Patent Description:
This disclosure relates generally to a hydraulic decoking system for removing coke from containers such as coking drums used in oil refining, and more particularly to a control valve of the hydraulic decoking system.

In conventional petroleum refining operations, crude oil is processed into gasoline, diesel fuel, kerosene, lubricants or the like. It is a common practice to recover heavy residual hydrocarbon byproducts through a thermal cracking process known as delayed coking. In a delayed coker operation, heavy hydrocarbon (oil) is heated to a high temperature (for example, between <NUM>° F and <NUM>° F, or between <NUM> and <NUM>) in large fired heaters known as a fractionation unit, and then transferred to cylindrical vessels known as coke drums which are as large as <NUM> feet (<NUM>,<NUM> meters) in diameter and <NUM> feet (<NUM>,<NUM> meters) in height. The heated oil releases its hydrocarbon vapors for processing into useful products, leaving behind solid petroleum coke. This coke residue must be broken up in order to remove it from the vessel and is preferably accomplished by using high pressure water directed through nozzles of a decoking (or coke cutting) tool in a process known as hydraulic decoking.

The high pressure water is supplied by a decoking jet pump. Typical flow rates and pressures during hydraulic decoking are <NUM> gallons per minute (gpm) (<NUM>,<NUM> cubic meters per second) at <NUM> to <NUM> pounds per square inch (psi) (at <NUM>,<NUM> to <NUM>,<NUM> MPa). The decoking control valve is a multipurpose valve that can route the high pressure water from the pump to either the cutting tool or recirculate it back to the tank. The cutting tool has drilling and cutting nozzles, and is lowered into the coke drum through an opening in the top of the drum. The high pressure water can be routed through either the drilling or cutting nozzles, depending on the mode of operation. Switching the flow from one set of nozzles to another is achieved through a depressurization and pressurization sequence where the supply of high pressure water to the tool is stopped until the pressure inside the tool falls below a specified value, and then restoring the full high pressure water supply again. As mentioned above, the decoking control valve is used to control this flow of water from the pump to the tool.

In addition to controlling the flow to the tool, the decoking control valve is capable of performing additional functions; providing minimum bypass flow for the pump when recirculating back to the tank to prevent damage to the pump, and supplying water at low flow and low pressure to slowly fill piping to prevent "water hammer. " One such multipurpose decoking control valve was first developed and described in <CIT>, which is commonly owned by the assignee of the present disclosure.

This single multipurpose piston-type valve removed the need for using several valves in a decoking system. The valve has one inlet port, two outlet ports, and has three operating positions. Depending on the operating position, the water from the inlet port is directed to either one or both of the outlet ports. In order to isolate an outlet port from the inlet port, the valve actuator drives the piston until it bears on a conical annular seat to create a watertight seal. However, this leads to the disadvantage of the valve actuator needing to provide sufficient force to develop the watertight seal between the piston and the valve seat. This, in turn, results in seat failure due to the inherent repeated opening and closing of the valve, rendering the valve unserviceable and limits the valve's mean time between repair. The objective of the present disclosure is to increase the mean time between repair of a decoking control valve by replacing the seats with an alternate improved sealing mechanism.

Document <CIT> discloses a known decoking control valve from the prior art.

According to the first aspect of the present disclosure, a decoking control valve using a hydraulic rod seal is disclosed. The decoking control valve may also comprise a piston, a cylinder, and a hydraulic rod seal at the outlet ports. The piston is capable of moving within the cylinder along a translational direction. The cylinder additionally houses the hydraulic rod seal within a groove of the cylinder that places the hydraulic rod seal next to the piston. The hydraulic rod seal features a seal ring that interacts with the piston, and the seal rings are activated by an activating agent. When the piston moves within the cylinder, the seal ring activates at one outlet port, and allows fluid to flow out of another outlet port.

The following detailed description of the preferred embodiments of the present disclosure can be best understood when read in conjunction with the following drawings, where like structure is indicated with like reference numerals and in which:.

