Tabata Tusa BCU-174 User manual

SERVICE MANUAL
BCU-174 (APA)
Active Purge Assist BCJ Power Inflator
Volume I

BCU-174 (APA)
V1.0 – 7.14.2010 2
SECTION PAGE NO.
I GENERAL INFORMATION 3
1.0 Important Information 3
1.1 Lubricants and Sealants 3
II REPAIR GUIDLINE 4
2.0 BCU-162 Schematic diagram 4
2.1 BCU-162 Schematic parts list 5
2.2 BCU-163 Schematic diagram 6
2.3 BCU-163 Schematic parts list 7
2.4 Tools Required 8
III GENERAL (USER) RECOMMENDED MAINTENANCE 9
3.0 General Care Guidelines 9
3.1 Determining Service Intervals 10
3.2 Determining Service Application 10
(A) Exposure of Equipment 10
(B) User Maintenance 10
(C) Experience and Application 10
(D) Future Application 10
IV INSPECTION TECHNIQUES AND TROUBLESHOOTING 11
4.0 Inspection Techniques 11
(A)O-rings 11
(B) Sealing Surfaces 11
(C) Hoses & Rubber Components 11
4.1 Troubleshooting Guidance 12
4.2 Troubleshooting 12
V DISASSEMBLY/ASSEMBLY 13
5.0 Disassembly Procedure, BCU-163 13
5.1 Disassembly Procedure, BCU-162 15
5.2 General Cleaning Methods 21
5.3 Repair & Replacement Schedule 22
5.4 Assembly Procedure, BCU-162 23
5.5 Assembly Procedure, BCU-163 30
VI SPECIFICATION 33
6.0 Torque Specifications 33
6.1 Performance Specifications 33
VII TABATA Co., WORLDWIDE 34
7.0 Contact Details 34

BCU-174 (APA)
V1.0 – 7.14.2010 3
1.0 IMPORTANT INFORMATION
This manual is designed for use by authorized service technicians who have completed a
training course in TUSA regulator repair. This manual is intended for use only in connection with
the TUSA Regulator Repair course as prescribed by Tabata Co., Ltd and is not meant for
general distribution. Accordingly, Tabata Co., Ltd makes no representations or warranties of any
kind concerning the techniques or procedures contained within this manual. It is assumed the
authorized service personnel repairing and servicing regulators have average mechanical
ability, a good understanding of the operation of SCUBA equipment and adequate diving
experience.
This manual is not intended for use by divers in overhauling or attempted repair of SCUBA
equipment in the field. Such practice by untrained persons is strongly discouraged and should
be attempted only by trained personnel when absolutely necessary.
Tabata Co. Ltd 2008 Copyright.
All rights reserved. The content of this manual constitutes the confidential information of Tabata
Co., Ltd. Its receipt or possession does not convey any right to reproduce all or any portion or
specification hereof, without the expressed written consent of Tabata Co., Ltd. All publisher
rights under the copyright law will be strictly enforced.
1.1 LUBRICANTS AND SEALANTS
This Power Inflator is approved for food grade (pure) type silicone grease (MT-SG G501 Shin-
Etsu) or per fluorinated polyether grease lubricant (TRIBOLUBE-71) or (CHRISTO-LUBE MCG
111, DC111) lubricant only.
NOTE: TRIBOLUBE or CHRISTO-LUBE must be used for any type of Enriched Air Diving.
TUSA products should not be used with air mixtures containing more than 40% O2
(oxygen).

BCU-174 (APA)
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2.0 SCHEMATIC DIAGRAM BCU-162 (APA)
ANNUAL REPLACEMENT -

