WO2002050458A1

WO2002050458A1 - Leak-proof valve with self-controlling shutting force

Info

Publication number: WO2002050458A1
Application number: PCT/RO2001/000003
Authority: WO
Inventors: Matei Cojocaru
Original assignee: Matei Cojocaru
Priority date: 2000-12-21
Filing date: 2001-02-14
Publication date: 2002-06-27
Also published as: RO119480B1; AU2001241303A1

Abstract

The present invention is about a leak-proof valve with self-controlling shutting force, designed for use in installations for fluid transport and distribution. The valve consists of a cylindrical valve body (1) fitted a shutter wall (a), communication passages (b) and a stopcock seat (c) driven by a shutting force control mechanism (B) that is handled by a driving mechanism (C). The shutting force control mechanism is fitted with a stopcock disk (d) and two systems that take over and distribute the axial forces exerted by the pressure of the fluid and it acts continuously upon the shutting force of the stopcock, maintaining it to a value established by design. This feature allows the embodiment of a valve whose sealing force may have a constant value, may be self-regulating or may determine the valve to work as a safety valve when the pressure surpasses the critical value.

Description

Leak-proof Valve with Self-controlling Shutting! Force

The present invention is about aleak-proof valve with self-controlling shutting force, designed for use in installations for fluid transport and distribution- It is known a valve whose shutting element is a metallic membrane (patent France - no. 2677424). A piston acts on the surface of the metallic membrane, displacing it towards the seat of the inlet pipe duct and accomplishing the closing.

The valve is highly leak-proof with respect both to environment and to the driving mechanism, and it is used especially in installations for highly pure and very noxious fluids. It presents die following drawbacks: — the membrane is subjected to high elastic deformation, by means of both the piston action and the pressure of the fluid; — for large cross-sections of the valve and high pressures of the fluid, the force acting on the membrane is very high; — the limited possibilities of membrane elastic deformation cause the increasing of the valve overall dimensions; — file shutting force bringing the membrane into contact with the seat isn't controlled, therefore the possible overloads and its deformation on the sealing surface may cause its exfoliation. The technical problem solved by the present invention is the construction of a highly reliable, easy to handle leak-proof valve having a large field of application in installations for fluid transport and distribution.

According to this invention, the valve comprises a valve casing with a shutting force control mechanism acting on it. This mechanism is handled by a driving mechanism and wrapped in a protective casing.

The invention presents the following advantages:

— he valve is highly leak-proof with respect both to its component mechanisms and to environment; — file shutting force is self-controlling and is maintained to a value established by design; — it reduces the force necessaiy to drive the valve to a value close to the one of the force that seals the shutting element; — quick and convenient handling;

— considerably simplified anticorrosive plating procedures; — the possibility to apply the self-acting handling , with nr.-ni-mμιι expenses; — the possibility to function as a high precision safety valve also; — high operational reliability.

An embodiment of the present invention is shown below, in relation to file drawings 1...9, which represent:

— fig. 1 — longitudinal section of the valve;

— fig. 2 — tructural scheme of the shutting force control mechanism shown with the stopcock in its closed position; — fig.3 — structural scheme of the shutting force control mechanism shown with the stopcock in its opened position; — fig.4 — structural scheme of the shutting force control mechanism shown with the stopcock in its closed position and having the upstream levers inclined with an initial angle; — fig. 5 — structural scheme of the shutting force control mechanism shown with the stopcock in its opened position and having the upstream levers inclined with an initial angle; . fig.6 — mounting drawing of the metallic elastic membranes for high-temperature fluids; fig. 7 — constructional and mounting drawing of the stopcock and the metallic elastic membranes for a valve used for high-purity fluids; -fig.8 — constructional and mounting drawing for a shutting force control mechanism fitted with rigid supports and elastic membranes; - fig.9 — constructional and mounting drawing for a shutting force control mechanism fitted with

