Patent Application
20070113902
1. Technical Field
The invention is related to relief valve assembly which can be equipped for use at either vessels carrying oils or chemical products, or at chemical tank.
2. Description of the Prior Art
Conventional type of relief valve (ie: U.S. Pat. No. 6,604,544/RE37,989/U.S. Pat. No. 5,060,688/U.S. Pat. No. 5,873,384), due to it's constructional limitation that lifting disc and weight are placed inside of upper body, causes low close pressure of valve, subsequently releases unnecessarily excessive amount of gas and consequently leads to the problem with environmental pollution and decrease in safety of tank and further uneconomical result.
And in case of relief valve used for vessel, a small amount of pressure gas which releases through the path between disc seat assembled with upper body and pressure disc does not release upwards to vertical direction but to sideways to a wide spread owing to the influence of wind by the characteristics of ocean circumstances and therefore can not guarantee the safety against fire and safety accidents.
Conventional type of relief valve, as it's lifting disc and standard weight are placed inside of upper body, does not allow proper release of pressure gas, therefore makes it difficult to release the gas in short time, causes hammering phenomenon and is further quite inconvenient for cleaning and repairing when relief disc and weight are contaminated owing to the volatile steam containing gas compound and high viscosity of solvent based foreign ingredients.
Moreover, while relief valve is kept sealed relief disc, weight and stem are always exposed to released gas so easy to erode and therefore call for raw materials of high erosion resistance which are expensive thus uneconomical. Additionally, conventional type of relief valve, when increasing or decreasing the weight automatically requires disassembling whole upper & lower body out of tank and then working for replacement of weight and therefore causes poor work efficiency and takes long period of work time. All these troubles are not to be overlooked in relief valve assembly construction.
Reviewing these troubles further, as mentioned earlier the reason why close pressure of conventional type of relief valve is getting down in close cycle is that lifting disc and weight are placed inside of upper body so it is quite unavoidable to see disc and weight in the state of floating unnecessarily for a long time by the pressure of releasing gas while valve being closed. In other words, as disc and weight placed inside upper body are not provided with enough atmospheric pressure so close pressure is naturally reduced and therefore valve opens for long time more than necessary. And releasing gas passing through between pressure disc and disc seat assembled with upper body, without casket-shaped housing(50) that can lead out gas upwards to vertical direction, releases to sideways to a wide spread with top part of upper body as a start point, so there arises more possibility of safety accident of workers and danger of fire.
As another inventional example, there is a relief valve that has been claimed to get rid of excessive release of pressure gas inside tank and publicized as international reference No. WO 02/095275. The detailed construction of the main parts of this is intended to fix magnet in lower part of stem with which lifting disc and weight are assembled, and also fix magnet inside of lower body and then have these upper/lower magnets get closer or contact each other. Namely, these magnets are in the state of dragging each other by magnetic force.
In such circumstances, pressure gas generated inside of tank, makes farther the gap between the magnets in the state of above-mentioned magnetic force and at the same time pushes upwards lifting disc and weight and then releases out to outside of upper body namely in the air but in the meantime magnetic force between above magnets might still be working even while pressure gas releasing out in the air. Therefore when the release pressure starts to decrease in accordance with reduction to releasing amount of pressure gas after initial release of pressure gas, lifting disc and weight are forced to move down by magnet force and pressure disc closes valve. These technical considerations might be worthwhile to suggest.
However, in reviewing further above-mentioned international publication No. WO 02/095275, it has been noticed as a problem that this additional construction is so complicated with lifting disc and weight fixed to stem, magnet of lower part of stem and magnet inside of lower body, and therefore causes increase to manufacturing cost, makes it difficult to handle due to heavy weight and also does not fit for the vessel that needs weight reduction. Therefore it's not easy for manufacturing, transporting, facilitating, and maintaining (repairing and replacing units) so quite inconvenient in workability, and furthermore causes unreasonable trouble that in replacing magnet it is necessary to separate from tank even lower body which is of heavy weight.
In addition to above, relief valve in above-mentioned international publication No. WO 02/095275 also has the same problems and defects as afore-mentioned conventional type of relief valve because it's stem, lifting disc, weight, magnet in lower part of stem, magnet inside of lower body are all inside of upper body and lower body.
