Dräger CDR 4500 Instructions For Use Manual page 44

Maintenance
4.3.4 Replacing a nose cup valve disc
1. Pull out the old valve disc towards the inside.
2. Insert the stud of the new disc into the hole from inside, and pull it
towards the visor until the undercut of the stud is visible. The valve
disc should make even contact with the inside surface.
4.3.5 Replacing the speech diaphragm or O-Ring
1. Pull the nose cup out of the groove in the screw ring.
2. Unscrew the screw ring with a spanner.
3. Turn the spanner over and carefully insert it in the holes of the
grille, taking care not to damage the foil on the diaphragm.
4. Turn the speech diaphragm to release it and remove it.
5. Remove the O-ring from the connector with the sealing ring lifter.
6. Check speech diaphragm and O-ring and replace if necessary.
7. Press the edge of the nose cup into the groove in the screw ring
and ensure that it engages all around. The edge of the nose cup
must fit all around the full circumference of the screw ring. The
center marks on the front port and on the nose cup must match.
4.3.6 Replacing the exhalation valve disc
1. Remove the exhalation valve cover.
2. Grip under the edge of the valve disc and pull the holding stud out
of the hole.
3. Clean the valve seat.
4. Moisten the new valve disc with water and press it into the hole
until it engages. The valve disc must make even contact all
around.
5. Refit the exhalation valve cover so that it clicks into place.
4.3.7 Replacing the inhalation valve disc
1. Pull the inhalation valve out by its tab.
2. Remove the old valve disc and fit new disc.
3. Press the inhalation valve into the mask connector until it makes
even contact all-round. The valve disc must not be pinched. The
disc must face inwards, and the stems face outwards.
44
4.4
The leak test should be performed with an appropriate test device
(e. g. the Testor or Quaestor series).
(1) Checking leak tightness
1. Moisten the face seal and exhalation valve with water.
2. Mount the facepiece on the test head.
3. Make sure that the face seal fits tightly onto all parts of the test
4. Seal the connector with the test adapter and produce a negative
The facepiece is considered leak-tight if the pressure drop is less than
1 cm H
(2).
(2) Test with sealed exhalation valve
1. Remove the exhalation valve.
2. Plug in the exhalation valve plug.
3. Generate a negative pressure of 10 cm H
4. If the pressure drop is less than 1 cm H
5. Repeat the leak test (1). If the facepiece is leaky, continue with (3).
(3) Leak test under water
1. Immerse the test head including the facepiece with exhalation
2. Produce a positive pressure of approx. 10 cm H
3. Slowly turn the test head under the water surface. Emerging
4. Take the test head with the facepiece out of the water, repair the
5. Remove the exhalation valve plug.
6. Install the exhalation valve.
7. Repeat leak test (1).
(Use Instructions for NIOSH-approved full facepieces)
Leak tests
head. Inflate the test head if necessary.
pressure of 10 cm H O (10 mbar).
2
O (1 mbar) per minute. If the facepiece leaks, continue with
2
remove the exhalation valve plug and insert a new valve disc.
valve plug in the water.
bubbles indicate leaks.
facepiece, or replace leaking components.
O (10 mbar).
2
O (1 mbar) per minute,
2
O (10 mbar).
2
Dräger CDR 4500