According to this invention, the valve comprises a valve casing A with a shutting force control mechanism B acting on it. This mechanism is handled by a driving mechanism C and wrapped in a protective casing D — fig. 1. The valve casing A is ent to ensure the connection between the valve and the pipe duct, to conduct the fluid through the valve section and to physically support the other component elements of the valve. The valve body 1 is connected to the pipe duct by means of two flanges 2 fastened to the valve body by two threaded joints. The sealing rings 3, pressed down by the special nuts 4, ensure the leak-tightness with respect to the valve body. The valve bod is fitted with a shutter wall a and communication passages b, through which the fluid flows. Two guidance cones S, used for fluid-flow conduction, are installed within the valve body and on the outside the body is fitted with a stopcock seat c that has a sealing gasket 6 mounted on it. The fluid passes through the comunication passages and enters a shutting force control mechanism B whose body 7 is fitted with a stopcock disk d. A cap 8, fastened by a retaining snap ring 9 and a retaining nut 10, is mounted at the upstream extremity of the shutting force control mechanism. The inner surface of the cap has longitudinal grooves e, in order to prevent the rotation movement of the protective casing. A cap 11 „ fastened by a retaining snap ring 12 and a retaining nut 13, is mounted at fiie downstream extremity of the shutting force control mechanism. The caps are used to guide and position the mechanism in its translation movement. At each extremity, the mechanism has a system that takes over and distributes the axial forces exerted by the pressure of the fluid. The pressure of fiie fluid acts upon an elastic membrane 14 that ensures efficient leak-tightness with respect both to environment and to the other component parts of the mechanism. The elastic membrane is fastened to the mechanism body on a sealing surface f by a securing ring 15 fitted with a limiting spur g used to limit the force that compresses the membrane. The securing ring is pressed down by a half-bearing 16 fitted with a woridng surface h shaped like a toroidal sector pressed down, in its turn, by another half-bearing 17 fitted with a working surface i also shaped like a toroidal sector and fastened by a retaining nut 18. The elastic membrane is supported by coaxial pressure rings: 19, 20, 21, 22 fitted with driving spurs: j, k, 1, m and a limiting spur n. These spurs are used to induce the translation movement of the rings, within established limits, when there is no pressure inside the mechanism. The pressure rings take over the forces exerted by fiie elastic membrane and transmit them to the levers 23 fitted with a working surface o shaped like a sector of a barrel. The sectors of the barrel and the bearing shaped like a toroidal sector form toghether the hinges of the levers.

The membrane is fastened to the valve body on a sealing surface p by a securing ring 24 fitted with a limiting spur r pressed down, in its turn, by a supporting ring 25. This supporting ring is fitted with a surface s supporting the levers and a retaining nut 26 fastens it.

In the described case, the lever axis is perpendicular to the valve axis, making together a plane disk. In the places where the levers come into contact with fiie pressure rings and the supporting ring, the levers are fitted with woridng surfaces whose sections are shaped like special curves. This particular shape ensures the tangential contact between these working surfaces and several established points on fi e rings, even when file levers become inclined with respect to the valve axis. A spring 27 mounted at the downstream extremity of the shutting force control mechanism maintains the stopcock closed.

The valve opening is made by a driving mechanism C. The frame 28 of this mechanism is fastened to the valve body by a retaining snap ring 29, a guide bush 30 and a retaining nut 31. A key 32 prevents fi e rotation movement of both the guide bush and file driving mechanism frame. A bush 33, driven by a driving nut 34, acts like a piston, sliding along a grooved surface t machined on the driving mechanism frame. The translation movement of the bush causes an axial translation movement of the shutting force control mechanism. The driving nut is fastened to the driving mechanism frame by a shding fit u and it may be engaged in a rotation movement by means of several folding handles 35. An adjusting washer 36, fitted with outer grooves v and fastened by a retaining nut 37, controls the axial clearance of the nut The shutting force control mechanism is wrapped in a protective casing D that prevents both the acces of impurities and the damage of the working surfaces. The protective casing body 38 is fastened to the driving nut by a shding fit w. At the upstream extremity, the protective casing body is fitted with a protective cap 39 mounted by a threaded joint. The cap is fastened to the valve body by a retaining snap ring 40, a grooved bush 41 that guides the shutting force control mechanism and a retaining nut 42. A key 43 prevents fiie rotation movement of the grooved bush.

