Method And Means To Operate Pumping System

Abstract

Hot and cold liquid molten congealable hydrocarbons are mixed and otherwise prepared for pumping by a conduit and pump system for pumping such liquids (e.g., hot asphalt). The system is cleaned by reversing the direction of the asphalt pump to thereby pass air reversely through the pump and the lines handling the asphalt, returning the asphalt to the place from whence it has been withdrawn. Air is pumped through the system prior to asphalt pumping to mix the hot and cold asphalt.

Description

BACKGROUND AND SUMMARY OF INVENTION

This invention relates to improvements in the method and means for handling liquid molten congealable hydrocarbons. One aspect relates to mixing. In one aspect it relates to cleaning pumping systems that handle hot liquids that congeal or solidify at ambient temperatures. A specific aspect of the invention relates to improvements in storing, pumping and cleaning a hot liquid asphalt pumping system by passing air reversely through it using the asphalt pump as an air compressor to accomplish this, in connection with which the invention will be described.

Asphalt at ambient temperatures is a solid material. It can be worked at temperatures from about 350.degree. F., or higher, depending on what kind of asphalt or tar is being handled. For example, roofing asphalt becomes liquid at about 350.degree. F. Similarly they each solidify at temperatures at or below those temperatures. Thus, in applying such materials on construction sites and while using them it is necessary to liquefy them and maintain them liquid which is done by the application of heat. It is also necessary to take precaution against the asphalt hardening in pipelines and the like by reason of getting too cool. One way of doing this is to empty the pipelines (normally by draining them onto the ground) as soon as the particular job or item of work is finished, thereby giving the asphalt no opportunity for cooling to the point where it congeals.

In fact, the difficulties and inconveniences of liquefying asphalt and other like materials once they have hardened in a reservoir, pipeline, or the like is so great that it is customary to apply heat to them for extended periods of time while in storage merely to keep them liquid.

Asphalt is kept molten or liquid during storage by applying heat. This is commonly done with a fire tube (or equivalent heating means) that extends into the storage vessel that holds the asphalt. The storage vessels with which I am concerned are normally mobile being mounted on trucks or trailers and are generally quite large (e.g., from about 6 ft. to about 9 ft. in their vertical dimension) hence a significant thermal gradient (e.g., at least 20.degree. F. in a 51/2 ft. diameter tank of the sort in the drawing or an amount sufficient to cause vigorous and readily visible thermosyphonic action upon applying heat through the fire tube) is established within the asphalt in the vessel. The portion of the asphalt below the fire tube thus is colder, even though molten, than that above the fire tube. The practice has been to draw asphalt from a level with or above the fire tube because the asphalt is hotter, less viscous, flows more readily, is less likely to congeal in cold lines or in temporary small job-site vessels, and because it is cleaner than if drawn from the cold body of asphalt below the fire tube. Experience has shown that debris of various particles settle into the aforesaid colder asphalt below the fire tube. These particles (debris) can be bits of minerals, coke, high melting particles, dirt, and a variety of unanalyzed bodies. Over a period of time the colder asphalt accumulates enough of this debris to make it troublesome to pump and otherwise undesirable to use and necessitates cleaning the storage vessel. Prior art cleaning intervals have been as often as every six months on truck mounted tanks.

The present invention resolves many of these problems because it provides means to agitate and mix the colder asphalt with the hotter material above it. This is done by providing a conduit that extends well below the fire tube to almost the bottom of the storage vessel and providing a reversible pump that is selectively operated to force air through this conduit in a quantity sufficient to agitate the colder material and/or to lower its density by bubble entrainment therein. This action mixes the colder and hotter portions of asphalt and disperses the debris (solid particles, etc.) throughout. Upon completion of the mixing the pump is reversed (preferably by driving it in its normal pumping direction, i.e., forward) thus drawing the freshly mixed asphalt from the bottom of the storage tank and dispensing it for use on such tanks as roofing, highway or road surfacing and repair, and the like. Advantages realized include use of the full volume of the storage vessel, withdrawal of the debris in dispersed form, reduction or elimination of downtime for cleaning the tank, and of course elimination of need for cleaning the tank.