The followings are with regard to the problems and defects of conventional type of vacuum relief valve.
Compared according to the
Another example of vacuum relief valve contrived to make up for these problems and defects, compared according to the
Along with this, conventional type of relief valve has the problem with difficulty of proper gas releasing due to another flow variation of releasing gas which is caused by extra weight of assist weight when adding assist weight to standard weight. Accordingly closure function of disk does not work consistently all the time when using standard weight only and when using both standard weight and assist weight as well.
In the relief valve which can be equipped for either vessels carrying oils or chemical products or for chemical tanks to safely release pressure gas (supersaturated gas) inside of tank out in the air, the invention is featured as structuring,
lower body(10) which is fixed through to tank and;
upper body(20) in which rib(22) is one-bodied with boss(23) having screw hole for assembling screw part(61) of stem(60) and with which disc seat(21) is assembled and;
lifting disc(30) which has ring(33) at lower side, protruding stage(34) contacting with disc seat(21) of upper body(20) & closing valve, the 1st hole(32) penetrated by stem(60) and the 2nd hole(31) in which stopper(62) assembled with stem(60) can move by cap nut(63) and;
weight(40) which is assembled with lifting disc(30) by bolt(80) and;
weight cover(70) which protects weight(40) and offers space inside to enable assembling assist weight(90) and;
fixable stem(60) which has screw part(61) assembled with boss(23) of upper body(20) and guides lifting disc(30) to move up and down and;
stopper(62) which is fixed to top part of stem(60) by cap nut(63) and restricts ascending distance of lifting disc(30) and;
casket-shaped housing(50) which is assembled with upper body(20) and leads releasing gas upwards out to vertical direction and;
water (sea water or rain) drain part(3) which is assembled by passing through flange(20-1) of upper body and flange(10-1) of lower body and drains water (sea water or rain) gathering inside of casket-shaped housing(50) to outside and;
vacuum relief valve(5) which is assembled with lower body(10) and functions to build up atmospheric pressure inside of tank.
And also in the relief valve which can be equipped for either vessels carrying oils or chemical products or for chemical tanks to safely release pressure gas (supersaturated gas) inside of tank out in the air, the invention is featured as structuring,
lower body(10a) which is fixed through to tank and;
upper body(20a) in which rib(22a) is one-bodied with boss(23a) having screw hole for assembling screw part(61a) of stem(60a) and with which disc seat(21a) is assembled and;
lifting disc(30a) which has protruding stage(34a) contacting with disc seat(21a) of upper body(20a) & closing valve, the 1st hole(32a) penetrated by stem(60a) and the 2nd hole(31a) in which stopper(62a) assembled with stem(60a) can move by cap nut(63a) and;
the 1st weight(40a) which is assembled with lifting disc(30a) by bolt(80a) and has in the center bushing(150) assembled with the 2nd hole(31a) of lifting disc(30a) and;
the 2nd weight(40b) which has ring(33a) at lower side and assembled with the 1st weight(40a) by bolt(80b) and;
weight cover(70a) which is assembled with the 2nd weight(40b) by weight cover bolt(110a) and;
fixable stem(60a) which has screw part(61a) assembled with boss(23a) of upper body(20a) and guides lifting disc(30a) to move up and down and;
stopper(62a) which is fixed to top part of stem(60a) by cap nut(63a) and restricts ascending distance of lifting disc(30a) and;
casket-shaped housing(50) which is assembled with upper body(20a) and leads releasing gas upwards out to vertical direction and;
water (sea water or rain) drain part(3) which is assembled by passing through flange(20-1) of upper body and flange(10-1) of lower body and drains water (sea water or rain) gathering inside of casket-shaped housing(50) to outside and;
vacuum relief valve(5) which is assembled with lower body(10) and functions to build up atmospheric pressure inside of tank.
In the relief valve assembly, casket-shaped housing is featured as being assembled with upper body(20) and flange(53) by bolts and nuts and building up small diameter part(D1) which forms narrow slot(G) with side of lifting disc(30), large diameter part(D2) which forms wide slot(G1) with side of lifting disc(30) when lifting disc(30) moves up and incline part(52) which is formed in the connection area between large diameter part(D2) and small diameter part(D1).
