(800) 378-1500
190 Summer St. Lunenburg, MA 01462
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The Building Blocks for Water Treatment Equipment

“Everything but the Chemicals”

Northeast Pump and Instrument (NPI) specializes in the design, sale, installation and repair of chemical feed equipment, systems and instrumentation for water and wastewater treatment. Our involvement in the industry spans more than 30 years and our technical staff boasts over 100 years of combined industry experience.


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Pulsation Dampeners

pulsation dampener

Pulsation Dampening
Positive displacement pumps create pulsation and hydraulic shock purely by the reciprocating nature of the pump's stroking action. During the discharge stroke of a pump, fluid pressure takes the line of least resistance, displacing the bladder in the dampener, thus compressing the trapped gas. As the pump begins its next cycle, fluid flow stops momentarily allowing the compressed gas to expand, forcing the bladder to push the accumulated fluid back into the the discharge line filling the void created by the pump's cycle shift. Whether a piston, plunger, air diaphragm, peristaltic, gear, or diaphragm metering pump, a SENTRY Pulsation Dampener placed at the pump's discharge will produce a steady fluid flow up to 99% pulsation free; protecting the entire pumping system from the damaging effects of shock.

Surge Suppression
When fluid in motion is abruptly stopped, a hydraulic surge is created in the system. Hydraulic surge is often referred to as "Water Hammer". The kinetic energy, released as pressure, can spike up to six times the system's operating pressure -- destroying system instrumentation, pumps, pipes, fittings, and valves. Without a suppression device, the shock wave travels the length of the pipe back to the pump, then reverses again, ocsillating back and forth until friction dissipates the pressure spike or a system component fails.

surge supressors

There are several major culprits that produce this "Water Hammer" effect -- quick closing valves, back surge, pump start up and pump shut down. Quick closing valves can be defined as valves that close within one and one-half seconds. Quick closing valves have the potential of stopping large volumes of energized fluid, producing violent water hammer. Pump start-ups also stops fluid in motion. During pump start-up, fluid in a pipe is static and must be accelerated; the pumped fluid is abruptly stopped when it contacts the static fluid in the pipe, again creating a chock wave. A SENTRY Surge Suppressor will absorb the resistance to acceleration and/or the water hammer surge created in each situation. As the surge enters the Suppressor, the gas inside is compressed, the fluid is accumulated and the shock wave is absorbed. When steady system flow rate is achieved, pressure ad fluid are slowly released back into the system by the suppressor.

During pump shut-down and in back surge situations fluid is reversed. When a pump is shut-off, fluid will reverse direction due to the differential pressure created by the momentum of the fluid in motion. In fact, if the pressure differential is below the vapor pressure of the fluid, a vapor pocket will form creating even higher transient pressures. The reversed flow creates "water hammer" as it slams into the pump's check valve. This effect is compounded in a back flow situation, where fluid is pumped over an elevation or vertically, creating an increase in power due to the fluid's accelerated velocity.

suction stabilizers

Suction Stabilization
Without a sufficient supply of fluid a pump will not perform efficiently. Fluid "starvation" is caused by unbalanced hydraulics from friction, acceleration, and head. A reciprocating pump further comlicates the issue by emmitting high-frequency pressure waves created by the inlet valves opening and closing. For example, in high inlet pressure sitautions, a pump's inlet valves create "water hammer" by their opening and closing action; increasing pipe and pump damage, and draining system efficiency. In suction lift and horizontal suction applications, the inlet valve action actually decreases inlet fluid pressure. A "starved" or cavitating pump will be unable to produce specified flow rates due to the incomplete filling of cylinders and liquid chambers; in addition, cavitation will result in premature failure of pump parts. A SENTRY Suction Stabilizer at the pump's inlet will act as an accumulator, reducing pressure fluctuations and aid in filling the pump head with fluid during each inlet stroke. In high suction lift applications it is also important not to lose the acceleration of the fluid created with each suction stroke of the pump. A Suction Stabilizer will momentarily maintain the flow of the accelerated fluid. The fluid flows into the stabilizer as the pump shifts, then out as the inlet valve re-opens -- maintaining even pressure and steady flow -- eliminating cavitation.

thermal expansion

Thermal Expansion
Many fluids increase in volume due to temperature changes -- as the temperature of a fluid rises, the fluid expands. In a closed or loop system a volumetric increase in fluid can create a rise in pressure beyond the limits of safety. The increase in pressure can result in ruptured pipes and fittings, destroyed in-line instrumentation and contaminated surroundings. A SENTRY Thermal Expansion Chamber properlu sized and installed in the pipeline will accumulate the expanded fluid preventing a dangerous rise in pressure.

(800) 378-1500
190 Summer St.
Lunenburg, MA 01462