PULSATION DAMPERS...The damper bladder is pre-charged with nitrogen or compressed air through the gas valve and takes the shape of the damper body. The compressible gas contained in

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OLD 0120

PULSATION DAMPERS

GENERAL DESCRIPTION

What is a pressure surge?

A pressure surge (also called water hammer) is a brief high increase or drop in pressure. It only lasts for fractions of a second, but the pressure peaks occurring can be many times the operating pressure.The peak values that arise can come in the form of both overpressure and negative pressure (cavitation). The propagation speed of the pressure waves can be up to 1400 m/s and depends on the material and the wall thickness of the pipe.

How do pressure surges arise?

Pressure surges in pipework occur due to sudden changes in liquid flow:

• Acceleration of liquid mass when pumps are switched on

• Breakdown in the delivery flow when pumps are switched off

• Abrupt stopping of a liquid that was in motion due to a quick-closing valve

• Sudden change in the direction of flow due to solenoid valves

• Abrupt change in the pipe cross-section due to narrowing or restriction

Where do pressure surges occur?

Pressure surges can arise in any pipe network:

• When pumps are switched on or off• At power failures in pumping stations• In the case of hydrant consumption in fire-fighting lines• In filling or metering lines (concrete factories, chemical

plants, large laundries, etc.)

What effects do pressure surges have?

• High increase in pressure or negative pressure (cavitation)

• Disturbing noises• Signs of material fatigue

The consequences are:

• Damage to integrated instruments and fittings• Breaks in pipework, noise and vibrations• Loosening or unsealing of joints

How do we prevent pressure surges?

In every system where pressure surges are to be expected or already present, they can be prevented by mounting a correctly dimensioned and low-maintenance ORELL shock absorber.

Pressure versus time graph when closing a quick acting gate valve on a feeding pipe.

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a.) The bladder is in precharged position and fills the damper completely. The punched screen prevents the bladder from passing through the fluid opening.

b.) The damper is filled with fluid and the gas in the bladder is compressed. The bladder has a trefoil shape.

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We reserve all rights in connection with this document. Changes are only allowed performed by Olaer AG using the CAD.

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DanielH

OLAER SCHWEIZ AG, Bonnstrasse 3, 3186 Düdingen, Tel. +41 (0)26 492 70 00, www.olaer.ch



Blatt1 v. 1

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DanielH

OLAER SCHWEIZ AG, Bonnstrasse 3, 3186 Düdingen, Tel. +41 (0)26 492 70 00, www.olaer.ch

How do ORELL pulsation dampers work?

The damper bladder is pre-charged with nitrogen or compressed air through the gas valve and takes the shape of the damper body. The compressible gas contained in the bladder can absorb or restore excess energy.The bladder fulfils the most important function on the damper. As an elastic element it guaranties an absolute separation between the gas cushion and the fluid.The bladder deformation is given by the damper construc-tion and always happens in the same manner (trefoil shape).Any uncontrolled collapse of the bladder leading to friction and other subsequent damages is therefore impossible.

Advantages of ORELL pulsation dampers

• Guarantied operation without outside energy• Minimum space requirements• Ideally adjustable to the available space• Minimum maintenance requirements• Thanks to the separation air cushion/water, no air from

the cushion can get into the piping system • The damper is supplied ready for use and precharged

with the necessary air cushion

The two basic positions of the bladder at EBV and EHV:

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ORELL damper application fields

Pumping stations

Pressure sideWhen switching on the pumpliquid is taken up from the damper as the air cushion in the bladder is compressed and as the standing liquid column offers a higher resistance. The pressure rises slowly and the liquid column is smoothly accelerated. No pressure peaks occur. At the same time, liquid is pushed under pressure into the damper for the next switch off of the pump.

Suction sideWhen switching on the pumpthe damper delivers a certain quantity of liquid and the standing column is smoothly accelerated. No underpressure or air suction occurs even at low inlet pressures.

When switching off the pumpthe liquid column flows back into the damper and compres-ses the air cushion. The pressure rises slowly and the liquid column is smoothly decelerated.

Blockage units in manufacturing plants

When the on-off or shut-off valve is open, the liquid flows unhindered and continuously through the pipings. The bladder precharge pressure is slightly lower than the dynamic pressure (approximately 75%) and the bladder fills the damper almost completely.

The closure of the valve suddenly interrupts the flow of the fluid which can find its way into the damper compressing the air cushion. The pressure rises slowly and the liquid column is smoothly decelerated.

When switching off the pumpthe damper presses the stored water volume back into the piping. Any breakaway of the liquid column will be avoided, which continues to flow thanks to its kinetic energy.

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Sanitary installations

Sanitary fittings such as single-lever mixers and solenoid valves of washing machines generate water hammering when shutting rapidly. The pressure surges propagate in the piping systems of the building.

Such water hammers generate disturbing noises and reduce the operating life of the fittings and pipings as well as of the connected sanitary appliances.By fitting a damper at the highest point of the rising pipeline (figure 1) or close to the water hammers generator (figure 2), pressure surges can be avoided.

Figure 2Figure 1

Volume compensation

The volume of a liquid varies according to its temperature. It increases as the temperature rises. When liquid is trapped for instance in a completely filled reservoir or in a piping closed on both ends, a temperature rise will generate a pressure increase, which can cause the reservoir or the piping to burst.By fitting a correctly dimensioned damper the pressure rise can be limited to a certain value determined in advance by absorbing the expanded volume of liquid by the damper.

Pulsation damping in piping systems with continuously flowing liquids

When using piston or diaphragm pumps pulsations occur in the piping system. Pulsations generate noise and vibrations and can damage measuring instruments, fittings, pipe connections, supports, etc. In sensitive systems pressure variations due to pulsations can actuate control systems and lead to operation breakdowns.In such cases, a pulsation damper is fitted directly after the pump in the piping. The special connection (T-piece) directs the pulsations into the damper and reduce their effect on the system.

Documents

PULSATION DAMPERS...The damper bladder is pre-charged with nitrogen or compressed air through the gas valve and takes the shape of the damper body. The compressible gas contained in