WO1992020951A1

WO1992020951A1 - Pulsation dampening device for pipes and machines

Info

Publication number: WO1992020951A1
Application number: PCT/AU1992/000234
Authority: WO
Inventors: Thomas Hume
Original assignee: Q.U.F. Industries Ltd.
Priority date: 1991-05-24
Filing date: 1992-05-25
Publication date: 1992-11-26

Abstract

A pulsation dampener (10) for pipes or machines (100) has an outer pipe (11) and a co-axial inner pipe (23) which defines a cushion chamber (24). A nozzle plate (27), between the inlet (17) and the cushion chamber (24) has a central nozzle (28) surrounded by a plurality of passages (29), the latter allowing flow from the inlet (17) through an annular upper chamber (25) to the outlet (24). When the pressure at the inlet (17) greatly exceeds the pressure at the outlet (21), a jet of fluid through the nozzle (28) is sprayed into the cushion chamber (24) and minute quantities of entrained air are released to compensate for air entrained from the air pocket in the cushion chamber (24) so that the fluid level (L) in the cushion chamber (24) will oscillate about a substantially constant level.

Description

TITLE: "PULSATION DAMPENING DEVICE FOR PIPES AND MACHINES" BACKGROUND OF THE INVENTION

1. Field of the Invention THIS INVENTION relates to dampening devices for pipes and machines.

2. Prior Art

The dampeners are particularly suitable for, but not limited to, the dampening of pulsations in fluid flow lines generated by machines such as dairy products homogenisers.

An homogeniser is a reciprocating, plunger type positive displacement pump. Fluid is drawn into the cylinder, through the suction valve, on the backward stroke of the plunger. As the plunger moves forward, the suction valve closes and the discharge valve opens. Depending on the number of plungers, their diameter, stroke length and reciprocating speed so varies the output of an homogeniser. When an homogeniser is placed in a process line, vibration often occurs in the piping, particularly on the discharge side of the machine.

These vibrations emanate from two types of pressure fluctuation in the system. There is a low frequency pulsation caused by the pulsating nature of the flow from the homogeniser. (For example, a single plunger homogeniser would have a flow/pressure curve as in Fig 1 of the accompanying drawings. ) This gives a large variation between high and low flow/pressure points of each reciprocation. This pressure variation is passed into the pipework after the homogenise.. If the homogeniser has three plungers, then the pulsations are much reduced since the difference between highest and lowest pressure is much less (see Fig 2). Five or seven plungers further smooth out the magnitude of the pressure/flow fluctuations.

There is also a high frequency vibration caused by the homogeniser discharge valves closing. These pulses of small amplitude and pressure difference do not cause severe vibration of pipework, but can cause damage to delicate instruments, such as pressure gauges and other instrumentation.

The way to reduce the vibratory effect of these pulsations is to place a pulsation dampener at the discharge of the homogeniser.

The most common form of pulsation dampener is an air cushion (see Fig 3) . The air trapped in the cushion allows "storing" of the flow during high flow/ pressure peaks and pushes energy and fluid back into the system at low flow/pressure troughs.

The discharge valve vibrations are also absorbed and reduced by the energy storing capability of the air cushion. Thus, a pulsation pattern occurring as shown in Fig 4 on a three plunger machine can be reduced to the pattern shown in Fig 5 by use of an "air cushion" pulsation dampener.

The air cushion is, thus, a very simple and satisfactory means of dampening damaged pulsations which can cause cracking of pipework welds, fracture of support brackets and abrasion of pipes against other pipes or brackets. It can easily be disassembled each day for cleaning and inspection. There is another, often unrealised reason that some systems require dismantling of the air cushion pipe each day and that is to recharge the air in the cushion pipe.

During production of dairy type products, the product generally passes through the homogeniser at 60 to 75°C. It is a fact that the air in the cushion pipe is very gradually lost, absorbed by the product, or water that may substitute for the product while waiting

(process water) or, during sterilising or intermediate

C.I. . Once the air is all absorbed in this manner, the vibration from plungers and valves returns. The vast majority of plants never suffer the problems of air loss in the air cushion, since production runs are of much shorter duration than the time required for the air in the cushion to be removed. In aseptic plants, where the homogeniser is placed after the sterilisation process, the homogeniser, and thus the pulsation dampening cushion, must be sterilised at 140°C for 30 minutes.

From the simple air cushion point of view, there are two problems: 1. The air in the cushion may not have been completely sterilised, which would result in product contamination.

2. The air expands to approximately two times its volume as the temperature is raised to twice the normal production level and some air is lost, thus, reducing the volume available after normal temperature is restored.

