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PARALLEL-BLADE
DAMPER:
A
type
of
damper
where
the
blades
rotate
in
the
same
direction.
PARALLEL
FANS:
Two
or
more
fans
that
draw
air
from
a
common
source
and
exhaust
into
a
common
duct
or
plenum.
A
parallel
fan
arrangement
is
generally
used
to
meet
volume
requirements
beyond
that
of
a
single
fan.
Two
identical
fans
in
parallel
will
effectively
deliver
twice
the
rated
flow
of
any
one
of
the
fans
at
the
same
static
pressure.
PARTICLE:
A
small,
discrete
mass
of
solid
or
liquid
material.
PARTICULATE:
A
particle
of
solid
or
liquid
matter.
PARTICULATE
MATTER:
Any
solid
liquid
material
in
the
atmosphere.
PEL
(PERMISSIBLE
EXPOSURE
LIMITS):
Limits
developed
by
OSHA
to
indicate
the
maximum
airborne
concentration
of
a
contaminant
to
which
an
employee
may
be
exposed.
PERMEABILITY,
FABRIC:
Measured
on
Frazier
porosity
meter
or
Gurley
permeometer.
Not
to
be
confused
with
dust
permeability.
The
ability
of
air
to
pass
through
the
fabric,
expressed
in
cubic
feet
of
air
per
minute
per
square
foot
of
fabric
with
0.5”
H2O
pressure
differential.
PERMIT:
An
authorization,
license
or
equivalent
control
document
issued
by
EPA
or
an
approved
state
agency
to
implement
the
requirements
of
an
environmental
regulation
such
as
a
permit
to
operate
a
facility
that
may
generate
harmful
emissions.
pH:
A
symbol
as
part
of
a
logarithmic
designation
to
indicate
acidity
of
alkalinity
on
a
scale
from
zero
to
14.
pH7
is
taken
as
neutral,
pH6
to
zero
increasingly
acid
and
pH8
to
14
increasingly
alkaline.
PHOTOCHEMICAL
PROCESS:
The
chemical
changes
brought
about
by
the
radiant
energy
of
the
sun
acting
upon
various
polluting
substances.
The
products
are
known
as
photochemical
smog.
PHOTOHELIC®
GAUGE:
Gauge
used
for
measuring
pressure
drop
across
filter
media
and
for
controlling
the
on/off
function
of
the
cleaning
system.
The
gauge
displays
static
pressure
in
inches
of
water
and
provides
adjustable
contacts
to
operate
the
cleaning
system.
This
is
a
registered
trademark
of
the
Dwyer
Company.
PIEZOMETER
RING:
A
device
consisting
of
a
number
of
pressure
taps
connected
to
a
common
manifold
to
measure
pressure.
PILOT
VALVE:
The
small
solenoid
valve
that
is
electrically
operated
to
relieve
pressure
on
one
side
of
the
diaphragm
and
cause
the
operation
of
a
larger
diaphragm
valve.
PITCH
DIAMETER:
The
mean
diameter
or
point
at
which
V-belts
ride
within
a
sheave.
This
dimension
is
necessary
for
accurate
drive
calculations.
PITOT
TUBE:
A
metering
device
consisting
of
a
double-walled
tube
with
a
short
rightangle
bend.
The
periphery
of
the
tube
has
several
holes
through
which
static
pressure
is
measured.
The
bend
end
of
the
tube
has
a
hole
through
which
total
pressure
is
measured
when
pointed
upstream
in
a
moving
gas
stream.
PLEATED
FILTER
ELEMENT:
Filter
elements
made
from
any
pleated
filter
media,
but
primarily
applying
to
those
equipped
with
100%
synthetic
fabric.
PLENUM:
Pressure
equalizing
chamber.
PLENUM
PULSE:
Type
of
pulsing
collector
where
entire
sections
of
the
clean
air
plenum
are
isolated
and
pulsed
with
either
compressed
air
or
air
from
a
high-pressure
blower.
PLY:
Two
or
more
yarns
joined
together
by
twisting.
PM10:
A
newer
standard
for
measuring
the
amount
of
solid
or
liquid
matter
suspended
in
the
atmosphere
(“particulate
matter”).
Refers
to
the
amount
of
particulate
matter
under
10
micrometers
in
diameter.
The
smaller
PM10
particles
penetrate
to
the
deeper
portions
of
the
lungs,
affecting
sensitive
population
groups
such
as
children
and
people
with
respiratory
diseases.
POINT
OF
OPERATION:
The
intersection
of
a
fan’s
static
pressure
curve
and
the
system
curve
to
which
the
fan
is
being
applied.
May
be
designated
as
velocity
pressure
divided
by
static
pressure
or
by
a
given
CFM
and
SP.
POINT
SOURCE:
A
stationary
location
or
facility
from
which
pollutants
are
emitted.
Also,
any
single
identifiable
source
of
pollution.
POLYMERIZED:
A
chemical
reaction
in
which
two
or
more
small
molecules
combine
to
form
larger
molecules
that
contain
repeating
structural
units
of
the
original
molecules.
POROSITY:
Sometimes
erroneously
used
as
synonym
for
permeability.
Originally
a
designation
for
the
amount
of
air
in
a
fabric
such
as
blankets.
