used as a reference. In comparison, the blended fuel ANFO 75% #1/25% RO, which was mixed, loaded,
and shot at -40° F (-40° C), produced an average velocity of 9247 ft/s (2818 m/s). This was 95% of the
reference value. A 50% #1/50% RO blend gave an average velocity of 8083 ft/s (2464 m/s) at -20° F (-29°
C). This was 83% of the reference value. It should be noted that MSHA restricts the use of RO ANFO to
surface mining only, and in holes with a minimum diameter of 6 inches (see Appendix, Generic Petition
items 17 and 18).

RECOMMENDATIONS

Item 11 of the MSHA Petition states in part: “When low temperatures cause the blended oil to become too
viscous for proper absorption (at least 6 percent fuel by weight) in the ammonium nitrate prills, use of the
blended oil shall be suspended.” To judge if a specific oil blend will mix properly with AN at a current
ambient temperature, the following practical field method is suggested.

Use two sizes of glass jars, with screw lids having an inner seal. To prevent spillage when pouring the AN,
one jar should fit inside the other (with the lids removed). Inside a building weigh 94.0 grams of AN or
more (94%) into the smaller jar, and 6.0 grams of well-mixed oil (6%) into the larger jar. Seal the jars and
place them outside (but under cover) along with a thermometer for at least four hours. Lay the oil jar on
its side. When ready to mix, carry the jars (keeping oil jar horizontal) into an unheated shed or truck cab.
Rotate the oil jar to see if it flows, and ‘coat the jar wall as much as possible. Remove the caps, pour the AN
into the oil jar, reseal, and shake for one minute. While shaking, swirl the prills so they tend to rub the oil
off the jar wall. The prills should not crumble when frozen or when cooled and mixed with oil, if they do,
the moisture content is probably too high. Rate the final mix as good, fair, or bad, as described in the
Appendix and listed in Table 3.

A limiting factor in mixing blended oil and AN at low temperatures at mine sites is the suspended carbon
in the oil settling to the bottom of the oil storage tank in the ANFO mix truck. Too keep the blended oil
uniformly mixed, a plumbing modification could be made. A recirculation loop could be added to mix the
contents of the oil storage tank, just before spraying is started. Even at very low temperatures, if the blended
oil can be sprayed uniformly onto dry absorbent prills, a good ANFO mix should be produced. Such a mix
should give good performance when properly primed and loaded.

CONCLUSIONS

Recycled oil ANFO can be safely and successfully mixed and used at low ambient temperatures to give
acceptable blasting performance. This is best accomplished by following the MSHA recommendations and
regulations. Small scale mixing trials, using the suggested field method, will determine if a specific oil
blend will mix properly with AN at a particular ambient temperature. If the blended oil and AN produce
a good ANFO mix at low temperature, it should shoot properly in large, dry, well-primed holes.


In the event proper absorption cannot be obtained as a result of high viscosity, additional diesel fuel may
be added to the blended oil and thoroughly mixed. However, records of the blend date, blend mix ratio, and
quantity of each ingredient as required by item 8 shall be maintained and made available for inspection by
MSHA for at least three years. Retesting for sensitivity to a No. 8 blasting cap, as specified in item 10, shall
not be required for this new blend.

12. The blended oil shall be transported and used in a closed system which prevents skin contact, inhalation
of vapors, and ingestion of the ANFO products.

13. Blasting records for each shot employing the blended oil shall be maintained and identified as a specific
blended oil batch. The records shall include the dates(s) of loading and blasting, weather conditions, type
of initiation system(s), primer type(s) and size(s), size and depth of all borehole(s), number and location
within the shot of all borehole(s) and all misfires, quantities of ANFO used in the shot, and quantities, as
well as type, of emulsions (heavy ANFO) employed in the shot. The use of any plastic hole liners shall also
be recorded. These records shall be maintained on the mine property and made available to MSHA upon
request for at least 3 years.

Emulsions (heavy ANFO) shall not be used with the blended oil unless the manufacturer of the emulsion
certifies compatibility of the emulsion and the blended oil. This compatibility certification shall be
maintained on the mine property and made available to MSHA upon request.

14. Misfires which are reasonably suspected to have been caused by the blended oil shall be reported to the
MSHA District Manager immediately.