Our UHT milk plant ran at 6,000 Litres/hour

(L/h) for some 13 years without a pulsation dampener. The pipework would occasionally vibrate badly, but, generally, the level of vibration during production was deemed tolerable.

Certainly, it was preferable to the problems of trying to design and fit a sterile pulsation dampener to the homogeniser since we could not find any company supplying a ready-made, tried, tested and true device for that purpose.

We, however, upspeeded the process to 10,000

Litres/hour (L/h) the vibrations in the pipework downstream of the aseptically positioned homogeniser were intolerable. They caused noise, vibration and, worst of all, cracking of pipework at regular intervals.

A simple experiment with air cushion pipes showed that vibrations could be eliminated with air cushions, at suction and discharge of the homogeniser.

Further experimenting with suction only, and then discharge side only, elicited the fact that the discharge side was responsible for 80%+ of the problem.

Over a period, we experimented with no less than four types of steam jacketed air cushions of some

1500mm air cushion pipe length. Each one was successful in removing the vibrations and proved sterile. The problem, however, that kept recurring was, that after

17-18 hours of continuous running (with aseptic intermediate cleans) , the air in the cushion would disappear and the vibrations would return.

About this time, we ascertained that APV

Gaulin in Germany had developed a pulsation damper with an internal bladder of EPDM rubber able to stand 140°C sterilising temperatures which was pre-inflated and thus avoided direct contact of product with the air.

We purchased one of these and found it performed well on vibration dampening. However, it lost air from the bladder (via the retaining mechanism) into the product during every run. Fortunately, the air within had been sterilised and did not cause a sterility problem.

We modified the bladder retaining/clamping mechanism to tighten its grip, but still the air escapes, albeit at a lower rate.

Seeking a new aseptic homogeniser for the UHT process of 12500-19000 l/h capacity, enquiries were made with three major homogeniser manufacturers and a number of factories in Europe. Nobody had a suitable aseptic damper with the ability to: 1. Guarantee sterility of any air within;

2. Not lose the air over time;

3. Clean up perfectly during CIP; and

4. Be easily disassembled for inspection. SUMMARY OF THE PRESENT INVENTION

It is an object of the present invention to provide a dampener which efficiently dampens the pulsations for relatively long periods and which does not lose air. It is a preferred object to provide a dampener which is compact and inexpensive to manufacture.

It is a further preferred object to provide a dampener which is easy to clean.

It is a still further preferred object to provide a dampener which guarantees the sterility of any air within when operated under aseptic conditions.

It is a still further preferred object to provide a dampener which ensures that the air within the dampener is exposed to radiant heat all along the cushion length during the sterilising period.

Other preferred objects will become apparent from the following description.

In a broad aspect, the present invention resides in a pulsation dampening device for pipes and machines including: an outer pipe having an inlet at or adjacent its lower end (in use) and an outlet at or adjacent its upper end; an inner pipe, within the outer pipe, closed at its upper end; an inner cushion chamber to contain air or other gas within the inner pipe; an outer chamber including an upper portion about the inner pipe and a lower portion adjacent the inlet; and plate means with at least one passage or nozzle to allow a jet of fluid to flow into the cushion chamber when the fluid pressure at the inlet exceeds the fluid pressure at the outlet. Preferably, the plate means also separates the upper and lower portions of the outer chamber and is provided with a plurality of passages or nozzles to allow the fluid to flow from the inlet to the outlet.

Preferably, a single central nozzle is provided in the nozzle plate (which forms the plate means) , so arranged that the jet flow of fluid through the nozzle strikes the top of the cushion chamber and sprays through the air in the cushion chamber, the jet flow being caused by the pressure below the nozzle plate (ie. at the inlet) being considerably greater than the pressure above the nozzle plate in the annular upper portion of the outer chamber and at the outlet, which is the back pressure of the downstream system.

Preferably, air, dissolved and/or entrained in the milk or other liquid, is released in minute quantities sufficient to maintain the quantity of the air in the cushion chamber against any loss from absorption or physical entrainment.

Under aseptic operating conditions, the central water jet and spray is at, eg. at 140°C and temperature ensures that the air in the cushion chamber is sterilised thoroughly during the sterilising period.

Preferably, the inner pipe is attached to the top cap of the outer pipe and can be removed by simply releasing the nut and lifting out the pipe to enable inspection of the interior of the outer pipe, the top of the nozzle plate, and the interior of the inner pipe. The central jet of fluid assists in C.I.P., ensuring perfect cleanliness of the cushion chamber interior in the inner pipe. Preferably, a bottom cap and nut is removable from the outer pipe to expose the bottom side of the nozzle plate for inspection.

