DE3414558A1 - HYDRAULIC PULSE DAMPER - Google Patents

Description

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The invention relates to a hydraulic pulse damper for liquid chromatography. This hydraulic pulse damper for use in a liquid chromatography column has a stiff membrane that can nestle into a receiving member and absorbs pulse energy and saves elastically as material stress (strain)

It is common to use pulse dampers in hydraulic systems for damping purposes of impulses to use. In such systems, impulses are dampened so that they do not have any sympathetic harmonics Generate reactions that could damage components or otherwise disrupt the operation of the system could, see e.g. US Pat. No. 3,782,418, column 1. With increasing pressures and decreasing flow rates in liquid chromatography, the field of high performance liquid chromatography (HPLC) has the use of

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Requires the use of pulse dampers. The range of operating pressures is from a few pounds per square inch to 5000 psi (34,473,785 N / m ² ) or even higher. In high-performance liquid chromatography, these pulsations are not only the source of damage to the columns but also interfere with the peak elution times, since flow fluctuations are associated with pulsating pressure.

In high-performance liquid chromatography, mostly uses a pulse damper that works with liquids that absorb pulse energy when they are compressed, see e.g., U.S. Patent 4,222,414 and U.S. Patent 4,234,427 (particularly Fig. 1b). Solids are also already being used to absorb pulse energy is used, for example, as disclosed in U.S. Patent 4,024,061 (alloeined in Fig. la). To absorb pressure pulses gas is also used which is separated from a flowing liquid flow by means of a membrane, see e.g. US-PS 4,163,461, also known are bubbles already filled with gas, see e.g. US-PS 3,782,418.

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Lines are used to absorb the pulse energy, see e.g. US Pat. No. 3,782,709, from which an adjustable spring which is pressed against a fluid-tight membrane. The ease with which the membrane moves is one Function of the tension in this spring at any given point in time. While the stiff membrane impulse energy from the When fluid transfers to the spring, the energy is stored in the spring. The spring constant determines the pressure range in which the damper is most effective. Another mechanical impulse damper is a flexible, resilient tube of non-circular cross-section through which fluid flow flows. When pressure pulses occur, the tube deforms flexibly into a circular shape, increasing the volume and the pressure of the pulse is facilitated. This is shown in the accompanying drawing Fig. 1c with the cross section "a" which has the normal shape and the cross-section "b" representing the fully deformed shape. This suggestion is from U.S. Patent 3,537,585 and from the publication by J. G. Nikelly et. al. "Pulse Dampener for High Pressure Liquid Chromatography," Analytical Chemistry, Vol. 51, p. 1585 (1979).

When operating high pressure liquid chromatographs, it has been found necessary to operate in a wide pressure range in order to accommodate the wide range of flow rates and column resistances. The pressure range typically extends from near zero pounds per square inch to about 6000 psi (41,368,542 N / m ² ). Conventional pulse dampers, which use liquids, gases, or springs to absorb the pulse energy, are usually not suitable for operation in such a large pressure range. It is true that a pulse damper working with compressible fluid could be constructed which could be used over a wide pressure range; The volume of liquid would then be so large that, especially at high pressures, a very large

large dead volume would arise. That would be for :; ! '. otrifibsvr-r- «Hold on

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harmful to high performance liquid chromatography.

The object of the invention is to provide a pulse damper for To create high performance liquid chromatography, the one allows satisfactory damping at low pressures.

Such Impulsöämpfer for high performance liquid chromatography to uri induncj, -. Cjunwiß stiff with, flox,> ί <membrane work that, to the extent in which the membrane einschrnieyt into a recess, energy elastic than material] ό-anspruchung. (strain) stores.

Such a pulse attenuator can be combined with conventional pulse attenuation techniques to provide pressure in a range of pressures close to zero to 41,368,542 N / m ² (0 to 6,000 pounds per square inch). Satisfactory damping behavior: achieve iu.

The pulse damper ::; ol i also with optimal damping work at low pressures and then adjust to obtain an optimal damping constantc at high pressure will.

In the case of the pulse damper, there should no longer be any volume expansion occur when the upper I. '. etriabs pressure limit is reached.