In the drawings 1,2 the valve is shown with the stopcock in its closed position. The elastic membranes are subjected to stresses that are considerably diminished by the system that takes over and distributes the axial forces exerted by the pressure of the fluid. This system also mainta nes a constant value and fiie same direction of the forces transmitted from the pressure rings to the levers, and finally it controls the points where these forces are applied. The shape of the elastic membranes and the materials they are made of are established according to fiie actual woridng conditions of the valves.

In order to simplify the explanation of the valve operation, the pressure rings are considered to work as a single ring whose frontal area A is equal to the sum of the pressure rings frontal areas and to transmit a single concentrated load F, taken over by a single lever — fig. 2. Denoting the upstream pressure by p and the downstream pressure by p', it results: p ≥ p' ; F = Ai. p = F_A + F_R = F_d + F_c ; F ' =A - P' = F Α' + F '_R. = F '_d + F '_c , with : F_A , F - the axial forces acting on the hinges ; F_R , F '_R > - fiie axial forces acting on the supports; F_d , F 'd - the axial forces acting on the stopcock disk ; F_c , F '_c - the axial forces acting on the stopcock seat.

The equilibrium conditions are : F_A + Fd — 0 F + F'd = 0

Denoting by li the distance between the point where the force is applied and the supporting point of the lever, by 1 the distance between the supporting point and the hinge centre and by 4 the stopcock area, it results:

F_A = i . F ; = ^ '^F ^ -|^L " ^Ai- P =^A< - P i j- - Ai. p' = A_d.p' ₌> ^L . A_i = Ad

— his is a constructional condition which ensures the equilibrium of the axial forces, no matter how high the pressure variations are.

Denoting by F_a the spring force and by F_e the force that seals the shutting element, it results: F_a = F_e . When the folding handles 35 of the driving mechanism C are turned around, the bush 33 acts upon the shutting force control mechanism B and it compresses the spring 27, opening the stopcock — fig. 1 ;3. In this case the upstream pressure equals the downstream pressure and the ollowing relations are obtained:

H _Aa = F • sinα = H_A'_{a >} with: V_Aα, V_A'_α - the vertical forces acting on the hinges ; V_Rα , V_R -_α - the vertical forces acting on the supports; H _Aα , H _A'_α - fiie horizontal forces acting on the hinges .

FA_OH ^{= v} _Aα + H_Aα , F_A'_α = V_A ^« _α + H _A'_β ; with: F_Aα F_A'_α - 1he axial resultants of fiie forces acting on the hinges, when the inclination angle of the levers is α . F_Aβ = V_Aα - cos ⁺ H_Aα» sin =--t- - F - cosα. cosα+ F » sinα . sinα = -— - F - co∑^α + Λl ϊ. - F -sin²α ;

Denoting by F_ma the force exerted by the driving mechanism, it results: _ma= F_a = F_e . When the spring 27 is released the stopcock is brought back to its closed position. The constructional solution of the valve allows a change of the equilibrium given by the axial forces, such that for F_A< F_d a valve with se f-regulating sealing force is obtained and for F_A > F_d a valve that may also work as a safety valve when the pressure surpasses the critical value is obtained. This change of equilibrium may be realised by displacing the point where the concentrated load is applied, by changing the inclination angle of the levers or by combining these methods. In addition, the above mentioned methods may be combined with a change of the flowing direction of the fluid, in accordance to the actual expected results. In order to illustrate these methods, three cases are analysed: one of them is for a valve with self-regulating sealing force and the other two are for a valve that starts working as a safety valve when fiie pressure surpasses the critical value.