In the relief valve assembly, another casket-shaped housing is featured as being assembled with upper body(20a) and flange(53a) by bolts and nuts and building up small diameter part(D1) which forms narrow slot(G) with side of the 2nd weight(40b), large diameter part(D2) which forms wide slot(G1) with side of the 2nd weight(40b) when the 2nd weight(40b) moves up and incline part(52) which is formed in the connection area between large diameter part(D2) and small diameter part(D1).
In the relief valve assembly, outside diameter of lifting disc(30) is featured as being larger than outside diameter of disc seat(21).
In the relief valve assembly, outside diameters of lifting disc(30a) & the 1st weight(40a) are featured as being larger than outside diameter of disc seat(21a) and smaller than outside diameter of the 2nd weight(40b).
In the relief valve assembly, water (sea water or rain) drain part(3) is featured as structuring,
vertical elbow(200) which forms screw(201) assembled through screw hole(20-2) in the flange(20-1) of upper body(20) screw hole(203) at the opposite side of screw(201) and;
horizontal elbow(300) which forms screw(303) assembled with screw hole(203) of vertical elbow(200),
gas releasing slot(302) upwards vertically and sea water or rain drain slot(301) downwards vertically.
In the relief valve assembly, another water (sea water or rain) drain part(3) is featured as structuring,
inner part which is penetrated by hole(401), body(400) which is shaped “J”, head part(404) which is fixed through the holes(20-3)(10-3) of upper body and lower body, tail part(405) which is at the opposite side of head part(404) and faces upwards vertically, gas releasing slot(402) which is formed inside of tail part(405) and sea water or rain drain slot(403) which is formed at the bottom of body(400).
In the relief valve assembly, Vacuum relief valve(5) is featured as structuring stem support(610) which is assembled through the hole(603) of lower part of body(600), the upper part of which is assembled with ring seat(620) contacting with closure disc(630) and which has rib(611) & boss(612) and;
bushing(640) which is assembled with boss(612) of stem support(610) and supports stem(660) assembled with closure disc(630) and;
screen cover(670) which is assembled with the lower part of stem support(610) and;
screen(690) which is assembled with screen cover(670) and screen hood(680) which is placed under screen(690) and has air hole(681) in the center and;
snap ring(650, 651) which is assembled with bushing(640) penetrating the center of screen(690) and prevents screen(690) from moving up and down.
The followings are to describe the composition and operating mechanism of the invention with reference to the drawings attached.
In relief valve of the present invention, as described earlier, lifting disc(30)(30a), weight(40), the 1st weight(40a) and the 2nd weight(40b) are not placed inside of upper body(20)(20a) or lower body(10)(10a). These are placed in the air upside of upper body(20)(20a) as illustrated in the drawings. Casket-shaped housing(50)(50a) is formed to guide releasing gas to flow upwards vertically. Water (sea water or rain) drain part(3) is newly formed and vacuum relief valve(5) of new construction is also formed. All the parts herein are featured as being of new construction.
Also in relief valve of the present invention, it is so easy to replace or repair the main parts inside of casket-shaped housing(50)(50a) without separating upper body(20)(20a) out of lower body(10)(10a). Therefore relief valve of the invention is easy to manufacture and maintain & repair. And with it's simple construction, it is light weighed and so easy to handle and accordingly pretty suitable for relief valve of tank in land and vessel as well.
So to speak, relief valve of the invention represents a great deal of constructional difference from conventional type of relief valve (ie: U.S. Pat. No. 6,604,544/RE37,989/U.S. Pat. No. 5,060,688, U.S. Pat. No. 5,873,384) and relief valve made by the technique from international publication No. WO 02/095275 and therefore it can resolve the problems and defects deriving from conventional type of relief valve.
Firstly, in the 1st performance lower body(10) is featured as having vacancy inside without any parts assembled as shown in the drawing and being so easy to manufacture and light weighed. Especially it does not need any parts obstructing release of gas and therefore enables itself releasing gas to pass through much properly.
