GB2203820A

GB2203820A - Water pressure safety valve and knocking damper

Info

Publication number: GB2203820A
Application number: GB08808088A
Authority: GB
Inventors: Thor Frolich Braathen
Original assignee: Individual
Current assignee: Individual
Priority date: 1987-04-23
Filing date: 1988-04-07
Publication date: 1988-10-26
Also published as: GB8808088D0; NO871689D0; SE467016B; SE8801469D0; FI881766A0; NO161281C; DK216588A; NO161281B; DE3809465A1; FI881766A; FI86467B; NO871689L; DK163374B; SE8801469L; DK216588D0; DK163374C; FI86467C

Description

WATER PRESSURE SAFETY VALVE AND KNOCKING DAMPER The present invention

relates to a safety valve, e.g. for a hot water heater with a pressure tank, intended for opening when an excess pressure starts building up in the pressure tank, and-of the kind as stated in the preamble of the following independent claim 1. Furthermore, the invention relates to a knocking damper means for mounting between the overflow hose/ pipe and the outlet in a safety valve.

The above mentioned safety valve should open for excessive pressure on a water heater, etc. when the incoming water pressure to the pressure tank increases of the pressure in the pressure tank encreases due to expansion of water when water is heated from a low to a high temperature.

Various requirements are made on safety valves, varying from one country to another, e.g.:

- 20 1. opening pressure 9 ato.

2. Closing pressure - 10% lower than opening pressure 8.1 ato.

3. Volume of water flowing out at a pressure 10% higher than the opening pressure, i.e. 9.9 ato, should be 6.5 1/min.

per Kw max. effect for heating the heater. At 3 Kw max.

effect the safety valve must, thus, permit a discharge of 19.5 1 water/min. at 9.9 ato incoming pressure on the safety valve.

4. Maximum pressure on incoming cold water pipe to safety valve 6 ato. At a higher pressure a reduction valve should be mounted.

5. It should be possible to mount an overflow hose to the outlet of the safety valve to conduct water to outlet, and with a minimum inner diameter of 12.5 mm in pipe or hose.

The safety valves presently used open at 9 ato and close at 10% reduction of said pressure. It is very difficult to 2 achieve a volume of water flowing out of 19.5 1/min. at 9.9 ato and, at the same time, make the safety valve close at a closing pressure of 8.1 ato.

In many waterworks it is difficult to maintain a normal water pressure as low as 6 ato in periods of low water consumption.

The water pressure may, for instance, increase by 50% at night.

When the outlet of a safety valve is connected to an overflow hose extending to an outlet this may cause completely changed characteristics of the safety valve, resulting in the following:

When incoming water pressure in the valve casing exceeds 9 ato the valve opens and fills -the overflow hose with water.

The outlet side/overflow side commonly free of pressure now receives a pressure substantially like the incoming pressurel the valve closes, but quickly opens again since the incoming pressure rises again. The valve opens and closes at rates of 50-150 strokes/min. These pressure impacts are so hard that safety valve, welds in the water tank, and pipes could be impaired. Embodiments of the present invention may provide a safety valve which complies with the above mention ed requirements and, consequently, eliminates the above mentioned difficulties or ameliorates them.

According to the invention a safety valve has the features appearing from the characterizing part of the following independent claim 1, and preferably those of the following dependent claims.

The invention is disclosed in more detail below in a descript ion of an embodiment shown in the drawings of the safety valve as well as a knocking damper means connected with said safety valve.

In the drawing Figure 1 shows the safety valve in a cross sectional view, 3 Figure 2 shows the safety valve with a connected overflow hose and an intermediate knocking damper means, and Figure 3 shows the same as Figure 2 at a larger scale and with the damper means shown in a sectional view.