The present invention is also concerned with cleaning out liquid asphalt from a pumping system, including the pump and the pipelines connected between it and the storage tank, so that asphalt will not have a chance to congeal or harden therein. Simply stated, this involves reversing the direction of the asphalt pump in such a way as to pump air as aforesaid through the pump, through the flow paths connected between the pump and the asphalt tank, and into the asphalt tank. This has the advantage of saving some asphalt by returning it reversely through the pipeline or other conduit in which it has been traveling and eliminates the well-known prior art practice of opening a valve and letting the asphalt run out on the ground where it is wasted.

Other objects, advantages and features of the invention will be appreciated from a reading of the following specification and claims in conjunction with the drawing wherein:

FIG. 1 schematically represents an asphalt storage, pumping, mixing and cleaning system, according to the present invention suitable for roofing asphalt it being understood that such system may be mobile, i.e., mounted on a truck or trailer;

FIG. 2 schematically illustrates a preferred form of gear pump; and

FIG. 3 schematically illustrates one assembled system for piping, pumping, control, and power supply.

A body of molten asphalt 1 is stored in an insulated storage tank comprising the inner holding tank 2, an outer jacket in the form of a lightweight tank 3 and a layer of suitable insulation 4 between the two tanks. The construction details of the tanks are well-known and inasmuch as they comprise no part of the present invention, are not further described. The tank may be mounted on a suitable vehicle 5 such as a trailer, a truck, or it may be mounted on a frame and be stationary at a work site.

The asphalt 1 is kept hot from the heat it receives from fire tube 7 which preferably is of the return tube type. Fuel gases from propane tank 8 and valve 9 are burned by the burning apparatus 10 and delivered into the lower end of the fire tube 7 which is U-shaped, and are thereafter vented to the atmosphere in a suitable fashion.

Propane tank 8 is connected by manifolding 11 to the burner valve and burner 9, 10. The propane tank 8 also preferably serves as a fuel source for the prime mover engine 41.

At the time the system is to be cleaned, some asphalt has been dispensed, hence asphalt seldom fills the tank 2 completely, there is ordinarily an air space 12 above the asphalt. Since the air in space 12 is in direct contact with the asphalt, it is approximately the same temperature as the asphalt.

During normal pumping or dispensing, asphalt is withdrawn from adjacent the bottom of the storage tank 2 by means of a flow path that includes vertically extending dip tube 14 which preferably goes to about one to two inches from the bottom of tank 2. The conduit 14 is part of the suction system for an asphalt pump 15. The rest of the flow path or tank to pump connection system comprises a horizontal line 16, a further vertical line 17 and tees 18, 19 and 20 inter-connecting the same. Tees are preferred in lieu of elbows so that gases can be vented and lines can be opened up and inspected or cleaned out. Thus the flow path from adjacent the bottom of tank 2 to the inlet or suction side of pump 15 comprises vertically upward through dip tube 14, the tee 18, horizontal line 16, the tee 19, then downwardly through pipeline 17 and tee 20 directly into the pump. The tee 19 could as easily be an elbow except that it is desired as good design practice to have a pipe plug 23, which is removable, available as a means for inspecting the vertical line 17 and cleaning same should it become coked up, plugged or the like.

A valve 22 functions as a vacuum breaker valve to avoid syphoning out the tank. Valve 22 is opened after pumping, mixing, and pipe cleaning are completed. Valve 22 is closed during pumping, mixing and cleaning operations. In case of pump failure or breakdown, the flow path from tube 16 through 17 and 20 can be drained by opening valves 22 and 24. Valve 22 is optional in my system.

The drain valve 24 is part of the well-known prior art apparatus and in the past has been used to drain the pipelines 16, 17 and the pump 15 so that asphalt would not have a chance to harden therein. While my invention prefers a system constructed with the valve 24 as a guard against emergencies, the benefits derived from using my present invention include not having to drain asphalt through the valve 24 and waste it by letting it run out on the ground.