Nextly, inside of upper body(20) which is assembled with lower body(10) by bolts and nuts, boss(23) is formed and united into one body with upper body(20) by rib(22). As there is hole in the boss(23), screw part(61) of stem(60) can be simply assembled through screw hole of boss(23). Therefore stem(60) of the invention, differently from conventional type of relief valve, does not move up and down together with weight, lifting disc and pressure valve at the same time but is rather fixed to upper body(20) and shows no movement.
Disc seat(21) is assembled with upper body(20) and disc seat(21) contacts with protruding stage(34) of lifting disc(30). Lifting disc(30) forms the 1st hole(32) in the center area and lets stem(60) pass through. Providing that stem(60) fixed to boss(23) is piston, lifting disc(30) can be called as a cylinder moving up and down. So only lifting disc(30) and weight(40) ascends together and releases gas out while stem(60) is in fixed position. In further detailed review for the construction of lifting disc(30), the 2nd hole(31) and the 1st hole are formed and ring-shaped stopper(62) which is fixed by cap nut(63) is inside of the 2nd hole(31). Therefore ascending distance of lifting disc(30) is restricted by stopper(62). In this case, stopper(62) can be assembled with the top of stem(60) by snap ring instead of cap nut(63). And as for the raw materials for stopper(60) it might be available to adopt metals, nonferrous metals, plastic or synthetic resins and so on.
And further, lifting disc(30) has ring(33) as shown in the drawing, and this ring can be fixed by welding or united into one body with lifting disc(30). The ring(33) make it easier for lifting disc(30) to ascend by releasing gas passing through the gap between disc seat(21) and protruding stage(34) of lifting disc(30). But in some case ring(33) can also be out of adoption.
Nextly, lifting disc(30) is assembled with weight(40) by bolt(80). When the weight of weight(40) needs to be added, it is simply required to keep upper body(20) and lower body(10) as is, unfasten weight cover fixing bolt(110), separate weight cover(70) from weight(40), place assist weight(90) on weight(40), and assemble again weight cover(70) with weight cover fixing bolt(110). But in case of conventional type of relief valve, it is required to separate upper body and lower body from tank, replace weight or assemble assist weight and then assemble again upper body and lower body with tank. Therefore it causes poor work efficiency and inconveniences and costs much time. However the invention is, needless to be compared with conventional type of relief valve, far convenient, safe and makes it possible to finish the work in short time in adding weight.
Next part is with regard to casket-shaped housing(50) which is another main part of the invention. This is almost same as casket-shaped housing(50a) which will be described later according to the 2nd performance.
Casket-shaped housing(50) represents the shape of casket which is relatively thin. It forms large diameter part(D2) and small diameter part(D1) and incline part(52) in the connection area between small diameter part(D1) and large diameter part(D2). This casket-shaped housing(50) is assembled with upper body(20) and fixed with flange(53) by bolts and nuts. It is quite natural to manufacture inside diameter of small diameter part(D1) of casket-shaped housing(50) larger than inside diameter of disc seat(21).
In the 1st performance of the invention, valve remains closed as shown in
One thing to be carefully reviewed here is that casket-shaped housing(50) of the invention is exposed to the air and lifting disc(30) and weight(40) are also exposed to the air inside of casket-shaped housing. In other words, differently from conventional type of relief valve, lifting disc(30) and weight(40) are not placed inside of upper body(20). Accordingly it must not be overlooked as an important fact that atmospheric pressure is well maintained all the time in lifting disc(30) and weight(40) of the invention.
Supersaturated gas swiftly releases in the air and the time collapses then the releasing pressure of gas is reduce. Accordingly lifting disc(30) and weight(40) starts descending slowly. By this time lifting disc(30) and weight(40) descends smoothly and swiftly to close valve on account of atmospheric pressure. So to speak lifting disc(30) and weight(40) are not placed inside of upper body(20) and therefore not influenced by the pressure of releasing gas at last stage and closed swiftly. The reason for this is that atmospheric pressure works well along with the weight of the parts together with the weight of lifting disc(30) and weight(40). Therefore it is available to close valve swiftly without excessive release of gas.