Safety valve A comprises a valve casing 1 with an inlet 2 for pressure water, and an outlet 7 for any overflowing water, as well as a diaphragm valve provided between the latter. The diaphragm valve comprises an annular seat 4 in a passage 21 connecting inlet 2 with outlet 7, a diaphragm 5 made of rubber or the like, which has its circumferencial portion clamped between an annular shoulder of a valve inlet 22 in valve casing 1 and an end disk 6a of a spring casing 6 which can be screwed into valve inlet 22. In spring casing 6 there is a spring biased spindle 8 with a spindle head Ba in resilient contact with the top face of the central portion 5a of diaphragm 5 which is, thus, with its lower face urged into resilient contact with seat 4. An annular chamber 20 extends around seat 4 and is also limited by casing 1 and the lower face of diaphragm 5, and is provided with a port 20a towards outlet 7 for discharge of overflow water 3a with diaphragm 5 being lifted from seat 4 by excessive pressure in the pressure tank and, thus, in inlet 2, and passage 21. At the same time water pressure will build up in annular chamber 20 which will act on the lower face of diaphragm 5 outside seat 4, resulting in further lifting of diaphragm 5 from seat 4 and, thus, increase of the annular valve slot of the valve permitting increased discharge of overflow watter 3a. The spring biased spindle 8 extending through a guide opening 10a in bottom 10 of spring casing 6 is surrounded by a compression spring 9 which is clamped between bottom 10 and spindle head 8a extending radially beyond seat 4. Head 8a of spindle 8 and the central portion 5a of diaphragm 5 are provided with co operating fastening means in the form of a preferably thread ed central bore 8b in the head 8a of spindle 8, and a central knob 5b on the top face of diaphragm 5, said knob 5b being intended for being screwed into bore 8b. A resilient compress ible buffer means 16, e.g. an annular rubber buffer, having 4 greater spring force than compression spring 9, is provided between a stop 17 in spring casing 6 and spindle head Ba with a desired axial clearance 19 between buffer means 16 and spindle head 8a, or stop 17, resp. corresponding to the maximum pressure lift of diaphragm 5. outer wall and one end of buffer means 16 is in contact with inner wall or stop 17, resp. of spring casing. Between the other end of buffer means 16 and diaphragm 5 there is a clearance 18 approximately equal to clearance 19 between buffer means 16 and spindle head 8a. Central bore 16a of buffer means 16 converges towards spindle head 8a and its narrow portion is in centered contact with the lower end of compression spring 9 which is, in turn, in centered contact with spindle 8. Upper end of spindle 8 extends freely through an opening 14a in a wheel 14 which is rotatable in contact with spring casing 6 by the aid of a circular stop 12 cooperating with a stop 6c on spring casing 6. Stops 12 and 6c comprise cooperating slant planes, if desired, slant planes and bosses. Consequently, when wheel 14 is turned spindle 8 is lifted via a stop disk 15 at spindle end 18c, and diaphragm 5 is, thus, raised from seat 4 for control of through flow of water and, if desired, for emptying the pressure tank. I It will appear from the disclosure above that spindle 8 is provided for further axial movement by the aid of said means 12, 14 provided outside spring casing 6 and against the resistance from buffer means 16, when the pressure tank is to be emptied.

Compression spring 9 on sprindle 8 has a predetermined length and a spring pressure showing as flat a spring characteristic as possible. It is clamped with a predetermined distance between bottom 10 of spring casing 6 and spindle head 8a.

The extent to which spring casing 6 may be threaded into valve inlet 22 is limited by cooperating stops 6b, 11 on spring casing 6 and the outer end 11 of valve inlet 22, resp.

to provide for the desired clamping force for the peripheral portion of diaphragm 5 and desired force of contact between the lower side of diaphragm 5 and seat 4.

When the safety valve is mounted on a pressure tank and is used, pressure water 3 in inlet 2 and passage 21 will act on central portion 5a of diaphragm 5 within the seat 4. When the water pressure increased for any reason to the above mention ed opening pressure of 9 ato diaphragm 5 is raised from seat 4 against the spring pressure of compression spring 9 which has a spring pressure adapted to said opening pressure for water. Water will flow on into annular chamber 20, and through outlet 20a of said annular chamber towards outlet 7 of the safety valve and, at the same time, pressure is built up in annular chamber 20 to act om the portion of the underside of diaphragm 5 which is outside seat 4. Consequently, diaphragm 5 is lifted further to let a larger volume of water pass if water pressure exceeds the opening pressure of 9 ato and reaches 10% overpressure, i.e. 9.9 ato. In the course of such compression of compression spring 9 this spring will yield or collapse. In order to prevent diaphragm 5 from being lifted too much, permitting an uncontrolled volume of water to pass through outlet 7, rubber buffer 16 is provided at a suitable distance 19 above spindle head 8a. Due to the fact tha buffer 16 has greater spring force than compression spring 9 it will prevent diaphragm 5 from being urged further upwards.

