ery stations, or any
battery rooms.
Application Description:
Since batteries are such an effective energy storage medium
for almost any backup power system, many industries use
backup battery banks for emergency power. The need for gas
monitoring occurs while these backup batteries are being
charged. Typically, batteries are continuously trickle charged.
After an incident that requires battery use, a higher charge is
used to quickly restore the batteries to full capacity. This
charging process generates hydrogen gas which is emitted
into the battery storage room. The faster the charge rate is,
the higher the hydrogen generation rate is.
Backup batteries are normally of the lead acid type, however
some are liquid based, gel cells, or even sealed type batter-
ies. No matter which of these battery types they are, hydro-
gen is generated while being charged.
Hazard:
Hydrogen is a highly flammable gas. The National Fire
Protection Association lists the lower explosive level (LEL) for
Hydrogen as 4% by volume. If sufficient hydrogen collects in
a room, it can potentially explode if ignited. This type of
explosive hazard can destroy equipment as well as causing
injury or death to personnel. The likelihood of this happening
depends on the number of batteries, their charge rate, the
size of the room, and the ventilation available for the room.
Although this may not be a common occurrence, the potential
hazard exists with any type of enclosed backup battery sta-
tion. This danger can be eliminated by monitoring for a hydro-
gen buildup, and taking appropriate action if a build up
occurs.
RKIs Solution:
RKI has developed the Model PS2 for this type of appli-
cation. The PS2 is a low cost, stand alone, continuous
gas monitor designed specifically for trouble-free hydro-
gen gas monitoring. The PS2 uses a long life, low main-
tenance metal oxide sensor for detection of hydrogen gas.
The unit has two alarm levels, typically set to 10% LEL
(0.4% volume hydrogen) and 30% LEL (1.2% volume
hydrogen). If these alarm levels are exceeded, the PS2
activates a 10 amp relay for each level, and also its own
audible and visual alarm. If action is taken at the first
alarm level (for example, turning on a ventilation fan in a
room to clear out the hydrogen), then the second alarm
level should never be exceeded. The second alarm level
typically would be used for more drastic action, such as
turning on a bigger fan, cutting off the battery charge, or
sounding a louder or remote alarm to bring attention to the
problem.
The PS2 is a simplified, stand alone fixed system that is
easy to install. It comes in a compact wall mounting
enclosure, with terminals inside for power and remote
alarm connections. The unit can be powered by 24 VDC,
or optionally by 115 VAC (which ships with a 6 foot power
cable), or 48VDC. Since hydrogen is lighter than air
(vapor density for H2 is 0.1), emissions will typically rise.
The PS2s sensor is on the end of a 30 foot cable, so that
it can be mounted above the batteries. RKI recommends
that a yearly check of sensor response is performed. A
low cost calibration kit is available through RKI that will
deliver a small amount of hydrogen to the sensor and con-
firm that the sensor will go into alarm. The PS2s metal
oxide sensor has an extremely long life-span. It is not
uncommon for this sensor to last 5 to 10 years or even
longer. The PS2 is an economical, trouble-free solution
that is ideal for monitoring battery rooms.
Equipment Needed:
73-1020RK-01 . . . . . . . .PS2 for LEL detection, 24VDC
73-1021RK-01 . . . . . . . .PS2 for LEl detection, 115VAC
81-PS2H2-LV . . . . . . . . . . . . . . .Cal Kit, PS2, H2, 34L
BACKUP BATTERIES EMITTING HYDROGEN
World Leader In Gas Detection & Sensor Technology
www.rkiinstruments.com
RKI Instruments, Inc. 1855 Whipple Rd Hayward, CA 94544
!
Phone (510) 441-5656
!
(800) 754-5156
!
Fax (510) 441-5650