The next refers to the 2nd performance of the invention. It shows little difference in operation from the 1st performance but represents slight difference to be reviewed in construction. In other words, upper body(20) in the 1st performance & upper body(20a) in the 2nd performance and disc seat(21) in the 1st performance & disc seat(21a) in the 2nd performance represent all the same constructions. And lifting disc(30) in the 1st performance has almost same construction as lifting disc(30a) in the 2nd performance.
A slight difference noticeable is that stopper(62) in the 1st performance is place inside of the 2nd hole(31) of lifting disc(30) but stopper(62a) in the 2nd performance is placed inside of bushing(150) of the 1st weight(40a). In addition to above-mentioned, the 1st performance adopts one weight(40) but the 2nd performance adopts two weights namely the 2nd weight(40b) and the 1st weight(40a). Of course, the weight of weight(40) in the 1st performance equals to the total weight of two weights namely the 2nd weight(40b) and the 1st weight(40a) in the 2nd performance.
Further slight difference in placement is that in the 1st performance ring(33) is in lifting disc(30) but in the 2nd performance ring(33a) is in the 2nd weight(40b). The reason for this difference is that in the 1st performance outside diameter of lifting disc(30) is larger than outside diameter of disc seat(21) so it is better to fix ring(33) in lifting disc(30) however in the 2nd performance outside diameters of lifting disc(30a) and the 1st weight(40a) are a little larger than outside diameter of disc seat(21a) and outside diameter of the 2nd weight(40b) is larger than outside diameter of disc seat(21a). And therefore it is better to fix ring(33a) in the 2nd weight(40b).
And in the 2nd performance, it needs to be further noted that bushing(150) assembled inside of the 1st weight(40a) can be removed when necessary.
Further, casket-shaped housing(50a) used in the 2nd performance is assembled with the top part of upper body(20a) and flange(53a) by bolts and nuts and has small diameter part(D1) forming narrow slot(G) with side of the 2nd weight(40b) and large diameter part(D2) forming wide slot(G1) with side of the 2nd weight(40b).
In conclusion, the function of casket-shaped housing(50a) in the 2nd performance is almost same as that of casket-shaped housing(50) in the 1st performance and accordingly might be quite easy to understand without another explanation.
As illustrated, relief valve in the 1st & 2nd performances of the invention does not open valve for longer time than necessary because close pressure increases in close cycle. According to a test of the invention it has been found that the ascending ratio of close pressure in close cycle increases by about 30˜40% against conventional type of relief valve.
As another reference, in the 1st performance packing(100) can be assembled in a lower face of weight(40). It can also be replaced with O-ring. Packing(100) might be safe in using because it prevents the gas inside of tank from leaking out of relief valve. However relief valve is manufactured so precisely that it does not necessarily call for packing(100).
As is the same case, packing(100a) can also be removed in the 2nd performance.I
Differently from conventional type of relief valve, lifting disc(30)(30a), weight(40), the 1st & 2nd weight(40a)(40b) of the invention are not placed inside of upper body(20)(20a). And these are little exposed to releasing gas in a state of closure of relief valve so do not cause erosion. Accordingly these do not have to use expensive raw material of high erosion resistance and were therefore found very economical. Additionally in a test a good result has been noticed that casket-shaped housing(50)(50a) enables releasing gas to move upwards vertically and safely pass out in the air and therefore almost eliminate the possibility of danger of fire or safety accident.
Consequently out of overall review, it has come to the conclusion that relief valve in the 1st & 2nd performances of the invention never falls in function behind relief valve made by the technique from international publication No. WO 02/095275 mentioned earlier, is much cheaper in manufacturing, simple in construction, light weighed, excellent in maintenance and repairing and safety.
Next to be reviewed is water (sea water or rain) drain part(3) of the invention.
Water (sea water or rain) drain part(3) of the invention can be adopted not only for relief valve of the invention but also for conventional type of relief valve. Namely it must be provided that conventional type of relief valve adopts casket-shaped housing(50)(50a) same as or similar to the present invention.
As illustrated earlier, relief valve of the invention represents various features and merits against conventional type of relief valve. But on the other hand, when sea water or rain gathers inside of casket-shaped housing(50)(50a) it gets concentrated and interrupts ascending & descending operation of lifting disc. Along with this it puts a bad effect on the proper releasing of gas. And it further makes parts such as lifting disc, weight, upper body as well as casket-shaped housing(50)(50a) apt to be eroded.