When water pressure decreases compression spring 9 will te nd via spindle head 8a, to urge diaphragm 5 into contact with seat 4. Eventually, such contact is achieved at said closing pressure of 8.1 ato.

Spring casing 6 has a constant distance from bottom 10 to seat 4 when the spring casing is threaded into valve inlet 22 with its stop 6b in contact with outer end 11 of valve inlet 22. Due to the fact that compression spring 9 is manufactured with the desired spring pressure and that there are small tolerances of the remaining components, the desired contact pressure of diaphragm 5 on seat 4 is achieved when the components are moutned. A set screw is, thus, not required to 6 achieve correct spring pressure.

Annular chamber 20, which may also be denominated overflow chamber, may be varied as regards volume by receiving an in creased depth in manufacture, possibly also with modificat ion of outlet 20a.

By the aid of the above mentioned components of safety valve A and their performance the following is achieved:

Diaphragm 5 will tighten both the pressure side and the over flow side. Diaphragm 5 will always open when pressure in creases even if there is pollution and calcareous deposits because it does not comprise any skirt or metal in contact with the metal seat between which parts a calcareous deposit might settle.

Compression spring 9 is designed for a determined spring pressure and minimal increase of said spring pressure in case of additional compression, i.e. as flat a spring characteristic as possible.

Spring pressure is adapted for sealing the safety valve up to e.g. 9 ato with a determined diameter of passage 21 with seat 4. When the inner diameter of seat 4 is, e.g. 10 mm.

the resulting pressure surface on central portion 5a of diaphragm 5 will equal 2,ijr2 is 5 x 5 x 3,14 = 78,5 mm. 2.

The spring force is calculated on the basis of this area and a water pressure of 9 ato which is the opening pressure.

When the water pressure increased above the opening pressure of 9 ato, e.g. to 9.8 ato, i.e. an overpressure of 10%, diaphragm 5 will, as mentioned, be lifted more from seat 4 because of the build-up of pressure in annular chamber 20.

The annular valve slot of the valve will, thus, increase for increased discharge of overflow water 3a. This pressure in annular chamber 20 acts on the portion of the central portion 5a of diaphragm 5 which is supported by head 8a of spindle 8 7 which has so large a diameter that it extends radially outside seat 4. This means, in short, that the incoming water pressure receives a larger "plunger" to lift with and, thus, overcomes the opposed spring pressure of compression spring 9. In this manner the desired space between seat 4 and diaphragm 5 and, thus, sufficient discharge of water is achieved at an over pressure of 10%. The performance of the safety valve is based on the fact that compression spring 9 will collapse at increas ing water pressure in excess of 9 ato and that an uncontrolled 1() volume of water inters the overflow or outlet 7 via annular chamber 20 and its outlet 20a. In order to prevent this the movement of spindle 8 may be limited to a maximum lift of, e.

g. 0.5 mm by the aid of a mechanical stop. This will permit sufficient discharge of water at a permissible overpressure up to, e.g. 9.8 ato. For emptying the pressure tank of the hot water heater a larger clearance between diaphragm 5 and seat 4 is desired, e.g. 1.5 mm. For this reason the mechanical stop is, thus, made resilient with a greater spring pressure than pressure spring 9, which is achieved by the aid of rubber buffer 16.

Rubber buffer 16, thus, has the following functions:

1. It supports diaphragm 5 in the area between spring casing 6 and spindle head 8a preventing the diaphragm from cracking irrespective of pressure. Rubber buffer 16 may, e.g. have a clearance 18 of 0.5 mm to the outer portion of diaphragm 5, and a corresponding clearance 19 between the lower end of rubber buffer 16 and spindle head 8a. Consequently, buffer means 16 permits the diaphragm and spindle head 8a to be lift ed 0.5 mm by the overpressure, but it prevents compression spring 9 from collapsing by supporting diaphragm 5. However, spindle 8 and, thus, diaphragm 5 may be lifted totally 1.5 mm from seat 4 when a heater is to be emptied by the aid of above mentioned wheel 14 and compression of rubber buffer 16.

Rubber buffer 16 provides for accurate control of spindle 8 and, thus, diaphragm 5 for correct opening and closing of the safety valve.

8 In stead of a rubber buffer, obviously, a compression spring may be used although such a spring will not have the same advantageous functions as rubber buffer 16 as regards centering compression spring 9, and supporting the top face of diaphragm 5 during pressure increase and possibly knocking.

