DE2338128A1 - Water hammer prevention device - pipe sections shaped to modify water pressure - Google Patents

Abstract

The bypass valve and the sections of the flow channel in frontof and behind the valve are geometrically formed and the surfaces of these sections are finished in such a way that when the valve is opened the alteration produced in the static pressure of the fluid on the closing element almost compensates for the alteration in the dynamic force exerted on this element. This prevents the closing element from oscillating noisily.

Description

Junkers 685 PI-I 1-Gü / Str July 24, 1973

JUNKERS & CO. GMBH, in Wernau / ITeckar

Flow channel for a fluid with a pressure relief valve through which it flows

The invention relates to a flow channel for a Fluid, with a pressure relief valve limiting the pressure of the fluid, in particular a bypass valve through which the fluid flows, whose closing member can be lifted from its valve seat against a closing force by the pressure of the fluid.

In the known devices of this type, the closing member of the pressure relief valve is caused by occurring in the flow Pressure fluctuations made to vibrate. If the closing element is caused by a disturbance variable from that defined by the inlet pressure Is brought to the operating position, the flow rate changes and thus also that exerted by the flow on the closing element resulting force, which depends on the flow rate. The subsequent return movement of the closing link,

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for example, by the action of a closing spring, changed the flow rate in the opposite direction. The repetitive change in force caused by this interaction is a periodic vibration exciter for the closing element, which together with the closing spring a Vibration system forms. These vibrations, which affect neighboring parts, e.g. the gas valve of a gas-heated one Propagating water heaters make noises that can be significantly annoying.

The invention is based on the object of a radiation channel of the type mentioned, whose valve closing member does not tend to oscillate, or in which the oscillations are so attenuated that they are no longer disturbing.

The solution to this problem is based initially on the knowledge that the closing link will swing open Interfering influences can at least largely be avoided if the force exerted on the closing member by the flowing fluid is independent is made of the fluid flowing through the valve. This force consists of a static and a dynamic force component together. The static force component comes from the difference in the static pressures of the fluid and after the closing link. The dynamic force component results from the entry and exit impulses that the exerts flowing fluid at the valve opening in the opening direction on the closing member.

In evaluating these findings, it is proposed according to the invention that that the pressure relief valve and the sections of the flow channel located upstream and downstream of the valve are geometrical designed in such a way and the surfaces of these parts in contact with the fluid are designed so that when the valve is open the at a change in the amount flowing through the change in the static compressive force acting on the closing element

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of the fluid, at least the change that also occurs in the dynamic force acting on the closing member approximately compensated.

It is thereby achieved that a closing element which is brought out of the operating position by a disturbance variable is caused by the Changes in the flow rate does not tend to oscillate, and the associated annoying noises largely be prevented.

The two forces acting on the valve closing member flowing fluids can be determined by calculation. The calculation leads to useful solutions if, according to claim 2, the pressure relief valve is designed in such a way that the exit pulse of the valve flowing out of the valve opening acting on the closing element fluids is negligibly small.

The force exerted by the flowing fluid on the closing element of the pressure relief valve can thereby be kept constant in a simple manner be held that upstream of the closing member, a throttle stud is arranged, the effective cross-section of which is approximately half is as large as the area of the closing member acted upon by the static pressure of the fluid in the closed position. to This result can be obtained by considering the following:

The force K exerted on the closing element is composed of a dynamic and a static force. The. static force is calculated from the product of the static pressure difference ρ before and after the closing element and that of this pressure difference acted upon surface F of the closing member. The dynamic force can be negligibly small, taking into account what is proposed according to claim 2 Exit impulses easily through the entry impulse as products of the mass flowing through per unit of time and the Calculate the inlet speed ν.

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In the case of an upstream throttle, the mass m in With reference to the effective throttle cross-section f and the flow velocity ν can be calculated. The speed ν results from the reduction that the static pressure experiences along the flow channel. After these considerations express the force K as follows:

K = ρ P + 2 f (p ₀ - p)

in which ρ is the static pressure difference at the beginning and end of the entire flow channel.

If you insert vert F for 2f according to the invention, then lift after multiplying the brackets, the summands pf and 2fp arise. In this case, the one exerted on the closing link Force K actually no longer depends on the flow rate, but only on the size of the static pressure difference ρ of the entire diffusion channel depends.

The force exerted on the closing element can also be kept largely constant in that, according to the invention the flow channel is designed in such a way that the friction pressure loss in the section before or after the closing element etv / a corresponds to the dynamic pressure on the closing element, or if a throttle point is arranged behind the closing element, its more effective Cross-section is approximately as large as the surface of the closing element acted upon by the inlet pressure in the closed position.

A size can also be set for every possible combination of throttles and resistors in front of and behind the closing element calculate for these links at which the force on the valve disc remains constant in the working area of the valve and the Conditions of claim 1 met.

A space-saving and cost-saving arrangement results when the throttle point is arranged directly in front of the valve seat

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is and widens into a flat valve seat surface perpendicular to the flow.

A negligibly small exit pulse can be achieved by using the closing element as a valve disk flat seat and the opposing seat is designed as a narrow annular surface.

Furthermore, the measure characterized in claim 10 achieved that by limiting the stroke to a value that corresponds approximately to the effective throttle cross-section, certain possible unstable states when the control range is exceeded can be avoided.

In FIGS. 1 to 4 of the drawing there are 4 exemplary embodiments of the invention shown schematically.

