CA1074093A

CA1074093A - Rock drill lubricants with low mist properties

Info

Publication number: CA1074093A
Application number: CA268,908A
Authority: CA
Inventors: William E. Jordan (Jr.); Fred T. Crookshank; Gayle P. Hebert
Original assignee: Texaco Development Corp
Current assignee: Texaco Development Corp
Priority date: 1976-01-12
Filing date: 1976-12-30
Publication date: 1980-03-25
Also published as: DE2657268A1; GB1538524A; JPS5287404A

Abstract

ROCK DRILL LUBRICANTS WITH LOW MIST PROPERTIES
(D#73,816-1-F) ABSTRACT OF THE DISCLOSURE
Stray fog from rock drill lubricants can be substantially reduced by incorporating into said rock drill lubricants minor portions of an amorphous ethylene-propylene copolymer.

Description

~074C~93 BACKGROUND OF THE INVENTION
This invention relates to rock drill lubricant compositions having low air mist emitting properties. In particular, this invention is directed to rock drill lubricants which will minimize the quantity o~ oil mist exhausted with the air from a rock drill, particularly when used in confined areas.
The construction and mining industries, faced with the task of excavating large quantities of rock or ore, depend upon rock drilling operations to accomplish this often horrendous task. Many excavating operations involve drilling blast holes, blasting or fragmentation and then removal of the fragmented rock by earth moving equipment.
Drilling the blast holes stresses the importance of effective rock drilling operations. The most widely accepted method for drilling blast holes in rock formations and for some broaching operations is the compressed air powered rock drill. Broaching consists of drilling a number of holes close together and then breaking out the rock between them. To meet the requirements of the mining, quarrying and construction industries the percussion technique has been adopted to many sizes and models of rock drill. These percussion drills operate on a principle similar to that employed in drilling with a hand-held star drill and hammer. A reciprocating piston activated by compressed -~
air strikes the drill steel and the resulting blow crushes the rock under the cutting edges of the drill bit. Except for a ~074093 few specialized drills, the drill steel is rotated a few degrees after each power stroke and the cuttings are periodically or continuously removed from the hole by compressed air or water or a mixture of both.
All drills using the percussion technique have similar demanding lubricant requirements. In addition, the range of severe and adverse operating conditions encountered and the numerous type of rock dril]s utilized presents many problems to the lubrication engineer. Many suppliers formulate special lubricants for rock drill use.
A review of a variety of rock drill applications exemplifies the severe conditions to which these machines are subjected and are still expected to provide trouble free performance. Highway construction often requires large and at times spectacular rock cuts through rough and mountainous country. Mining and quarrying operations, although less apparent, depend solely on the excavation of ore or rock for their raw materials. Other transportation systems, including railroads, highways and canals as well as the construction of dams, hydroelectric plants, and water supply and sewer systems often involve the removal of rock by rock drill operations.
In above-ground operations ambient temperatures and moisture conditions vary from subzero and dry as in the Artic to hot and humid as in the tropics. In underground mining and tunneling projects, temperatures and humidity often remain relatively constant. However, problems relating to rock dust, fogging and ventillation become prime considerations and,accordingly,operating methods useful above ground must be modified.

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~074~)93 Rock drills may be classified into several general types. Jackhammers or sinkers are handheld tools and are used primarily for downhole work. They seldom weigh over 100 pounds and depend on their weight and that of the operator for feed pressure. Rock cuttings may be removed by air, water or a combination of the two. Stoppers are similar to jackhammers or sinkers and are used primarily to drill upward holes for mine roof bolting, working overhead ore and other overhead drilling. To reduce entry of water and rock dust into the drill some have an anvil or tappet between the hammer and the drill steel. In other instances, air is blown out through the front head to protect the drill.
Drifter drills are the most widely used and are generally classified by piston diameter, usually ranging from 2 5/8 inches to 5 1/4 inches. The larger drifters are usually mounted on hydraulic booms which in turn are mounted on a wheeled or crawler chassis. At times, these larger drifters and their associated mountings are referred to as blast hole drills. When several drills are mounted on a single mobile unit, the resulting arrangement is generally referred to as a jumbo.
Downhole drills are used for large diameter, deep hole drilling with the bit and percussion mechanism combined into a single unit which operates at the bottom of the hole. Operating air is supplied through the drill pipe that supports the drill.