Components 8a, 19, 20, and -21 cooperate and may be mutually varied, resulting in the following:

The diameter of spindle head 8a. may, e.g. be enlarged to provide a larger lift and, thus, increased passage of water, or vice versa. Together with rubber buffer 16 spindle head 8a provides total support for diaphragm 5.

By varying the clearage 19 between rubber buffer 16 and spindle head Sa a desired discharge of water at maximum over pressure may be determined. Due to the fact that rubber buffer 16 can be compressed aditionally by the aid of said wheel 14 a sufficient lift of diaphragm 5 may be achieved for emptying the tank of the hot water heater. A controlled two step spring pressure is, thus, available.

Annular chamber 20 between the lower face of diaphragm 5 and valve casing 1 with outlet 20a of said chamber will determine the desired differential pressure on the pressure side and outlet side and, thus, the build-up of pressure in annular chamber 20 which is necessary for maximum lift of diaphragm from seat 4.

An increase of the diameter of passage 21 will result in in creased total volume of through flow, but in that case the spring pressure of compression spring 9 must be increased as well because of the resulting larger central pressure area on the diaphragm.

By correct variations of said components the requirements valid in different countries as regards the function of the safety valve may be satisfied.

9 The structure and function of the safety valve was disclosed above in case the overflow or outlet 7 is not connected with a hose or pipe to an outlet or tank. When such a hose or pipe 33 is directly connected with outlet 7 of safety valve A problems with knocking will arise because of build-up of pressure in outlet 7 and hose 33 causing the diaphragm 5 to be lifted higher up from seat 4. Sufficient volumes of water will flow through the safety valve, and the pressure of incoming water 3 will sink below the opening pressure to close the safety valve. Then pressure increases again above opening pressure, the valve opens, and there is knocking.

This happens in all kinds of valves. In order to remedy this disadvantage a knocking damper means B is provided, as shown in Figures 2 and 3, between overflow hose/pipe 33 and outlet 7 of safety valve A. Knocking damper means B comprises a chamber 32 for water and air with an inlet 32a to be connect ed with outlet 7 of safety valve A, and an outlet 32b to be conencted with overflow hose/pipe 33. Chamber 32 comprises an upper chamber portion L for air at a higher level than inlet and outlet 32a,32b, and a lower chamber portion V for water. As shown in the drawing, chamber 32 is preferably spherical with radially opposed inlet 32a and outlet 32b.

Outlet 32b is preferably smaller than inlet 32a, and said openings are horizontally aligned in a mounted state of knocking damper means 5.

Chamber 32 has a volume that is large enough to accommodate the pulsating volume of water flowing out of safety valve A when knocking occurs. Said pulsation and knocking is suppressed by the aid of the volume of air caught in upper chamber portion L. This means that the knocking damper means acts according to the "blast -box" principle.

Claims

CLAIMS:

1. A safety valve for a hot water heater with a pressure tank, designed to open when overpressure occurs in the a pressure tank, and comprising a valve casing (1) with an inlet (2) for pressure water, and an outlet (7) for any overflow water, as well as a valve (4,5,8,9) provided between the latter and comprising an annular seat (4) in a passage (21) connecting inlet (2) with outlet (7), a diaphragm (5) clamped with its peripheral portion between an annular shoulder in a valve inlet (22) in valve casing (1), and an end surface (a) of a spring casing (6) which can be screwed into valve inlet (22), and with a spring biased spindle (8) with spindle head (8a) in resilient contact with the top face of-a central portion (5a) of diaphragm (5), which is, thus, with its lower face urged into resilient contact with seat (4), an annular chamber (20) around seat (4), said chamber being limited by casing (1) and the lower face of diaphragm (5) and provided with an outlet (20a) towards outlet (7) for discharge of overflow water (3a) when diaphragm (5) is lifted off seat (4) in case of an overpressure in the pressure tank and, thus, in inlet (2) and passage (21) with a simultaneous build-uj of pressure in annular chamber (20) to act on the lower face of diaphragm (5) outside seat (4) to lift diaphragm (5) still more above seat(4) and to increase the-annular valve slot permitting increased discharge of overflow water (3a), and where spindle (8) extending through a guide opening (10a) in bottom (10) of spring casing (6) is surrounded by a compress ion spring (9) clamped between bottom (10) and spindle head (8a) extending radially past seat (4), c h a r a c t e r i z e d i n that head (8a) of spindle (8) and the central portion (5a) of diaphragm (5) are provided with cooperating fastening means (8b,5b), and that a compressible buffer means (16) having greater spring force z than compression spring (9) is provided between a stop (17) in spring casing (6) and spindle head (8a) with a desired clearance (19) between buffer means (16) and spindle head (8a), 4t or stop (17), respectively, corresponding to maximum pressure lift of diaphragm (5), and that spindle (8) is provided to be additionally moved in an axial direction against the spring force of buffer means (16) by the aid of means (12,14) provided outside spring casing (6) in order to empty the pressure tank.

