SENTRY Frequently Asked Questions

  • "What is the difference between a pulsation dampener, surge suppressor, inlet stabilizer, thermal expansion chamber, accumulator and standpipe?"
    These designations, with the exception of standpipe, are used to describe pressure vessels containing a flexible bladder or bellows inside that separate an inert pressurized gas (air or Nitrogen) from a system fluid in the lower chamber. Generally referred to as dampeners, their use and location in a liquid piping system determines the name designation. A standpipe is simply a pipe with a cap on one end, and does not separate a gas charge from the product being pumped.

  • "Can I use a SENTRY dampener to dampen airflow?"
    Generally, SENTRY dampeners are used to minimize hydraulic pressure/flow fluctuations. There are some applications where a SENTRY dampener has been successfully used to dampen pneumatic pulses. Consult BLACOH or your local distributor for an analysis of your specific application.

  • "Can I use a plastic model in a water hammer or surge application?"
    Water hammer is usually caused by a quick closing valve located somewhere in a liquid piping system. When a valve closes quickly, a pressure spike above 150 psi (10.3 bar) is usually created. SENTRY plastic dampener models can only be used for pressure up to 150 psi (10.3 bar) at ambient temperature. For water hammer or surge, a SENTRY metal dampener model with a higher pressure rating must be used.

  • "What is the difference between air controls on SENTRY Automatic, Adjustable, Chargeable and Inlet Stabilizer models?"
    Different air controls are used for different types of applications:

    Chargeable Models have a charging valve that allows for a predetermined pressure charge to be applied and held in the dampener. No permanent source of compressed gas is required to be attached to the dampener. Chargeable models are used primarily with metering, piston and peristaltic pumps for pulsation dampening. Chargeable models are also used for surge suppression to prevent water hammer from quick closing valves, for make-up fluid to prevent pump cycling, and for suppression of pump startup or shutdown pressure spikes.

    Adjustable Models use a self-relieving regulator to set dampener pressure. A compressed air line must be permanently attached to the regulator. The regulator allows for an easy, convenient method for readjusting the dampener if the system fluid pressure changes. Adjustable models are designed for use on air operated diaphragm pumps in systems with a constant discharge pressure.

    Automatic Models have an automatic poppet type valve located in the non-wetted section of the dampener which allows for an increase in compressed air pressure to balance an increase in system liquid pressure. As liquid system pressure increases, the bladder is pushed further up into the dampener until it touches the internal automatic valve. This contact opens the valve and allows an increase of compressed air to enter the dampener. When the air pressure equals the system liquid pressure, the dampener is in balance and pulsations are minimized. If a change in pressure occurs this process is repeated. Automatic models are designed for use on air operated diaphragm pumps in systems with a varying discharge pressure. A compressed air line must be permanently attached to the dampener.

    Inlet Stabilizer (J Model) air controls consist of a compound pressure gauge, a pressure/vacuum tight ball valve and a venturi valve. When compressed air is passed through the venturi valve at high speed, a low pressure area is created which is used to evacuate the air from the inlet stabilizer, creating a vacuum internally. Conversely, when the flow of air through the venturi valve is diverted into the inlet stabilizer, a pressure charge is obtained. When pump inlet conditions are optimized, pump efficiency is maximized.

Certifications (top)

  • "Do BLACOH products meet European ATEX safety standards?"
    Yes. Many BLACOH models and sizes have ATEX certification with new models and sizes added on a daily basis. Consult BLACOH for the latest status on ATEX certifications.

  • "Do BLACOH SENTRY dampeners comply with the European Pressure Equipment Directive (97/23/EC)?"
    BLACOH SENTRY Pulsation Dampeners, Surge Suppressors and Inlet Stabilizers comply under Sound Engineering Practices (SEP). In some cases, however, compliance requires a lowered pressure rating. Contact BLACOH for specific information.