Referring first to <FIG>, a decoking system <NUM> includes a pair of coke drums <NUM>, a cutting and boring (decoking) tool <NUM>, a drill stem <NUM>, a pair of towers <NUM>, a flexible water supply hose <NUM> and a rotary joint <NUM>. The partial cutaway of the left coke drum <NUM> show it is full of coke <NUM> to be removed, while the partial cutaway of the right coke drum <NUM> shows the decoking tool <NUM> being lowered through the coke <NUM> during boring of a pilot hole <NUM>. The water from the tank is pressurized by the jet pump (not shown) and supplied to the decoking tool <NUM> via the decoking control valve <NUM> (<FIG>), piping, flexible water supply hose <NUM>, rotary joint <NUM>, and drill stem <NUM>. The decoking tool <NUM> is mounted at the lower end of the drill stem <NUM> such that both can move translationally (specifically, vertically) along the length of the coke drum <NUM>. The upper end of drill stem <NUM> is coupled to the rotary joint <NUM> which provides rotational motion to the drill stem <NUM> and the decoking tool <NUM>.

Referring now to <FIG> and <FIG>, a cross-sectional view of a decoking control valve <NUM> of the prior art is shown in two respective operating positions. <FIG> shows the first operating position, in which the inlet fluid is directed to the second outlet port <NUM> while being sealed from the first outlet port <NUM> via means of a valve seat <NUM>. <FIG> shows the third operating position, in which the inlet fluid is directed to the first outlet port <NUM> while being sealed from the second outlet port <NUM> via means of another valve seat <NUM>. Using this design, in order to isolate an outlet port from the high pressure water at the inlet port <NUM>, the actuator drives the piston until it bears on a conical annular seat to create a watertight seal.

The decoking control valve <NUM> of the prior art has two disadvantages as described herein. As shown in <FIG>, the piston <NUM>, reciprocates inside the cylinder <NUM>. The pressure P is sealed by creating necessary contact pressure between the piston <NUM> and the valve seat <NUM>. Since the pressure P to be sealed is high, the contact pressure and the axial force necessary to create the contact pressure is high as well. The high axial force is to be supplied by the valve actuator (not shown). Generating a high force repetitively causes rapid wear on the moving parts inside the valve actuator, limiting the mean time between repair of the valve actuator. Also, repeated engagement of the piston <NUM>, made of a hard material, with the valve seat <NUM>, made of a softer material, with a high force damages the valve seat <NUM>, eventually causing leakage. Once the valve seat <NUM> begins to leak, the decoking control valve <NUM> must be removed to be repaired. Thus, the damage to the valve seat <NUM> results in lower mean time between repair of the decoking control valve <NUM>.

Referring now to <FIG> and <FIG>, two operating positions of the decoking control valve <NUM> of the present disclosure are shown. It is contemplated that the decoking control valve <NUM> will have at least three operating positions. <FIG> displays the decoking control valve <NUM> in the first operating position wherein the first outlet port <NUM> is blocked, the piston <NUM> being in place over the respective hydraulic rod seal <NUM>. When in this position, the decoking fluid may flow in from the inlet port <NUM> and out of the second outlet port <NUM> and will not flow out of the first outlet port <NUM>. <FIG> displays the decoking control valve <NUM> in the third operating position where second outlet port <NUM> is blocked, and the piston <NUM> is in place over the respective hydraulic rod seal <NUM>. When in this position, the decoking fluid may flow in from the inlet port <NUM> and out of the first outlet port <NUM> and will not flow out of the second outlet port <NUM>.

The decoking control valve <NUM> of the present disclosure is capable of overcoming the shortcomings of the prior art decoking control valve <NUM> by replacing the valve seat <NUM> with an alternate sealing system as described herein. <FIG> shows an enlarged partial cross section of the decoking control valve <NUM> of the present disclosure. To seal the pressure P between the piston <NUM> and the cylinder <NUM> as the piston <NUM> moves in the direction of travel T, a hydraulic rod seal <NUM> is used in place of a valve seat <NUM> of the prior art. The hydraulic rod seal <NUM> is housed in a groove <NUM> in the cylinder <NUM>, and is composed of a seal ring <NUM> that may be energized by an activator, which may include an O-ring <NUM> or any other element that may be suitable for energizing the seal ring <NUM>. Once the decoking control valve <NUM> is in operation, the seal ring <NUM> may also be energized by the pressure P acting on the activator. The pressure P is sealed at the first radial interface <NUM> between the piston <NUM> and the seal ring <NUM>, and also at the second radial interface <NUM> between the cylinder <NUM> and the activator. The contact pressure necessary for sealing is generated by the geometry of the seal ring <NUM>. The radial thickness of the seal ring <NUM> in comparison to the depth of the groove <NUM> is such that engagement of the piston <NUM> with the seal ring <NUM> squeezes the seal ring <NUM> in the radial direction between the piston <NUM> and the cylinder <NUM> and develops the contact pressure. The valve actuator may supply force only to engage the hydraulic rod seal <NUM> and to overcome the seal friction. The material for the seal ring <NUM> is chosen such that it has a coefficient of friction low enough to reduce the force required to overcome the seal friction. As a result, the axial force requirement from the valve actuator in the present disclosure is significantly lower than in the prior art, which will substantially lower the wear rate of the moving components inside the valve actuator and increase the mean time between repair.