15. Material Safety Data Sheets for the recycled oil and diesel fuels shall be maintained on the mine
property and made available to MSHA upon request.

16. The oil blending facility shall not be put into operation until an on-site inspection is conducted by
MSHA and detailed drawings of the entire used oil and blending facilities, including product flow
directions, are submitted and approved by MSHA.

17. The prill/blended oil mixture shall not be used in blasting operations in confined spaces or underground.

18. The prill/blended oil mixture shall be used only on the Mine property. Mixing of the
blended oil and ammonium nitrate prill is intended for immediate use in loading holes and is not allowed
to be stored as a mixed product. The prill/blended oil

mixture shall be used in minimum hole diameters of 6 inches.

19. A lockout system shall be provided on the oil storage tank facilities to prevent unauthorized tampering.
Only properly trained authorized personnel shall have keys to operate the lockout system.

20. Within 60 days after the petition is granted, revisions to the mine's approved 30 CFR Part 48 training
plan shall be submitted to the District Manager. These proposed revisions shall include initial and refresher
training regarding compliance with the petition for modification.


APPENDIX
Footnote: * Reference to specific brand names does not imply endorsement by the Bureau of Mines.
Refrigeration Equipment and Frost Control Method

To provide stable temperature conditions (within about + 3° F (1.7° C), two cooling units were employed.
A Lab-Line Instruments, Inc.* model 3566, explosion-proof, upright refrigerator-freezer (in a single
compartment) was used down to 20° F (-6.6° C). To control temperature and minimize frosting, the
refrigerator door opening was covered with clear plastic. Two small flaps were cut to allow hand and arm
access. In addition, the tests were done in winter with the room door open to the outdoors. Temperatures
were monitored with thermocouples.

A Revco Scientific * model ULT-1050-5A chest freezer with digital set point temperature control was used
from 10° F (-12° C) to -40° F (40° C). The opening was fitted with cross support bars to hold up a flexible
sheet of transparent cellulose acetate plastic (8 mil or 0.2 mm thick), which was taped in place. Two arm
holes were cut out, and water proof plastic sleeves (cut from chemical splash coveralls) were sealed on with
vinyl tape. The sleeves had elastic cuffs to seal at the wrists. For clear viewing, a small electric hot air
blower was used to remove frost, and a 6 volt flashlight bulb (hanging from a wire) was installed inside.
Since the freezer is 27" (69 cm) deep and mixing was done near the bottom, stable low temperatures could
be maintained, with the room cold.

ANFO Mixing and Evaluation Method

To cool and mix the oils with AN, and observe the ANFO for oil separation, a three- jar procedure was used.
At room temperature, 94.0 grams of AN was weighed into a 4 oz (125 cc) jar, 6.00 grams of oil in an 8 oz
(250 cc) jar, and 6.00 grams of absorbent cotton in a quart (1000 cc) jar. These were tall-form, wide-mouth
glass jars selected to fit inside of each other. Each was sealed with a screw cap (with an inner seal), and put
in the freezer to cool over night. The oil jar was laid on its side. An additional 8 oz jar cap was made into
a retaining ring by cutting out a 1.5" (4 cm) hole. This was used to hold an 80 mesh (175 micron) brass
filter screen.

For each test the oil jar was first rotated in the horizontal position to observe if the oil would flow at the test
temperature and to coat the jar wall as much as possible. The AN was then poured into the oil jar, and it
was capped and shaken vigorously for one minute. In comparison the mixing time in an ANFO truck is
about 30 to 45 seconds total for the vertical and horizontal augers. The degree of mixing (in the jar) was
judged approximately as good, fair, or bad, depending on the number of prills which remained stuck on the
glass by the oil. In a good mix the prills had “rubbed” most of the oil off the glass, and only a few prills and
the AN fines remained stuck. In a fair mix up to about two square inches (13 cm?) of prills adhered. Ina
bad mix, more of the glass area remained covered, so that it was difficult to see inside the jar even with the
light bulb held against the glass.

After mixing, the cut-out cap (with filter screen) was attached and the jar was inverted and put inside the
quart jar, with the filter pressing against the cotton. This assembly was left in the freezer for six hours, to
allow any unabsorbed oil to drain down and be absorbed by the cotton.


