dresser safety valve free sample

This disclosure relates to pressure relief valves, and more particularly, to pressure relief valves suitable for use in multiple service applications.

Typically, a pressure relief valve may be used to control or limit pressure in a system or vessel, which can build up by, for example, a process upset, instrument or equipment failure, or fire. The pressure may be relieved by allowing the pressurized fluid to flow from an auxiliary passage through the pressure relief valve and out of the system. The pressure relief valve may be designed or set to open at a predetermined set pressure to protect pressure vessels and other equipment from being subjected to pressures that exceed their design limits.

In some cases, a pressure relief valve may incorporate a nozzle responsible for directing fluid flow from a piping to exhaust system during an overpressure situation. The smallest diameter in the nozzle (i.e., the “controlling diameter,” or bore) may be at least partly responsible for the flow or relieving capacity of the pressure relief valve. In addition, due to the difference in fluid properties between compressible (e.g., gas) and incompressible (e.g., liquid) fluid media, one or more components of the pressure relief valve may need to be replaced and/or adjusted depending on the fluid media type (i.e., compressible or incompressible). Such a change in component(s) (such as, for example, a disc holder) may be necessary due to different force response each fluid applies to a “mass-spring-damper” system of the pressure relief valve.

Further, the operation of the mass-spring damper system may be relevant in meeting or exceeding certain regulatory requirements of pressure relief valves. For example, such regulatory requirements may place limits on a set pressure tolerance (e.g., ±2 psi or ±3% of set pressure), blowdown (e.g., less than or equal to 3 psi or 7% of set pressure), pressure relief valve relief operation (e.g., at or above certified capacity at 10% above the set pressure), and “chatter” or “flutter” (e.g., no “chatter” or “flutter” during normal pressure relief valve operation). For purposes of the present disclosure, “set pressure” may be defined as an inlet pressure at which the pressure relief valve commences to open under service conditions (i.e. first measurable lift). Also, for purposes of the present disclosure, “blowdown” may be defined as a difference between the set pressure and a pressure at resealing of the pressure relief valve, expressed as a percentage of the set pressure. Further, for purposes of the present disclosure, “chatter” may be defined as an abnormal, reciprocating motion of the movable parts of the pressure relief valve in which a disc contacts a nozzle of the pressure relief valve, and “flutter” may be defined as an abnormal, rapid reciprocating motion of the movable parts of the pressure relief valve in which the disc does not contact the nozzle.

In one general embodiment, a pressure relief valve includes a base, a bonnet, a nozzle, and a disc. The base includes a fluid inlet and a fluid outlet. The bonnet is attached to the base, and the base and the bonnet define a cavity in fluid communication with the fluid inlet and the fluid outlet. The nozzle is disposed within the fluid inlet and attached to the base, and the nozzle includes a substantially annular seat, a substantially cylindrical seat inlet, and a substantially cylindrical bore in fluid communication with the seat inlet. A ratio between a bore diameter and a seat diameter is a constraint ratio. The disc is disposed within a disc holder and includes a surface facing the fluid inlet to receive a first fluidic pressure against the surface. The disc is adapted to contact the seat and seal the fluid inlet to substantially prevent fluid communication between the fluid inlet and the cavity when the valve is in a closed position. The disc and the disc holder are adapted to be urged by an increase of the first fluidic pressure to a second fluidic pressure such that contact between the disc and the seat is removed at the second fluidic pressure to allow fluid communication between the fluid inlet and the cavity. One or more dimensions of at least one of the disc, the disc holder, and the nozzle are functions of the seat diameter and limited by the constraint ratio.

