RU2364779C2 - Safety valve - Google Patents

Abstract

FIELD: mechanical engineering.

SUBSTANCE: invention refers to the field of fitting engineering, specifically to spring-loaded high-lift safety valves and intended for protection of reservoirs and pipeline systems against overpressure that exceeds allowable limit in chemical, oil-and-gas and other industries. Safety valve contains body, stem with locking element and at least two springs. The springs are installed in tiers. One end of springs acts on stem with locking element. The other end of springs is pressed up and fixed relative to fixed support. Fixation of each tier springs pressing is performed independently from each other.

EFFECT: extension of the range of use for spring-loaded high-lift safety valves and increase in their flow rate.

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Description

The invention relates to valve manufacturing, in particular to safety valves, and can be used in chemical, oil and gas and other industries to protect tanks and piping systems from exceeding the pressure in them above the permissible limit.

One of the problems in the operation of tanks and piping systems for high parameters, for nominal pressure PN 20 MPa (200 kgf / cm ²⁾ and for nominal diameter DN 100 ÷ 600, is the inability to use safety valves (PC). This is due to the fact that with an increase in DN and PN, the buoyancy force along the rod associated with the shut-off element sharply increases, as well as the fact that the spring must ensure tightness in the valve, full capacity at full opening pressure P _across and closing pressure P _s at predetermined limits.

The complexity of meeting these requirements at the same time is due to the fact that the manufacturing technology of the spring does not allow the manufacture of a spring, which would at the same time ensure tightness in the shutter due to the large installation force, and its optimal rigidity, which would facilitate the lifting of the locking member relative to the housing seat on

which, in turn, would ensure the full capacity of the PC and, therefore, the optimal flow rate of the working medium through the PC, where dc is the diameter of the bore in the saddle of the casing. The manufacture of such a spring is limited by the spring index

where D _about - the average diameter of the coil, d is the diameter of the rod (wire).

Reducing the stiffness of the spring by increasing the number of turns in the spring leads to an increase in free height and, as a consequence, to a loss of its stability and performance.

PCs are known, see "Catalog 2005, Pipe Fittings", Blagoveshchensk Valve Plant OJSC, pp. 30-36, adopted as a prototype.

These are direct-acting valves in which the body seat is blocked by a shut-off element under the influence of a spring-loaded stem. When the pressure of the medium the shut-off body at a pressure P _of the full opening lying above the seat body, and with a pressure drop before the blocking member closes the PC body seat at a pressure P _of the closure.

The disadvantage of these valves is that they cannot be used for large nominal DN passages and high nominal PN pressures due to the need to use springs for large installation forces from 3500 kgf and higher while maintaining the appropriate stiffness, ensuring full PC lift. In this case, it is necessary to have a relatively soft spring with a large margin of adjustment stroke and a large installation force, which limits the use and creation of a PC with a passage diameter in the saddle of no more than 75 mm.

At low pressures of the working medium, PN up to 16 kgf / cm ² and DN 200, the bore in the saddle is limited to 142 mm.

The aim of the present invention is to expand the range of applications of spring full-lift PCs according to DN and PN and increase their throughput (flow rate of the working medium) due to the possibility of increasing the diameter of the bore in the seat of the valve body.

This goal is achieved by the fact that in the known valve comprising a housing, a stem with a locking member and a spring, springs of at least 2 are installed in tiers, one end of which acts on the stem with a locking member, and the other is pressed and fixed relative to the fixed support, moreover, the fixation of the preload of the springs of each tier is carried out independently of each other.

In science and technology, no technical solutions have been found that include these features. In accordance with this, the proposed technical solution meets the criterion of "significant differences".

The drawing shows a General view of a PC.

The safety valve consists of a housing 1, a locking element 2, a rod 3, on which supports 4, 5 and 6 are installed with springs 7, 8 and 9.

The bearings 10, 11 and 12, the pressing springs 7, 8 and 9, are each fixed independently from each other, for example, by nuts 13 relative to the fixed support 14.

The safety valve operates as follows. With increasing pressure of the working medium under the shut-off element to a pressure P _{, the} valve opens. In this case, the buoyancy force along the stem 3 is perceived by the springs 7, 8 and 9, which are compressed to the stroke, which ensures the full lift of the PC, and upon reaching the pressure P _s at the valve inlet, the PC closes. Setting the springs to pressure P _{n is} done manually by changing the degree of preloading of the springs in one of the ways, for example, through a threaded screw-nut pair, using, if necessary, a torque amplifier - a multiplier, the gain (gear ratio) of which is i = 5 ... 125.

Sealing of the sealing surfaces of the connection of the locking body-seat of the housing is carried out by acting on the stem of the total installation force of the springs, and the full capacity of the PC is ensured by the optimal reduced stiffness of these springs, which are located in the torsion and fixing separately the degree of their preload.

In each tier, several spring-loaded springs can be installed, thus increasing the axial force along the rod, thereby achieving sealing of the shut-off body-seat connection to almost any DN and PN.

Ensuring the full capacity of the PC, the required flow rate of the working environment and, therefore, the security of the protected object is ensured.

Depending on the purpose of the PC, the latter may have a closed or open version with or without a device for manual control (detonation).

The concept of creating full-height PCs, based on the unification of individual parts and assembly units, including technological ones, will make it possible to build unified parametric series of PCs for almost every DN on the corresponding PN.

The use of new PCs will improve the reliability of pipeline systems and reduce operating costs by:

- replacement of pulse-safety devices (ISP), where it is necessary to seal two valves, on one PC. In addition, the ISP requires special systems (capacities) for the removal (discharge) of the working medium from the piston cavity after the actuation process (discharge of excess P _p ), which is associated with additional operating costs and, as a result, a decrease in the reliability of the IPA compared to PC;

- high speed PC response, an order of magnitude higher than in the IPA;

- low inertia (practically absent) when the PC is triggered, compared with the ISP, which reduces the loss of an expensive work environment;

- high throughput, it will be possible to replace several safety valves with low throughput previously installed at the facilities.

New PCs can be used in pipelines, including long ones, and on tanks with high and ultrahigh parameters according to DN and PN.

Claims (1)

A safety valve comprising a housing, a stem with a locking member and a spring, characterized in that the springs, at least two, are installed in tiers, one end of which acts on the stem with a locking member, and the other is pushed and fixed relative to the fixed support, and the spring tension is fixed each tier is carried out independently of each other.