REFERENCES

1. U.S. Bureau of Mines. Apparent Consumption Of Industrial Explosives And Blasting Agents In The
United States, 1992. Mineral Industry Surveys, August 23, 1993, 13 pp.

2. U.S. Bureau of Mines. Safety Recommendations For Sensitized Ammonium Nitrate Blasting Agents.
Dep. Interior, BuMines IC 8179, 1963, 15 pp.

3. Damon, G. H., C. M. Mason, N. E. Hanna, and D. R. Forshey. Safety Recommendations For Ammonium
Nitrate-Based Blasting Agents. Revision of Information Circular 8179. BuMines IC 8746, 1977, 31 pp.

4. US. Dept. of Labor, Mine Safety and Health Administration. Hazardous Waste Fuels In Mining. IR
1195, 1989, 19 pp.

5. Duhalt, R. V. Environmental Impact Of Used Motor Oil. The Science of the Total Environment, 79
(1989) 1-23. Netherlands.

6. Vandermeulen, J. H., A. Fonda, and C. Stuttard. Toxicity Vs Mutagenicity Of Some Crude Oils,
Distillates And Their Water Soluble Fractions. Water Research. Vol. 19, No. 10, pp. 1283-1289, 1985. Great
Britain.

7. National Safety Council. Ammonium Nitrate/Fuel Oil Mixtures as Blasting Agents. Data Sheet 1-730-86,
7 pp.

8. McDonald, G. P., and M. S. Stern. Practical Application Of Used Oils In The Manufacture Of Bulk
Explosives. Paper in Proceedings Of The Nineteenth Annual Conference On Explosives And Blasting
Technique (San Diego, CA. Jan. 31 - Feb. 4, 1993) International Society Of Explosives Engineers,
Cleveland, OH, 1993, pp. 89-99.

9. For information contact MSHA, Denver Technical Center, PO Box 25367, Denver,CO 80225, phone
303-231-5430.

10. Federal Register, U.S. Environmental Protection Agency, 40 CFR Parts 260, 261, 266, 271, and 279,
Hazardous Waste Management System: Identification and Listing of Hazardous Waste: Recycled Used Oil
Management Standards, Final Rule Vol. 57, No. 176, September 10, 1992.

11. American Society for Testing and Materials. Standard Test Method for Low Temperature Viscosity
of Automotive Fluid Lubricants Measured by Brookfield Viscometer. D2983-87 in 1993 Annual Book of
ASTM Standards: Volume 05.02, Petroleum Products and lubricants (Il). Philadelphia, PA, 1993, pp. 258-
266.

12. Recommendations on the TRANSPORT OF DANGEROUS GOODS, Tests and Criteria, Second
edition, ST/SG/AC.10/11/Rev.1, United Nations, New York 1990, pp. 19-25.


The frequency of testing and analyses for these specifications may be reduced upon the adequate submittal
of records to the MSHA District Manager showing a demonstrated record of meeting the specifications, and
a written authorization from the MSHA District Manager allowing the reduction in testing frequency.

5. The recycled oil shall be checked for water and ethylene glycol in the sight tube of the recycled oil
storage tank prior to blending with diesel fuel. If either is observed, it shall be drained from the batch prior
to blending.

High viscosity oils of 90W or above shall be restricted to less than 10 percent of the total quantity of
recycled oil in the storage tank.

6. The blend of recycled oil and diesel fuel (hereinafter called blended oil) shall not exceed 50 percent (by
volume) recycled oil. When blends exceeding 30 percent recycled oil are to be used, an absorption test on
the recycled oil shall be performed prior to blending with fuel oil to determine the proper mixing ratio.

7. The recycled oil shall be mixed continuously while being blended with diesel fuel or immediately after
adding the diesel fuel. Mixing shall ensure recirculation of at least three times the total volume of diesel fuel
and recycled oil.

The blending date, blend mix ratio of diesel fuel to recycled oil for each batch, and the quantity in gallons
of each ingredient in the blended oil batch shall be recorded. The gallons of each grade of diesel fuel shall
also be recorded. These records shall be maintained at the mine property and made available to MSHA upon
request for at least three years.

