US2449012A - Pipe exchanger scraper - Google Patents

Description

P 1943- T. E. SCHLEY 2,449,012

PIPE EXCHANGER SCRAPER I Filed July 19, 1945' 2 Sheets-Sheet 1 715 4: 5. Jaw/(7 INVENTOR T. E. SCHLEY PIPE EXCHANGER SCRAPER 1 Sept. 7 1948.

2 Sheets-Sheet. 2

Filed July 19, 1945 A'NVENTOR.

77mm: 5. fo /6). 2 16%; 77'0PA/E/ Patented Sept. 7, 1948 UNITED STATES PATENT- OFFICE Thomas E. Schley, Beaumont, Tex, minor to Sooony-Vacuum Oil Company, Incorporated,

New York, N. Y., a corporation of New York Application July 19, 1945, Serial No. 605,975

This invention has to do with devices for clearing deposits from the heat transfer surfaces of double pipe heat exchangers and the like. For example, in the separation of wax from petroleum fractions containing the-same, it is customary to chillthe petroleum fraction by pumping it through the interior pipe of a double pipe heat exchanger. That is to say, the pipe through which the oil is pumped is surrounded by another pipe or jacket and a cooling material such as chilled brine is pumped through annular spaces between the two pipes. The oil in the interior pipe being chilled tends to form deposits upon the inside of the wall of the pipe through which it flows. These deposits not only slow down the rate of heat exchange through the pipe wall, but also the material which is deposited is the wax which it is desired to separate from the oil and it must not be allowed to remain within the cooler. So it is customary to provide scraping devices of various kinds to remove this material from the wall of the pipe; The most usual and simplest form of scraper for this purpose is a blade of helical form carried on and rotated by a central shaft, which blade not only serves to scrape the deposit from the walls but also to some extent serves to force the material on through the cooling tube L much in the same manner as the screw in a meat grinder forces the meat toward the cutting blades. However, in most instances, the necessity for advancing the material through the exchanger by virtue of the action of the helix or scroll is not of importance and in many cases a blade carried on the'ends of the arms of a spider issufllclent.

One major difflculty arises in connection with all rigidly mounted blades particularly when the material beingchilled is cooled down. at some portion of the apparatus to a temperature below the freezing point of water. Hydrocarbon oils are capable of dissolving various amounts of water. In operation in an oil refinery, they are frequently in contact with steam or with waterand it is not uncommon for the hydrocarbon fraction being chilled to carry with it not only dissolved water but some water actually carried along inthe form of droplets. Of course, whenlan oil carrying dissolved water is cooled, the dissolved water drops out. From these two sources it will be seen that water is very frequently present in exchangers utilized for this purpose and when temperatures are lowenough, this water collects upon the interior walls of the heat exchanger in the form of ice. With rigidly mounted scraper assemblies, this ice soon give rise to physical diii'idevices for supporting the scraper blades.

3 Claim]. (01. 257-102) to turn the scrapers and in the extreme case gives The invention may be understood mostreadily by reference to the drawing attached to this speciflcation, Figure 1 of which shows a cross-section of a double pipe heat exchanger within which there is mounted a scraper designed according to the present invention. Figure 2 shows the assembled scraper mechanism in perspective. In these two figures, in which like parts where shown are similarly'numbered, i is the outer pipe of the double pipe heat exchanger and '2 is the inner pipe thereof, 3 being the space in which chilling medium flows. Mounted centrally within pipe 2 and extending axially thereof is scraper shaft l which may, if desired, be a solid shaft but is more usually a tube with appropriately inserted solid pieces at the end to carry drive mechanism, such as gears and the like, with which this invention is not concerned. Mounted upon pipe 4 at spaced intervals along the length thereof are carrier Each carrier device consists of a clevis 5 formed of two upstanding lugs. which lugs are drilled for the insertion of a pivot pin 8.

Pivotally mounted upon the pivot pin 8 between the two lugs forming each clevis 5, there is a roughly T-shaped rocker arm 1. Upon the outward side of rocker arm I, there is formed a plate supporting lug 8 to which scraper blade 8 is attached by bolt ill, the arrangement being such that when the scraper blade 8 is in contact with the interior of pipe 2, it lies in aplane roughly parallel to a line through the center of shaft 4 and the center of pivot pin 8. Rocker arm I is' extended beyond the plate supporting lug I to form a lever arm extension H, which in its normal position lies at an angle of approximately with the line joining the shaft and pivot centers.