In another general embodiment, a pressure relief valve includes a base including a fluid inlet and a fluid outlet, a bonnet attached to the base, and a pressure control system. The valve has a set pressure substantially equal to a pressure at the fluid inlet at which fluid communication is established between the fluid inlet and the fluid outlet. The valve has a resealing pressure substantially equal to a pressure at the fluid inlet at which fluid communication is substantially ceased between the fluid inlet and the fluid outlet. The base and the bonnet define a cavity in fluid communication with the fluid inlet and the fluid outlet. The pressure control system is configured to receive a first fluid and regulate the first fluid such that a difference between the set pressure and the resealing pressure is within a predetermined percentage of the set pressure during operation of the valve with the first fluid. The first fluid is one of substantially all gas or substantially all liquid. The pressure control system is configured to receive a second fluid and regulate the second fluid such that a difference between the set pressure and the resealing pressure is within the predetermined percentage of the set pressure during operation of the valve with the second fluid. The second fluid is substantially all liquid if the first fluid is substantially all gas and substantially all gas if the first fluid is substantially all liquid.

In another general embodiment, a method for using a pressure relief valve having a base including a fluid inlet and a fluid outlet; a set pressure substantially equal to a pressure at the fluid inlet at which fluid communication is established between the fluid inlet and the fluid outlet; and a resealing pressure substantially equal to a pressure at the fluid inlet at which fluid communication is substantially ceased between the fluid inlet and the fluid outlet, includes the steps of providing a liquid to the fluid inlet such that a difference between the set pressure and the resealing pressure is within a predetermined percentage of the set pressure during operation of the valve with the liquid; and without modifying the valve, providing a gas to the fluid inlet such that a difference between the set pressure and the resealing pressure is within the predetermined percentage of the set pressure during operation of the valve with the gas.

In another general embodiment, a method for using a pressure relief valve having a base including a fluid inlet and a fluid outlet; a set pressure substantially equal to a pressure at the fluid inlet at which fluid communication is established between the fluid inlet and the fluid outlet; and a resealing pressure substantially equal to a pressure at the fluid inlet at which fluid communication is substantially ceased between the fluid inlet and the fluid outlet, includes the steps of providing a gas to the fluid inlet such that a difference between the set pressure and the resealing pressure is within a predetermined percentage of the set pressure during operation of the valve with the gas; and without modifying the valve, providing a liquid to the fluid inlet such that a difference between the set pressure and the resealing pressure is within the predetermined percentage of the set pressure during operation of the valve with the liquid.

In one aspect of one or more general embodiments, the valve may have a set pressure substantially equal to the second fluid pressure and the valve may have a resealing pressure substantially equal to a third fluid pressure at the fluid inlet at which fluid communication is substantially ceased between the fluid inlet and the fluid outlet. A difference between the set pressure and the resealing pressure may be within approximately 7% of the set pressure during operation of the valve with a gas fluid when the constraint ratio is within the range.

In one aspect of one or more general embodiments, the valve may have an overpressure substantially equal to approximately 110% of the set pressure, and fluid communication between the fluid inlet and the fluid outlet may reach a full capacity flow rate of the valve at the overpressure when the constraint ratio is within the range.

In one aspect of one or more general embodiments, the valve may have a set pressure substantially equal to the second fluid pressure, and the valve may have a resealing pressure substantially equal to a third fluid pressure at the fluid inlet at which fluid communication is substantially ceased between the fluid inlet and the fluid outlet. A difference between the set pressure and the resealing pressure may be within approximately 10% of the set pressure during operation of the valve with a liquid fluid when the constraint ratio is within the range.

In one aspect of one or more general embodiments, the valve may include an adjusting ring having a bore for receiving the nozzle therethrough. The difference between the set pressure and the resealing pressure may be based, at least in part, on the position of the adjusting ring on the nozzle.

In one aspect of one or more general embodiments, providing a liquid to the fluid inlet such that a difference between the set pressure and the resealing pressure is within a predetermined percentage of the set pressure during operation of the valve with the liquid may include providing a liquid to the fluid inlet such that a difference between the set pressure and the resealing pressure is within a first predetermined percentage of the set pressure during operation of the valve with the liquid. Providing a gas to the fluid inlet, without modifying the valve, such that a difference between the set pressure and the resealing pressure is within the predetermined percentage of the set pressure during operation of the valve with the gas may include providing a gas to the fluid inlet, without modifying the valve, such that a difference between the set pressure and the resealing pressure is within a second predetermined percentage of the set pressure during operation of the valve with the gas.