BRIEF DESCRIPTION OF THE DRAWINGS To enable the invention to be fully understood, preferred embodiments suitable for connection to the downstream side of a homogeniser for dairy products (eg. milk) under aseptic conditions, will now be described with reference to the following accompanying drawings:

Fig 1 is a graph of the flow pressure curve of a single plunger homogeniser;

Fig 2 is a similar graph for a three plunger homogeniser (the average flow being indicated by dashed line) ;

Fig 3 is a side view of the installation of a typical air cushion in a dairy plant;

Fig 4 is a graph of the pulsation pattern (over one crank shaft revolution) of a three plunger homogeniser without an air cushion;

Fig 5 is a similar graph of the homogeniser fitted with the air cushion;

Fig 6 is a schematic view of the installation of a first embodiment of the dampener of the present invention;

Fig 7 is a sectional side view of the dampener of Fig 6, on an enlarged scale;

Fig 8 is a sectional plan view taken on line 8-8 on Fig 7; and Fig 9 is a part sectional end elevational view of a second embodiment of the dampener.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring to Fig 6, the pulsation damper 10 of the present invention is shown connected to the outlet pipe 100 of a homogeniser (not shown) in a UHT milk line, and to a pipe 101, eg. connected to a packaging machine in which the UHT milk is packed in sterile containers, eg. of 250 ml or 2L capacity.

Referring to Fig 7, the pulsation dampener 10 has an outer pipe (eg. of EX 100mm stainless steel tube) which has a screw-threaded male flange 12, 13 (welded) at each end. A blank cap 44 closes the upper end of the outer pipe 11 and is secured by a nut 15 engaged with the male flange 13 and is sealed by an O-ring 16. An inlet pipe 17, at the base of the dampener

10, is connected to the homogeniser outlet pipe 100 via welding or suitable fittings. The inlet pipe 17 has a peripheral flange 18 releasably connected to the male flange 12 via a nut 19 and is sealed thereto by an O- ring 20.

An outlet pipe 21, directed to one side of the dampener, is provided adjacent the upper end of the outer pipe 11 and is provided with a flange 22 for connection to the pipe 101. An inner pipe 23 (eg. of EX 76mm stainless steel tube) is welded at its upper end to the cap plate 14 to close its upper end, its lower end being spaced above the inlet pipe 17.

The interior of the inner pipe 23 defines the cushion chamber 24 which contains air above a variable fluid level L. The inner and outer pipes 23, 11 define an annular upper chamber 25 and a lower chamber 26 adjacent the inlet pipe 17.

A nozzle plate 27 is provided in, and sealed to, the wall of the outer pipe 11 and is spaced a small distance (eg. 20-50mm) below the lower end of the inner pipe 23. A central nozzle* 28, directed towards the cushion chamber 24, is surrounded by a plurality of nozzles or fluid passages 29 directed towards the annular upper chamber 25. As shown, the cross-sectional area of the central nozzle 28 is equal to the total cross-sectional area of the (eighteen) fluid passages 29. This ratio is not critical. In certain applications, only a single central nozzle 28 could be provided, the total milk flow being through the jet into the cushion chamber. In other applications, the single nozzle could be replaced by a plurality of smaller jets, eg. of the same total cross-sectional area. The operation of the dampener 10 will now be described for use under aseptic conditions. The dampener 10 is assembled as illustrated and installed (see Fig 6) and air is contained in the cushion chamber 24. For sterilising of the dampener (and the air), water at, eg. 140°C is flushed through the dampener, the water passing through the passages 29 and up the annular upper chamber 25, where the radiant heat about all of the cushion chamber 24 sterilises all of the air therein. The dampener 10 is then connected to the outlet pipe of the homogeniser and the milk flows through the inlet pipe 17, through the passages 29, and the annular upper chamber 25 and out the outlet pipe 21. (The milk will rise in the cushion chamber to a variable level L, which contains the air in the cushion chamber 24.) When the pressure at the inlet pipe 17 exceeds the pressure in the upper annular chamber 25, milk flows throughout the central nozzle 28 in the nozzle plate 27 and the jet of milk strikes the top of the cushion chamber (ie., the underside of cap plate 14) and sprays the air in the cushion chamber 24. Air, dissolved or entrained in the milk, is released in minute quantities sufficient to maintain the quantity of the air in the cushion chamber 24 against any loss of air therefrom from absorption or physical entrainment in the milk. The level L of the milk rises in the cushion chamber 24. When the pressure at the inlet pipe 17 drops below that of the upper annular chamber, some of the milk will flow out of cushion chamber 24 and the level L will fall. In an experimental example of the dampener, the overall length of the inner pipe was in the range of 600-700mm and the dampener operated successfully for periods exceeding 24 hours, where dampeners, eg. of the type shown in Fig 3 of 1500mm x 76mm ceased useful operation after, eg. 17-18 hours as the air within the dampeners had become exhausted.