8. The recycled oil and blended oil shall not be modified by heating, adding additives (with the exception
of diesel fuel), or in any other way that could change the relevant properties of the recycled oil.

9. The blended oil shall be remixed within 24 hours of being drawn into any bulk mixing vehicle. This
remixing shall either recirculate at least 25 percent of the total volume of blended oil remaining in the
storage tank or at least two consecutive viscosity samples, taken at least 5 minutes apart, shall be within 10
percent of each other immediately before loading into the bulk mixing vehicle.

10. Each new batch of blended oil shall be tested for sensitivity of the blended oil and ammonium nitrate
prills to a No. 8 strength detonator prior to their loading in any holes. For each new batch of blended oil,
this test shall be performed on at least 3 samples, each having minimum dimensions of 3-3/8 inches in
diameter and 6-3/8 inches long. Each detonator shall be placed near the center of each sample. Each sample
container must be non-rigid, such as paper products, to minimize confining effects upon initiation. Records
of whether or not each sample detonated shall be maintained on the mine property and made available to
MSHA upon request for at least 3 years.

11. When low temperatures cause the blended oil to become too viscous for proper absorption (at least 6
percent fuel by weight) in the ammonium nitrate prills, use of the blended oil shall be suspended. Viscosity
tests and absorption tests at various temperatures may be performed to obtain their correlation with
temperature. Once these correlations are obtained, in the field viscosity tests of the blended oil, at
temperatures which are the same or below the temperature at which the holes are to be loaded, can be
performed to verify proper absorption.


LOW TEMPERATURE LIMITS FOR MIXING RECYCLED OIL, DIESEL FUEL,
AND AMMONIUM NITRATE TO MAKE ANFO-TYPE BLASTING AGENTS

By

Thomas C. Ruhe
US Bureau of Mines, Pittsburgh Research Center
Pittsburgh, Pennsylvania, USA

T.S. Bajpayee
US Bureau of Mines, Pittsburgh Research Center
Pittsburgh, Pennsylvania, USA

ABSTRACT

The Bureau of Mines conducted research to determine the safe operating conditions for using recycled
(used) lubricating oil from mining equipment as a partial replacement for diesel fuel to make ANFO-type
blasting agents. The use of recycled oil (RO) saves energy, reduces oil imports, and reduces mining costs.

Low ambient temperatures may cause these recycled oils to become too viscous for proper absorption by
ammonium nitrate (AN) prills and result in poor blast performance, safety hazards, and environmental
problems. To help quantify and resolve these issues, viscosity, mixing, and performance tests were
conducted at various temperatures. Diesel fuels No. 1 and No. 2 were studied separately and in blends with
25, 50, and 75% RO.

Good quality ANFO mixes (94-6) were produced with dry absorbent prills and blended fuel (No. 1 diesel
plus RO) at temperatures as low as -40° F (-40° C) with 75% No. 1/25% RO, and at -20° F (-29° C) with
50/50. Diesel fuel No. 2 also made good mixes as low as -30° F (-34° C) with 75% No. 2/25% RO, and
at 0° F (-18° C) with 50/50.

Reference detonation velocity tests were conducted in 1.4" (3.6 cm) diameter steel pipe at 70° F (21° C)
on No. 1 diesel ANFO (94-6), giving an average value of 9722 ft/s (2964 m/s). Comparison tests showed
good ANFO performance at low temperatures. Blended fuel ANFO (75% No. 1/25% RO) mixed, loaded,
and tested at -40° F (-40° C), produced an average velocity of 9247 ft/s (2818 m/s). A 50/50 blend gave
a velocity of 8083 ft/s (2464 m/s) at -20° F (-29° C).

Based on these results, a practical field method has been developed to help evaluate whether a specific oil
blend will mix properly with AN at a low ambient temperature. This method will help to promote the safe
and reliable use of RO ANFO at low temperatures, with adequate performance.