BCU-174 (APA)
V1.0 – 7.14.2010 5
2.1 SCHEMATIC PARTS LIST BCU-162 (APA)
ITEM No. PART No. DESCRIPTION QTY. ANNUAL OVERHAUL TORQUE N•m
1 BCU-162-010 INFLATE BUTTON ASSY 1
2 004 O-RING 2 ●
3 BCU-162-020 INFLATE SPRING 1
4 008 O-RING 1 ●
5 BCU-162-040 SPRING BASE 1
6 BCU-162-130 EXHAUST SPRING 1
7 BCU-162-110 EXHAUST BUTTON 1
8 BCU-162-140 EXHAUST BUTTON COVER 1
9 BCU-162-160 MOUTHPIECE 1
10 BCU-162-200 QUICK BODY 1
11 BCU-029-080 STEM GUIDE 1
12 BCJ-U29-07 PURGE SPRING 1
13 113 O-RING 1 ●
14 BCU-162-170 PURGE BUTTON 1
15 BCU-162-060 INFLATE PLUG 1 1
16 014 O-RING 1 ●
17 BCU-162-050 INFLATE POPPET 1 0.2
18 003 O-RING 1 ●
19 BCU-162-120 EXHAUST STEM 1
20 007 O-RING 1 ●
21 BCU-162-190 EXHAUST AXLE 1
22 BCU-162-220 EXHAUST AXLE SPRING 1
23 011 O-RING 4 ●
24 BCU-162-210 EXHAUST AXLE CHAMBER 1
25 012 O-RING 2 ●
26 BCU-029-120 PLUG 1 1.8
27 BCU-029-101 PURGE SEAT 1
28 BCU-162-180 PURGE STEM 1 0.2
29 BCU-162-150 PISTON CHAMBER 1
30 BCU-162-100 PISTON SPRING 1
31 BCU-162-240 O-RING 1 ●
32 BCU-162-090 PISTON 1
33 BCU-162-070 CORD RETAINER 1
34 010 O-RING 1 ●
35 BCU-162-080 PISTON HOUSING 1
36 BCU-162-230 WIRE END RETAINER 1
37 BCU-163-080 WIRE ASSY. 1 ●

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2.2 SCHEMATIC DIAGRAM BCU-163 (APA)
ANNUAL REPLACEMENT -

BCU-174 (APA)
V1.0 – 7.14.2010 7
2.3 SCHEMATIC PARTS LIST BCU-163 (APA)
ITEM
No. PART No. DESCRIPTION QTY. ANNUAL OVERHAUL TORQUE
N・ｍ
1 BCU-163-020 OPEV VALVE CAP 1
2 BCU-163-030 OPEV SPRING 1
3 BCU-163-040 VALVE PLATE 1
4 BCU-163-050 OPEV VALVE 1
5 BCU-163-060 VALVE BASE 1
6 BCU-163-160 GUIDE PIN 2
7 024 O-RING 1 ●
8 BCU-163-150 OPEV BODY ASSY. 1
9 BCU-163-090 WIRE TOP RETAINER 1
10 ST-004-02 STRAP 1 ●
11 BCU-163-070 INFLATE HOSE 1
12 BCU-163-130 LOCATOR 3
30 BCU-162-100 PISTON SPRING 1
31 BCU-162-240 O-RING 1 ●
32 BCU-162-090 PISTON 1
33 BCU-162-070 CORD RETAINER 1
34 010 O-RING 1 ●
35 BCU-162-080 PISTON HOUSING 1
36 BCU-162-230 WIRE END RETAINERWIRE END RETAINER 1
37 BCU-163-080 WIRE ASSY. 1 ●

BCU-174 (APA)
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2.4 TOOLS REQUIRED
The following tools are recommended for servicing the BCU-174. Open-ended wrenches, Allen
keys, pliers, screwdrivers and a Vice are considered standard workshop tools and may not be
listed. All tools pictured below are available from local sources and Tabata except special tools.
Special tools are designed exclusively for TUSA SCUBA equipment; they are available from the
TUSA Factory Service Departments only using the indicated item number.
ITEM DESCRIPTION PARTNO.
1 7/32” wrench
2 7/16” wrench
3 1/2” wrench
4 Mask/Multi tool ST-004-89
5 Pin Wrench SPA-6
6 Double hook O-ring pick D-HOOK-PICK
7 4” screw driver (slotted)
8 Brass pick set (2 picks) BRASSPICK
9 Silicone grease Refer to section 1.1
10 Torque wrench
11 Needle Nose pliers
12 5/32” Drive
13 O-ring tool MT-1A W
14 O-ring tool MT-2A BL
15 O-ring tool MT-4A Y
16 O-ring tool (inner body) MT-6A

