Diaphragm pump systems
Chemical dosing & metering lines
Hydraulic power unit circuits
Slurry & viscous fluid handling
Pulsating cooling water circuits
Any flow with cyclic pressure variation
Stem Dampener vs. Dash Pot
Both options prevent false actuation from turbulent or pulsating flow. Use this table to choose the right damping method for your application.
| Stem Dampener (-SD) | Dash Pot (-DP) | |
|---|---|---|
| Damping location | On the stem (internal) | External pneumatic assembly |
| Adjustability | Fully adjustable | Adjustable via needle valve |
| Best for | Pulsating pumps, compact installs | Severe turbulence, larger pipe sizes |
| External components | None | Separate dash pot assembly |
| Ordering suffix | -SD | -DP |
Specifications
| Damping Type | Mechanical — integrated into stem |
| Adjustability | Fully adjustable, field-tunable |
| Ordering Suffix | -SD |
| Compatible Series | All standard PEECO series |
| External Assembly Required | No |
| Typical Use Case | Positive-displacement pumps, pulsating flow |