MIL-C-7024 fluid, Type I will not be used to calibrate jet engine fuel system
accessories. Jet engine fuel systems will use MIL-C-7024 Type II fluid.
Accessories will be thoroughly flushed with cleaning solvent, P-D-680, after
calibration and preserved with light oil, MIL-C-6529.
Aeroquip Corporation Series 3700 and 3750 Quick Thread Couplings. The advantages of quick-disconnect
couplings include ease and speed when connecting and disconnecting fuel systems. They also help to eliminate gas loss
and other hazards caused by exposed fuel.
Types. The more common types of quick-disconnect couplings are described in the following paragraphs.
(a) Screw-type. This type, as shown in figure 2-14, is connected by rotating the union nut until teeth
fully engage the teeth of the lock spring. A distinct clicking noise is heard as the teeth engage.
(b) Quick-threading/indicating-type. This type, as shown in figure 2-15, is connected by twisting the
socket In a clockwise direction onto the threaded nipple portion.
(c) Inst-o-matic push/pull-type. This type, as shown in figure 2-16, is connected by pulling back the
spring-loaded outer shell of the socket, and while in this condition, by pushing socket firmly onto the nipple and releasing
the socket shell.
(d) Full grip push/pull-type. This type, as shown in figure 2-17, is connected by pushing the mating
(e) Straight flow ball valve-type. This type, as shown in figure 2-18, is connected by mating the
socket to the nipple portion and then turning the socket in a clockwise direction.
(f) Ball lock-type. This type, as shown in figure 2-19, is connected by pushing socket onto nipple
assembly and rotating socket cam collar clockwise.
Inspection of Aeroquip Corporation series 3700 and 3750 quick thread couplings. Quick-disconnect
couplings can be inspected for excessive wear by measuring the length variation of the coupling assembly as follows:
(a) With system pressure at zero and the coupling connected, compress the coupling lengthwise and
measure from the back of the nipple half adapter hex to the back of the socket half adapter hex.
(b) Record the measurement as value A.
(c) Extend the coupling by pulling lengthwise and repeat the measurement.
(d) Record this measurement as value B.
(e) Compare values A and B to determine amount of length variation.
(f) Refer to table 2-8. If length variation exceeds the given value for the particular dash size, early
failure is indicated. Replace coupling assembly if this occurs.
Maintenance. Proper care and handling of quick-disconnect couplings must be exercised to prolong
coupling life and ensure the integrity of the system in which they are employed.
(a) Tools. Do not use gripping tools to connect or disconnect coupling halves as these actions can
normally be readily accomplished by hand.
(b) Use. Couplings of the types listed have undergone extensive engineering prior to production. All
have been subjected to extensive vibrational and other testing. They will perform satisfactorily and will not separate
during use if they have been properly connected and are otherwise in serviceable condition.
Care. Avoid dirt or other foreign matter contamination when couplings are in the disconnected
condition. Contamination can inflict coupling damage and will, when coupling halves are connected, cause system
contamination. Should contamination occur, wipe with a clean, dry lint-free cloth or use a clean brush. If a brush is used,
assure no bristles remain in the coupling connecting areas after brushing.
(d) Handling. Handle quick-disconnects as you would any other fine piece of equipment. Although they
are not delicately designed, do not abuse them by dropping or inflicting other types of abuse.