CCOP /SOP AC Preliminary Report 12
August 1989
VIBRO AIRLIFT DEVELOPMENT AND TRIALS,
LAUCALA BAY, FUI
Robert Smith·Techsec
Prepared by: Committee for Co-ordination of Joint Prospecting for Mineral Resources in SouthPacific Offshore Areas (CCOP /SOPAC)Tonga Project: TG.6
•Contributed by: Commonwealth Fund for Technical Cooperation (CFTC) , and AustralianInternational Development Assistance Bureau (AIDAB)
[2]
[3]
TABLE OF CONTENTS
Page
LIST OF FIGURES 4
ACKNOWLEDGMENT 5
INTRODUCTION 6
OBJECTIVE 6
HARDWARE EQUIPMENT
The A-frame 6
Airlift Drill and Components 8
DEPLOYMENT AND OPERATION 11LAUCALA BAY TRIALS 13
CONCLUSIONS 16RECOMMENDATIONS 16
APPENDICES
I A-frame Components 19
II Vibrocore Air Drill Components . . . . . . . . . . . . . . . . . . . . . . . . . .. 20
III Work Log. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 21IV Dewatering Cone & Bulk Sampling. . . . . . . . . . . . . . . . . . . . . . . .. 23
V Recommended Modifications to System 24VI Walking Beam Arrangement for Vibrolift . . . . . . . . . . . . . . . . . . . .. 25
Figures1
2
34
5
67
[4]
LIST OF FIGURES
Page
Erected A-frame 7
Airlift drill and components 8
Drill bit assembly 9Sampler with eductor hose 10Deploying the vibro airlift 12
Coarse sand and coral fragments 13
Sample location map, Laucala Bay 15
[5]
ACKNOWLEDGMENT
The development of this sampling system was made possible through the guidance andassistance of Dr Robert Woolsey and his engineering assistant. Their assistance is gratefullyacknowledged.
[6]
INTRODUCTION
Previous sampling programmes using SOPAC's Geomarex vibrocoring system in coarse sand
and gravel deposits, of the type commonly used in building and construction materials, have met
with mixed success in that penetration depths achieved were minimal. The problem was
highlighted in discussions during the 17th Session of CCOP jSOPAC where a need to conduct
subsurface sampling of a possible offshore sand deposit in Tonga was identified. Because mining
of this material would require significant capital investment, it was therefore considered important
that the specifications and extent of the material are both well defined.
Dr Robert Woolsey of the Marine Minerals Technology Centre of the University of
Mississippi was present during these discussions. He has extensive experience developing and
using low technology subsurface sampling systems built from locally available materials. This
expertise was offered to CCOP jSOPAC to develop such a system for our needs.
As the Mineral Resources Department (MRD) research vessel Latui is no longer in service,
an alternative A-frame lifting system was needed which could be taken, set up, and used in
member countries on vessels of opportunity.
OBJECTIVE
1) Design and fabrication of an A-frame for vibrocorer and vibro airlift drill systems.
2) Fabricate an airlift system which would resolve problems previously found when sampling sand
and gravel deposits with CCOP jSOPAC's Geomarex vibrocorer.
3) Demonstrate the effectiveness of low technology systems to the CCOPjSOPAC Work
Programme.
HARDWARE EQUIPMENT
The A-frame
Figure 1 is a photograph of the A-frame in its erected state. The frame is constructed
entirely out of aluminium providing a lightweight yet sturdy structure. It can be broken down into
[7]
Figure 1. Erected A-frame
sections that can be handled by two men and can be transported to the investigation site on the
small boats typically found in the work region.
The A-frame has a span of 7 m which will allow either the 6 m drill barrel of the vibrocoringsystem or the airlift system to be handled. The frame is easily assembled and secured. Insecuring the A-frame, angle iron brackets bolt to the frame base and in turn these are welded to
the steel deck of a barge type platform. In the event of encountering a wooden deck the frame
could be bolted directly to the deck. Two stays running back from the top of the A-frame tower
provide extra strength and support with eye hooks and turnbuckles allowing for tensioning of stays.