According to this water (sea water or rain) drain part(3) of the invention, as explained above-mentioned, has been contrived to resolve out the problems previously pointed out by draining all the time sea water or rain gathering inside of casket-shaped housing(50)(50a) outwards properly.
The following is to review more details.
Accordingly, sea water or rain gathering inside of casket-shaped housing(50) passes through the screw hole(20-2) in the flange(20-1) of upper body(20) and enters inside of hole(202) of vertical elbow(200). And then screw(303) of horizontal elbow(300) is assembled through screw hole(203) of vertical elbow(200). In this case it is much better to assemble gas releasing slot(302) upwards vertically without fail. Additionally it is better to place drain slot(301) for sea water or rain at the opposite side of gas releasing slot(302) and downwards.
According to above-mentioned, once vertical elbow(200) and horizontal elbow(300) are assembled, sea water or rain entering inside of hole(202) of vertical elbow(200) runs through hole(304) of horizontal elbow(300) and passes out downwards through sea water or rain drain slot(301). And large amount of sea water or rain more than the amount which can be released through sea water or rain drain slot(301) can also overflow through gas releasing path(302) downwards.
By the way, here comes needs to explain the reason for forming gas releasing slot(302) in horizontal elbow(300).
As indicated in the drawing, in the flange(20-1) of upper body(20) there is screw hole(20-2) in order to drain out sea water or rain gathering inside of casket-shaped housing(50) and assemble vertical elbow(200). Therefore when supersaturated gas inside tank releases out in the air forcing up lifting disc(60), part of releasing gas enters screw hole(20-2) of upper body(20). Accordingly, part of releasing gas releases out through screw hole(20-2), hole(202) of vertical elbow(200) and hole(304) of horizontal elbow(300). Therefore, horizontal elbow(300) necessarily requires forming gas releasing slot(302) upwards vertically to ensure the safety of workers and reduce the danger of fire. In this case, the diameter of gas releasing slot(302) is larger than that of sea water or rain drain slot(301) and therefore the gas does not release through drain slot(301) for sea water or rain. As for this reason, when the gas releases through releasing gas slot(302) buoyant pressure is imposed to sea water or rain drain slot(301).
Nextly to be reviewed is the 2nd performance as shown in
The 2nd performance inserts head part(404) inside of hole(10-2)(10-3) of same center point which penetrates flange(20-1)(10-1) of upper body and lower body and fix by welding.
In further review on
This 2nd performance, as 1-piece type, has structural difference from the 1st performance which is 2-piece type but shows the same function. Therefore the detailed explanation on the function may be referred to the 1st performance illustrated earlier.
Water (sea water or rain) drain slot(3) of the invention is assembled with relief valve which has casket-shaped housing(50)(50a). Therefore it release all the time sea water or rain gathering inside of casket-shaped housing(50)(50a) before concentrating and interrupting the ascending & descending operation of lifting disc. And it also safely releases part of supersaturated gas flowing back downwards inside of casket-shaped housing upwards vertically only when supersaturated gas inside of tank releases through relief valve.
The next refers to vacuum relief valve(5) in
In
And further, fixing method of screen(690) is brand-new and simple as well. And the problems with the weight imposed on screen(690) and the upwards & downwards movement of screen(690) have been resolved. Along with this screen cover(670) and screen hood(680) are made out of thin iron plate and accordingly very light weighed, inexpensive in manufacturing cost. Therefore it is convenient for assembling with body(600) and easy for maintenance & repairing. Of course a reduction in the size of body(600) is featured as being easy for manufacturing, maintenance & repairing and reducing the cost.
In other words, vacuum relief valve of the invention, compared with conventional type of vacuum relief valve, gets lighter and smaller, has reduced number of parts & offers simple construction. Therefore it offers conveniencies in manufacturing and makes it easier to assemble, transport, maintain & repair. It also provides competitive price, especially even with a long term of operation screen(690) does not droop or move downwards and therefore durability of screen(690) greatly increases.