— By displacing the point where the concentrated load is applied, the distance li is reduced only

with: l_lm — the reduced value of the distance U; F_Am — the reduced axial force acting on fiie hinge; _Rκ — the increased axial force acting on the support. _a ^{= F}e = _a+ F_A - F_A __ιm_n = F * _aa+ ^■ p *". A*^■»■i-. -^■ *i " j h

When the stopcock is opened, it results:

F_a + F_A+ F_R . sin²α - F_A∞ - F_RM . sin²α = Fm_a m_a = F_a + F_A - F_{A m} - sin²α .( F_Kyr F_R ) < _ma

Therefore, when the dimensiomng of the driving mechanism will be made, the force taken into account will be the one necessary to open the stopcock (F_∞a ).

— By displacing the point where the concentrated load is applied, the distance li is increased only for the upstream levers, while the other constructional parameters are maintained. When the stopcock is closed, it results-.

- • F = F_Aκ > F_d = F_A ; F = F_AM + F_{Rm ;} ^th: l_lM — the increased value of fiie distance lχ,

₄ — the increased axial force acting on the hinge; ^FR_m — he reduced axial force acting on the support.

^Fa_s - F_e + F_{A M} - F_d ; with: _a$ —he valve spring force.

Establishing the critical value of the pressure that causes fiie opening of the stopcock, it results: k = P ⁺ ι;^FA_Mk-^Fd_k ^=Fa_s;F_AMk= ^FAM ^+J --Ai. pι;F =F_d+ A_d.p₁;

If this solution is used, the inclination angle of the levers increases when the pressure of the fluid surpasses the critical value, due to the evolution of the axial forces acting on the hinges and it reverts to zero when the pressure of the fluid reverts to the critical value. Denoting by p₂ the pressure increase above fie critical value, it results:

' '1M" .Ai» p_k+ 3t -Ai-p2 + -^ M_.Ai.(pk + pa )• sin²α - -j -Ai- --jL -Ai - p₂ -

1

J -.Aj. p₂→- y^M _{' '}iPk +p₂)»sin²α -

. Ai . ( p_k + p₂ ) . sin²α =0

P2= ( k + p₂).sin²α;sinα - _jj p_j ; α - arcsin ^ _pk ^

— The upstream levers of the shutting force control mechanism are inclined with an initial angle α. , while fie other parameters are maintained — fig.4; 5. *oti = F_A + F_R . sin²o-i ; with : _Aαι — the axial force acting on the hinge, correspondent to the angle αi .

^Fa _s ⁼F_e +F_Aαι . F_d = F_e + F_R . sin²θ_j

Establishing the critical value of the pressure that causes fiie opening of fiie stopcock, it results:

Pk ⁼ P ⁺ Pi ■ '> ^FAkα_ - ^Fd = ^Fa_s ; wifii: ^FA _αi — the critical force acting on the hinge, correspondent to the angle cq .

Fλ + F_R . sin²αι + - . Aj . p! . sin²αj - _dfc = F_e + F_R . sin²αi ; — r¹. Ai . p_t . sin²αi = F_e ;

αi = arcsin ffi l-l_t A- _!

If the pressure surpasses the critical value, the displacement of the stopcock is maximum and the pressure pr that makes the stopcock to revert in its closed position decreases with the increase of the angle a, for this type of valve. Denoting by α_} the angle made by the upstream levers, it results:

1

-r7a_s ; (1 - li) . A, . pr • (sin αi - sin α ) = F_a«. .1 ; a *_ss - 1

Pr=

(1 - li) • Ai - [ sin ( i + α) - sin α]

In order to limit the pressure pr to a preferred value, the value of the angle α may be limited, either by changing fi e connection between the driving mechanism C and fiie shutting force control mechanism B or by using other methods.

These types of safety valves may function either as regular valves that start working as safety valves only determined by an accidental increase of pressure, or as safety relief valves mounted at the delivery points.