In ordinary operation asphalt is withdrawn from adjacent the bottom of the tank 2 by means of the heretofore described pump suction line and delivered by the pump 15 through its discharge line 30. I have illustrated a system suitable for supplying roofing asphalt which ordinarily means that the tank 2 and its associated apparatus is located on a truck or trailer on the ground and the asphalt must be pumped up through line 30 one, two or more stories to a temporary storage vessel such as barrel 31 from whence it is applied to roofing felt and the like. Valve 32 is preferably a lever opening gate valve that is closed when pumping into the barrel 31. A rope or cable 32A may extend from the lever to either the roof or the ground to facilitate operating valve 32. Valve 32 is opened to stop asphalt going to the roof by pumping the asphalt through the return path comprising horizontal conduit or pipe 33, elbow 34 and vertical return pipe 35 into the air space 12 through which it falls back into the body of liquid asphalt 1.

Conduit 35 is a pipe which terminates adjacent the top of storage tank 2. The bottom part of vertical pipe 35 does not depend down into the body of asphalt but instead is in communication with the air space 12.

The pump 15 is preferably a reversible gear pump. It is driven through a reversible gear drive transmission 40 (RGT) which in turn receives power from a suitable motor 41 by means of a clutch 42. The gear transmission has multiple forward speeds and one reverse speed. The motor 41 is preferably a four-cycle gasoline engine adapted to run on propane from tank 8 although it may be any suitable internal combustion, electrical, or other sort of drive means. Fuel is preferably supplied to motor 41 from propane tank 8 via fuel line 11. Similarly, the clutch 42 is a suitably selected part of power transmission equipment and may include, in combination with the engine and the reversible gear transmission (RGT) a torque converter, automatic transmission of the sort so commonly found in automobiles, or the like.

The important thing is that the power drive means 40, 41, 42 can be reversed in such a manner as to reverse the direction that gear pump 15 turns. It is also essential that gear pump 15, or more broadly the pumping means, be reversible, able to pump gas in the reverse direction, and able to pump liquid in the forward direction. The drive means 40, 41, 42 are all commercially available as is the gear pump 15.

FIG. 2 schematically shows a preferred form of reversible gear pump 15 installed in the flow path to receive asphalt from a suction line that includes the vertical flow portion dip tube 14 and conduits 16, 17 plus the fittings 18, 19, 20 and to discharge through conduit 30. FIG. 2 also shows how the piping can be simplified from the schematic of FIG. 1 if the pump has a discharge at right angles to its suction. Arrows in FIGS. 1 and 2 show the direction of operation and flow for liquid, here, asphalt. When air is pumped reversely as in mixing and conduit cleaning the air and pump parts move in the opposite directions.

Pump 15 is preferably a Viking Pump series 124 or 4124 with either mechanical or packed seals. The pump has a housing 51 with inlet and outlet connections 52 and 53, a rotor gear 54 within the housing which rotor is driven by motor 41, a stator or vane 55, and an idler or pinion gear 56 that is driven by the rotor 54.

My invention comprises the method of mixing asphalt in the tank and of cleaning the hot molten liquid asphalt out of the pumping circuit which primarily comprises the delivery or pump suction lines 14, 16 and 17. This is done by opening valve 32 and -- by manipulating the clutch 42 and reversible drive 40 -- putting the pump in reverse so that fluid passing therethrough goes in a direction opposite to that indicated by the arrows in the drawing. The valve 32 may be either open or closed during air pumping depending on whether the operator wants to use hot air from within the air space 12 (open 32) or is amenable to using a mixture of same with whatever air is drawn in reversely from the open end of conduit 30.