  • "Do BLACOH SENTRY dampeners have the Canadian CRN designations?"
    Yes. While most BLACOH models are exempt from this requirement, certain SENTRY models have been registered and have received CRN designation. Consult BLACOH for more specific Information.

  • "Does BLACOH have a 3A designated dampener?"
    3A has recently approved a pulsation dampener design and BLACOH will be submitting a design for acceptance in the near future. Consult BLACOH for the latest status on "3A" designations.

  • "Do BLACOH SENTRY dampeners have ASME coding on the dampeners?"
    No. ASME (American Society of Mechanical Engineers) standards do not apply until the internal diameter of the dampener exceeds 6 inches. BLACOH SENTRY models up to 370 cubic inch (6L) sizes are under this dimension. All BLACOH SENTRY dampeners have a burst pressure three or more times higher than the maximum allowable working pressure (MAWP) specified. Consult BLACOH for specific ASME information on other model sizes.

Sizing & Materials (top)

  • "What sizes are available?"
    BLACOH SENTRY dampeners are available from stock in sizes from 4 cubic inches (.065L) to 10 gallons (37.8L). Sizes up to 100 gallons (378L) are available through special order.

  • "How do I size a dampener, suppressor or stabilizer?"
    Proper sizing is based upon several variables. Consult BLACOH or your local distributor for sizing and application assistance.

  • "What materials are available?"
    BLACOH SENTRY products are available in a full range of chemically resistant materials, with bladder materials for even the most corrosive applications.

  • "What is the material Aflas that you offer in bladders?"
    Aflas is basically a Viton rubber filled with 20% PTFE. It is primarily for strong acids and/or high temperature applications up to 400°F (204°C).

  • "What are the minimum and maximum temperature limits?"
    Operating temperatures are based on the maximum temperature of the wetted dampener components only. Non-wetted dampener components may have a lower temperature limit. Temperature and certain chemicals may reduce the maximum allowable working pressure (MAWP) of the dampener. SENTRY products can be used with operating temperatures ranging from -40°F (-40°C) up to 400°F (204°C). Refer to the Installation & Operation Manual for more detailed information. When consulting material specifications for temperature ranges, be sure to check the bladder material, and the wetted and non-wetted body material. If you are unsure of the proper component materials or you need further assistance, contact BLACOH or your local distributor. CAUTION: Plastic materials lose strength as temperature increases which reduces the maximum pressure sustainable by the material.

  • "Can I order special inlet connections?"
    BLACOH can customize almost any type of dampener or stabilizer inlet connection, including NPT and BSP threads, ANSI and DIN flanges, tri-clamp fittings, socket weld ends, butt weld ends, metric flare type fittings, and many more.

  • "Are material and pressure test certificates available?"
    Yes. BLACOH maintains traceability of most materials used in SENTRY dampeners. Additionally, each and every SENTRY dampener is factory tested prior to shipment at design pressure or higher to assure proper and leak-free operation. A pressure test certificate can be provided upon request. Any material and/or pressure certification must be requested at the time of order.

Pressurization (top)

  • "What is the maximum pressure rating available?"
    SENTRY dampeners with maximum allowable working pressure (MAWP) ratings up to 4,000 psi (276 bar) are available from stock depending on the specific design and material of the dampener. Pressure ratings up to 25,000 psi (1,724 bar) are available through special order.

  • "What pressure should the dampener, suppressor or inlet stabilizer be charged to?"
    Charging pressure depends on the specific model and application. Refer to the appropriate Installation & Operation Manual for detailed information.

  • "What compressed gas do I use to charge the dampener?"
    Charging pressure depends on the specific model and application. Refer to the appropriate Installation & Operation Manual for detailed information.

Installation & Maintenance (top)

  • "Where should the dampener, suppressor or inlet stabilizer be installed?"
    Within 10 pipe diameters of the source of the pressure fluctuation; i.e. at the pump discharge for pulsation, at the pump inlet for inlet stabilization, upstream of a quick closing valve for water hammer, and at the discharge of a centrifugal pump for start-up and/or shutdown.
     