In the flow channel 10 according to FIG. 1, between an inlet and an outlet 13 is a provided with a closing member 14 · Relief valve arranged. The closing element 14 designed as a valve disk is counteracted by the action of a spring 16 pressed against an annular valve seat 17 by the flow. An adjustable stop 18 limits the stroke of the actuator 14-.

The surface 19 of the valve disk facing the inlet 12 is subjected to a static pressure ρ cies when the valve is closed Medium acted upon. The valve opens when the inlet pressure The force exerted on the closing element 14 overcomes the spring force. The medium flows radially through the annular gap between the valve seats 17 and 19 into the outlet 13 The total exit pulse is negligibly small. Only the static and dynamic ones caused by the inflow are effective Forces on the closing member 14- a. The resultant of these forces, which are normally caused by the crowd flowing through is dependent, depends in the embodiment of FIG. 1 only from the inlet pressure ρ, because the inlet 12 or the outlet

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are geometrically designed so that the drag coefficient of the flow resistance measured at the pressure relief valve is approximately is equal to one, i.e. the frictional pressure loss is equal to that Back pressure at the valve.

In the flow channel according to FIG. 2, there is a throttle point in the inlet 12 21 arranged. This can be in the flow path; of the inlet or immediately in front of the valve seat, as shown in the drawing is to be arranged. The throttle point 21, which widens in the direction of flow, turns into an annular, approximately sharp-edged valve seat 20 over. The flat surface of the valve disk 14 is designed as a counter seat 19.

In the third exemplary embodiment (FIG. 3), the throttle point 21, which is also arranged directly in front of the valve seat, goes expanding in an arc shape into a flat valve seat 22, which with an annular opposing seat 23 of a cup-shaped Closing member 14 'cooperates.

In the exemplary embodiments according to FIGS. 2 and 3, the cross section is A of the throttle point is half as large as the area B of the closing element acted upon by the inlet pressure in the closed position of the valve. With this dimensioning, the static and dynamic changes in force are the same when there is a change the flow rate largely so that the closing element in the event of a change in quantity or also in the event of a change in the inlet pressure ρ is practically not excited to vibrate.

According to the fourth exemplary embodiment (FIG. 4) Et a throttle point 25 is arranged in the outlet 13. In this case, the goal set is achieved when the effective throttle cross-section Λ ^{1 is} approximately as large as the cross-section B of the closing element

In addition to the insensitivity to vibrations achieved with these measures of the valve results from precise coordination

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of valve seat flaclie and throttling that the pressure gradient at any amount of water within the work area remains practically constant. When the closing link is through the stop When the limited maximum stroke is reached, the pressure-volume characteristic increases of the valve, which is a constant in the control range, suddenly opens. This kink in the curve on The end of the control range can be desirable in some cases, namely to trigger any switching processes.

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Claims (10)

Junkers 685 6 - Protection claims: M .J flow channel for a fluid, with an overpressure valve limiting the pressure of the fluid, in particular a bypass valve through which the fluid flows, the closing member of which can be lifted from its valve seat against a closing force by the pressure of the fluid, characterized in that the overpressure valve and the upstream and downstream Sections (12 and 13) of the flow channel (10) located behind the valve are geometrically designed and the surfaces of these parts in contact with the fluid are designed so that when the valve is open, the change in the amount acting on the closing element when the flow rate changes static compressive force of the fluid at least approximately compensates for the also occurring change in the dynamic force acting on the closing member. 2. flow channel according to claim 1, characterized in that that the pressure relief valve is designed in such a way that the one acting on the closing member (14, 14 ') The exit pulse of the fluid flowing out of the valve opening is negligibly small. 3. flow channel according to claim 2, characterized in that that upstream of the closing member (14, 14 ') a throttle point (21) is arranged, which is more effective Cross-section (A) is about half the size of the one in the closed position area acted upon by the static pressure of the fluid (B) of the closing link (14, 14 '). - 9 -409886/0292 Junkers 685 _ 9 _ 4. flow channel according to claim 2, characterized in that that the frictional pressure loss in the section in front of the closing member (14,14 ') is about the dynamic pressure before Closing member corresponds. 5. flow channel according to claim 2, characterized in that that the friction pressure loss in the section after the closing member (14,14 ') is about the dynamic pressure before Closing member corresponds. 6. Flow channel according to claim 2, characterized in that a throttle point (25) is arranged downstream of the closing member (14, Figure ⁴ ), the effective cross section (A 1) of which is approximately as large as that of the static pressure of the fluid in the closed position acted upon surface (B) of the closing link (14) .. 7. flow channel according to claim 3 »characterized in that that the throttle point (21) is arranged directly in front of the valve seat (22) and widens into a flat valve seat surface (22) perpendicular to the flow transforms. 8. Flow channel according to one of the preceding claims, characterized in that the closing member (14 ¹ ) is cap-shaped with a wall thickness decreasing towards the edge, and that the edge (23) of the cap-shaped closing member (14 *) with the valve seat (22) cooperates. 9. Flow channel according to one of the preceding claims, characterized in that the closing member is designed as a valve disk (14) with a flat seat surface and the opposing seat (17, 20) is designed as a narrow ring surface. - 10 - 409886/0292 Junkers - 10 - 10. Flow channel according to one of the preceding claims, characterized in that the closing member a stop (18) is assigned to the outlet cross section limited at the valve seat to a value which is approximately as large as the effective throttle cross-section. 409886/0292