Rocky Mountain Air Solutions supplies a large selection of hydrogen
to Denver, along with many other specialty gases.
Rocky Mountain Air Solutions frequently supplies hydrogen and other specialty gases to
research laboratories and many other industries, so we felt it would be helpful for our Denver customers to be updated on the safe use of
hydrogen in laboratories.
With
escalating costs associated with the limited helium supply, operators and designers of laboratory
equipment are increasingly
turning to their gas
suppliers for hydrogen. The use
of hydrogen is found in several facilities, from medical research facilities to
universities, analytical laboratories, and chemical process buildings. Nonetheless, it is extremely
important to comprehend the risks
that are posed through the use,
distribution, and storage of hydrogen along with the fire and safety code rules
controlled by the National Fire
Protection Association’s Compressed Gases and Cryogenic Fluids Code (NFPA 55) and
the International Fire Code (IFC) and International Building Code (IBC). Recent
updates to NFPA 55 have redefined the Maximum Allowable
Quantities (MAQ) expressly created for hydrogen. These
MAQ’s are distinguished for each storage area, determined
by storage in either an unsprinklered or completely
sprinklered building and restricted further based on whether or not the hydrogen cylinders are being contained in
gas cabinets. The corresponding
volumes are expressed as standard cubic feet (cuft) of hydrogen at 1 atmosphere
of pressure. In an unsprinklered
building where not all cylinders are stored in gas cabinets, the MAQ is restricted
to 1,000 cuft, whereas that number is multiplied
to 2,000 cuft if all cylinders are stored in gas cabinets. Similarly,
for sprinklered units where not all cylinders are
stored in gas cabinets, the MAQ is
also 2,000 cuft. That number is increased to 4,000 cuft if all
cylinders are stored in gas cabinets.
NFPA further has limitations determined
by hydrogen use in
control areas or using outside storage, part II of
this series will discuss the infrastructure requirements
for compliance.
We will
further our discussion by selectively
describing some of the primary areas and necessities
for hydrogen installation in regards to
fire-resistance rating and ventilation.Section 6.3.1.3.1 of NFPA states
that for flammable gases stored or utilized
in amounts greater than 250 cubic
feet, a 1-hour fire resistance rated constrction will be utilized to
separate the area. The compressed
gas cylinders require separation by
10’ or a fire-resistant wall; however,
they require separation by 20’ or
a nonflammable wall having a minimum fire resistance rating of .5 hours
from incompatible elements like oxygen. For locations having hydrogen systems, proper
safety placards must be
permanently placed as well.
Additionally, Section
6.16 details that indoor storage and use
areas must be given either natural or
mechanical ventilation, so long as the natural ventilation is
verified to be adequate for the gas employed. If using a mechanical ventilation process, the system
must function while the building is occupied, with
the rate of ventilation not reaching
lower than 1 ft3/min per square foot of floor area of storage/use and being
equipped with an emergency power system for alarms,
vents, and gas detection. The system must also keep track of
gas density to guarantee correct
exhaust ventilation. Part III of this
series will discuss the other NFPA 55 requirements for separation and controls.
To continue the series that explains updates to NFPA 55 governing the safe use of hydrogen in
laboratories, we will further our discussion selectively explaining some of the important areas and requirements for hydrogen installation in terms of separation and
controls.Section 7.1.6.2 of NFPA 55 states that any flammable or
oxidizing gases are required to be separated by 20’ from each other, while section
7.1.6.2.1 dictates that this length can be limitlessly reduced when separated
by a barrier comprised of noncombustible material a minimum of 5’ tall that provides a fire resistance rating of at least .5 hours.
The safe use of controls in hydrogen systems are declared by NFPA 55, IFC, & IBC, creating a slightly more nuanced neccessity for
compliance. Section 414.4 of the IBC
demands that controls must be suitable for the intended application, with
automatic controls being required to operate fail-safe. Section 2703.2.2.1 of the IFC demands suitable materials for hazardous media, the main negative result being that 316L
SS or copper piping shall be utilized and identified in accordance with ASME A13.1
with directional arrows every 20’. The
system should also contain no concealed valves or breakable connections, using
welded or copper brazed joints where the piping is concealed. NFPA 55 dictates that these brazing materials
should have a melting point higher than 10,000°F.Aside from piping requirements, these codes also require the use of emergency shutoff valves on supply piping at the point of use and
source of compressed gas, along with backflow prevention and flashback
arrestors at the point of use.
As the concluding
part in the NFPA 55 series governing the hydrogen’s correct use within laboratories, we will conclude our discussion by explaining
uses where the
Maximum Allowable Quantities (MAQ’s) is less than the demand for hydrogen gas
cylinders.
It is not unusual to come across
installations where the requirement for
hydrogen is greater than the MAQ’s, frequently in instrumentation employements
and/or chemical reactions like hydrogenation. These are frequently come across in installations using hydrogen where there is no outside storage and control to line pressures of less than 150 PSIG is not achievable . The NFPA 55 code and the IBC and IFC requirements will allow for these volumes to be present inside a building; however, important enhancements to the building are necessary, effectively demanding that the
facility build a hydrogen shelter. The upgrades include improvements
to the structure fire rating, transportation, fire detection, a limitation on
the number of occupants,
and a building story
limit. These
installations also have strict distancing requirements and floor and wall
ratings as well. Although
feasible, this scenario is not ideal and should be avoided if possible. A
more efficient resolution would be to combine the
facility’s requirements into several, smaller systems where the compressed gas cylinders may be
set up entirely in gas
cabinets.
Larry Gallagher
CONCOA
2/10/2016