Metallic elastic membranes 14, whose shapes ensure a good resistance and elasticity, are used for fluids with high temperatures and pressures — fig.6.

For high-purity fluids the valve is mounted in vertical position and the metallic elastic membranes 14, the stopcock seat c and the stopcock disk d have suitable shapes, allowing the /Ml J* niτnr of fluid when the installation is emptied — fig. 7. In this case there is »» additional advantage, namely the surfaces of the inlet and outlet pipes may achieve a ^Mgh finish by means of a convenient machining procedure.

A valve with a simplified shutting force control mechanism ø_**y oe used in installations with small cross-sections of the valve and low pressures of the fluid- Within this simplified mechanism fiie securing ring 15 that fastens the elastic membrane 14 to the mechanism body 7 and the securing ring 24 that fastens the elastic membrane to fiie valve body I have their shapes modified and are rigid supports that take over fiie forces transmitted by the membrane — fig.8. The above simplified mechanism presents the following advantages: considerably simplified construction practice, reduced dimensions and lower costs. However, there are some drawbacks, namely the high stresses the elastic membranes are subjected to and the disturbed operation of the controlling forces. A valve with a simplified shutting force control mechanism may also be used for fluids having good lubricating properties. For this type of simplified mechanism the valve body 1 is fitted with a slot x where a sealing gasket 44 is installed, and the mechanism body 7 is fitted with a cylindrical sealing surface y — fig.9. This mechanism presents the following advantages: good dimensioning and distribution of the controlling forces, simplified construction practice, reduced dimensions and lower costs. The drawback of this mechanism is the possible damage of sealing, due to wear. The valve features have been experimented on a model fitted with a simplified shutting force control mechanism, according to fig. 8, and they fully correspond to the stipulations. During the elaboration of the patent documentation there were taken into account all the conclusions obtained by hydraulic calculations, by strength calculations and by analysing the actual possibilities of cheap construction of the component parts of a valve having a nominal diameter of 80 mm and a nominal operating pressure of 5 Mpa.

Claims

1) Leak-proof valve with self-controlling shutting force, consisting of a valve casing, with a stopcock as shutting element handled by a driving mechanism and being characterized by the fact that it has a cylindrical body (1) fitted with a shutter wall (a), communication passages (b) and a stopcock seat (c); this body also acts as the frame of a control mechanism for the shutting force (B), consisting of a body (7) fitted with a stopcock disk (d), two caps (8; 11) positioning the mechanism and guiding it in its translation movement, and two systems that take over and distribute the axial forces exerted by the fluid, each of them consisting of an elastic membrane (14), with sealing role, pressure rings (19...22) supporting the membrane and levers (23), articulated to the mechanism body and simply resting on the valve body, that take over fiie axial forces exerted by the fluid from the pressure rings and act continuously upon Λe shutting force of the stopcock, so that when fiie pressure of the fluid increases it may )«»ve a constant value, it may increase for the valve with serf-regulating sealing force or it _*aay decrease for Ae val * designed to (also) work as a safety valve.

2) Leak-proof valve with self-controlling shutting force, as per claim 1, characterized by the fact that, because it is designed to handle high-purity fluids, it is designed to work in a vertical position, and the membranes (14), the stopcock seat (c) and the stopcock disk (d) are designed in such a manner that their shapes ensure full draining of fluid when fiie installation is emptied.

3) Shutting force control mechanism, as per claim 1, characterized by the fact that fiie securing rings (15) that fasten the elastic membranes (14) to the mechanism body (7) and fiie securing rings (24) that fasten fiie elastic membranes to the valve body (1) have their shapes modified and are rigid supports for fiie membranes, taking over the axial forces exerted by the fluid directly from them.

4) Shutting force control mechanism, as per claim 1 , characterized by the fact that the frame, substituted by the valve body (1), has a slot (x) where a sealing gasket (44) is installed, and the mechanism body (7) is fitted with a sealing surface (y); these parts take over directly the axial forces exerted by fiie fluid.