A 5-ton hand winch fitted with 100 m of 9 mm steel wire rope is used to raise and lower the drillunits or sampling device. (See also Appendix I).
[8]
Airlift Drill and Components (see also Appendix II)
The airlift drill (Figure 2) was fabricated from locally purchased materials which can be foundin most building hardware shops.
To allow for ease of transportation the airlift drill breaks down into three sections, the drill
bit (Figure 3), drill barrels, and the vibro motor head attachment (Figure 1). This arrangement
also allows for optional hole depths of 3 m, 6 m and 9 m simply by adding an additional 3 m
length of 76 mm (3 inch) schedule 80 black iron pipe.
eductor hose ----- :--- .•.....--------:.- air hose
water hose --~ __ ~
;...a.------- vibro motors
power cable
drill barrel
water pipe to drill bit
Figure 2. Airlift drill and components at site.
[9]
The barrel or drill pipe (Figure 3) was fabricated from 76 mm (3 inch) black iron pipeschedule 80, a thick walled pipe which helped to increase the overall weight of the airlift.
airline----
drillbarrell---~
drillbit--_
Figure 3. Drill bit assembly.
The air and water line pipes were fabricated from 13 mm (0.5 inch) ID 'C' grade galvanised
pipe which was available in 6 m sections. The air and water pipes were cut into 3 m lengths and
threaded so the sections could be screwed together.
The air delivery line is a standard 13 mm (0.5 inch) rubber hose using a standard quick
release bayonet fitting for connections.
[10]
The water hose is a 36 mm (1.5 inch) PR pressure hose with quick release camlock fittings
for attachment to the water pump and to the water pipe at the top of the drill unit.
The educt or hose or delivery hose for the drill cuttings comprises two sections of 76 mm (3inch) x 18 m reinforced wire ribbed transparent suction hose with camlock quick release fittings.
Present hose lengths allow us to drill in water depths of up to 14 m.
Finally the sampler was constructed from a 200 litre drum with 76 mm (3 inch) camlock
fitting welded to the top of the drum. The sampler is a very important part of the system as thevelocity of the incoming material must be reduced, and the excess water in the sample must be
removed, without losing all the sample (Figure 4).
Figure 4. The sampler with eductor hose hooked up.
[11]
The only modification to this low technology airlift system was the inclusion of two Geomarex
electric vibrator motors which were bolted to the top of the drill column. The motors served two
purposes:
I) they added weight to the system and
2) they assisted with the penetration and retrieval of the airlift.
In addition to the above equipment, the following power units are needed to operate the
airlift:
I) Air compressor: An Ingersollrand 110 air compressor (Figure 1) is used. This unit
provides the necessary volume of air (110 cubic ft/min) that is needed to lift the
cuttings from the drill bit to the sampling hopper. This type of unit is used to drive
jack hammers commonly seen at construction road repair sites.
2) Water pump: This unit provides a jet of water which is used to break up the
sediment being penetrated as well as providing a fluid medium to move the drill
cutting to the surface. The unit used, a Honda 3 inch, is capable of a maximum
delivery rate of some 1,100 lit res per minute.
3) Vibrocore motors: Two electric submersible vibrocore motors were bolted to the
head of the drill unit to provide vibratory action in the drill string. This not only aids
penetration but the vibratory action is essential when extracting the drill bit and pipe
from the hole. Power source for the vibro motors is a 6.5KV A power chief 3-phase
generator.
4) Winch: To deploy and retrieve the airlift a 5-ton hand winch with 100 m of 9 mm
steel cable is used.
