Removal of the Pressure Holding Valve

TASK 28-28-49-000-001-A
Removal of the Pressure Holding Valve

WARNING: MAKE SURE THAT THE GROUND SAFETY-LOCKS ARE IN POSITION ON THE LANDING GEAR. THIS WILL PREVENT UNWANTED MOVEMENT OF THE LANDING GEAR, AND THUS POSSIBLE INJURY TO PERSONS AND DAMAGE TO THE AIRCRAFT AND/OR EQUIPMENT.

WARNING: OBEY THE FUEL SAFETY PROCEDURES.

ZONE: 152
FIN: 241QM ** ON A/C NOT FOR ALL
FIN: 242QM ** ON A/C NOT FOR ALL
FIN: 243QM ** ON A/C NOT FOR ALL

1. Reason for the Job
Self explanatory
2. Job Set-up Information
A. Fixtures, Tools, Test and Support Equipment

REFERENCE	QTY	DESIGNATION
No specific	AR	ACCESS PLATFORM 2M (6 FT)
No specific	AR	CONTAINER 5 L (1.32 USGAL)
No specific	AR	PLUG - BLANKING
No specific	AR	SAFETY CLIP - CIRCUIT BREAKER
No specific	AR	WARNING NOTICE(S)

B. Work Zones and Access Panels

ZONE/ACCESS	ZONE DESCRIPTION
152	AFT CARGO COMPARTMENT
147AZ

C. Referenced Information

REFERENCE	DESIGNATION
TASK 28-00-00-910-001-A	Fuel Safety Procedures
TASK 28-10-00-910-002-A	Access to the Fuel Tanks and the Work Areas
TASK 28-25-00-650-001-A	Pressure Defuel
TASK 32-12-00-010-001-A	Open the Main Gear Doors for Access
TASK 57-17-11-000-001-B	Removal of Access Cover 148AZ or/and the ACT-Equipment Support Door
Pressure Holding Valve (241QM, 242QM, 243QM) ** ON A/C NOT FOR ALL
Pressure Holding Valve (242QM, 243QM) ** ON A/C NOT FOR ALL

3. Job Set-up
Subtask 28-28-49-941-050-A ** ON A/C NOT FOR ALL

A. Safety Precautions
(1) You must obey the fuel safety procedures when you do work on the fuel system (Ref. AMM TASK 28-00-00-910-001).
(2) On the APU section of overhead panel 25VU, make sure that the APU/MASTER SW pushbutton switch is released (the ON legend is off).
(3) On the FUEL section of panel 40VU, make sure that all the L TK PUMPS and R TK PUMPS pushbutton switches are released (the OFF legends are on).
(4) Put the WARNING NOTICE(S) in position:

On the APU section of overhead panel 25VU to tell persons not to operate the APU/MASTER SW pushbutton switch
On the FUEL section of panel 40VU to tell persons not to operate the fuel system
On ENG/APU FIRE panel 1WD on overhead panel 20VU to tell persons not to operate the fire extinguishing system.
On the Additional Center Tank (ACT) section of control panel 28VU to tell persons not to operate the fuel system.

(5) Put the WARNING NOTICE(S) in position to tell persons not to operate the Main Landing Gear (MLG) doors.

Subtask 28-28-49-650-050-A ** ON A/C NOT FOR ALL

B. Defuel the center tank (Ref. AMM TASK 28-25-00-650-001).

Subtask 28-28-49-865-050-A ** ON A/C NOT FOR ALL

C. Open, safety and tag this(these) circuit breaker(s):

PANEL	DESIGNATION	FIN	LOCATION
** ON A/C NOT FOR ALL
121VU	FUEL/ACT VENT VLV/MAN/SPLY	62QH	L21
121VU	FUEL/ACT VENT VLV/AUTO/SPLY	61QH	L20

Subtask 28-28-49-010-050-A ** ON A/C NOT FOR ALL

D. Get Access
(1) Open the right MLG door (Ref. AMM TASK 32-12-00-010-001).
(2) Put an ACCESS PLATFORM 2M (6 FT) in position at the right MLG door.
(3) Get access to the fuel center tank (Ref. AMM TASK 28-10-00-910-002).
(4) Remove access cover 147AZ (Ref. AMM TASK 57-17-11-000-001).

4. Procedure
Subtask 28-28-49-020-050-B ** ON A/C NOT FOR ALL

A. Removal of the Pressure Holding Valve
(1) Put a CONTAINER 5 L (1.32 USGAL) below the pressure holding valve (1).
(2) Remove the pressure holding valve (1) from the bracket (3).
(3) Remove and discard the packing (2).
(4) Put the PLUG-BLANKING in each disconnected line end.

[Rev.10 from 2021] 2026.04.02 06:17:59 UTC