RU2272207C1 - Safety device for pressure vessel - Google Patents

Abstract

FIELD: valving.

SUBSTANCE: safety device for pressure vessel comprises housing, diaphragm, calibrated bursting rod, block of the pusher with the pressing disk, and knife block. The device is also provided with the vacuum support which carries the diaphragm provided with the pusher block with pressing perforated disk on its side. The pusher block has two ties, traverse, and protecting shield. The protecting shield defines rigid frame that receives the calibrated bursting rod.

EFFECT: enhanced reliability.

3 cl, 2 dwg

Description

The invention relates to chemical, petrochemical, oil refining, energy, refrigeration and other industries using pressure vessels.

To protect vessels operating under pressure, membrane-based safety devices are widely used, the principle of which is based on cutting the membrane with a fixed knife at the time of its maximum allowable deflection [1].

The disadvantage of devices of this type should be considered increased requirements for uniformity of thickness, mechanical properties and condition of the membrane surface, since the magnitude of the deflection depends on these parameters.

An alternative technical solution is the use of the initial bursting element in the form of a calibrated rod in the design of the membrane safety device.

In relation to the present invention, the closest in technical essence and the achieved effect is a safety device comprising a housing, a membrane, a calibrated bursting rod and a pusher mounted on the membrane and connected to the calibrated rod. In addition, the safety device is equipped with a lever with a knife fixed at one end, and the knife is pivotally connected to the body wall and the pusher [2].

This design has the following disadvantages.

After the device is triggered, the separated part of the bursting rod under the action of inertial forces is carried away by the flow of the working medium into the system, which in some cases can lead to failure of the protected equipment.

Swivel joints used to transmit movement from the pusher to the knife, as a result of the corrosive effects of the working medium, can provide significant resistance to the movement of the pusher until the device fails.

The device cannot be used in technological processes if counter-pressure or vacuum rarefaction conditions periodically occur in the protected system.

When the device is activated, the casing experiences significant dynamic loads: when the rupture rod is destroyed, the pusher jerks up and strikes the lower part of the jumper, and after depressurizing the device, the pusher moves down under the action of gravity without support (in the form of a membrane) until until it hits the top of the jumper again or hits the cutting part of the knife against the body wall. Together, the impact of these factors can lead to the destruction of the elements that make up the device.

The supporting surface of the pusher overlaps up to 40% of the passageway of the device, which leads to an increase in the dimensions of the device to ensure the necessary flow rate when dumping the working medium.

The breaking rod is screwed into the pusher and the lower end is rigidly fixed to the jumper. As a result, when the pusher moves upward, the calibrated part of the rod experiences bending forces arising from the technological impossibility of achieving absolute coincidence of the axes of the hinge device, the bursting rod, and the threaded hole in the jumper and pusher, which leads to an unpredictable change in the limits of operation of the device.

The purpose of the invention is to increase the reliability and manufacturability of the use of a safety device while maintaining the existing advantages of the prototype. This goal is achieved through the use of the following solutions.

To enable the device to operate when backpressure occurs in the drainage pipe or vacuum depression in the protected vessel, the use of a vacuum support in the form of a perforated disk, which simultaneously serves to attach the membrane to the housing, is provided.

A protective shield has been introduced into the design of the device to prevent the rod from unscrewing itself in the normal mode and trapping its separated part after operation.

Instead of a hinge device, a beam is used, which is part of the knife block, freely rotating on the axis and resting on one end of the pressure plate, while at the other end there is a knife that serves to steal the membrane when the device is triggered. To evenly distribute the loads on the pressure plate and improve the membrane opening when the device is triggered, two symmetrically located knife blocks on both sides of the pressure disk are used.

In order to reduce dynamic loads during the destruction of the rod on the structural elements of the device at the ends of the pusher rods, it is provided to install rings of soft material that deforms upon impact (dampers).

To ensure the possibility of increasing the cross section of the device after operation, the pressure disk is perforated.

To evenly distribute the load on the head of the bursting rod, centering washers are installed under it.

Figure 1 presents the membrane safety device, a General view, figure 2 is a section aa in figure 1.

The device comprises a housing 1, through a technological fitting 2 attached to the protected device 3, a vacuum support 4, between which the membrane is clamped 5. A pusher block is fixed to the membrane 5, which consists of a push perforated disk 6, on which rods 7 are installed, which serve to transmit breaking strength through the traverse 8 and the set of centering washers 9 on the rupture rod 10, which is installed in the threaded hole of the yoke 11, which is rigidly attached to the body. To prevent the rod from unscrewing in the normal mode and catching it about of the divided part after operation, a protective screen is provided 12. In the lower part of the device, knife blocks are installed, which are freely rotating on the axis of the rocker arm 13, resting on one end on a perforated pressure plate 6, while on the other end there are knives 14, which serve to open the membrane 5 in in case of device operation. The axis of the beam is installed in the bracket 15, rigidly connected with the wall of the housing 1.

Safety device operates as follows.

The load from the pressure of the medium through the membrane 5 and the pusher block, consisting of a pressed perforated disk 6, rods 7 and a cross beam 8, assembled in a rigid frame, is transferred to the bursting rod 10, one end of which is fixed in a fixed yoke 11, and the other is connected with the crossarm 8 of the block pusher. At a pressure lower than the set pressure, the bursting rod 10 accepts part of the load, unloading the membrane 5. When the pressure in the vessel reaches the set pressure, the voltage in the calibrated neck of the bursting rod 10 reaches the tensile strength of the rod metal and its neck is destroyed - breaking. The membrane 5, devoid of the supporting effect of the rod 10, under the influence of the pressure of the medium is deformed upward and, bumping into the knives 14, cuts through. Further, the flow of the effluent liquid or gaseous medium opens the passage section of the device.

Information sources

1. Olkhovsky N.E. Safety membranes for equipment protection in the chemical, petrochemical and oil refining industries., "Chemistry", L. 1970, p. 68.

2. A.S. USSR No. 769186, class F 17 C 13/00, publ. 10/7. 1980, BI No. 37.

Claims (4)

1. A safety device for a pressure vessel, comprising a housing, a membrane, a calibrated bursting rod, a pusher block with a pressure disk, a knife block, characterized in that it is equipped with a vacuum support, on which a membrane is fixed with a pusher block attached to it with a perforated pressure disk, on which the rocker arms of two knife blocks rest, while the pusher block contains two rods, a traverse and a protective screen, forming a rigid frame in which a calibrated bursting rod is installed. 2. The safety device for the pressure vessel according to claim 1, characterized in that the vacuum support is made in the form of a perforated disk. 3. The safety device for the pressure vessel according to claim 1, characterized in that at the ends of the rods of the pusher block rings of soft metal are installed. 4. The safety device for the pressure vessel according to claim 1, characterized in that the rupture rod is provided with centering washers.

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