TABLE 3 - ABSORPTION VERSES TEMPERATURE OF OILS BY AN PRILLS

IN MAKING 94-6 ANFO
No. 1 (#1) and No. 2 (#2) Diesel Fuel, and Mixtures With Recycled Oil (RO)
TEMPERATURE _| QUALITY OF MIX (94-6 ANFO) |
°F °c cae 75% #1+ | 50% #1+ | 25% #1+ PR 75% #2+ | 50% #2+ | 25x F2+
25% RO [50% RO | 75% RO* 25% RO | 50% RO | 75x RO’
40 4 Good Good Good Good Good Good Good Good
30 1 Good Good Good Good Good Good Good Good
20 7 Good Good Good Good Good Good Good Fair
10 -12 Good Good Good Fair Good Good Good Bad
0 -18 Good Good Good Bad Good Good Good -
-10 -23 Good Good Good oo Good Good Fair .
-20 +29 Good Good Good - Good? | Good* Bad
-30 | -34 |} Good Good Fair -- Good* | Good? : -
-40 -40 Good Good Bad - Good? Fair® - -

' Currently the MSHA maximum permitted % of RO is 50% in mixed oil.

? Waxy skin formed on top of oil, but oil flowed when jar rotated.

> Oil flows when jar rotated.

* Waxy, oil would not flow unless jar shaken.

5 Waxy, oil would not flow when jar shaken, but did flow and was absorbed when shaken with AN prills.

TABLE 4 - DETONATION VELOCITY OF 94-6 ANFO MIXTURES VERSES TEMPERATURE
Made With #1 and #2 Diesel Fuel and Mixtures With Recycled Oil (RO)
Shot In 1.4" (3.6 cm) diam. Steel Pipe, With a 1/3 lb (165 g) Primer,

DETONATION TEMPERATURE OF MIXING,
OIL(S)_IN_ANFO VELOCITY LOADING, AND SHOOTING
(94% AN + 6% TOTAL OIL)
ft/s ws aa °C
#1 Diese Fuel 3763 za76 +70 421
#2 Diesel Fuel Bae 307 +70 +21
8036 2449
50x #1 + 50x RO 8036 ue -20 -29
9259 2822
75% #1 + 25% RO 252 oat -40 -40



TABLE 1 - DETONATION VELOCITY OF 94-6 ANFO MIXTURES VERSES TEMPERATURE
Made With No. 2 (#2) Diesel Fuel, and Mixtures With Recycled Oil (RO)
Shot In 4" (10.2 cm) diam. Steel Pipe, With a 1/2 Ib (255 g) Primer,
Ata Loading Density of 0.83 to 0.86 g/cc.

OIL(S) IN ANFO DETONATION VELOCITY TEMPERATURE

(94% AN + 6% TOTAL OIL) | tts n/s ef [ec

6% #2 Diesel Fuel (100% #2) 12,200 3,730" 59 15
3x #2 + 3% RO (50 - 50) | 10.800 3.280 68 20 |

2x #2 + 4% RO (33 - 67) 12,500 3,810 7 5

1.5% #2+ 4.5% RO (25 - 75) 12,300 3,750 68 20

1x #2 + 5% RO (17_- 83) 13,000 3,970 86 30

‘Explosive Co. advertising literature velocity values for ANFO,
shot in the ground (in 4" diam./10.2 cm holes), vary from 12,500 to
12,900 ft/s (3810 to 3930 m/s), at a loading density of 0.85 g/cc.

TABLE 2 - VISCOSITY VERSES TEMPERATURE OF OILS USED IN MAKING ANFO
Recycled Oil (RO), No. 1 (#1) and No. 2 (#2) Diesel Fuel, and Mixtures

VISCOSITY _IN CENTIPOISE

oF °c RO 75x #1+ | 50% #1+ | 25% Flt |] #2 | 75% #2+ | 50x #24 | 25x Foe

25% RO | 50% RO | 75% RO’ 25% RO | 50% RO | 75% RO
_—=———

70.0 | 21.1 | 156° || 1.52 | 3.19 7.92 26.9 || 2.59 5.29 | 12.6 37.3

60.0 | 15.6] 217 || 1.67 | 3.61 9.39 34.1 |] 2.93 6.14 | 15.3 47.9

50.0 | 10.0 | 312 || 1.86 | 4.13 11.2 44.2 || 3.35 7.31 | 19.1 63.8

40.0] 4.4) 471 |} 2.08 | 4.70 13.5 56.0 || 3.85 8.80 | 24.2 87.2

30.0 | -1.1 || 680 || 2.37 | 5.53 16.9 76.6 1 4.55 | 10.6 31.8 121

20.0 | -6.7 || 1092 2.69 6.52 21.4 106 5.41 13.2 41.8 173
10.0 | -12.2 || 1822 3.07 7.80 27.4 148 6.45 16.6 56.4 254
5.0 [ -15.0 || 2379 || 3.27 8.51 30.9 174 7.07_| 18.8 65.9 313

