Reviewers Note: Words/phrases in blue will be links to specific diagnostic procedures when this document is published in Freshdesk.

CNG Cylinder Product Description and Operation Manual

PDO.0033 Ver. 3.0 April 25, 2023
Introduction
About this Manual

This manual contains specific information pertaining to the characteristics and operation of Type 4 compressed
natural gas (CNG) cylinders designed and manufactured by Hexagon® Agility®.* It should not be applied to
cylinders made by other manufacturers.
It is the responsibility of the vehicle OEM or third party installer to provide this manual to the appropriate
personnel and to ensure its accessibility. Appropriate personnel includes, but is not limited to, those who are
responsible for the handling, installation, operation, maintenance, and inspection of the cylinders.
A thorough understanding of the information provided in this manual is required for the safe operation of the
product. If further information is needed or questions arise, contact Hexagon Agility.
This document contains material from the Hexagon Agility ENP-558 Cylinder Inspection Manual which it
supersedes.
Hexagon Agility endeavors to maintain a comprehensive and accurate product and service information. We reserve the right to make changes at any time to manuals
and other materials. Please contact Hexagon Agility FleetCare to ensure you have the latest version.

*Applies to cylinders labeled under Agility Fuel Solutions, Hexagon Lincoln, and Lincoln Composites

Safety
In Case of Emergency
WARNING
In the event of an emergency, call 9-1-1, and evacuate the area.
Information for first responders may be found in Hexagon Agility publication ENP-084.

General Safety Precautions
Always use proper personal protective equipment (PPE) when working on CNG cylinders, fuel systems, and
vehicles.
Required PPE includes but is not limited to the following items:
1. safety glasses
2. hard hat
3. work gloves
4. When specified: nitrile or latex gloves
5. steel-toed shoes
6. high-visibility vest
7. fall arrestment harness

Warning Messages and Symbols Used in this Document
WARNING
WARNING indicates a hazardous situation which, if not avoided, could result in death or serious injury.
CAUTION
CAUTION indicates a hazardous situation which, if not avoided, could result in minor or moderate
injury.
NOTICE
NOTICE is used to address practices not related to physical injury, such as best practices or tips to
help an operation or procedure go smoothly and prevent equipment damage.

Description
Hexagon Agility cylinders are designed to be robust and reliable for the entirety of their service life. As such, they
require relatively low maintenance.

Cylinder Construction
Hexagon Agility Type 4 cylinders are made by winding composite over a polymer liner with metallic end bosses.
dome protection

composite shell

liner

boss

Hexagon Agility Type 4 cylinder cutaway showing components

Cylinder Envelope
Each cylinder requires a certain amount of space for production variation and expansion due to pressurization.
The envelope requirement for a particular cylinder may be found in the Hexagon Agility Design Parameters (DP)
document.

Application
For storage of compressed natural gas (CNG) in vehicular applications.

Cylinder Design Codes
Hexagon Agility designs and manufactures cylinders to the requirements of 49 CFR §571.304 (FMVSS 304),
CSA/ANSI NGV 2, ECE R110, and ISO 11439. Every cylinder is marked with the code for which it is certified.

Valves and T-PRDs
Hexagon Agility performs a thorough evaluation of valves and thermally-activated pressure relief devices (TPRDs) to determine which devices are best suited for cylinders it manufactures. Only approved valves and TPRDs are to be used. Hexagon Agility Statement of Service document defines the approved list of T-PRDs and
valves for each cylinder, along with their acceptable positioning.

Mounting Hardware
Hexagon Agility cylinders are designed to be secured using straps, or—for cylinders with end mounting
features—fixed and sliding end mount blocks.**

fixed block

sliding block

strap assembly

Figure 2. Hexagon Agility cylinder mounting types
Hexagon Agility does not prohibit the use of customer sourced mounting hardware; however, the customer
assumes full responsibility and liability for design selection. Customer designed or purchased hardware must
account for assembly tolerances, compliance of the supporting structure under the full range of vehicle motion,
temperature effects and weathering, and cylinder expansion with pressure.
NOTICE
Clearance must be maintained between cylinders and vehicle components and accessories and fuel
system components. Hexagon Agility recommends that any customer sourced mounting hardware be
able to withstand a 20g load in any direction.
**Contact Hexagon Agility for approved hardware.

Operation
Service Conditions
The rated pressure, temperature, and service life of the cylinder varies based upon the design code used and
intended application. This information is provided on the cylinder DP.

Gas Composition
CNG composition requirements are specified by the applicable cylinder code.

Filling
CAUTION
Exercise care not to fill cylinders with liquid methane which can form from a high-pressure cascade
system in cold conditions.
Hexagon Agility cylinders may be filled without flow restrictions when the ambient temperature is above 10°F (12°C), or the cylinder is at a pressure greater than 100 psi (7 bar).
NOTICE
If a cylinder is below 100 psi (7 bar) and the ambient temperature is less than 10°F (-12°C), condition the
cylinder by filling it directly with a compressor to 450 psi ± 50 psi (31 bar ± 3 bar), wait 1 hour, and then
refuel normally. Alternatively, the cylinder may be conditioned by placing it in an environment with a
temperature above 60°F (16°C) for 8 hours.

Depressurization (Venting) and Defueling
Removal and replacement of cylinder valves, fittings, and/or PRDs requires removal of all CNG through
depressurization or defueling.
WARNING
Never attempt to repair a cylinder or remove a pressurized fitting (e.g., valve or T-PRD) without verifying
the cylinder is empty.
Hexagon Agility cylinders may be vented without flow restrictions; however, it is recommended that cylinders be
vented slowly. Rapid venting causes a significant drop in temperature, which may lead to ice buildup and damage
to surrounding components.
NOTICE
After rapid venting, leave cylinder valve open while residual gas in the cylinder expands as it warms to
its surrounding temperature. Allow cylinder to warm for 4 hours before refilling.
Cylinders in systems equipped with an excess flow device (EFD) must be defueled at a slow rate to avoid
triggering the EFD. If the EFD closes during defueling, follow valve OEM instructions to reset the device. Most
devices can be reset by closing the valve and slowly reopening it.
Cylinders equipped with electric solenoid valves should be defueled at a slow enough rate as to not close the
solenoid. If the solenoid closes, close the manual shutoff, re-energize the solenoid, and slightly crack open the
manual shutoff to resume flow. Refer to electric solenoid cylinder valve OEM instructions.
WARNING
*A faulty cylinder solenoid valve may give the impression a cylinder is empty when it is not. If there is
any question whether the solenoid is working, follow electric solenoid cylinder valve OEM instructions.