2. A safety valve as defined in claim 1, c h a r a c t e r i z e d i n that pressure spring (9) has a predetermined length and a spring pressure showing a substantially flat spring characteristic and is clamped with a predetermined distance between bottom (10) of spring casing (6) and spindle head (8a), and that the extent to which spring casing (6) may be threaded into valve inlet (22) is limited by cooperating stops (6b, 11) on spring casing (6), and the outside end (11) of valve inlet (22), respectively, to provide a desired clamping force of the peripheral portion of diaphragm (5) as well as desired force of contact between the underside of diaphragm (5) and seat (4).

3. A safety valve as defined in claim 1 or 2, c h a r a c t e r i z e d i n that buffer means (16) is an annular rubber buffer which is in contact with the inner wall and stop (17) of spring casing (6) with its outer wall and one end, and the other end of which has a clearance (18) to diaphragm (5) approximately equal to clearance (19) between buffer means (16) and spindle head (8a).

4. A safety valve as defined in claim 3, c h a r a c t e r i z e d i n that central opening (16a) of buffer means (16) converges towards spindle head (8a) and that its most narrow portion is in centered contact with the lower end of compression spring (9) which end is, in turn, in centered contact with spindle (8).

12 5. A safety valve as defined in any preceding claim, c h a r a c t e r i z e d i n that upper end (8c) of spindle (8) passes freely through an opening (14a) in a wheel (14) which is rotatably in contact with spring casing (6) with a circular stop (12) cooperating with a stop (6c) on spring casing (6), which stops (12 and 6c) comprise co operating slant planes, if desired, slant planes and bosses, so that turning and, thus, axial movement of wheel (14) will cause spindle (8) to be lifted via a stop disk (15) at spindle end (18c) and, thus, diaphragm (5) from seat (4) for control of through flow and, if desired, to empty the pressure tank.

6. A safety valve as defined in any preceding claim, c h a r a c t e r i z e d i n that the cooperating fastening means (8b,5b) consist of a preferably threaded central bore (8b) in head (8a) of spindle (8), and a central pin (5b) on the top face of diaphragm (5) to be threaded into bore (8b).

7. A knocking damper means to be mounted between an overflow hose/pipe and an outlet ina safety valve (A), especially a safety valve as defined in any of the preceding claims 1-6, c h a r a c t e r i z e d i n a chamber (32) for air and water, comprising an inlet (32a) for connection with outlet (7) of safety valve (A), and an outlet (32b) for connection with an overflow hose/pipe (33), said chamber (32) comprising an upper chamber portion (L) for air at a higher level than inlet and outlet (32a,32b), and a lower chamber portion (V) f or water.

8. A knocking damper means as defined in claim 7, c h a r a c t e r i z e d i n that chamber (32) is spherical with radially opposed inlet and outlet (32a,32b).

9. A knocking damper means as defined in claim 7 or 8, c h a r a c t e r i z e d i n that outlet (32b) is smaller than inlet (32a).

13 10. A knocking damper means as defined in claim 8 or 9, c h a r a c t e r i z e d i n that inlet and outlet (32a, 32b) are horizontally aligned in a mounted state of said knocking damper means (B).

11. A knocking damper means substantially as herein described with reference to and as illustrated in the accompanying drawings.

12. A safety valve substantially as herein described with reference to and as illustrated in the accompanying drawings.

13. A safety valve assembly comprising a safety valve according to any of claims 1 to 6 or 12 coupled to a knocking damper means according to any of claims 7 to 11.

Publiblied. 1988 at The Patent Office, State House, 66/71 High Holborn, London WC1R 4TP. Further copies may be obtained from The Patent Office, Wes Branch, St Mary Cray, orpington, Kent BR5 3RD. Printed by Multiplex teOhniQues ltd, St Mary Cray, Kent. Cori- 1/87.