‘ Currently the MSHA maximum permitted % of RO is 50% in mixed oil.
? Comparison values of new vehicle lubricating oils at 70° F (21.1° C):
SAE 30 HD motor oil = 236 cP, SAE 40 HD motor oil = 451 cP



MSHA Generic Petition (revised 9-1-94)

Compliance with MSHA regulations and the terms of an MSHA Proposed Decision and Order (PDO) does
not necessarily constitute compliance with the regulations of other government agencies. For example, the
practice of using used oil is subject to regulation in Title 40 Code of Federal Regulations which are
administered by the U.S. Environmental Protection Agency (EPA). These regulations may impose more
stringent or different requirements than required by MSHA. Therefore, Companies using used oil should
ensure that they are in compliance with EPA and other applicable governmental agency regulations.

1. Only petroleum-based lubrication oil, which is recycled from equipment at the Mine, shall be
used for the purpose of blending with fuel oil in the creation of ANFO. Provisions shall be in place to ensure
that the used oil is not contaminated with PCB's.

2. The used oils shall be recycled by filtering and then stored in a storage tank used exclusively for this
purpose. The contents of the storage tank shall, after testing and meeting specifications as provided in item
4 below, be considered a batch and no additional oil or other products, with the exception of diesel fuel,
shall be added until the contents of the tank have been fully depleted.

3. The two filters used in the filtering system shall be 60 mesh and 100 mesh arranged in series. These
filters shall be cleaned/replaced on a regularly scheduled basis, and whenever the filter becomes clogged
to the extent that a pressure of 50 psi exists at the pump outlet. The pump will regulate flow such that no
oil passes into the tank when 50 psi occurs at the pump outlet. Records, including the dates, of all filter
cleaning/replacing activities shall be kept on the mine property and made available to MSHA upon request
for a period of at least three years.

4. Tests or analyses shall be conducted on each storage tank of recycled oil after the entire contents of the
storage tank are thoroughly mixed and before blending with fuel oil to ensure that the used oil meets the
following specifications:

(1) Arsenic 5 ppm maximum

(2) Cadmium 2 ppm maximum
(3) Chromium 10 ppm maximum
(4) Lead 100 ppm maximum
(5) Total Halogens 1,000 ppm maximum
(6) Flash point 100° F minimum

These specifications were derived from Table 1 in 40 CFR 279.11.

Flash point shall be verified using either a closed-cup ASTM D3941-90 test or open-cup ASTM D1310-86
(Reapproved 1990) test.

Any test result on the contents of a storage tank which is outside these specifications shall have the contents
retested immediately. Any two consecutive test results on the same contents of a storage tank which are
outside these specifications shall be reported to MSHA, and the contents of the storage tank shall not be
blended with diesel fuel for use in making ANFO unless prior authorization is obtained from MSHA. The
contents of the storage tank shall be considered a batch of recycled oil after it is proven to be within these
specifications. Prior to filtering the oil in the storage tank, the oil shall be considered "used oil."



Adapter attachment. The temperature was controlled to within 0.1° C by an attached cooling jacket,
connected to a bath circulating antifreeze solution. Each viscosity reading was checked at several different
speeds. The values compared closely, indicating Newtonian behavior.'' The 5° F (-15° C) values are at
the lower operating temperature limit of the bath.

Obtaining accurate viscosities at lower temperatures would be impractical in the field and difficult in the
laboratory. According to reference 11, many mineral oil- based automotive fluid lubricants are non-
Newtonian at low temperatures, because they develop shear-rate-sensitive wax or wax-polymer gels.
Accurate viscosity measurements on such gels would only allow for minimum stirring action, to avoid
breaking down their structure. However, the RO used must be well stirred to put its carbon sediment in
suspension.