PORTHOLE:
The
opening
in
a
cartridge
dust
collector
that
provides
access
to
the
filters.
POUNDS
PER
100
POUNDS
OF
GAS:
A
common
quantitative
definition
of
pollution
concentration.
PPM
(PARTS
PER
MILLION):
The
number
of
parts
of
a
given
pollutant
in
a
million
parts
of
air.
Units
are
expressed
by
weight
or
volume.
PRECIPITATORS:
Any
number
of
devices
using
mechanical,
electrical
or
chemical
means
to
collect
particulates.
Used
for
measurement,
analysis
or
control.
See
Electrostatic
Precipitator.
PRE-COATING:
The
application
of
a
relatively
coarse,
dry
dust
to
a
bag
or
cartridge
before
start-up
to
provide
an
initial
filter
cake
to
enhance
immediate
high
efficiency.
PRESEED:
Precoating
of
a
dust
collector
filter
(cartridge
or
bag-type)
with
material
to
create
a
dust
cake
and
ensure
peak
collection
efficiency
at
system
start-up.
Usually
done
when
collecting
very
small
particles,
such
as
welding
particulate,
etc.
PRESSURE,
ATMOSPHERIC:
The
pressure
due
to
the
weight
of
the
atmosphere.
It
is
the
pressure
indicated
by
a
barometer.
Standard
atmospheric
pressure
is
29.92
inches
of
mercury.
PRESSURE
DROP:
The
differential
pressure
between
two
points
in
a
system.
The
resistance
to
flow
between
the
two
points.
PRESSURE,
STATIC:
The
potential
pressure
exerted
in
all
directions
by
fluid
at
rest.
For
a
fluid
in
motion,
it
is
measured
in
a
direction
normally
90°
to
the
direction
of
flow.
Usually
expressed
in
inches
water
gauge
when
dealing
with
air.
PRESSURE,
VELOCITY:
The
kinetic
pressure
in
the
directional
flow
necessary
to
cause
a
fluid
at
rest
to
flow
at
a
given
velocity.
Usually
expressed
in
inches
water
gauge.
PREVENTION
OF
SIGNIFICANT
DETERIORATION
(PSD):
EPA
program
in
which
state
and/or
federal
permits
are
required
that
are
intended
to
restrict
emissions
for
new
or
modified
sources
in
places
where
air
quality
is
already
better
than
required
to
meet
primary
and
secondary
ambient
air
quality
standards.
PRIMARY
COLLECTOR:
A
dry
or
wet
collector
that
is
followed
by
a
secondary
collector
with
greater
filtering
efficiency.
PROCESS
WEIGHT:
The
weight
per
hour
that
is
run
through
the
process.
Commonly
used
in
APC
codes
to
determine
the
maximum
allowable
pollution
exhausted.
PROMULGATE:
To
make
a
new
law
known
and
put
it
into
effect.
The
EPA
promulgates
a
rule
when
it
issues
the
final
version
in
the
Federal
Register.
PSI
(POUNDS
PER
SQUARE
INCH):
A
measure
of
pressure
.1
psi
equals
27.7”
water
gauge.
PSIA
(POUNDS
PER
SQUARE
INCH
ABSOLUTE):
The
absolute
pressure
without
reference
to
another
point.
Atmospheric
pressure
is
14.7
PSIA.
PSIG
(POUNDS
PER
SQUARE
INCH
GAUGE):
The
pressure
relative
to
atmosphere.
For
instance,
10
PSIG
equals
24.7
PSIA.
This
is
the
more
common
pressure
term.
PSYCHROMETRIC
CHART:
A
graphic
depiction
of
the
relationship
between
pressure,
density,
humidity,
temperature
and
enthalpy
for
any
gas-vapor
mixture.
Used
extensively
in
comfort
ventilation.
PULSE
CYCLE:
As
used
in
conjunction
with
pulse-jet
baghouses
the
interval
of
time
between
pulsing
a
row
of
bags
and
that
row
being
pulsed
again.
PULSE
DURATION:
The
length
of
time
a
pulse
lasts.
Generally
described
as
the
length
of
time
the
electrical
signal
holds
the
pilot
valve
open
(20-40
milliseconds),
however
would
more
correctly
be
the
description
of
the
length
of
time
the
manifold
is
pressurized
(120-180
milliseconds).
PULSE
INTERVAL:
The
time
between
pulsing
one
row
of
bags
and
pulsing
the
next
row.
PULSE
JET:
Generic
name
given
to
all
pulsing
collectors.
PULSE-JET
CLEANING:
A
cleaning
method
where
a
momentary
burst
of
compressed
air
is
introduced
through
a
tube
or
nozzle
to
the
top
cap
of
a
bag.
A
bubble
of
air
flows
down
the
bag,
causing
bag
walls
to
collapse
behind
it.
Generic
name
given
to
all
pulsing
collectors.
PULSE
PIPE:
Pipe
used
to
transport
compressed
air
from
the
diaphragm
valve
to
the
pulse
nozzle
in
reverse
pulse
cleaning
systems.
In
some
manufacturers’
equipment,
the
pulse
pipe
delivers
the
compressed
air
directly
into
the
filters
being
cleaned.
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