BCU-174 (APA)
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3.0 GENERAL CARE GUIDELINES
Tusa recommends to all Authorized Dealers that they take individual time with each customer to
explain and demonstrate the following simple steps for care and maintenance of the Buoyancy
Compensator Jacket. This will help to ensure the following goals:
•Personalized contact with the customer insuring satisfaction.
•Help to insure long life of the new purchase through maintenance.
•Communication of findings during tuning or overhaul service.
•Help prevent problems described if these steps are not taken.
1. After exiting the water and with the cylinder valve still on and regulator in place, inflate the
Buoyancy Compensator Jacket (BCJ) bladder full of air. Close the cylinder valve and purge the
remaining pressure from the regulator and remove both regulator and BCJ from the cylinder.
2. Tilt the BCJ as to direct any water in the bladder to the rear Pressure Relief (dump) Valve(s).
Purge any water that may have collected in the bladder.
3. Using a hose, direct fresh water into the mouth piece of the Power Inflator while depressing the
Manual Inflate Button. Fill the BCJ bladder approximately 2/3 full of fresh water. Fill the
remainder of the BCJ bladder with air until the bladder becomes full.
4. Agitate the fresh water and air mixture by shaking the BCJ to dilute any salt or contaminated
water that may have entered the bladder. Using the rear Pressure Relief (dump) Valve(s), purge
the water from the BCJ bladder. Do not purge the water from the bladder using the Power
Inflator mechanism as this may re-contaminate the Power Inflator mechanism with contaminated
water. It may be necessary to fill the bladder with air several times to completely drain the water
from the bladder.
5. Soak both the BCJ and Power Inflator in a bath of clean, fresh water to clean any salt or
contaminated water from the exterior of both the BCJ and Power Inflator mechanism.
6. After sufficient time has passed, fill the BCJ bladder 2/3 full of air and hang the BCJ to dry. Do
not completely fill the bladder with air for extended periods of time. A fully pressurized bladder
puts unwanted stress on the Pressure Relief (dump) Valves and bladder seals. Before storing
your BCJ, be certain that it is completely dry.
DO NOT expose the BCJ and Power Inflator to extreme heat or direct sunlight when not in use.
Temperatures exceeding 180°F / 80°C for extended periods of time may cause permanent
damage to some internal valve components leading to a lack of performance or failure. If you
suspect the BCJ and Power Inflator have been exposed to excessive heat, please have it
examined by your authorized TUSA service center.

BCU-174 (APA)
V1.0 – 7.14.2010 10
3.1 DETERMINING SERVICE INTERVALS
TUSA recommends that the servicing of dive equipment be done on an annual basis or before
any extended trip. Equipment being used for rental, training or any technical diving may require
more frequent service intervals. Most components in the BCU-174 have very high-expected
usable life. However, it is very important to have all equipment inspected at an authorized TUSA
service center.
3.2 DETERMINING SERVICE APPLICATION
As you can see it is important to determine your customers dive habits to determine the best
possible recommendation for service. Other factors to consider include the exposure of the
equipment, extent of user maintenance, experience and application from the user and future
planned use of the equipment.
(A) EXPOSURE OF EQUIPMENT
Diving cold-water 4°C (40°F) or lower can potentially cause the BCU-174 to “freeze up” and is
strongly discouraged.
Diving in low visibility or contaminated water requires more frequent servicing and overhaul to
keep residue from building up inside the valve components.
Diving in tropic salt-water environments tends to subject the Power Inflator to constant moisture
exposure and will lead to accelerated corrosion of BCU-174 components.
(B) USER MAINTENANCE
A Power Inflator that has been maintained correctly by the user will require fewer parts to
replace worn or corroded components at time of overhaul. Poor user maintenance may indicate
service or overhaul may be required sooner than normal to prevent failures.
(C) EXPERIENCE AND APPLICATION
Technical or extreme diving requires a Power Inflator to be in top condition at all times. This
may require more frequent overhauls and replacement of key o-rings to maximize reliability.
(D) FUTURE APPLICATION
A user planning an extended dive trip, training course or use for applications discussed above
would benefit from an overhaul prior to the planned extended use to insure maximum
performance and reliability.

BCU-174 (APA)
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4.0 INSPECTION TECHNIQUES
We encourage the service technician to develop good habits and practice in inspection
techniques during service and overhaul. Observing the exterior condition of the Power Inflator
can offer clues on what may be found during overhaul. Finding sand or salt deposits on the
exterior crevices between mating parts may indicate a Power Inflator that is not properly
maintained by the customer. One may almost certainly discover more sand or salt deposits
inside the Power Inflator unit. Further examination must proceed especially looking for small
cracks or damage in the Power Inflator body, LP hoses, corrugated hoses etc. Mishandling may
lead to severe stress imparted into the LP hose resulting in cracks. Please refer to disassembly
of the BCU-162/163 for further discussion.
(A) O-RINGS
O-rings are common off-the-shelf well-engineered reliable sealing devices. A few words about
handling them are required. O-rings can be ordered in different sizes, rubber compounds and
hardness (durometer). It is important not to substitute o-rings from other sources in replacing
TUSA Power Inflator seals. Use only factory-supplied o-rings. As part of the TUSA annual
service policy it is recommended that all o-rings be replaced to maintain warranty. Further
details are available from the factory distributor. Do not attempt to clean or lubricate o-rings
outside of the recommendations in Section 5.1.
(B) SEALING SURFACES
All metal parts used in TUSA Power Inflators are made of either a corrosion resistant stainless
steel or chrome plated brass. Handle all metal components with care to avoid scratches, dings
or dents. Pay particular attention to the assembly of all components and which surfaces are
used for sealing against o-rings, orifice and seats. Handle these surfaces with particular care to
avoid scratches, dings or dents.
(C) HOSES AND RUBBER COMPONENTS
The examination, care and handling of all rubber components are well documented through out
the TUSA Dealer Service Manual. Look for deterioration and cracking of rubber components
resulting from age, misuse, or exposure to caustic cleaning compounds. Contact your factory
representative should you have further questions.

