SERVICE BULLETIN
INFORMATION ONLY
Bulletin No.:

CYL-TSB-004

Date:

May 7, 2014

Subject:

Cylinder Bracket and Strap Installation

Models:

Quantum Type 4 Cylinders

Background
A number of cylinder bracket assemblies are available from various
manufacturers that can be used to secure the Quantum Type 4
gaseous fuel cylinders to a vehicle. These bracket assemblies must
be properly assembled and installed.
Condition
If the cylinder bracket assemblies are improperly installed or the
preload applied to the cylinder straps is incorrect, the cylinder bracket
assembly can fail to properly retain the cylinder. If this occurs a fuel
line may loosen or fatigue due to cylinder movement or the cylinder
could be damaged. Either scenario could lead to a fuel leak creating
a fire hazard.
Cause
Improper cylinder bracket alignment or strap preload may result in uneven pressure being applied to the
cylinder strap isolator. This uneven pressure may result in premature isolator failure, damage to the
cylinder and or cylinder bracket assembly. The preload applied to properly secure the cylinder in the
brackets will vary depending on the cylinder manufacturer and or cylinder bracket manufacturer.
Correction
The installer is ultimately responsible for ensuring the proper alignment and installation processes for the
cylinder and cylinder brackets being installed.
The following specification is only valid for the Quantum cylinder bracket assembly (PN 115959)
when used in a bed mount application with a Quantum 25” diameter Type 4 cylinders measuring
60” or less and not approved for any other sized cylinder.
Bracket Asm. Part Number

Cylinder Diameter

Installed Spring Height

115959

25” (Nominal)

1.22” (31mm)

Important: The installed spring height specification shown in the table is
for a 25” diameter Quantum Type 4 cylinder installed in the specified
bracket using new cylinder isolators, new locking fasteners, and with
less than 500 psi (3447 kPa) of pressure in the cylinder.
Reuse of the cylinder isolators or strap hardware will affect the final
assembly and may result in damage to the cylinder and or cylinder
bracket assembly.
This bracket has been tested to support a cylinder in the horizontal
position only.
5/7/2014 Revision A

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SERVICE BULLETIN
INFORMATION ONLY
When using a cylinder bracket assembly other than the one noted above, Quantum recommends the
following precautions:
Installation:
 Use the cylinder bracket manufacturer’s recommended assembly instructions.
 Verify that the rubber isolator is properly seated on the cylinder brackets and straps.
 Verify the preload applied the cylinder bracket strap has not altered the shape of the strap.
 Verify the cylinder will NOT move freely in the completed cylinder bracket assembly.
The following recommendations should be followed when servicing any cylinder in any bracket assembly
to ensure proper retention and service life.
Servicing:
 If a locking fastener is used, always replace the cylinder strap nuts and or bolts when they have
been removed with equivalent replacement parts.
 Always replace the cylinder isolators when the cylinder strap has been loosened or removed.
Important: A Type 4 fuel cylinder will expand and contract as the internal pressure increases and
decreases. In order to compensate for expansion and contraction the cylinder strap rubber isolator is
designed to deform slightly. Always install new isolators in order to achieve accurate bracket strap spring
height. Accurate bracket strap spring height can only be achieved at cylinder pressures below 500 psi
(3447 kPa).



Always check the bracket assembly spring height when the cylinder pressure is below 500 psi
(3447 kPa).
DO NOT check the bracket assembly spring height on a bracket strap after it has been in service.

Important: Do not verify the cylinder strap preload on a fully pressurized cylinder. A Type 4 cylinder will
expand and contract as the internal pressure increases and decreases. In order to compensate for
expansion and contraction the cylinder strap rubber isolator is designed to deform slightly. The rubber
isolators will eventually settle slightly causing the bracket assembly spring height to vary from the initially
installed spring height.


Inspect the cylinder brackets, straps, mounting frame, and mounting hardware for cracks,
corrosion, deformation, or other damage.

Contact Information:
For all other inquiries, contact Quantum:
E-Mail: [email protected]
Phone: 800.816.8691
Fax:
949.930.3401
Parts Information
None

5/7/2014 Revision A

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