~07~093 Percussion rock drills are designed to operate on air pressures of approximately 90 pounds per square lnch.
In addition to supplying the drilling energy, the air carries very fine droplets of misted oil to the moving parts of the drill. With few exceptions the drills are totally lubricated by the air and oil mixture. Adequate lubrication of rock drills depends upon a relatively small, constant flow of misted ~il to the drill. Hence the location of the air line oiler with respect to the drill is another factor which requires consideration. While the oiler should not interfere with the operator, long distances from the drill should be avoided since the oil particles would tend to reclasify and collect as slugs in the line.
Attempts to compensate for intermittent oil mist flow caused by excessive distances between the lubricator and drill by increasing the oil feed rate can cause other operating problems. For example, fogging at the exhaust from the drill and "dieseling" often result from excessive oil feed rates.
The misted oil in the compressed air supplied to the rock drill is the main source of lubricant for all of the internal drill components. The lubricant is expected to form an adequate film on moving parts. This oil film must seal clearances, prevent rust and corrosion and protect the heavily loaded components from wear. A
proper rock drill lubricant must have several important characteristics. Since some of the oil mist exhausts from the rock drill, the oil cannot possess a disagreeable odor or contain toxic or nauseous additives, particularly when being used in a confined area. To assure correct oil feed rates, sealing characteristics and film strength, the - :

1074~)93 viscosity grade of the oil used must be selected on the basis of the ambient temperature. The lubricant must have rust and corrosion protection quallties in order to preserve clearances in the rock drill and prevent the formation of abrasive rust particles. In order to protect the heavily loaded parts in the drill, anti-wear and extreme pressure characteristics are also considered essential and must often be provided b~ additives when the film strength of the base oil alone is not sufficient. Since the oil must adhere to the part being lubricated, even in the presence of water, adhesiveness of the lubricant is a necessity. The rock drill lubricant must also be resistent to deposit formation in order to avoid the formation of hard carbonaceous materials or vanishes which would prevent proper valve functioning in the rock drill.
Rock drill lubricants should also be able to emulsify water that enters the drill in order to maintain the protective oil film that resists rust and corrosion as well as preventing metal-to-metal contact. Finally, the lubricant must demonstrate an anti-foam action to eliminate the possibility of drills running dry as a result of foam in air line oilers being mistaken for a satisfactory oil level. Thus, a rock drill lubricant must be specifically tailored to meet the demanding lubrication requirements of rock drills.

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~074~93 As the air exhausts from the rock drill, one means to assure that proper lubrication is being maintained is to test for the presence of oil in the exhaust air by holding a piece of white paper near the exhaust parts. When using rock drills in confined areas such as mines and other underground excavating sites, stray fog and fine oil mist from the rock drill lubricant can create an occupational health hazard to the work crew. Recent U.S. legislation, such as the Federal Occupational Safety and Health Act (OSHA), is evidence of the increasing awareness of providing healthy working areas for industrial workers. Therefore, not only must the rock drill lubricant not possess a disagreeable odor or contain toxic or nauseous additives but ideally the lubricant should be so formulated that stray fog and fine mist generation from these lubricants is minimized.
Although polymeric additives are known to surpress mist generation in lubricants, their utilization in rock drill lubricants to date has not achieved the mist surpres-sion required, particularly when drilling in confined areas.
It is therefore an object of this invention to provide a rock drill lubricant which will have a low stray fog quality when utilized, particularly when used for lubricating rock drills in confined spaces.

SUMMARY OF THE INVENTION

There is provided according to this invention a process for reducing the stray fogging of a rock drill ..
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'. - . : ' ~

~o74093 lubricant during rock drill operations which comprises supplying to a compressed air powered rock drill, for use as a lubricant, a rock drill lubricant composition comprising a major portion of a mineral oil base, rock drill lubricant having a viscosity of 100 to 3000 SUS at 100F and a minor portion, sufficient to reduce the stray fogging qualities of said rock drill lubricant composition, of an amorphous ethylene-propylene copolymer having an amorphous structure a number average molecular weight of between about 10,000 and 100,000, a propylene content of 20 to 70 mole percent and a w/Mn of less than about 5 The ethylene-propylene copolymer found useful for this purpose has an amorphous structure, a number average molecular weight, preferably between about 30,000 and 80,000, and a propylene content of preferably 30 to 55, mole percent.
Minor quantities of this copolymer, between about 0.01 and 1.0, preferably between about 0.04 and 0.35, wt.% of the rock drill lubricant composition are found to be effective in reducing the air misting of the rock drill lubricants to a satisfactory level. Concentrations of the copolymer higher than 1.0 wt.% may beused but there is no apparent further improvement in product quality or mist surpression.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Broadly, we have found that the stray fog generation of a rock drill lubricant can be significantly reduced by incorporating therein small quantities of an amorphous ethylene-propylene copolymer. Further, this particular copolymer maintains the stray fogging at accept-able low levels during prolonged rock drill operations.