Evaluation of ANFO Mixing Versus Temperature

To determine how well the oils and blends listed in the viscosity table would actually mix with AN prills,
individual absorption test trials were performed at temperatures in the range of 70° F (21° C) to -40° F (-
40° C). The results from 40° F (4° C) to -40° F (-40° C) are listed in Table 3. The methods used for
cooling and mixing the oils and AN and evaluating the ANFO “quality of mix” are described in the
Appendix.

Low Temperature Detonation Velocity

To evaluate the actual performance of ANFO at low temperatures, selected mixes from Table 3 were
prepared cold. All ingredients and components of the explosive charge were precooled. The ANFO mixing
and loading, into an insulated primed steel tube, was done inside a freezer. The tubing size was 1.88" 0.d.
(1.44" id.) x 16" long [4.77 cm (3.65 cm) x 40.6 cm]. A continuous velocity probe was mounted inside,
and a 1/3 Ib (165 g) cast pentolite primer was attached. This is the USA Gap Test For Solids (run at zero
gap). The charge temperature was monitored via an imbedded thermocouple. Reduced scale charges were
made because all items had to be transferred in and out of a freezer through a 4" (10 cm) diameter opening,
to maintain the low temperature and keep frost out. The cold assembled charges were transported in dry
ice, and fired in a bunker at the temperatures listed in Table 4.

RESULTS

The absorption tests (Table 3) showed that blended oils will give good stable mixes with prills at quite low
temperatures. After the brief one minute mixing time, and six hour standing time in the freezer, there was
no noticeable unabsorbed oil draining to the bottom. In all tests, out of 6.00 g of oil originally weighed into
each mixing jar, the maximum amount drained was 0.07 g (see Appendix for details). With dry absorbent
prills good quality ANFO mixes were made at temperatures as low as -40° F (-40° C) with 75% #1/25%
RO, and at -20° F (-29° C) with 50/50. Diesel fuel #2 also made good mixes as low as -30° F (-34° C) with
75% #2/25% RO, and at 0° F (-18° C) with 50/50. It should be noted that RO from other mines may have
a higher viscosity than this sample. If so, a lower percentage of other RO (in the blended oil) may be
necessary to obtain equal absorption at these temperatures.

Table 4 lists the detonation velocity values obtained from the reduced scale 1.4" (3.6 cm) diameter charges.
Standard #1 diesel ANFO (94-6), which shot at an average of 9722 ft/s (2964 m/s) at 70° F (21° C), was


EXPERIMENTAL WORK
Preliminary Tests

Part of item 6 of the Generic Petition specifies: “The blend of recycled oil and diesel fuel (hereinafter called
blended oil) shall not exceed 50 percent (by volume) recycled oil.” In preliminary tests, the USBM found
that blended oil containing up to 83% RO can be absorbed by AN prills at moderate temperatures to make
ANFO (1% No. 2 diesel + 5% RO + 94% AN), which gives good detonation velocities at temperatures in
the range of 59° to 86° F (15° to 30° C). See Table 1. However, there are a number of reasons why it may
not be advisable to use more than 50% RO in blended oil. Due to the possibly higher carbon content of RO,
the oxygen to fuel balance of the ANFO may be shifted (if 6% oil is used - as per Petition item 11). This
could produce excessive levels of carbon monoxide. In addition, the concentrations of lead (and other heavy
metals) in the blasting fumes would be increased. The ANFO may become cap sensitive due to increased
levels of impurities from the RO, especially in hot conditions. Likewise, the water in RO may reduce
sensitivity at some low temperatures (such as winter ambient conditions at northern mines).

Specifications of Oils and Ammonium Nitrate Used

The Bureau obtained two analyzed samples of RO (A and B) from a mine approved by MSHA to use ANFO
made from RO on site. Sample A was used only for the preliminary tests (Table 1). Sample B was used
for all other tests. These oils both met the EPA requirements for allowable levels of heavy metals (lead
etc.), halogens (chlorinated solvents, and PCB’s), and minimum flash point as listed in the Appendix
(Generic Petition - item 4).

The oils are black in color, and a fine black residue settled out on standing. The residue is presumed to be
a combination of carbon, graphite, and other insoluble materials. Because of this, all containers were shaken
well before any sample was withdrawn. The particle size of this residue is controlled by item 3 of the
MSHA Petition, which requires a 100 mesh (147 micron) filter.