The following is the invention with further advantageous details explained in more detail using schematically illustrated embodiments. In the drawings shows:

Fig. Ia-Ic various known pulse dampers, of which Fig. la a pulse damper with compression of a solid;

1b shows a pulse damper with compression of a liquid;

Fig. Ic a pulse damper with expansion of the volume within Figure 9 shows a tube of non-circular cross-section;

FIG. 2 shows a longitudinal section through a pulse damper according to FIG

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Invention;

FIG. 3 shows a cross section through the pulse damper according to FIG. 2;

4a-4b side views of a rigid membrane according to the invention, which show the deformation and nesting of the membrane in a receiving member;

5 shows a cross section through a further exemplary embodiment a pulse damper according to the invention, which also has a conventional pulse damper with compressible Has liquid;

6 shows a longitudinal section through a further embodiment a pulse damper with two diaphragms that have different thicknesses and stiffnesses around one To enable damping in a wide pressure range;

Fig. 7 is a graphic representation of the; predicted and

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A rigid membrane is provided upstream of a high pressure liquid chromatograph in contact with the pressurized liquid. The membrane is arranged in the vicinity of a receiving member and can nest in this receiving member or smear into the receiving member if it is bent due to absolute pressure increases or pressure pulses in the liquid. With increasing pressure, the membrane gradually deforms and hugs the formed recess. The energy absorbed by the membrane increases with increasing deformation. The material, shape, and thickness of the membrane are selected so that the deformation occurs at pressures ranging from nearly zero to about 6,894,757 N / m ² (0 to 1,000 pounds per square inch - psi). In a preferred embodiment, the shape of the receiving member is chosen so that a flat area is available in the center which first comes into contact with the membrane, so that the nestling occurs from the center outwards, whereby a pressure increase with the increase an increasingly greater resistance is opposed to the absolute pressure.

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The membrane damper can be used in combination with other known Impulse attenuators are used in other pressure ranges work. Membrane dampers can also be used, which have several membranes with different characteristics, to be used in a large pressure area.

In order to avoid damage to columns and other components and to be able to work with reproducible peak elution rates, pulses in high pressure liquid chromatography systems have to be ^{dampened in a pressure range from a few to approx. 41 368 542 N / m 2} (some - approx. 6000 psi). Conventional pulse damping techniques that work by compressing liquids, solids or gases

or store pulse energy mechanically, are suitable for adequate damping of pressure pulses above approx. 6 894 757 N / m ² (1000 psi). The compressibility of these media is usually too high to be able to dampen pulsations effectively if the absolute pressure or pulsating pressure is less than 6 894 757 N / m ² . It is true that the volume of the medium to be compressed could be increased in order to achieve adequate damping even at low pressures; but this would increase the total volume of the system and the dead volume in the flowing stream at high pressure would increase. Both are undesirable for high-performance liquid chromatography.

The invention is based on the knowledge that the use of a rigid membrane enables the energy flor pressure pulsations elastic iüls Materialbeanspruchuncj (strain) -Enerc; ie r.u save. There is also increased energy from the ab co Iu Lf: ■ wruck «jospoichr-rt, but · that only consumes storage capacity. The membrane acts as a pulse damper as long as its storage capacity is not used up, i.e. as long as the absolute pressure does not exceed a certain given limit. Below this limit is the energy of pressure pulses absorbed by the rigid membrane as it deforms. The pressure limit is reached when the membrane is fully

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is constantly deformed, i.e. when it is completely in the Receiving member has nestled, as explained in detail will.

As used herein, the term "rigid membrane" refers to a membrane that is not flexible enough to withstand Its bending does not absorb any significant energy, and it is not so stiff that it is absorbed by pressure pulses in the liquid exerted forces would not be movable. The rigidity of each membrane is determined by the material, shape and ' Determines the thickness of the membrane. As will be explained in detail, these factors are chosen so that the membrane at gradually deformed with increasing pressure. The pulse damper can be designed in this way by selecting the values mentioned accordingly will be that it allows effective damping at low pressure, i.e. at pressures below 1000 atmospheres. With the membrane is a receiving member used which has a shaped Has a cavity to which the membrane hugs when it bends. The task of the receiving member is to tear of the membrane at higher pressures and the introduction of unnecessary dead volume. To do justice to higher pressures can be a conventional damper, such as a damper based on the compressibility of a liquid be provided in series connection. According to an alternative, a further, more rigid membrane can be parallel to the first membrane be provided. In the latter case the characteristics of the membranes are chosen so that the first membrane is approximately in the cavity dos receiving gliodes has then fully nestled in when the second membrane begins to deform into a lilnfclimiegstellung.

The pressures damping with the pulse damper according to the invention can vary between oinicjen wenicjon and Li: j: -; u 34 473 7-5 N / m ² (approx. 5000 psi). The range of effective activity depends on the thickness and size as well as the tensile strength of the material of the membrane. As soon as a certain mem-

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bran is established, the pressure area is fixed. However, since conventional impulse dampers, as will be described, ^{function adequately at pressures above about 6,894,757 N / m 2} (1000 psi), the particular usefulness of the diaphragm damper of the invention is at pressures below this level.