In the embodiment shown in Fig 9, the inlet pipe 17a is provided in the outer pipe 11 above the lower end of the latter which is sealed by an end-cap 40 and an O-ring 41, secured by a nut 42 on male flange 12.

The inlet pipe 17a has a union 43 for connection to the outlet pipe 100 of the homogeniser. The operation of the embodiment 10a is identical to that of the dampener

10 of Figs 6 to 8. It will be readily apparent from the skilled addressee that the dampener 10, 10a can be used in any application where pulsations must be damped in fluid lines (water pipes, hydraulic pipes) and it is particularly suitable for food production lines where the dampener and the air therein must be sterilised.

The inner pipe 23, being attached to the top cap plate 14 of the dampening device 10, is removed by simply unscrewing the nut 15 on the top and lifting out the pipe 23. This allows inspection of the interior of the outer pipe 11, the top of the nozzle plate 27 and the inside of the inner pipe 23. Again, the central jet of fluid assists in C.I. ., ensuring perfect cleanliness of the inner pipe interior. Removal of the bottom nut 19 and inlet pipe 17 exposes the bottom side of the nozzle plate 26 for inspection. Thus, disassembly is effected by removal of two nuts only. Two other nuts release the complete dampener 10 from the pipework system. The only parts needing occasional replacement are the o-ring seals (16,20) at the top, bottom, inlet, and outlet of the dampener.

Various changes and modifications may be made to the embodiments described and illustrated without departing from the scope of the present invention defined in the appended claims.

Claims

1. A pulsation dampening device for pipes and machines including: an outer pipe having an inlet at or adjacent its lower end (in use) and an outlet at or adjacent its upper end; an inner pipe, within the outer pipe, closed at its upper end; an inner cushion chamber to contain air or other gas within the inner pipe; an outer chamber including an upper portion about the inner pipe and a lower portion adjacent the inlet; and plate means with at least one passage or nozzle to allow a jet of fluid to flow into the cushion chamber when the fluid pressure at the inlet exceeds the fluid pressure at the outlet.

2. A device according to Claim 1 wherein: the plate means separates the upper and lower portions of the outer chamber and is provided with a plurality of passages or jets to allow the fluid to flow from the inlet through the outer chamber, to the outlet.

3. A device according to Claim 1 or Claim 2 wherein: the plate means comprises a nozzle plate with a single central jet, so arranged that the jet flow of fluid through the jet strikes the top of the cushion chamber and sprays through the air in the cushion chamber, the jet flow being caused by the pressure below the nozzle plate, at the inlet, being considerably greater than the pressure in the annular upper portion of the outer chamber and at the outlet, which is the back pressure of the downstream system.

4. A device according to any one of Claims 1 to 3 wherein: air, dissolved or entrained in the fluid, is released from the fluid in minute quantities sufficient to maintain the quantity of air in the cushion chamber against any loss from absorption or physical entrainment.

5. A device according to any one of Claims 1 to 4 wherein: the inner pipe is sealably attached to a removable top cap on the outer pipe to enable the inner pipe to be removed for inspection of the interior of the outer pipe, the top of the plate means, and the interior of the inner pipe.

6. A device according to Claim 5 wherein: a bottom cap, or an inlet pipe connected to the inlet, is removable to enable inspection of the bottom of the plate means.

7. A pulsation dampening device for pipes and machines, including: an outer pipe having an inlet at or adjacent its lower end (in use and an outlet at or adjacent its upper end) ; an inner pipe,within the outer pipe, closed at its upper end and with a mouth at its lower end spaced above the inlet; an inner cushion chamber within the inner pipe; an outer chamber including an annular upper portion about the inner pipe and a lower portion adjacent the inlet; and plate means with at least one nozzle below the cushion chamber and a plurality of passages below the outer chamber; so arranged that in use, air or other gas is contained in the cushion chamber above and variable level of fluid, the fluid flows through the passages from the inlet to the outlet, and when the pressure in the fluid at the inlet exceeds the pressure at the outlet, a jet of fluid flows through the nozzle into the cushion chamber and at least a portion of any gas dissolved or entrained in the jet of fluid is released into the air or gas sufficient to maintain the quantity of fluid in the cushion chamber against any loss of air or gas from the cushion chamber due to absorption or physical entrainment in the fluid.

8. A device according to Claim 7 wherein: the level of fluid in the cushion chamber is not raised to the level of the top of the inner pipe or fall below the bottom of the inner pipe.

9. A device according to Claim 7 or Claim 8 wherein: the cross-sectional area of the nozzle (or nozzles) is substantially equal to the total cross- sectional area of the passages.