  • "How should the SENTRY dampener be installed?"
    Since pressure is equal in all directions, the SENTRY dampener can be installed in a vertical, horizontal, or upside-down position. A vertical installation is recommended for better drainage of the dampener. Limitations for horizontal and upside-down mounting include high specific gravity, high viscosity, settling of solid material, or possible air entrapment, which could result in shortened bladder/bellows life and/or reduced dampening performance.

  • "What direction is the bladder (or bellows) installed?"
    Elastomeric (rubber) bladders are always installed with the open end away from the dampener inlet, whether in dome or flat top models. PTFE bellows are installed with the open end of the bellows facing up in flat top models. In dome top models, PTFE bellows are assembled with the open end of the bellows facing down.

  • "What maintenance is required for dampeners?"
    Dampeners require very little maintenance. There is only ONE wear part - the elastomeric bladder or the PTFE bellows. There is no need for lubrication. Elastomeric bladder replacement should be part of a preventive maintenance program. Dampeners used in conjunction with diaphragm pumps should have the bladders replaced at least every second time the diaphragms in the pump are replaced. Periodic inspection of the dampener and fasteners should be conducted to visually check for signs of over-pressurization, fatigue, stress, or corrosion.

  • "What are the torque specifications for the bolts (fasteners)?"
    Each BLACOH SENTRY dampener model has its own fastener torque specifications. Refer to the appropriate Installation & Operation Manual for detailed information or contact BLACOH for assistance.

  • "Can I reuse the fasteners (nuts and bolts) on the dampener?"
    DO NOT re-use old nuts and bolts. After the initial torque of fasteners, bolts will usually lose up to 20% of their strength when re-torqued. Failure to replace both nuts and bolts upon each vessel reassembly will void the product warranty given by BLACOH Fluid Control, Inc. and BLACOH Fluid Control, Inc. will have no liability whatsoever for any vessel failure or malfunction. Replace nut and bolt fasteners on metal models at each re-assembly with fasteners of equal grade/strength value. Where dampeners are used in corrosive environments, nut and bolt fasteners should be regularly inspected and replaced with nut and bolt fasteners of equal grade/strength value if corrosion is observed.

Troubleshooting (top)

  • "How can I tell if the dampener is working properly?"
    If the dampener is sized and installed correctly, pump pulsations should be reduced to a very minimal amount. If a pressure gauge is installed at the pump discharge, the gauge pressure reading should usually only vary by 3 to 10 psi (.207 to .689 bar). Inlet stabilizers work the same way on the inlet side of the pump. Consult BLACOH or your local distributor if the dampener does not appear to be working properly or, if the residual pulsation is greater than expected.

  • "Why is the gauge not reading 0 psi when the pump is off and the dampener is depressurized?"
    The gauge has probably been damaged by momentary system over-pressurization. Check for a quick closing valve in the system which when closed can cause a pressure spike in excess of the maximum gauge pressure rating. CAUTION: Remove all pressure from the dampener AND pumping system before disassembly, removal or maintenance of the dampener.

  • "Why does the dampener lose pressure?"
    The primary reason a dampener will not hold pressure is a failed bladder/bellows. The dampener should be inspected and the bladder/bellows replaced if it has failed. A spray solution of soap and water should be used to check the fittings around the control package at the top of the dampener as vibration over time can loosen these fittings. For a thorough system test, the dampener should be removed from the system. Charge the dampener to working pressure and submerge under water. Any leakage will be seen as air bubbles. CAUTION: Remove all pressure from the dampener AND pumping system before disassembly, removal or maintenance of the dampener.

Warranty (top)

  • "What is the warranty policy for SENTRY dampeners?"
    All SENTRY products are guaranteed for workmanship and materials for two (2) years from shipment, with the exception of PTFE bellows which carry a three (3) year guarantee of performance. Certain limitations and restrictions apply. Refer to BLACOH's Manufacturer's Limited Warranty and Return Policy for complete details.

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