DEPLOYMENT AND OPERATION
Figure 5 is a photograph of the airlift all ready for deployment. To begin, the water pump is
primed and started. Once the water jet is visible at the drill bit, the air compressor and vibro
motors are started and the airlift is then lowered to the seabed. Once the drill bit has penetrated
the seabed the unit is continually lowered until the desired penetration depth is achieved. As the
airlift is penetrating the seabed, the cuttings are sampled at the sampling hopper by collecting all
[12]
Figure 5. Deploying of vibro airlift.
cuttings for the designated sampling interval in a suitable container. For example, if the sampling
interval were 1 m, the airlift would be lowered until a metre of penetration was achieved and then
stopped briefly, allowing for flushing and circulation of that interval. At that point the sample and
catcher would be removed from the sampling hopper and a clean container inserted to collect the
next sample. This process would be continued until the hole was completed. During the drillingprocess the air compressor, water pump, and vibro motors would be kept running from the time
the airlift spudded the hole until completion of the hole. One drawback to this system is that if
any of the power units fail, the drill string may become stuck in the hole, depending on depth of
penetration at the time of failure.
[13]
LAUCALA BAY TRIALS
The airlift and the A-frame were mounted on a barge hired from Fiji Industries and towed to
a drill location in Laucala Bay.
The airlift was then tested in three different environments (see Appendix III for Work Log).The first was in shallow water, 70 em deep, approximately 0.5 km east of the present Fiji
Industries carbonate sand dredging site. Here approximately 2 m of penetration was achieved
before rock was encountered. Figure 6 illustrates the material penetrated which consisted of a
very coarse sand and gravel with large shell fragments and broken pieces of staghorn coral.
Because of the large compressor used the cuttings were able to be lifted through a head of some6 to 7 m.
Figure 6. Coarse sand and coral fragments.
The second location was in a water depth of 12 m and it was here that full penetration wasachieved, approximately 6.5 m. Cutting returns were a coarse carbonate sand with some coral
[14]
rock, shell and staghorn fragments. At this site the lifting potential of the air was greatly
increased because of the pressure differential due to the 12 m water depth. Round trip time for
the hole, that is deployment to retrieval, was 30 minutes. The third location was west of theVunidawa river. Here three holes were drilled as indicated in Figure 7. Full penetration of
6.5 m was achieved in all three holes. The substrate drilled was a fine sand to mud with some
clay bands. Round trip time for each hole varied from 30 minutes for the first hole to 14 minutesfor the last hole.
[15]
LEGENDH Vibro CAirlif-t SCAMple S-tCA-tion
SCALEGrid Co-ior cls. UTM (in Me-tres)
o 1000
SUVA
3000 METRES
LAUCALA BAY
Inltlo.!test site
655000
o DELAITUBANI
\
H 2H 3 0
o
REW'A DELTA
NUKUBUCD REEF
~MAKULUVA Is
660000
Figure 7. Sample location map, Laucala Bay
7997<400
7992400
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CONCLUSIONS
The trials with the airlift and A-frame were very successful and the desired results were being
achieved. The system worked better than anticipated in the coarse sand and gravel deposit, and
equally well in the softer silt sand and mud deposits. For future CCOP jSOPAC workprogrammes requiring the sampling of sand and gravel deposits, or bulk sampling for placer
deposit, this airlift system may be the best suited system as compared with the vibrocorer or theAcker drill rig.
With some modification the airlift depth of penetration can be increased to 9 m, but thiswould only be considered after more operational experience had been gained using the 6.5 m
assembly. A 20 minute video tape, showing the airlift operations in Laucala Bay, is available at
CCOP jSOPAC Techsec.
RECOMMENDATIONS
The following are recommended improvements to the system assembled at Techsec and tested
in Laucala Bay, February 1989.
1) Purchase a suitable compressor of same capacity used in trials (110 cm Ingersollrand).
2) Purchase a stronger eductor hose. This should avoid the crimping problems that were foundwhen working in the shallower water environment. There the hose weight was not supportedby the water, as it was when used in deeper water.
3) Construct an additional air manifold and bit assembly as a spare.
