US2795560A - Preventing pipe line corrosion - Google Patents

Description

June 11, 1957 P. s. WlLLlAMS 2,795,560 1 PREVENTING PIPE LINE CORROSION Filed Dec. 51, 1952 PhilLp muiams {brave-a bar 2,795,560 PREVENTlNG PIPE LINE CORROSION Philip S. Williams, Tulsa, Okla, assignor to Esso Research and Engineering Company, a corporation of Delaware Application December 31, 1952, Serial No. 328,907

3 Claims. (Cl. 252-387) The present invention is concerned with an improved method for preventing corrosion in pipe lines through which hydrocarbon products are transported. The invention is more particularly concerned with a novel method of placing the inhibitors in the critical regions in the pipe line or at the points where it is most essential to have inhibiting substances present. In general, such areas or regions coincide with those where water accumulates. In accordance with the present invention, water soluble, oil insoluble corrosion inhibiting substances are added in the form of pellets to the fluid being transported through the pipe line. Thus, at points in the line where water tends to accumulate and where corrosion occurs, the pellets will be dissolved in the water layer and thus will materially decrease the corrosion that would otherwise occur at these points.

It is well known in the art to utilize various corrosion inhibitors as well as other means for preventing corrosion in pipe lines, storage tanks and the like. It is also known that corrosion is most likely to occur where water or moisture is present. With respect to the transportation of petroleum liquids by pipe line, a particular problem exists in that as the pipe line passes over the usual terrain low spots occur in the line. It is practically impossible to keep out of a petroleum liquid pipeline system even with refinedproducts since water will enter the system wherever there is access to the atmosphere, as in storage tanks, for example. In addition, in the case of crude oils, it is not considered practical or economic to remove all or" the water from the oil before transmitting it to the refinery. Hence, since water is usually present as a separate phase in petroleum liquids being transported through a pipeline, it will tend to settle out and accumulate in low spots and in regions of low turbulence, since Water is heavier than the petroleum liquid.

It has been observed that internal corrosion of pipe lines is worst along the bottom of the lines and in dips in the lines where water and scale particles settle. To prevent such corrosion it is desirable that a relatively high concentration of a suitable inhibitor be present at these points where water and scale particles tend to accumulate. By and large it is not practical to accomplish this result merely by adding an inhibitor in conventional liquid or powdered form to the oil in the pipeline. If conventional oil soluble inhibitors are employed they would remain in the oil phase and would not pass into the water phase. If conventional water soluble inhibitors were added to the oil they would remain dispersed in the oil phase and would enter the separated water phase only to a small extent if at all.

Thus it is an object of the present invention to provide a method for inhibiting internal corrosion in pipe lines in the areas in which water and scale particles tend to settle out. It is a further object of the invention to provide a method by which inhibitors can be introduced into a pipe line and conducted to regions where moisture tends to accumulate to thereby prevent corrosion in such regions.

In accordance with this invention these objects are ac- 2,7955% Patented June Il, 1957 lying on the surface or near the surface of non-level terrain.

Oil 3 is shown passing through the pipe line 1 together with added pellets 4. In the regions A and C, water does not tend to settle out and accumulate due to the fact that in these regions the line has either a positive or negative slope. However, in region B, constituting a natural water trap, water or moisture 2 tends to accumulate. Also in places where the velocity of the fluid stream diminishes, as for example where valves, T-connections, etc. are inserted in the line, water may also tend to settle out and accumulate. In addition, where the line is fairly level some water may settle out along the bottom of the pipe line. In any of these areas the accumulated moisture tends to accelerate corrosion.

In accordance with this invention corrosion in such areas is prevented by introducing into the pipe line pellets 4 of selected size and density so that they will settle out in the same areas as does moisture and as do scale particles. These pellets are composed of or contain corrosion inhibitors and are preferably slowly water soluble and oilinsoluble so that they will resist disintegration for an appreciable length of time until they finally settle into a region of accumulated water. Preferably also the pellets are of a range of densities and size so that while some of them will settle out at one particular point in the pipe line others will travel on to other particular settling points along thel ine. In settling out in the same areas as those in which the water accumulates these pellets will slowly dissolve in the water and thus exert the desired inhibiting action. Thus, in operation the oil insoluble pellets are swept along with the oil flow in the pipe line. However, in region B, a certain number of these pellets will settle out into the water layer and become dissolved therein, thus placing a high concentration of inhibitor in a region where severe corrosion would otherwise occur. Other pellets will pass on through the pipe line to the next region similar to region B, where water accumulates and some of those pellets will settle out there, dissolve in the water, and exert their inhibiting action. Thus by utilizing a plurality of pellets of a range of sizes and densities it will be pos sible to send pellets through a section of pipe line to reach every area where water tends to accumulate.

As mentioned, the pellets are selected from a class of corrosion-inhibiting materials that are characterized by being soluble in water and relatively insoluble in the hydrocarbon phase or oil phase. It is not essential that the pellets be completely water soluble since any insoluble components that might tend to block the pipe line as they accumulate would be removed during the conventional periodic scraper runs.