Diesel fuels No. 1 and No. 2 are designated herein after as #1 and #2. Three different diesel fuel samples
were bought. A locally obtained #2 was used only for the preliminary tests listed in Table 1. To insure
proper specification fuel for the other work in this USBM study, certified, analyzed samples of #1 and #2
were purchased directly from a refinery. These were dyed dark red to help observe the mixing with AN
prills.

Standard bulk blasting agent grade AN prills were purchased from a local explosive supplier. The bulk
density is about 0.85 g/cc at room temperature. To maintain dry storage conditions, the prills were
transferred to plastic buckets with two sealed inner plastic bags and lids.

Viscosity Measurements

To help evaluate the mixing of ANFO at low temperatures, viscosity measurements were made in the range
of 70° to 5° F (21° to -15° C) on the following oils: RO, #1, #2, mixtures of #1 with 25, 50, and 75% RO,
and mixtures of #2 with RO. The results are listed in Table 2. The viscosity measurements were made with
a Brookfield * model LVDV II + (rotary spindle) digital readout viscometer, with UL Adapter attachment,
except for the RO viscosities from 30° to 5° F (-1° to -15° C), which were made with the Small Sample



INTRODUCTION

The United States mining industry consumed about 4.1 billion pounds of AN-based industrial explosives
in 1992.' Of these, about 3.2 billion pounds was ANFO and ANFO-type blasting agents. The usual ANFO
formulation contains about 94% by weight ammonium nitrate and 6% diesel fuel oil. If recycled (used)
lubricating oil could be safely substituted for the fuel oil, up to about 27 million gallons could be consumed.
This use of recycled oil (RO) can save energy and reduce oil imports. Consumption of used oil (generated
by mines) on site, by blending it with diesel fuel to make ANFO-type blasting agents, could offer
considerable cost savings to the industry.

Recycled oil in ANFO may create blasting safety and performance problems, as well as health and
environmental concerns.?**>*7 In order to help define, quantify, and resolve these issues, the US Bureau
of Mines (USBM) is conducting a research project to generate relevant experimental data to present to the
mining industry and MSHA. The goal is to promote the safe and efficient use of RO in blasting agents on
a year-around basis. Currently, because of a lack of data and definitive methods, the use of RO in ANFO
(mixed at the mine site) is discontinued when winter temperatures are low in the US. The concern is that
the cold oil will be too viscous for proper absorption by the AN prills. However, the use of recycled oil to
make blasting agents in a cold climate has been demonstrated in Canada by McDonald et al.* The focus of
this USBM study is to provide experimental data on oil viscosity, ANFO mixing, and performance at lower
temperatures.

In the US, the oil is collected mainly from engine crankcases, machines, and hydraulic systems. Non-
chlorinated degreasing solvents can also be a minor constituent. Only petroleum based fluids can be used.
Water, emulsions, glycols (antifreeze), and other synthetics must be excluded.

Recycled oil which contains an excessive amount of undesirable contaminants can change the sensitivity
of ANFO. For example, gritty particles, heavy metals with catalytic properties, or gasoline could make the
blasting agent cap sensitive, especially at high ambient temperatures. A high water or heavy oil content
could reduce the sensitivity, especially at low ambient 4emperatures. Excessive contamination in the form
of heavy metals, chlorinated solvents, PCB’s, or other synthetic materials, could cause health and
environmental problems.

Currently the permitted use of recycled oil in ANFO and heavy ANFO in the United States requires
compliance with all applicable governmental agency regulations. This includes the Mine Safety and Health
Administration (MSHA)’, the Environmental Protection Agency (EPA)'° , and for nonmining uses the
Occupational Safety and Health Administration (OSHA) has such jurisdiction (29 CFR 1905). MSHA
regulations (30 CFR 57.6309(b) & 77.1304(a)] currently prohibit the use of crankcase oil in making ANFO.
Only through the Petition For Modification (PFN) procedures presented in 30 CFR Part 44° can these
regulations be modified for the petitioning mine. MSHA issues a guide (to the PFN) called the “Generic
Petition.” It lists 20 detailed technical requirements covering the selection, treatment, storage, analysis,
blending, and record keeping for the use of RO in ANFO. The full text is included in the Appendix of this
paper (at the request of MSHA).