Upon the lower side of the outer end of this lever arm there is formed a boss II for a purpose later explained. Rigidly fixed to the opposite side of ing against the fixed spring holding arm l3 serves to move rocker arm I pivotally about its mounting upon pin in clevis 5 and so urges blade 9 into contact with the interior of the pipe in which the assembly is placed. This assembly is sufficiently yieldable so that the deposits of the nature of ice and the like or irregularities in the pipe or minor springing of the shaft will not adversely affect proper contact of the blade with the pipe surface with a force sufficient to remove the yieldable deposits normally formed thereon.

- In the drawing only two blades are shown. It is to be understood that any appropriate number of blades may be used, say four blades, or three blades or six blades, the only change necessary being a proper staggering of the location of the supports for the various blades in order that they may all be carried properly by the central shaft. It is also within the spirit of this in-- ticularly'in long double pipe exchangers, it is advisable that the scraper assembly be broken up into short lengths, each complete in itself, and composed of a central shaft-with its surrounding blades, the whole to be Joined together by proper keying and mounted upon proper ,head and tail shafts which are to be supported in bushings provided at either end of the usual double pipe heat exchanger, both the head and tail shafts as is usual extending through said bushings and bearings to support the usual external drive mechanism whereby they are rotated.

Scrapers of thisconstruction have been installed and utilized under rather diillcult conditions of operation and have been found to be singularly free from build up in power requirements and breakage resulting from icing and similar causes.

I claim:

1. In a double pipe heat exchanger, an interior wall scraper comprising a shaft located centrally and extending axially of the interior pipe of said heat exchanger and a plurality of axially extending scraper blades carried thereby, mounting means for said scraper blades, each mounting means comprising a rocker arm pivotally engaged to a clevis lug mounted upon said shaft and extending to form a lever at an angle with a line drawn through the shaft center and the lug pivot center with blade-fastening means located upon said rocker arm between said pivot and the end thereof, said mounting means also comprising a rigidly fixed spring-carrying arm extending from said shaft in alignment with said lever arm, spring retaining means upon the outer end of the rocker arm, spring retaining means upon the outer end of said spring-carrying arm, and a compression spring mounted therebetween and .4 biasing the scraper blade into contact with the pipetwall by rotation of the rocker arm about its p vo 2. A wall scraper assembly for removing deposits from the interior wall of the interior pipe of double pipe heat exchangers and the like, comprising a centrally located, axially extending scraper shaft and a plurality of axially extending scraper blades carried thereby, each blade being supported by a plurality of mounting means, each mounting means comprising a clevis lug affixed to said shaft; a generally T-shaped rocker arm having one arm of the T pivotally mounted in said clevis lug with the other arm extending as a lever in a direction generally at right angles to a line drawn through the shaft center and clevis pivot center, the shank of the T extending toward the pipe wall along a line generally parallel to said center line, means for afllxing the blade to the shank of the T-shaped rocker arm, and spring retaining means upon the lever extremity of said T-shaped rocker arm; a spring supporting arm rigidly aflixed to said central shaft opposite said clevis lug and extending therefrom in alignment with the cross arm of said T-shaped rocker arm, spring retaining means upon the extremity of said spring supporting arm; and a compression spring mounted between the two said spring retaining arms acting to rotate the rocker arm about its pivot and to force the scraper blade carried thereby into engagemen with the interior pipe wall.

3. A wail scraper assembly for removing deposits from the interior wall of the interior pipe of a double pipe heat exchanger and the like, comprising a centrally located, axially extending scraper shaft and a plurality of axially extending scraper blades carried thereby, each blade being supported by a plurality of mounting means, each mounting comprising a pivot support affixed to said shaftf a generally T-shaped rocker arm having one T arm end pivotally mounted in said pivot support with the other T arm end extending as a lever in a direction generally at right angles to a line drawn through the shaft center and pivot center,- the shank of the T extending toward the pipe wall along a line generally parallel to said center line, means for aillxing the blade to the shank of the T- shaped rocker arm, and spring retaining means upon the lever extremity of said T-shaped rocker arm; a spring support afllxed to said shaft and extending therefrom in alignment with the lever extremity of said T-shaped rocker arm, spring retaining means upon the extremity of said spring support; and a compression spring mounted between the two said spring retainers and acting to rotate the rocker arm about its pivot and to force the scraper blade into engagement with the interior pipe wall.

THOMAS E. SCHLEY.

REFERENCES crrEb The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 605,668 Edison June 14, 1898 2,009,734 Hiller et al. June 30, 1935 2,183,995 Fuller June 27, 1939 2,282,298 Vogel May 5, 1942

Images