In one aspect of one or more general embodiments, the valve may further include a nozzle disposed in the fluid inlet and an adjusting ring disposed around an outer surface of the nozzle at a first position, such that the difference between the set pressure and the resealing pressure is within the predetermined percentage of the set pressure during operation of the valve with the liquid and the gas when the adjusting ring is at the first position. Adjusting the adjusting ring along the nozzle in a direction toward the fluid inlet to a second position different from the first position may cause the difference between the set pressure and the resealing pressure to be within a second percentage of the set pressure less than the predetermined percentage during operation of the valve with the liquid and the gas when the adjusting ring is at the second position.

In one aspect of one or more general embodiments, providing a gas to the fluid inlet such that a difference between the set pressure and the resealing pressure is within a predetermined percentage of the set pressure during operation of the valve with the gas may include providing a gas to the fluid inlet such that a difference between the set pressure and the resealing pressure is within a first predetermined percentage of the set pressure during operation of the valve with the gas. Providing a liquid to the fluid inlet, without modifying the valve, such that a difference between the set pressure and the resealing pressure is within the predetermined percentage of the set pressure during operation of the valve with the liquid may include providing a liquid to the fluid inlet, without modifying the valve, such that a difference between the set pressure and the resealing pressure is within a second predetermined percentage of the set pressure during operation of the valve with the liquid.

Various implementations of a pressure relief valve (PRV) according to the present disclosure may include one or more of the following features. For example, the PRV may obtain industry performance specifications (e.g., ASME Section VIII and/or API Stds. 521, 526, and/or 527) with respect to several properties (i.e., relieving capacity, blowdown, set point tolerance, and chatter) on both compressible and incompressible media. The PRV may obtain such specification on both compressible and incompressible media. For instance, the PRV may allow for switching between media without making any adjustments to components of the PRV. As another example, the PRV may obtain such specification on both compressible and incompressible media without adjustment of a disc and/or disc holder. Further, the PRV may obtain such specification on both compressible and incompressible media without adjustment of or modification of an adjusting ring of the PRV.

Various implementations of a pressure relief valve (PRV) according to the present disclosure may also include one or more of the following features. The PRV may include optimal geometrical dimensions of one or more components, such as a disc, a disc holder, a nozzle, and/or an adjusting ring, as well as other components. The PRV may include such optimal dimensions based on a dimensional ratio of a bore and a seat of the PRV. As another example, the PRV may allow for increased manufacturing efficiency, by reducing the number of different valve components necessary to meet a variety of different services. The PRV may also allow for reduced inventory by allowing valve users to maintain a single PRV operable for both liquid and gas service. As another example, the PRV may provide for better performance (e.g., less chatter) in a liquid service as compared to a typical pressure relief valve specifically designed for gas service. Further, the PRV may provide for better performance (e.g. shorter blowdown) in a gas service as compared to a typical pressure relief valve specifically designed for liquid service. As yet another example, the PRV may have improved set pressure tolerance, including improved tolerance between different media types, as compared to conventional pressure relief valves. Also, the PRV may facilitate improved flow capacity as compared to conventional pressure relief valves.

A pressure relief valve (PRV) according to the present disclosure may include a disc, a disc holder, a nozzle, and a mass-spring-damper system that allows for a fluid (e.g., gas, liquid, or multiphase fluid) within a system, such as a piping system or pressure vessel, to be relieved by operation of the PRV when the fluidic pressure of the fluid exceeds a predetermined threshold. In some embodiments, the PRV may be used for liquid, gas, and multiphase applications while meeting one or more industry performance criteria (e.g., blowdown, set pressure tolerance, relief operation, and other criteria) without changing any components of the PRV for the specific service media, such as the disc holder, the disc, or other components. In some embodiments, one or more geometrical relationships between and/or among the components of the PRV may allow for dual operation between liquid and gas media without modifications of such components between such operation.