Various improvements are contemplated to prolong the life of the hydraulic rod seal <NUM> in order to achieve longer mean time between repair of the decoking control valve <NUM>. The seal ring <NUM> is made from a wear resistant material to increase its wear life. Additionally, the radial gap (not shown) between the piston <NUM> and the cylinder <NUM> is controlled to avoid extrusion of the seal ring <NUM> under pressure P. A guide ring <NUM> in an inset <NUM> of the cylinder <NUM> energized by a coil spring <NUM> protects the hydraulic rod seal <NUM> by taking up uneven loading exerted by the piston <NUM> due to misalignment of the piston <NUM> in the cylinder bore <NUM> or any other reason for the misalignment. The guide ring <NUM> is installed on the non-pressure side of the hydraulic rod seal <NUM>, and centers the piston <NUM> in the cylinder bore <NUM> before it engages with the hydraulic rod seal <NUM>. The guide ring <NUM> used herein is substantially similar to the one disclosed in <CIT>.

The decoking control valve <NUM> of the present disclosure uses two sets of hydraulic rod seals <NUM> and guide rings <NUM> in place of two valve seats <NUM> of the decoking control valve <NUM> disclosed in the prior art. One set of hydraulic rod seals <NUM> and guide rings <NUM> works in cooperation with the first outlet port <NUM> and another set of hydraulic rod seals <NUM> and guide rings <NUM> works in cooperation with the second outlet port <NUM>. The distance by which the two sets are separated is such that the piston <NUM> can only be engaged with a maximum of one of the sets at a time. Therefore, for a given set of hydraulic rod seals <NUM> and guide rings <NUM> the piston <NUM> is not always engaged to each. To prevent the blow-out of the hydraulic rod seals <NUM> and the guide rings <NUM> from the groove <NUM> and inset <NUM>, respectively, when the piston <NUM> is not engaged, the grooves <NUM> and insets <NUM> positively retain the hydraulic rod seals <NUM> and the guide rings <NUM>. To make assembly possible, the grooves <NUM> and insets <NUM> are split radially. The hydraulic rod seals <NUM> described herein may be composed of any suitable material.

When the piston <NUM> disengages from the seal ring <NUM>, the high differential pressure across the seal ring <NUM> may push the seal ring <NUM> out of its groove <NUM> despite of positive retention. To avoid this, the pressure may be equalized across the seal ring <NUM> just before retracting the piston <NUM> completely from the seal ring <NUM>. Therefore, the seal ring <NUM> is in a pressure equilibrium when the piston <NUM> is retracted, eliminating any unbalanced forces acting on it. <FIG> shows the same cross section as <FIG>, but with the piston <NUM> starting to withdraw from the seal ring <NUM>. In this position of the piston <NUM>, the drilled port <NUM> of the piston <NUM> equalizes the pressure P across the seal ring <NUM>. Note that in <FIG>, the drilled ports <NUM> are entirely on one side of the seal ring <NUM>, therefore the seal ring <NUM> is sealing the pressure P, whereas in <FIG>, the two ends of the drilled ports <NUM> are on either side of the seal ring <NUM>, thereby eliminating the pressure differential. The diameter of the drilled port <NUM> should be small in comparison to the width of the seal ring <NUM>. There can be multiple such drilled ports <NUM> around the circumference of the piston <NUM>.