4) Purchase a bigger water pump. The Yanmar YDP diesel powered series model. YDP 4E isrecommended - principally because of the wet working environment.
5) Construct a dewatering core for bulk sampling (Appendix IV).
6) Increase water supply pipe to 1.5 inches and the jet to 1 inch ID (Appendix V) to increasewater volume and pressure which would aid the breaking up of the sediments being drilled.
7) Add cleats to the ropes used to support and manoeuvre the pipe string and hoses.
8) Add a T-bar arrangement or walking beam (Appendix VI) which is a manual pull down typearrangement to help penetration in coarser and more consolidated sediments.
9) Provide hinged points at the foot of the A-frame to aid standing of the tower.
10) Extend winch handle to allow two men to crank winch.
[17]
11) Fit a sounder transducer to the drillhead, to measure the penetration. The preferred type is apipeless type unit with good water proofing qualities, because of the potential wet and dirtyworking conditions.
12) Construct an additional system of only the drill barrel, water and air pipes, the drill bit, andmanifold assembly.
[18]
[19]
APPENDIX I
A-FRAME COMPONENTS
"A" FRAME__
l.2.3.4.5.6.7.8.9.
10.ll.12.13.14.15.16.17.18.
TOP CROSS MEMBERTOP "A" FRAME x 2BOTTOM "A" FRAME x 2"A" FRAME SUPPORT FRONT x"" "REAR" If " "WINCH MOUNTNG BRACKET x 2
BASE MOUNTING BRACKET x 20PULLEY PIN x 210" PULLEY x 3CONNECTING PLATE x 4 (4" x 8" x 1/2")"A" FRAME BOLTS & NUTS 98 x 1/2""A" FRAME HOLDING DOWN BOLTSPULLEY PIN x 2PIN LOCK PLATE x 2STAY LUGS x 6STAY WIRE x 2SHACKELS 1/2" x 4
II
7 (FROM DRAWING BY JOE MAUSIO)
8
CAMlOCKI •
• I'zI~ PIPE
I;; PIPE
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APPENDIX II
VIBROCORE AIR DRILL COMPONENTS
VI BROCORE AIR DRILL (GUN)
oo
CAMLOCKT~'~.~£=:::r'C GRADE
PIPE 8\".1.
.•.• 11---6'74 CLEARANCE
_-1- 1 HOLE
3,; Mis PLATE
o
o ooo
-+-----2
-H~+----- 3 ----+-1
1+-++-1----- 4 ----H~I
I~·COLLER
o 0 5---++4-I •
4'z PIPE x 20 LENGTH
--+-----6
, I "21',z PIPE x 21:lz LENGTH
II;COLLERo
8'
-4-----7---4189
I:t-~~.c::::::.-.---IO "II~HOLE
~§- \ x3" BOLTS and NUTS
I VIBROCORE MOUNTING2 TOP CORE TUBE3 TOP WATER TUBE4 TOP AIR TUBE5 ALLAN SCREW x 8
115" 6 BOnOM CORE TUBE7 AIR TUBE HOUSING8 AIR TUBE SLEEVE
9 DRILL BIT10 WATER JETII Mis BOLTS and NUT'S x 16
3 •127<t
(FROM DRAWING BY JOE MAUSIO)
December-January 1989
January 23-31
February 11
February 13-17
February 20
February 21
February 22
1250
1325
1445
1530
1700
February 23
1200
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APPENDIX III
WORK LoG
Design and fabrication of A-frame and ancillary equipment atMaxlane Engineers.
Negotiations with Fiji Industries for the use of barge for vibro airlifttrials.
Locating items as supplied by list necessary for vibro airliftconstruction.
Mobilisation of equipment and training MRD Offshore staff at thesame time as collecting background geophysical data for vibro airlifttrials.
Arrival of Dr Bob Woolsey and Engineering Assistant.
Purchase and fabrication of vibro airlift at Techsec HO. Machinework done at IMEL, Walu Bay.