BCU-174 (APA)
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4.1 TROUBLESHOOTING GUIDANCE
Prior to troubleshooting the BCU-174 (APA) we recommend you become familiar with the
operation and design by reading Sections 2.0 and 5.0 through to 6.0. You will find that a good
basis and understanding of the Power Inflator function which will benefit your repair and
servicing abilities.
Attempt to duplicate the functional problem by doing an In-Water Test. A reported leak or bubble
from the Power Inflator may be traced to a specific o-ring much quicker with this method.
Record your findings as you examine and test the Power Inflator prior to and during the entire
service and overhaul procedure. Record the customers’ name and date of last service, unusual
conditions or debris present, components and seals replaced during this service and any other
pertinent information.
4.2 TROUBLESHOOTING BCU-174 (APA)
SYMPTOM CORRECTION
1. Self Inflation 1. Check Inflate Button O-ring (18)
2. Slow leaking BCJ 2. Check Purge Seat (27)
3. Slow leaking BCJ 3. Check OPEV Valve (4)
4. Slow leaking BCJ 4. Check rear dump valves
5. Slow leaking BCJ 5. Check Bladder for puncture
6. Leak at Inflate Plug 6. Check L.P. hose o-ring
7. Leak at Inflate Plug 7. Check L.P. hose valve
8. Leak at Inflate Plug 8. Check Plug O-ring (23)

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V1.0 – 7.14.2010 13
5.0 DISASSEMBLY PROCEDURE BCU-174 (APA)
Prior to disassembly, record the results of the preliminary inspection and the in water test.
Remember to retain any o-rings, filters or other components that are to be replaced in case
the customer requests to view the parts. For replacements, that were part of the Warranty
scheme annual service, it is no longer necessary to return these parts to your TUSA factory
distributor (Check with your regional distributor for details).
Remember to record your findings as you proceed to allow both a complete record of the
overhaul and future reference for servicing. The words “replace for annual service.” will
indicate all components to be handled in this manner.
Read and understand the Troubleshooting Section 4.1 to gain a better idea of which internal
parts may be worn, and to better advise your customer of the service that is required. Refer
all item numbers (99) to the “schematic” view or exploded view for this Power Inflator found in
Section 2.0 through 2.3.
Remove BCU-174 at the BCJ shoulder
valve.
Pay attention not to misplace the shoulder
Gasket.
Remove the Straps (10) from the Inflate
Hose (11).
Pull the Inflate Hose (11) free from the
OPEV Body Assy. (8).
5.0.1 BCU-163 Disassembl
y
5.0.2 BCU-163 Disassembl
y
Gasket

BCU-174 (APA)
V1.0 – 7.14.2010 14
Using a suitable Pin Wrench, remove the
OPEV Valve Cap (1). Rotate Cap counter
clockwise to remove.
Remove the OPEV Spring (2), Valve
Plate (3) and the OPEV Valve (4).
Push upward on the Valve Base (5) from
the bottom side of the OPEV Body Assy.
(8).
Once the Valve Base (5) is free, rotate it
180º to expose the Wire Assy. (37) and
Guide Pins (6).
Using a suitable probe, push both Guide
Pins (6) from the Valve Base (5).
Remove the Valve Base from the OPEV
Body Assy. (8) and Wire Assy. (37).
5.0.3 BCU-163 Disassembl
y
5.0.4 BCU-163 Disassembl
y
5.0.5 BCU-163 Disassembl
y
Rotate

BCU-174 (APA)
V1.0 – 7.14.2010 15
Now that the Wire Assy. (37) is free, pull it
from the OPEV Body Assy. (8) and
remove the Wire Top Retainer (9).
Remove the O-ring (7).
Set aside the OPEV Body Assy. (8) and
Wire Top Retainer (9) for cleaning.
Separate BCU-162 from the corrugated
Inflate Hose (11) by removing the two
remaining Straps (10).
Remove the Inflate Hose (11) and set
aside for cleaning.
Using a 7/16” wrench remove the Piston
Housing (35) from the Quick Body (10).
Remove the Piston Spring (30) and set
aside.
Set aside the Quick Body (10) to be
disassembled later in sections (5.1.5 –
5.1.16) of the manual.
5.0.6 BCU-163 Disassembl
y
5.0.7 BCU-163 Disassembl
y
5.1.1 BCU-162 Disassembl
y
This concludes the disassembly of the BCU-163 (APA).

