Ashcroft Options - Manual (Page 3)

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Ashcroft ® Accessories
Throttling Devices
A throttling device should be used when a pressure gauge is
subjected to rapid pressure fluctuations, which make the gauge
difficult to read because of rapid pointer movement. Such a
device reduces pressure impact, slows the speed and range of
pointer movement, and prolongs gauge life.
Throttling effect is obtained by installing a restricting orifice
between the gauge socket connection and the Bourdon tube.
Severe service applications are characterized by the presence of
significant levels of pressure pulsation and/or vibration. Gauges
should be protected from severe pressure pulsation by the
inclusion of a dampener such as a throttle plug/screw or porous
metal snubber. If the pulsation is extreme, a liquid-filled gauge,
with dampener, should be used. A liquid-filled gauge will also last
significantly longer than a comparable dry gauge when vibration
is present. If the vibration levels are extreme, the only solution
may be to remotely mount the gauge away from the source of
vibration. In that case capillary tubing may be used to connect
the gauge to the pressure source.
The simplest means of providing a
restriction in the socket, a throttle screw
or throttle plug, should be ordered with
the gauge. Threaded or pressed into
an instrument socket, the throttle screw
orifice selected is based on the viscosity
of the pressure fluid, rapidity of pressure
fluctuations, and the amount of damp-
ening effect desired.
A smaller orifice should be used for
low viscosities, high frequencies, high
pressure and reduced pointer ampli-
tude. To accommodate these variables,
throttle screws are available in these
sizes: 0.0135, 0.020, 0.031, 0.040, and
0.070 inches, in brass and stainless
steel. When orifice size or service condi-
tion is not specified, a 0.020-inch orifice
will be supplied on Duragauge ® pressure
gauges and a 0.0135, on 25-35 1009
and 63 and 100mm 1008S.
THROTTLE SCREWS
Throttle screw
Type NPT Material Weight
Number Conn. (oz.)
25-1106B 1 ⁄
4
Brass 4
50-1106B 1 ⁄
2
Brass 8
25-1106D 1 ⁄
4
Steel* 4
50-1106D 1 ⁄
2
Steel* 8
25-1106S 1 ⁄
4
Stainless steel 4
50-1106S 1 ⁄
2
Stainless steel 8
* Internal parts are stainless steel.
Threads onto a gauge socket and pro-
vides restriction by means of a moving
pin, which may be placed in either of
five different sized holes, and thus
allows the user to vary the amount of
dampening to suit requirements. The
pulsating pressure moves the pin up
and down, providing a self-cleaning
action. Dampeners are shipped with
a pin in the “middle” hole, and may be
used in either a vertical or horizontal po-
sition. Maximum pressure is 5000 psi.
PULSATION DAMPENER
Porosity
Max Pore Cap. CFH at 1 psi
For use with
Opening (Inches) Diff. Press.
D 0.005 6.5
E 0.0025 3.0
G 0.0008 1.1
HX 0.0006 0.4
Used for dampening and filter-
ing, the snubber has a metal
disc available in four standard
grades of porosity. The one
best suited for the application
can be selected from the chart,
using the same guidelines as for
throttle screws. Due to the large
filter area, the snubber has less
tendency to clog than orifice-
type devices. All-metal construc-
tion permits the snubber to be
washed in a variety of common
solvents.
Oil
(50 to 500 S.S.U.)
Air, Steam
and Gases
Mercury
Manomometers
Water & Light Oils
(Under 50 S.S.U.)
Type NPT
Material
Max psi
Number Conn. Housing Filter Disc Rating
25-1112B 1 ⁄
4
Brass 316 10,000
50-1112B 1 ⁄
2
stainless steel
25-1112S 1 ⁄
4 303 316 15,000
50-1112S 1 ⁄
2
stainless steel stainless steel
25-1112M 1 ⁄
4
R Monel Monel 15,000
50-1112M 1 ⁄
2
PRESSURE SNUBBER