Mobilisation of equipment onto Fiji Industries barge.
Set up A-frame. Vibro airlift ready for towing to drill locations.
Towed to location, moor barge. Prepare to drill first hole.
Start water pump compressor vibro motors. Drill hole (WD 8 m).
Retrieve system drilled (1.5 m hit rock). Site was on reef slope intolagoon.
Reposition barge - start water pump compressor, etc. Drill hole onreef top (WD 70 cm).
Stop all systems. Water pump died. Retrieve vibro airlift. Drilled2m.
Shut down, secure barge for night. Return to RSYC.
Obtain water pump from Dive Centre as CCOP/SOPAC pump needscomplete overhaul. Require new fittings for water line.
On location prepare to test system.
[22J
1310 Start drilling. Hit rock at 2 m on slope to lagoon floor(WD 10-11 m).
Reposition barge, secure.
1350 Start system.
1430 Retrieve airlift. Full penetration of 6 m achieved. (WD 12 m).Demonstrate system to John Harper and Bruce Richmond.
1730 Secure barge for night. Return to RSYC.
February 24
0915 Fiji Industries tug tows barge to drill location west of Vunidawachannel.
10331050
Site 1 :Start system (WD 2 m).Stop system, secure barge to prevent driftduring drilling.
Start system (WD 3 m).Stop system after drill retrieved. Drilled 6 m.Sampled every 2 m.
11071139
1220Site 2 :Start system (WD 2 m).Stop system, drilled 6 m. Visit by Director and staff of Techsec.Also MRD engineering staff visit to observe operations.Transportation by Beranaliva.
13261340
Site 3 :Start system (WD 2 m).Stop system drilled 6 m.Sampled every 2 m. Tests very successful.
1430 Secure barge for tow back to Lami base.
1630 Secure barge on mooring at Lami for weekend.
February 25
February 27
Departure of Dr Bob Woolsey.
Demobilisation of A-frame and drill system, cleaning and storage atTechsec HQ.
[23]
APPENDIX IV
DEWATERING CONE 8 BULK SAMPLINGfrom a sketch by Dr Woolsey
os-,
76mm"~---I
a'5m
Inlet6mm pipe with ~camlack fitling /'
10gauge or Immsheet metal
os-,C Sample catchment trough
SIDE VIEW
Battel
76mm 0 pipewafer overflow
sample 0oullet
SampleInlet '---
lJv''"'--------=--~~tack welded
76mm » pipe withcamlock fitting PLAN VIEW
[24]
APPENDIX V
RECOMMENDED MODIFICATIONS TO SYSTEM
Some Recommended Modifications to System by Dr Woolsey
1. Water System
Using the volume type pumps, the volume and pressure may be increased by increasing thewater hose and supplying pipe to 1.5 inch (38 mm) and jet to 1 inch (25 mm) J.D.
EXAMPLEthreads in
I" (25mm)set pipe JE~: ~:;: :::::::::::,::::~,::::~36·75 mm
galvanized pipe
36·75 mm x 24·5mm bell reducer
2. Preparation of Coarse Coral Material and Deep Drilling Applications
a) The present system can be modified for drilling coarse grained material by adopting ahammer lift action as drilling takes place and by adapting the winch and A-frame to handle awalking beam. See Appendix III figure.
b) For deeper drilling (15 to 20 m) in consolidated material the system can be modified bychanging the upper 3 m section which is fitted with vibrator engine mounts to a straightsection of pipe.
Example : 3 x 0.076 m section pipe.
EXAMPLE3 x 0·076 m section pipe
-. UP
TI
41
IIII
IIIIIIIII...i.
[25]
APPENDIX VI
1"2" PIPE"T-HANDLE" TOP VIEW
411 Channel
/STOP BAR: fixed to frame SIDE VIEW
WALKING BEAM
(
WINCH
Pivot point(on winch tromel-:
WALKING BEAM ARRANGEMENTfor Vibrolift System