In Figs. 2 and 3, a pulse damper 10 according to the invention is shown. It has a housing 19, which has a middle Area 13 "defines through which a fluid flows, ^ and in which Druckimpvilse are damped in the fluid. The fluid will introduced through an inlet port 14 and through an outlet port 15 discharged. In a preferred embodiment, contours 17 can be streamlined at the inlet and outlet be provided in order to keep turbulence to a minimum. Inside the housing 19 is. a rigid membrane 11 is arranged, which is held in place by a lip 16, for example. The membrane can be made from materials such as 17-4 PH steel, a high carbon steel, tungsten or titanium. The thickness can range from a few thousandths to a few hundredths of an inch. The membrane is attached so close to the inner wall of the housing 19 that it has a recess 18 isolated from the fluid in the central area 13. The recess 18 is usually evacuated or only contains a residual amount of gas. In operation, fluid flows through inlet port 14, fills central region 13, and flows through the outlet opening 15 out of the damper, and the flowing fluid comes into contact with a surface of the membrane 11. When the diaphragm pressures of a few tens exposed to a few hundred pounds per square inch, it gradually deforms outward. In the event of deviations from Average pressure, impulse energy becomes more elastic in the form of a long time Material stress saved as absolute or average Pressure does not exceed the limit at which the membrane 11 nestles completely in the recess 12 has, as already mentioned. At a certain maximum

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len pressure, be it from an impulse or from a sustained one

Average pressure, the membrane has completely applied to the contour 12. When the absolute pressure continues to rise or pulses of greater amplitude continue to occur, the membrane of the pulse damper 10 has no effect more cushioning more.

In Figs. 4a-4d the bending sequence is shown for a female member of particular shape. According to FIG. 4a, the stiff membrane 20 has not yet experienced sufficient pressure to deform at all. It is supported at its edges by a receiving member 21 and rests above a profiled or shaped recess 24. In FIG. In FIG. 4c, the center of the membrane 2Q has touched the recess 24 at a center point 23. To the extent that the average pressure increases or pressure pulses continue to occur, the membrane 20 is further deformed in the areas between the center 23 and the edges of the receiving member 21 until it has nestled completely in the recess 24. A further increase in pressure then no longer creates any further deformation. From this point on, the membrane damper no longer offers any additional damping. The resistance to deformation increases progressively after contact with the center 2 3. The gradual increase in the resistance to deformation with increasing pressure enables the membrane to continue to have a dampening effect at the highest and higher pressure ranges. The increase in resistance (or stiffness) of the diaphragm is caused by the shape of the recess, which is chosen to provide increasingly larger support as the pressure urges the diaphragm further into the recess. The area of the membrane that can still be bent is becoming increasingly smaller. In other exemplary embodiments, the shape, thickness and material for the membrane can be selected differently and the recess can have different contours.

give wonlnn to increasing the resistance of the membrane to Tailor-made print. In this way a wide range of resistance profiles can be achieved as a function of pressure. the The mechanical properties of the diaphragm generalized in this way are known, see e.g. the tables in Chapter by Roark and Young "Formulas for Stress and Strain" (1975),

As the membrane deforms, the volume increases and the capacity of the system increases so that the pressure decreases. That is reflected by the formula for everyone Pulse damper is applicable to that with liquid as an energy store work.

Compressible Fluid Damper: Io ^{= ex} P ⁽ ~ r £ ~ ^{} where c} = ^xv

Po = pressure at the top of a pulse P = pressure at the bottom of a pulse C = capacity of the damper

V = system volume + fluid volume in the impulse chamber R = hydraulic resistance, pressure / throughput t '= duration that the damper is fluid system pressure must deliver

X = I-'hedron constant. of the fluid
Membrane damper

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Capacity C =>. "

E = Young's module
t = membrane thickness
'C = the length of time the damper must deliver fluid system pressure

a = diaphragm diameter
R = column _{resistance EpQ}

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y - Poisson's number

P = pressure at the end of the pulse duration Po = pressure at the beginning of the pulse duration.

Another embodiment of the invention is shown in FIG shown, in which a membrane 36 with a formed in a receiving member 38, associated recess 37 with a with compressible liquid working damper 29 is combined. In the damper 29 is a flexible tube 30, for example from Kalrez (TM) wrapped around a mold 31, which is in one of a cap 39, a forehead insert 41, a cylinder 35 and a receiving member 38 formed housing is. The interior of the housing is kept fluid-tight by O-ring seals 40. Flowing liquid occurs during operation through an opening 32, flows through the helical, flexible tube 30, and is then discharged from an outlet opening 33 to become. When pressure pulses occur in the flowing fluid, the walls of the tube 30 expand and transmit the energy of the pulses to a compressible liquid. This liquid 42 is in contact with the membrane 36 and transmits the absolute pressure or pressure pulses from the fluid flowing in the tube 30 to the membrane 36. At low Continuous press or small