Anyhow, with the pump running in reverse and valve 32 open air is moved through the pump, reversely back up through line 17 and through line 16 then down through line 14, pushing asphalt ahead of it to the reservoir 2. By moving air through such lines for a sufficient length of time, almost all of the asphalt can be removed from the lines thus assuring that it will not be able to congeal therein and plug them up thus creating a problem when the system has started up again. Such asphalt as may coat the pipelines or the pump very slightly will be removed in very short order when the system is started up to pump hot asphalt again because the hot asphalt then will melt readily any such thin coating and carry it on through the system. Any back-syphon action is prevented by the air trap formed when horizontal pipe 16 is blown clear of asphalt.

The same things are done to prepare to pump asphalt, e.g., when coating a roof, valve 32 is optionally (preferably) opened and valves 22 and 24 are closed, the engine 41 is started and the gear transmission 40 is shifted to the reverse (i.e., the air pumping) speed, the clutch 42 is engaged, and the pump 15 is therefore caused to act as an air compressor to draw air in through conduits 30 and 33 and their inter-connecting fittings 18, 19, 20 and direct it through the conduits 17, 16, 14 and their connecting fittings (e.g., tees 18, 19, 20) to where it emerges from the lower end 60 of conduit 14 into the colder portion 61 of the asphalt 1 (below the fire tube 7). The burner 10 is meanwhile operating to send hot gases through the fire tube 7 and continues to do so. The pump 15 is driven for a time sufficient to agitate and mix the colder asphalt and hot asphalt. In a tank 2 of 64 inch diameter X 72 inches long (nominally 1000 gallons) this operating time is about 10 minutes minimum when running at 550 rpm a pump capable of delivering 35 gpm at 400 rpm. My preferred speeds at 550 rpm with the Viking gear pump of FIG. 2 are about 550 rpm for air pumping and 2200 rpm for asphalt pumping.

Preferably the steps in the preceding paragraph are carried out immediately before asphalt is to be pumped and dispensed. When the asphalt mixing step has thus been completed valve 32 is closed (valves 22, 24 remain closed during all normal operations), the clutch is disengaged, the gear transmission is shifted to the appropriate forward speed and the clutch is re-engaged whereupon asphalt is drawn into the lower end 60 of conduit 14, thence vertically upward and on to the intake of pump 15, and then discharged from the pump through conduit 30, to a place of use shown in FIG. 1.

As already noted the above steps are conducted in reverse sequence (i.e., asphalt is first pumped then air is compressed) to remove asphalt from the conduits 30, 17, 16, 14. Air is pumped as the final step, as aforesaid, to do this. The engine is then shut off. The burner 10 or other heating means is operated continuously through this procedure and thereafter if any asphalt remains in the tank.

While my invention has been described in connection with the handling of hot asphalt especially in roofing asphalt systems, it is to be understood that it is equally applicable to other systems for handling liquid congealable materials such as liquid molten congealable hydrocarbons including those selected from the group consisting of road asphalt, tar, paraffin, pitch, and so forth.

It has been known to use a reversible pump to clean concrete or cement out of concrete lines. See U.S. Pat. No. 3,572,652.

Claims

I claim as my invention:

1. A process of storing and pumping liquid congealable hydrocarbon comprising the steps of

providing a storage vessel, a reversible pumping means, and a flow path between the bottom of the vessel and the pumping means,

applying heat to the body of hydrocarbon in said vessel in a quantity at least sufficient to maintain said hydrocarbon liquid,

first operating the pumping means in the reverse pump direction to draw air through the pumping means and deliver it into the body of liquid hydrocarbon adjacent the bottom of the vessel for a time sufficient to mix said liquid hydrocarbon, and

thereafter operating the pumping means in the opposite direction to draw liquid hydrocarbon from adjacent the body of the vessel and into the pumping means.

2. The process of claim 1 wherein said step of first operating said pumping means further comprises drawing at least part of the air from the air space above said body of liquid hydrocarbon within said vessel.

3. The process of claim 1 further comprising the step of again operating said pumping means in said reverse pump direction after the last said step of operating whereby the hydrocarbon in sequence is mixed, pumped and dispensed, and the flow path for same is cleaned.