BCU-174 (APA)
V1.0 – 7.14.2010 16
Extract the Piston (32) from the Piston
Housing (35) by pulling it outward using a
pair of soft tip needle nose pliers.
NOTE: Show caution, do not scar or
damage the Piston (32)
Using a 7/32” wrench, remove the Cord
Retainer (33) from the Piston (32) by
unthreading it counter clockwise. You
may use a 7/16” wrench to hold back the
Piston (32).
Remove the O-rings (25 & 31) from the
Piston (32). Set the Piston (32) aside for
cleaning.
Remove the Piston Housing (35) and the
Wire End Retainer (36).
Cautiously remove the Inner Body O-ring
(34) from the Piston Housing (35).
The Wire Assy. (37) will be replaced
annually as part of the BCU-162 repair kit.
5.1.2 BCU-162 Disassembl
y
5.1.3 BCU-162 Disassembl
y
5.1.4 BCU-162 Disassembl
y
WARNING
A damaged Piston (32) can not be repaired, it must be replaced

BCU-174 (APA)
V1.0 – 7.14.2010 17
Begin disassembly of the Quick Body (10)
by removing the Inflator Plug (26) with a
1/2” wrench
Remove the Plug O-ring (23)
Remove the Exhaust Button Cover (8)
using the ST-004-89 (TUSA Mask/Multi
tool). Pry upward at the hinge of the
Exhaust Button Cover (8) to remove it.
Remove the Exhaust Button (7), Exhaust
Spring (6), Spring Base (5) and the Base
O-ring (4).
Firmly push the Exhaust Stem (19) inward
forcing out the Exhaust Axle Chamber
(24) from the opposite side of the Quick
Body (10).
5.1.7 BCU-162 Disassembl
y
5.1.6 BCU-162 Disassembl
y
5.1.5 BCU-162 Disassembl
y

BCU-174 (APA)
V1.0 – 7.14.2010 18
Disassemble the Exhaust Axle Chamber
(24) using a pair of needle nose pliers to
extract the Exhaust Axle (21) by gently
pulling outward.
Remove the Exhaust Axle Spring (22).
Remove the Exhaust Axle O-ring (2).
Remove the Exhaust Axle Chamber O-
rings (23, 25)
Remove the Exhaust Stem O-ring (20).
5.1.9 BCU-162 Disassembl
y
5.1.10 BCU-162 Disassembl
y
5.1.8 BCU-162 Disassembl
y
Remove the Exhaust Axle Chamber
assembly (24), Exhaust Stem (19) and the
Piston Chamber (29).

BCU-174 (APA)
V1.0 – 7.14.2010 19
5.1.13 BCU-162 Disassembl
y
5.1.12 BCU-162 Disassembl
y
5.1.11 BCU-162 Disassembl
y
Remove the Inflate Button (1) and Inflate
Spring (3)
Remove the Inflate Button O-ring (2) from
the stem of the Inflate Button (1).
Remove the Inflate Plug (15) using a coin
(Nickel or Quarter).
Remove the Inflate Plug O-ring (16).
Using a 5/32” socket, remove the Inflate
Poppet (17).
Remove the Inflate Poppet O-ring (18).
O-ring (18)

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Using a 4” screw driver inserted in the
open end of the Quick Body (10) locate
the slot of the Purge Stem (28).
While pressing the Purge Button (14) in,
unscrew the Purge Stem (28) and
remove.
Inspect the Purge Seat (27) for wear.
Replace if necessary.
Remove the Purge Button (14), Purge
Spring (12) and the Stem Guide (11).
Remove the O-ring (13) from the Purge
Button (14).
The Mouthpiece (9) may be removed
from the Quick Body (10) by gently prying
upward at its top end using the ST-004-89
(TUSA Mask/Multi tool).
5.1.14 BCU-162 Disassembl
y
5.1.15 BCU-162 Disassembl
y
5.1.16 BCU-162 Disassembl
y
This concludes the disassembly of the BCU-174 (APA).