The membrane 36 gives in to impulses and stores energy. at sufficiently high continuous pressure

or pulses with a sufficiently high pressure, the membrane becomes 36 completely deformed into the recess 37. If the continuous pressure ■ increases or

Pulses begin to appear beyond the limit at which the membrane 36 is completely embedded in the recess 37 the liquid compression damper 29 is like a conventional pulse damper of the known one shown in Fig. Ib Way of acting. Before this limit is reached, the membrane 36 offers, as already mentioned, an increasing resistance against a growing increase in pressure due to the gradual shrinkage of the membrane 36 in

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the recess 37. The gradual nesting or nestling is facilitated, for example, by the fact that the receiving part 38 with the recess 37 has a flat bottom 43. Another exemplary embodiment of the invention is shown in FIG. 6, in which two membranes 4 5 and 4 6 are arranged separately in a housing 47. Fluid flows in through inlet port 50 and out through outlet port 51. Each of the diaphragms 45, 46 acting as a damper is fastened in its position opposite an associated recess 48, 49. Each damper acts as an individual unit as described above. However, the size and shape of each damper is chosen so that its Betriebsverhai th is optimal in a certain pressure range. It is typical that the regions are chosen to be complementary to one another. For example, if the diaphragms 45, 46 are of the same shape and are made of the same material, the thinner diaphragm 45 will operate in a lower pressure range, for example from nearly zero to about 4 826 329.9 N / m ² (about 700 psi) and the thicker membrane operates in a higher pressure range, for example from about 3,447,378.5 to about 8,273,708.4 N / m ² (about 500-1200 psi).

The ll ^ bridge designs according to FIGS. 5 and 6 make it possible to use the pulse damper in a large pressure range. This is particularly advantageous because conventional pulse dampers only work effectively at pushers above about 6,894,757 N / m ² (1000 psi), while the diaphragm works well at lower pressures. As can be seen from curve b in FIG. 7, the diaphragm damper can be constructed so that it ^{operates effectively at pressures well below 5 515 805.6 N / m 2} (800 psi). In this way, pulsations in the pressure can be kept very low at low pressures. Conventional dampers, on the other hand, as shown by curve a, work most effectively at higher pressures, up to a few thousand pounds per square inch.

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Claims (9)

Palo Alto, California, V.St.A. Vl P600 D Hydraulic impulse damper Claims / 1.) Hydraulic impulse damper, - identified by - A fluid-tight housing with an inlet opening for insertion. ren a fluid into the housing and an outlet port for discharging the fluid from the housing; and a rigid membrane arranged within the housing in the vicinity of a recess formed in a receiving member is, the area between the membrane and the recess is sealed against the fluid, so that the membrane is increasingly in a nestled position in the recess bends when the pressure in the fluid increases, which is transferred from the fluid to the membrane, thereby creating the hydraulic pulse energy elastic in the fluid as stress and energy qc is stored in the membrane. 2. Hydraulic pulse damper according to claim 1, characterized in that da.s receiving member cli eino: there is an inner wall of the housing. 3. Hydraulic pulse damper according to claim 2, characterized in that the membrane begins to nestle ^{against the recess in the pressure range of approximately 689 475.7 to 4826 329.9 N / m 2} (100 to 700 psi). ^{EP0 COPY} 4. Hydraulic pulse damper according to claim 2, characterized in that the recess has a flat area in its central part. 5. Hydraulic pulse damper according to claim 2, characterized in that the membrane is within of the housing is arranged so that it is in direct physical contact with the fluid, whereby the hydraulic pulse energy can be transmitted directly to the membrane. 6. Hydraulic pulse damper according to claim 2,. ye Ic e η η-scichnct through combination with an IM: U eic ilexiblon Kohrs, which within dos GcihäuL ·. «;;:.; connected to the Ki.η Lass- and Aiiü-lassöffnuncj Ir. t, whereby the L ^c 'luiil within the cl; ·' pipe through the Gohäuno ye. le It et will, "MrvJ '.kt: <: l. fine Kinrich— • tunci sum transferring the Ivylraulischon impulse energy from the Tube to the membrane. 7. Hydraulic pulse damper according to claim 6, characterized in that the means for transmitting the hydraulic pulse energy is a compressible Has liquid .. 8. Hydraulic pulse damper according to claim 7, characterized in that the compressible liquid fills the space in the housing around the tube. 9. Hydraulic impulse damper according to claim 2, characterized in that in combination an additional membrane within the housing and a second associated receiving member is provided, which in the Inner wall of the housing is designed that the area between facing the second diaphragm and the second receiving member the fluid is sealed, and that the second membrane has properties that increase pressure in a different pressure range A as the stiff membrane dampen. BAD ORiGiNAL E ^ O GOPy