Now referring to <FIG> and <FIG>. <FIG> shows the same cross section as <FIG>, but with the piston <NUM> completely retracted from the seal ring <NUM>. In this position of the piston <NUM>, the guide ring <NUM> is subjected to the entire pressure differential. The guide ring <NUM>, however, is not meant to withstand any pressure differential. Therefore, to eliminate the differential pressure across the guide ring <NUM>, axial grooves <NUM> are added on the inside diameter of the guide ring <NUM>. <FIG> shows Section A-A of <FIG>. The axial grooves <NUM> allow the water to flow through, eliminating any pressure differential. Any other method or modification to the guide ring <NUM> to equalize pressure, e.g. through-drilled holes, should be considered to be within the scope of the present disclosure. Additionally, the use of springs to allow water to flow through, such as those shown in <FIG> of <CIT>, is contemplated.

Having described the various aspects of the present disclosure in detail and by reference to preferred embodiments thereof, it will be apparent that modifications and variations are possible without departing from the scope of the disclosure defined in the appended claims. More specifically, although some aspects of the present disclosure are identified herein as preferred or particularly advantageous, it is contemplated that the present disclosure is not necessarily limited to these preferred aspects.

It is also noted that recitations herein of "at least one" component, element, etc., should not be used to create an inference that the alternative use of the articles "a" or "an" should be limited to a single component, element, etc..

It is noted that terms like "preferably," "commonly," and "typically," when utilized herein, are not utilized to limit the scope of the claimed invention or to imply that certain features are critical, essential, or even important to the structure or function of the claimed invention. Rather, these terms are merely intended to identify particular aspects of an embodiment of the present disclosure or to emphasize alternative or additional features that may or may not be utilized in a particular embodiment of the present disclosure.

For the purposes of describing and defining the present invention it is noted that the terms "substantially" and "approximately" are utilized herein to represent the inherent degree of uncertainty that may be attributed to any quantitative comparison, value, measurement, or other representation. The terms "substantially" and "approximately" are also utilized herein to represent the degree by which a quantitative representation may vary from a stated reference without resulting in a change in the basic function of the subject matter at issue.

Having described the subject matter of the present disclosure in detail and by reference to specific embodiments thereof, it is noted that the various details disclosed herein should not be taken to imply that these details relate to elements that are essential components of the various embodiments described herein, even in cases where a particular element is illustrated in each of the drawings that accompany the present description. Further, it will be apparent that modifications and variations are possible without departing from the scope of the appended claims. More specifically, although some aspects of the present disclosure are identified herein as preferred or particularly advantageous, it is contemplated that the present disclosure is not necessarily limited to these aspects.

Claim 1:
A decoking control valve (<NUM>) comprising:
a cylinder (<NUM>) defining an inlet port (<NUM>) and a plurality of outlet ports; (<NUM>, <NUM>);
a piston (<NUM>) that moves along a direction of travel (T) within the cylinder (<NUM>) and is configured to allow decoking fluid to flow in from an inlet port (<NUM>) and out of a selective one of the outlet ports (<NUM>, <NUM>), thereby comprising at least three operating positions which result in fluid isolation of each port selectively in response to the piston (<NUM>) movement; characterized by
a plurality of hydraulic rod seals (<NUM>) housed within a respective groove (<NUM>) in the cylinder (<NUM>) at each of the outlet ports (<NUM>, <NUM>) and the hydraulic rod seals (<NUM>) each comprise a seal ring (<NUM>) which engages the piston (<NUM>), wherein:
the distance by which the hydraulic rod seals (<NUM>) are separated is such that the piston (<NUM>) can only be engaged with a maximum of one of the hydraulic rod seals (<NUM>) at a time;
when in a first operating position the first outlet port (<NUM>) is blocked with the piston (<NUM>) being in place over one of the hydraulic rod seal (<NUM>) such that the decoking fluid may flow in from the inlet port (<NUM>) and out of the second outlet port (<NUM>) and will not flow out of the first outlet port (<NUM>) and when in another operating position the second outlet port (<NUM>) is blocked with the piston (<NUM>) being in place over one of the hydraulic rod seal (<NUM>) such that the decoking fluid may flow in from the inlet port (<NUM>) and out of the first outlet port (<NUM>) and will not flow out of the second outlet port (<NUM>); and
the piston (<NUM>) further comprising at least one drilled port (<NUM>) which equalizes the pressure of the decoking fluid across the seal ring (<NUM>) with the piston (<NUM>) in a first position where the two ends of the drilled port (<NUM>) on either side of the seal ring (<NUM>) and seals the pressure of the decoking fluid across the seal ring (<NUM>) with the piston (<NUM>) in a second position with the two ends of the drilled ports (<NUM>) entirely on one side of the seal ring (<NUM>).