Surge tanks are commonly arranged with a compressor, or compressors, to provide additional air in to the tank if the liquid level rises above the normal condition. The change in level is detected by a level instrument, which may be a simple bypass level gauge containing a magnetic float which rises and falls with the liquid level activating magnetically sensitive switches attached to the level gauge or a more advanced level instrument, such as a radar or ultrasonic level detection instrument.

Bladder tanks are usually supplied in one of two configurations and are used to reduce pressure surges in pipelines.

AIR IN BLADDER

The air charge is contained within the bladder inside the tank. The air charge does not come into contact with the liquid in the tank and so cannot be absorbed. Air charge losses due to absorption are therefore minimal.

The pumped liquid from the main flows into and out of the main tank, it will come into contact with the tank walls and so compatible materials must be selected. 

The bladder is often made from a highly elastic rubber, such as butyl rubber, and may be sized to expand to fit the entire vessel. The bladder will typically be pre-charged at installation with a pre-determined pressure to give the correct operating level in the tank when the unit is connected to the main and at the operating pressure.

There must be an anti extrusion plate fixed at the outlet from the vessel to prevent the bladder from being drawn into the main at low pressures. The anti-extrusion plate and inlet size must be selected so that they do not impose a restriction on the flow into and out of the vessel, otherwise the unit will not function correctly as a surge tank.

[SWB sketch]

WATER IN BLADDER

The air charge is contained within the tank, whilst the liquid from the main flows into and out of the bladder. Like the air in bladder design, the liquid does not come into contact with the tank walls nor the air charge, so again, the air charge cannot be absorbed by the pumped liquid and so air losses due to absorption are minimal.

The pumped liquid from the main flows into and out of the bladder and will not come into contact with the tank walls, again compatible materials must be selected. 

As for the air in bladder design, the bladder is often made from a highly elastic rubber, such as butyl rubber, and may be sized to expand to fit the entire vessel. For this design the whole tank is pre-charged at installation with a pre-determined pressure to give the correct operating level in the tank when the unit is connected to the main and at the operating pressure.

Again, there must be an anti extrusion plate fixed at the outlet from the vessel to prevent the bladder from being drawn into the main at low pressures and like the air in bladder design, the anti-extrusion plate and inlet size must be selected so that they do not impose a restriction on the flow into and out of the vessel.

STANDARD FITTINGS
Each bladder vessel comes with these
standard features:
[installed bladder tanks]

Safety relief valve;
Pressure gauge;
Air fill valve;
Anti-extrusion plate; 
Drain connection;
Butyl bladder. 

OPTIONAL FITTINGS
Any bladder vessel may be fitted with the
following optional features:

Level gauge;
Level transmitter;
Pressure transmitter;
Drain valve. 

CONSTRUCTION AND MATERIALS

Flo-Dyne bladder vessels are pressure vessels and as standard are manufactured in ordinary carbon steel, low temperature carbon steel or 304/316 stainless steel to the requirements of PD5500, ASME VIII. We will CE mark the equipment if it is to be used within the European Union, if the equipment is to be used elsewhere we will apply a CE mark if requested.

Release of steam to atmosphere creates noise which is dangerous to plant personnel and is environmentally unacceptable. 

The steam may be released from either low pressure (LP steam vent silencer) of high pressure (HP steam vent silencer) as part of boiler start up system, a bypass vent or a safety relief valve vent system.

In each case Flo-Dyne offer the most economical approach by optimizing silencer design to produce a guaranteed solution through selection of silencer pressure drop and flow velocities appropriate to the duty.

Flo-Dyne's steam vent silencer model type BOS can be supplied with an inlet diffuser built to pressure vessel standards that will let down the inlet pressure to atmospheric pressure.

Not all steam that is vented is dry, so where there is moisture carried in the steam flow Flo-Dyne can provide a separator element to remove the excess moisture and prevent this hot liquid from being exhausted out through the vent to fall as "hot rain" in the area surrounding the vent.

The pressure drop across the inlet diffuser is selected according to the duty of the silencer, we can examine the pressure losses through the pipework and recommend the most suitable silencer pressure drop for the vent duty.

If there is a significant length pipework between the venting valve and the silencer, the pressure drop across the venting valve may lead to high noise levels being radiated by the pipework. Flo-Dyne can advise on noise levels radiated by pipework in such cases, and make recommendations for mitigation.

[silencer being packed] Silencers may be packed or pack free diffuser only types, depending on the duty requirements. Where a packed silencer is needed the packing material will often be chosen from glass fibre, mineral or ceramic fibre as considered appropriate for the operating conditions.

The structural design of the Flo-Dyne Vent Silencer is given the same thorough attention as its acoustic design. The external shell is constructed of seamless pipe in smaller sizes and continuously welded rolled plate in larger diameter silencers. 

Silencers may be mounted horizontally or vertically, pads or cradle type supports are available for easy installation.

In-Line silencers for to attenuate inlet noise from Axial, Centrifugal and Turbo Compressors.

