Installation of the Recirculation Check Valve

TASK 21-21-42-400-001-A
Installation of the Recirculation Check Valve

WARNING: MAKE SURE THAT AIR IS NOT SUPPLIED TO THE AIR CONDITIONING SYSTEM FROM THE MAIN ENGINE, THE APU OR A GROUND SOURCE. HOT COMPRESSED AIR CAN CAUSE INJURY TO PERSONNEL.

NOTE: The procedure is the same for the recirculation check valves 4020HM (4021HM).

FIN: 4020HM
FIN: 4021HM

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

REFERENCE	QTY	DESIGNATION
No specific	1	ACCESS PLATFORM 2M (6 FT)
No specific	AR	WARNING NOTICE(S)
No specific	Torque wrench: range to between 1.120 and 0.916 m.daN (99.12 and 81.06 lbf.in )

B. Work Zones and Access Panels

ZONE/ACCESS	ZONE DESCRIPTION
825

C. Referenced Information

REFERENCE	DESIGNATION
TASK 24-41-00-861-002-A	Energize the Aircraft Electrical Circuits from the External Power
TASK 24-41-00-861-002-A-01	Energize the Aircraft Electrical Circuits from the APU
TASK 24-41-00-861-002-A-02	Energize the Aircraft Electrical Circuits from Engine 1(2)
TASK 24-41-00-862-002-A	De-energize the Aircraft Electrical Circuits Supplied from the External Power
TASK 24-41-00-862-002-A-01	De-energize the Aircraft Electrical Circuits Supplied from the APU
TASK 24-41-00-862-002-A-02	De-energize the Aircraft Electrical Circuits Supplied from the Engine 1(2)
TASK 25-54-12-000-001-A	Removal of the Forward Cargo-Compartment Partition
TASK 25-54-12-400-001-A	Installation of the Forward Cargo-Compartment Partition
TASK 52-30-00-860-001-A	Open the FWD or Aft Cargo-Compartment Door with the Yellow Electric Pump
TASK 52-30-00-860-002-A	Close the FWD or Aft Cargo-Compartment Door with the Yellow Electric Pump
Recirculation Check Valve 4020HM (4021HM).
FOR [4020HM] (RECIRC CHECK VALVE 1)
TASK 06-41-53-00	FUSELAGE-DESCRIPTION AND OPERATION
FOR [4021HM] (RECIRC CHECK VALVE 2)
TASK 06-41-53-00	FUSELAGE-DESCRIPTION AND OPERATION

3. Job Set-up
Subtask 21-21-42-860-050-A

A. Aircraft Maintenance Configuration
(1) Make sure that:
(a) The aircraft electrical circuits are energized (Ref. AMM TASK 24-41-00-861-002).
(b) On panel 30VU:
1 The APU BLEED pushbutton switch is in the off position (the ON legend is off).
2 The ENG 1 BLEED and the ENG 2 BLEED pushbutton switches are in the off position (the OFF legends are on).
3 The WARNING NOTICE(S) is in position to tell persons not to operate the pushbutton switches.
(c) On the ground connector, the WARNING NOTICE(S) is in position to tell persons not to supply ground air.
(d) FWD cargo-compartment door 825 is open (Ref. AMM TASK 52-30-00-860-001).
(e) An ACCESS PLATFORM 2M (6 FT) is in position at FWD cargo-compartment door 825.
(2) Make sure that the access panel(s) are removed from partition FR34 (Ref. AMM TASK 25-54-12-000-001):
(a) FOR [4020HM] (RECIRC CHECK VALVE 1)

(Ref. AMM D/O 06-41-53-00),

(b) FOR [4021HM] (RECIRC CHECK VALVE 2)

(Ref. AMM D/O 06-41-53-00).

Subtask 21-21-42-865-051-A

B. Make sure that this(these) circuit breaker(s) is(are) open, safetied and tagged:

PANEL	DESIGNATION	FIN	LOCATION
** ON A/C ALL
FOR FIN: 4020HM (RECIRC CHECK VALVE 1)
122VU	AIR COND/RECIRC FAN/L/CTL	2HG	X20
122VU	AIR COND/RECIRC FAN/L/SPLY	1HG	X18
FOR FIN: 4021HM (RECIRC CHECK VALVE 2)
122VU	AIR COND/RECIRC FAN/R/CTL	11HG	W20
122VU	AIR COND/RECIRC FAN/R/SPLY	3HG	W18

4. Procedure
Subtask 21-21-42-420-050-A

A. Installation of the Recirculation Check Valve
(1) Remove the blanking plugs from the disconnected line ends.
(2) Clean the component interfaces and the adjacent area.
(3) Make sure that the parts retained from the removed component are clean and in the correct condition.
(4) Put the recirculation check valve (2) in position in the flange (3).
(5) Put the flange (3) (together with the recirculation check valve (2)) in position in the sleeve (5).

NOTE: The center line of the recirculation check-valve hinge must be in a vertical position.

(6) Install the clamp (1).
(7) TORQUE the clamp (1) to between 1.120 and 0.916 m.daN (99.12 and 81.06 lbf.in )

.
(8) Tighten the clamp (4).

NOTE: The end of the sleeve (5) must be within the painted marks on the flange (3).

5. Close-up
Subtask 21-21-42-410-050-A

A. Close Access
(1) Make sure that the work area is clean and clear of tools and other items.
(2) Install the access panel(s) removed from partition FR34 (Ref. AMM TASK 25-54-12-400-001):
(a) FOR [4020HM] (RECIRC CHECK VALVE 1)

(Ref. AMM D/O 06-41-53-00),

(b) FOR [4021HM] (RECIRC CHECK VALVE 2)

(Ref. AMM D/O 06-41-53-00).

(3) Remove the access platform(s).
(4) Close FWD cargo-compartment door 825 (Ref. AMM TASK 52-30-00-860-002).
(5) Remove the WARNING NOTICE(S).

Subtask 21-21-42-865-052-A

B. Remove the safety clip(s) and the tag(s) and close this(these) circuit breaker(s):

PANEL	DESIGNATION	FIN	LOCATION
** ON A/C ALL
FOR FIN: 4020HM (RECIRC CHECK VALVE 1)
122VU	AIR COND/RECIRC FAN/L/CTL	2HG	X20
122VU	AIR COND/RECIRC FAN/L/SPLY	1HG	X18
FOR FIN: 4021HM (RECIRC CHECK VALVE 2)
122VU	AIR COND/RECIRC FAN/R/CTL	11HG	W20
122VU	AIR COND/RECIRC FAN/R/SPLY	3HG	W18

Subtask 21-21-42-862-050-A

C. De-energize the aircraft electrical circuits (Ref. AMM TASK 24-41-00-862-002)

[Rev.10 from 2021] 2026.04.02 06:10:54 UTC