FIGS. 1A-B illustrate sectional views of one implementation of a pressure relief valve (PRV) 100. Generally, PRV 100 receives a fluid 101 (e.g., gas or liquid or a multiphase fluid) at and through an inlet 110 and directs the fluid 101 to and through an outlet 115 of the PRV 100 in order to relieve a pressure within a system. For example, the PRV 100 is typically in fluid communication with components, such as pressure vessels, heat exchangers, mechanical equipment (e.g., compressors, turbines and others) within a piping or conduit system and may be used to control or limit a pressure in such a system, including such vessels, heat exchangers, and/or equipment, which can build up by a process upset, instrument or equipment failure, fire, or other incident. Pressure is relieved through the operation of PRV 100 by allowing the pressurized fluid to flow from the inlet 110 through the outlet 115 at a predetermined pressure set point. For instance, the PRV 100 may be designed or set to open at a predetermined set pressure to protect pressure vessels and other equipment from being subjected to pressures that exceed their design limits.

FIGS. 2A-C (as well as FIGS. 3A-C) also illustrate a bore 121 of the nozzle 120 with a bore diameter 122. As illustrated, the bore 121 is disposed in a lower portion of the nozzle 120 directly adjacent the inlet 110, while a seat inlet 123 is disposed in an upper portion of the nozzle 120 adjacent the disc 135. The top surface of the nozzle 120 adjacent the seat inlet 123 is the seat 119. In some implementations, such a configuration (which may be opposite to that found in conventional pressure relief valves) may include several advantages. For example, by locating the bore 121 adjacent the inlet 110 rather than adjacent the disc 135, the PRV 100 may reduce chatter, reduce and/or eliminate cavitation, improve capacity control, and reduce acoustic noise. Further, in the illustrated embodiment, fluid flow through the nozzle 120 may be more stable due to, at least in part, the location of the bore 121 and seat inlet 123 as compared to conventional pressure reducing valves.

Due to the above-described behavior in liquid service, at least in part, certain industry specifications may require flow capacity of a pressure relief valve, such as the PRV 100, to be achieved by 10% overpressure (e.g., 110% of set pressure). In contrast, this requirement may not be needed for gas service since full lift is obtained much closer to the set point pressure. The adjusting ring 125, for liquid service, may be used to direct the flow of fluid 101, as opposed to creating pressure differentials as in gas service.

In certain embodiments utilizing the dimensions of the PRV 100 illustrated in Table 1, the PRV 100 may have better performance than conventional pressure relief valves that do not utilize such dimensions relationships. For example, Table 3 (below) illustrates performance (e.g., blowdown) data for both an incompressible fluid (i.e., water) and a compressible fluid (i.e., air) for the PRV 100 as compared to a conventional pressure relief valve. Of particular note, Table 3 illustrates data for the PRV 100 and a conventional pressure relief valve at two different media without adjustment of either valve (e.g., without changing components, including disc, disc holder, and/or nozzle, to account for the media). Further, in some embodiments. Table 3 illustrates data for the PRV 100 and a conventional pressure relief valve for two different media without modification of the corresponding adjusting rings of either valve. For example, one instance of a conventional pressure relief valve for a liquid application is Consolidated Model 1900LA safety relief valve provided by Dresser, Inc.

As illustrated in Table 3, the PRV 100 performs better than the conventional liquid pressure relief valve on both liquid (i.e., water) and gas (i.e., air). More specifically, PRV 100, for example, meets certain industry standards for both liquid and as applications without change to any component of the PRV 100 or modifications/changes to the adjusting ring. For instance, industry standard ASME Boiler & Pressure Vessel Code Section VIII requires blowdown be less than or equal to 3 psi or 7% of set pressure, whichever is greater, in a gas service. As illustrated in Table 3, the PRV 100 meets this standard for both water and air (i.e., incompressible and compressible media) while the conventional pressure relief valve designed for liquid service has blowdown up to twice the standard when in a gas service.