Satisfactory inhibitors that may be used include alkali metal nitrites and alkali metal chromates, e. g., sodium nitrite or sodium chromate. These inhibitors will function most satisfactorily in the absence of reducing agents such as hydrogen sulfide. Thus they would be most useful in lines handling fairly sweet crudes or petroleum products. In systems in which appreciable quantities of hydrogen sulfide are present other inhibitors are preferred. For example certain water-soluble urea-aldehyde type condensation products such as that known commercially as Uformite may be used. Other suitable inhibitors include certain quaternary ammonium salts such as a Cu; alkyl, trimethyl ammonium chloride known commercially as Arquad S.

anoqpeo 1. eases the inhibitor materia itsel ma have oi fficient plasticity under pressure to enable it to act as its own binding agent in preparing the pellets. In other cases ix iarvb odi nt ma b eqoiro hu ext ih, o o odium s ate; o an o .numer usovo t et o Wat lu le adhe i e mete e om h emp oyed as binding agents. Particularly desirable are binding agents that render the pellets slowly water soluble to exe the r usefuilife L to e i disint ra io in t velling through the pipe line. Such materials as starch, hydrated magnesium silicate, sucrose; wood hour, or other cellulosic materials may also be used as fillers or extenders to prov de P per hs t Whe h eo vie re u r er o deo i on o ide m h a e v lv he em- P ved i u obleom uot I i e ov rvdo r b t t s nh b o un e oe ta o o t hs house n oni o t n w h odi m oarbohat o o h a k m er a o s t dju the p velue 8 o 9 o h g e i n dlz The de y o th .polle m var op eo lv u i i preferred that the density. of these added pellets be greater than the density of the hydrocarbon phase and equal to or greater than the density of ,the water phase. A very desirable density i. e., specific gravity, is in the range from 1.1 to 2.0. The specific gravity of some of the pellets may actually be as high as aboutS which'is of the order of magnitude of the specific grayities of two frequently occurring corrosion products, ferrous sulfide and iron oxide. Thus some of the pellets would tend to settle out in the same areas as do scale particles.

As to the size of thepelletsthis will depend tosomeextent on the conditions in the pipe line. In general, the pellets should be no smaller. thanabout 0.05 inch in thicknesspr diameter and ingeneral theyshould not be'larger than about 0.5 ineh. It is preferred that pellets in the range of 0.1 to .25 inch beused; Preferably the charge of p l et in roduc at aovoorti s t o in the p pe line eomprise an assortment of siz es so that some of them will settle out closer to the point of introduction than r ah u e nvvi h a p ural y of e s i 8- s nt a v the am ie th r vw lzo .te oor f W11 to settle out in a given region while others are carried along through the pipeline to a secondregion.

.It is not essential that the pelletsbe spherical in shape hsphe ovoid K h? eh edre e l i fl to h carried a o mo tofiioiohflvth ou h he P eli to h e n o et n ho,P 1 .P P QK vnot he abrasive. in o r t s t t y willhot tribute appreciably to the wear of pipe line pumps.

The number of pellets to be added at any particular part of the pipe line will depend on several factors including the volume of petroleum liquid being handled, the distance between stations, and so on. The pellets can be added to the line most conveniently on the intake side of the pumps at eaeh'pnmping station along the line, either through a standpipe arrangement if there is some head on "theli alte side ot the'pump, or most simply by adding theiii to mean tank supplying the pump. The efiiciency of distribution of pellets through each section" of the line can'ibe assured by-adding "suflicient pellets at each pumping station so that a few will be carried to the receiving tank at the next' pumping station, as determined by sampling the incoming oil at that pumping station.

It is to be understood that this invention is not to be limited to the specific inhibitor compositions nor to any other specific features herein disclosed. It is intended th'at the scope Qfthis invention be limited only by the ap- Pe fQ ol m ,iyha im s:

1. An improved process for inhibiting internal corrosion in a pipe line transporting hydrocarbon fluid containing small amounts of water which comprises introducing a plurality of solid pellets containing a water soluble, oil insoluble corrosion inhibitor within the pipe line so t a .theoel i t a u d t ra e along with the fl i s Pel ets ev h de s eete thant hydrocarbon flu and e li ae as g ea a wat 'said p l a n a thickness inlt he range from about0.05 to 0.5 inch.

j V 2. A process as defined in claim 1 in which the pellets have a specific gravity in the range from 1.1 to 2 and a thickness in the range of 0.1 to 0.=25 inch.

3. Aiprooe esdefi e o i 1 in whi the .1 ra ity o pe ets ompr e ean e o t ht Pe l a n differente zo a deh i e .R fiereho C t ih the. file 9f t i P lfi UNITED STATES .PATENTS 2,351,465 Wachter June 13, 1944 2,473,455 Sorg' ..7 June '14, 1949 2,599,385 Gross et al June '3, '1952 2,636,000 R'ohrbac k et a1 Apr. 21, 1953 2,6;84332 et al. Iune'20, 1 954

Claims (1)

1. AN IMPROVED PROCESS FOR INHIBITING INTERNAL CORROSION IN A PIPE LINE TRANSPORTING HYDROCARBON FLUID CONTAINING SMALL AMOUNTS OF WATER WHICH COMPRISES INTRODUCING A PLURALITY OF SOLID PELLETS CONTAINING A WATER SOLUBLE, OIL INSOLUBLE CORROSION INHIBITOR WITHIN THE PIPE LINE SO THAT THE PELLETS ARE URGED TO TRAVEL ALONG WITH THE FLUID, SAID PELLETS HAVING A DENSITY GREATER THAN THE HYDROCARBON FLUID AND AT LEAST AS GREAT AS WATER, SAID PELLETS HAVING A THICKNESS IN THE RANGE FROM ABOUT 0.05 TO 0.5 INCH.

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