Lobe type and multi-vane compressors generate high-energy noise levels at the fundamental and initial harmonic frequencies. With no absorptive pack, rugged construction and high quality materials, this multi-chamber design is tuned to handle these frequencies and is very effective in reducing tonal radiation from the pipe work connected to these machines. 

[blower silencer] Using powerful computer design programs
Flo-Dyne are able to predict and analyse the
performance of each silencer application.

Flo-Dyne engineers are able to adjust internal dimensions and observe the effects on performance, to ensure optimum performance is achieved to adjust internal dimensions and observe the effects on performance. Pressure vessel fabrication techniques are used with pressure ratings given. Carbon steel construction is standard, but other materials are available for special applications. 

The graph shown below shows actual measured dampener performance that equates to over 30 dB reduction in pulsation level at the fundamental pulsation frequency and the first harmonic at a flow rate of 29000CFM @ 68°F from a rotary blower.

In-Line silencers for to attenuate inlet noise from Axial, Centrifugal and Turbo Compressors.

Suction stabilisers to eliminate acceleration head and pressure pulsation in suction lines

Pulsation dampeners are often necessary for multi-plunger high pressure reciprocating pumps which produce damaging levels of pulsation and vibration. These forces can be significantly reduced by the Flo-Dyne non-charged maintenance-free pulsation dampener which is completely filled with the pumped liquid. Our unique spherical in-line design results in optimized low weight and cost and is ideal where rubber bladder or metallic diaphragm types cannot be applied. 

[discharge dampener] Liquid filled pulsation dampeners work due to two crucial features of the design.

Volume
The volume is selected by Flo-Dyne to provide sufficient bulk so that when each plunger discharges its slug of liquid the compressibility of the liquid will absorb a proportion of the pulsation energy. The volume of the dampener must be chosen to be massive compared to the slug of liquid discharged by each plunger on each stroke, and not too large as to be uneconomical for manufacture.

Where required we can offer discharge pulsation dampeners that work upon this feature of compressibility of the volume alone, however such dampeners tend to be both massive 
and expensive.

Pressure drop
Every Flo-Dyne's liquid filled pulsation dampener has inlet / outlet nozzles which impose a back pressure onto the pump. It is well known that pressure drop alone will reduce pulsation levels, however, Flo-Dyne's proven arrangement will both impose a pressure drop as well as impart a rotational velocity to the liquid volume creating a fluid flywheel. This arrangement improves on simple single orifice type arrangements and introduces the added benefit of flywheel smoothing as well as energy absorbtion due to increased friction losses at the walls of the equipment that simply are not there with simple flow through designs.

[discharge dampener] Proven Design
The Flo-Dyne liquid filled pulsation dampener is a proven design which has been keeping reciprocating pumps running smoothly for over 40 years.

The equipment is fit and forget, it is maintenance free with no moving parts and may be permanently welded into the line. Typically the dampener will reduce discharge pressure pulses by 75% depending on the type of pump, connected piping system and liquid handled. 

Carbon steel construction is standard, but other materials such as 304/316 stainless steel, duplex or super duplex steels are available for pressures ranging from 50 Bar G to 400 Bar G as standard.

Units can be built to all British, European, American and Indian pressure vessel codes. 

All pressure equipment can be CE marked to comply with the European Pressure Equipment Directive requirements.

Many high speed multi-plunger pumps create tones and pulses that can be harmful to the piping system and be extremely annoying.

Typical applications include multi-plunger hydraulic pumps, gear pumps and refrigeration compressors.

With the Flo-Dyne acoustic filter, it is possible to completely eliminate these tones and pulses by the application of our simple low pass acoustic filter design.

Using a multiple chamber design with connecting choke tubes, we are able to provide proven acoustic attenuation that will virtually eliminate tones and pulses from high speed positive displacement pumps and compressors 

Treatment of noise created by high pressure multi-plunger hydraulic pumps, is achieved
by the application of a low pass design acoustic filter,
[acoustic filter] which is designed to attenuate the dominant frequency and the most significant harmonics. 

Each acoustic filter can be built to be welded directly into the piping with connecting nozzles supplied bevelled and ready for welding to the pipe system, or each unit may be supplied with couplings or flanges to match the mating connection.

The multi-chambered acoustic filter is designed to filter or attenuate the predominate frequency and significant harmonics of the pump. Using computer simulation response curves, Flo-Dyne engineers can 
check each acoustic filter design for each application.

Pulsation analysis is required to examine the pulsation levels in suction and discharge pipework for positive displacement pumps on liquid duties. Analysis is undertaken to API674 standard to insure the smooth running of pumps and the vibration free operation of pipework. 

Flo-Dyne can analyse your pipework system for pressure pulsations and recommend solutions to achieve compliance with API674.

We will make recommendations for changes to the configuration to avoid the purchase of unnecessary equipment, or optimise the design of suitable protection measures if absolutely necessary.