1074~93 The rock drill lubricants whose stray fogging qualities can be successfully suppressed by admixing there-with the amorphous ethylene-propylene disclosed herein include a wide variety of mineral oil base rock drill lubricants. In fact, where stray fogging of a rock drill lubricant is a problem, the addition of a quantity of an amorphous ethylene-propylene copolymer will control the stray fogging. Rock drill lubricants must be capable of lubricating all manner of pneumatic percussion tools oper-ating at ambient temperaturs ranging from -30 to +110F
under either wet or dry condistions. These lubricants usually are additive-containing naphthenic oils which are opaque and have a blue bloom. The additive package enhances the ability of the oil film to resist water wash-off, enables the oil to emulsify with water to prevent moisture contact with steel surfaces of lubricated parts, offers rust protection, suppresses forming in air line oilers, provides .

superior copper corrosion protection and exhibits good extreme pressure properties. In general, rock drill lubricants have viscosities covering a broad spectrum, viz, 100-3000 SUS ~D 100F.
The ethylene-propylene copolymers we utilize are amorphous by infra red analysis and have a narrow molecular weight distribution. These copolymers may be prepared as described in U.S. 3,522,180. This patent discloses that amorphous ethylene-propylene copolymers may be prepared in a hydrogen moderated reaction at moderate temperatures and pressures in the presence of a solvent soluble Ziegler-Natta catalyst. In U.S. 3,522,180, amorphous ethylene copolymers having a number average molecular weight of lO,000 and 40,000, a propylene content of 20 to 70 mole percent and a MW/Mn of less than 5 are disclosed as viscosity index improvement additives for lubricating oils. We have found that these same copolymers are useful as stray fog suppressing additives for rock drill lubricants. In fact, we have found that the number average molecular weight of the amorphous ethylene copolymers we employ may be lO,000 and 100,000 although we prefer to use those whose number average molecular is 30,000 to 80,000.
The concentration of the amorphous ethylene-propylene copolymers necessary to suppress the stray fogging of rock drill lubricants should be between about 0.01 and 1.0, preferably between about 0.04 and 0.35, weight percent of the final rock drill lubricant blend. Those skilled in the art will realize that some experimentation may be necessary to arrive at the minimum concentration required by both economic and service requirements. In general, the ..
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1074~93 more severe the stray fog of oil appearing in the exhaust air from the rock drill,the higher the concentration of a given amorphous ethylene-propylene copolymer necessary for satisfactory service.
Our invention is illustrated in detail in the following examples.
EXAMPLE I
This example shows the stray fog surpression pro-perties of a number of polymeric materials when added to a rock drill lubricant. In a series of tests a small quantity of each material was added to a rock drill lubricant composition and the fogging properties of the resultant blend evaluated by visually observing the quantity of oil mist formed above a small quantity of the oil while a stream of air was passing through the oil. The rock drill lubricant used was compounded from naphthenic oils and contained an additive package providing water wash-off re-sistance, rust and corrosion resistance, foam suppression, water emulsification and extreme pressure resistance. The rock drill lubricant used in this series of tests had the following properties:
Gravity, API 22.1 Flash, COC, F 355 Viscosity, SUS ~ 100OF 190.6 SUS ~? 210F 44.3 Pour, AST~, F -35 The fogging characteristics were determined visually in an apparatus consisting of a vertical glass cyclinder, 2 inch I.D., 12" long, attached to a stainless steel plate. After cleaning the cylinder with a light solvent and blowing it dry, 180 ml. of the oil under test ' ' ~ ' . , : .

1074~)93 were introduced into the cylinder filling it to a height of approximately 2 1/4 inches. Air was introduced into the cylinder through a 0.018 inch orifice in the stainless steel plate at a regulated pressure of 35 psig while the cylinder was maintained in an upright position. After allowing one minute for the formation of an oil mist to stabilize, an observer made a visual evaluation of the quantity of mist or fog which had formed in the vicinity of the top of the tube and assigned a qualitative rating as follows:

Very Good - No mist or fog to barely mist or fog Good - Very slight mist or fog Fair - Slight mist or fog Poor - Much mist or fog The additives tested included a polymethacrylate VI improver (Run 2), an acrylate polymer fuel oil pour depressant (Run 3), a polyisobutylene tackiness agent (Run 4) and an amorphous ethylene-propylene copolymer VI
improver having a narrow molecular weight distribution and prepared in a hydrogen moderated reaction utilizing a Ziegler-Natta catalyst (Run 5).
The screening test results are shown in Table I
below: .