In reviewing more details, the invention has adopted the method that screen cover(670) and screen hood(680) made out of press process are manufactured separately from body(600) and assembled with body(600) by bolts and nuts.
At the bottom area of body(600) there is hole(603) which allows the air outside of tank to enter inside of tank. Stem support(610) is assembled with this hole(603) as shown in the drawing. In this case, it is quite natural to assemble stem support(610) with ring seat(620) which contacts with close disc(630). But in some case it is also available to eliminate ring seat(620) and use stem support(610) instead. In other words, ring seat(620) can be united into one piece with stem support(610). In addition, boss(612) is formed in the center of rib(611) in stem support(610). Bushing(640) penetrates inside of above-mentioned boss(612). Bushing(640) has hooking tier(641) and hooking tier(641) is hooked with a upper face of boss(612) when assembled with boss(612) and can therefore eliminates the problem with drooping downwards.
Nextly, a lower face of bushing(640) penetrates the center of screen(690). Therefore it is required to form in the center of screen(690) the hole which has a little larger diameter than outside diameter of bushing(640). Further to this, round fan-shaped screen cover(670) is placed at a lower face of afore-mentioned stem support(610). For this, screen cover(670) & stem support(610) are fixed at a lower face of body(600) by bolt(607).
Following the above-mentioned, one snap ring(650) is assembled with a upper face of bushing(640). And screen(690) is inserted to assemble with bushing(640) then another snap ring(651) is assembled with a lower face of bushing(640). Therefore the position of screen(690) can be firmly fixed on bushing(640) as shown in
What is then followed is to insert stem(660) to penetrate the center of bushing(640) and also assemble stem(660) and close disc(630) by screw(661) of stem(660). Of course it is common technique to assemble cover(605) on a upper face of body(600).
The invention with above-mentioned construction assembles screen(690) using bushing(640) with long length and two snap rings(650, 651) so does not impose any over weight on screen(690). By stably fixing screen(690) like this way screen(690) never droops downwards even with long term of operation. Along with this screen(690) does not move up and down so the durability naturally improves a lot. And bushing(640) with long length plays a guiding role to lead stem(660) to properly move up and down without trembling sideways and therefore keeps screen(690) from being exposed to excessive force and enables precise operation of close disc(630).
The invention reviewed as above does not place lifting disc and weight inside of upper body or lower body but rather has these exposed in the air to make atmospheric pressure act properly. And by adopting simple construction it makes it available to release out releasing gas swiftly and smoothly. And by increasing close pressure in close cycle it makes it also available to keep valve from being opened for longer time than necessary and prevents excessive release of gas. Therefore it offers benefits of the safety of tank and economical advantages as well.
And more the invention, when using assist weight additionally, makes it available to keep assist weight covered safe inside weight cover. And therefore the invention, differently from conventional type of relief valve, does not allow any flow variation by releasing gas regardless of number of weight used.
And also by adopting the construction of casket-shaped housing, the invention allows releasing gas to move upwards vertically in the air and accordingly makes it available to protect workers and keep away from the fire. Additionally the invention basically does not allow lifting disc and weight to take a position inside of upper body or lower body. Therefore when valve is in a state of closure, lifting disc and stem are little eroded owing to gas or high viscosity of solvent based foreign ingredients. Accordingly it makes it available to use normal type of metal instead of high-priced raw material and accordingly improves economical efficiency further.
Along with this, the invention makes it possible to simply disassemble and replace main parts without separating upper body from lower body and therefore guarantees excellent properties in maintenance and repair and more convenient cleaning work for parts.
And also, drain part(3) of the invention makes it available to drain all the time sea water or rain gathering inside of casket-shaped housing before concentrating and interrupting ascending & descending of lifting disc.
Vacuum relief valve of the invention is simple in construction, so easy to manufacture, maintain and light weighed therefore much suitable for relief valve of storing tank including vessel for oil or chemical product. And because of light weight & simplified construction it is convenient not only in assembling but also in cleaning and therefore much economical. It can also fix screen stably by using bushing and snap ring and therefore remove the problems with drooping and up & down movement of screen. And also it enables stem to properly move up and down without trembling and accordingly improves durability of screen a great deal.