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~074C~93 This serles of tests showed that the mist forming tendency of a rock drill lubricant can be supressed with some polymeric materials while little success is achieved with other polymeric materials.
EXAMPLE II
Those additives of Example I which were capable of suppressing the mist formation of the rock drill lubricant were sukjected to further evaluation in a test which more closely approximates end-use conditions.
Minor additions of the polyisobutylene (0.22 wt.%) and the amorphous ethylene-propylene copolymer (0.16 wt.%) of Example I were added to each of two rock drill lubricants. Rock drill lubricant no. 1 was that of Example I while rock drill lubricant no. 2 had the following properties:
Gravity API 19.5 Flash, COC, F 485 Viscosity Viscosity, SUS @ 210F 96.3 Pour, ASTM, F +5 The testing of these blends was conducted by forming an oil mist of each blend, reclassifying the oil mist, and measurin~ the quantity of oil misted and reclassified to determine the quantity of oil mist lost as stray fog. A commercial oil mist lubricator, a C.A.
Norgren Company Model S 3406-6S Micro-Fog Lubricator, was employed to form the oil mist from the test blends. In this mist unit clean dry air entering the unit at a controlled pressure passed through a venturl creating '-: .
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~074093 a pressure differential between a quantity of oil in an oil reservoir of the mist unit and the open end of an oil feed tube passing from the throat of the venturi to below the surface of the oil. Oil passed up the tube and into the venturi section where the momentum of the air caused the oil to be broken up into very fine particles. A baffle arrangement caused the larger particles to fall back into the oil reservoir while the smaller particles, ranging from a maximum of about five microns to a minimum of less than one micron, were carried from the mist unit by the air stream into a manifold assembly. The oil mist passed through the manifold assembly to a reclassifier manifold where the oil mistwas reclassified and recovered for measurement in a collection cup. The oil mist was reclassified by passing the mist through ten 0.093 inch I.D. lengths of tubing known as reclassifiers located at the end of the reclassifier manifold. These reclassifiers served both to increase the mist velocity and to increase oil particle size with the result that the oil mist "wetted outn, i.e. was reclassified into wet spray and droplets which were recovered in a collection cup located below the row of reclassifiers.
Not all of the oil formed into mist in the mist unit was recovered in the collection GUp; some was reclassified and droped out within the manifold assembly and retained therein while some of the mist passed through the reclassifiers and was lost. This "lost mist" is termed stray fog.
Each of the lubricants was evaluated in three runs, in the first run of each series the rock drill lubricant containing neither polymeric material was evaluated, in the second run the lubricant contained the polyisobutylene of Example I and in the third, the amorphous ethylene-propylene copolymer of Example I. In each series of runs, the inlet air pressure to the mist unit was maintained at 23 psig and each run was conducted for two hours. The oil in the mist unit reservoir was maintained at a selected constant temperature during each run. The viscosity of the oil under test determined the temperature -800F for rock drill lubricant no. 1 and 120F for rock drill lubricant no. 2. All the test equipment was enclosed in a controlled environment chamber to assure that the air feed line, the manifold and the mist unit were maintained at the same conditions.

Prior to the start of each run, the mist unit and its oil charge were weighed and the mist manifold assembly and collection cup were cleaned and weighed individually. Following each two hour run, each of these three items were weighed again. These weight determinations permitted the calculation of the following quantities, viz,:

~074~93 1. Quantity of oil misted (mist unit weight loss)

2. Quantity of oil reclassified (collection cup weight gain)

3. Quantity of oil drop out (manifold weight gain)

4. Quantity of oil carried off as stray fog (difference between the weight loss of the mist unit and the combined weight gain of the manifold and the collection cup) The results of these tests are presented in Table II below. All results are reported in terms of pounds per hour. Manifold drop out, reclassified oil and stray fog are also reported as a percentage of the total oil converted into oil mist.

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~0740~3 These tests showed that, although both olefinic polymers tested reduced both the mist rate fo:rmation and the c;tray fog loss, not only did the amorphous ethylene-propylene copolymer reduce the mist rate appreciably more than the polyisobutylene but this copolymer significantly reduced the stray fog losses more than did the polyisobutylene.

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Claims

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1. A process for reducing the stray fogging of a rock drill lubricant during rock drill operations which comprises supplying to a compressed air powered rock drill, for use as a lubricant, a rock drill lubricant composition comprising a major portion of a mineral oil base, rock drill lubricant having a viscosity of 100 to 3000s?s at 100°F and a minor portion, sufficient to reduce a stray fogging qual-ities of said rock drill lubricant composition, of an am-orphous ethylene-propylene copolymer having an amorphous structure, a number average molecular weight of between about 10,000 and 1000,000, a propylene content of 20 to 70 mole percent and a ?w/?n of less than about 5.

2. A process according to Claim 1 wherein the minor portion is between about 0.01 and 1.0 weight percent.

3. A process according to Claim 1 wherein the minor portion is between about 0.04 and 0.35 weight percent.

4. A process according to Claim 1 wherein the ethylene-propylene copolymer has a number average molecular weight of between about 30,000 and 80,000.

5. A process according to Claim 1 wherein the ethylene-propylene copolymer has a propylene content of between 30 and 55 mole percent.