8710.0000 BG
Pressure Chamber
small size
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03.11
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Name
Fig.: Pressure chamber
Description
This unit model 8710 is a pressure/vacuum
chamber for calibrating barometric instruments
(aneroid barometers, barometric sensors, barographs, mercury barometers etc.).
Mechanical design
(refer to figure page 2)
The housing of the pressure chamber (1) consists
of a welded, ribbed steel construction featuring a
flange (2) on top of the unit and a rectangular
door flange. The opening at the top is either covered by a round aluminium plate or - for calibrating mercury barometers - by a mountable acrylic
glass hood (3) with a removable sealing plate (4).
The sealing of the chamber is achieved by two Oseals in the flange. The front panel door (5) consists of a solid steel frame holding a full-sized
acrylic glass pane. The sealing is also achieved
by an O-seal in the flange. When closing the door
with four handwheels (7) a uniform sealing pressure is applied - without any influence from the
hinges.
Inside the pressure chamber a vibrating table
(model 8712) may be operated, connected to an
external power supply of 12 V DC. From a crossbar mount (8) several instruments that are to be
tested e.g. aneroid barometers, may be suspended. For mounting a mercury barometer the
crossbar (9) inside the mountable glass hood is
used.
For connecting a standard test barometer or other
external instruments, two air inlets (10) are provided on the left of the chamber. As a reference
sensor a precision digital barosensor with integrated LCD is used. The reference sensor is connected to the pressure chamber by means of a
hose. On the right of the chamber 6 electric feedthrough terminals (13) are provided, e.g. for connection of barometric sensors or for a remote
vernier control used for calibrating Hg-barometers
etc.. At the base (14) the main control levers are
located:
The switch valve "pressure/vacuum" (15), the
controlling valve for the pump connection (16)
which enables to close and to open, i.e. to regulate the air inlet from the pump, the controlling
valve (17) which is regulating or cutting of the
input of the outside air to the chamber, and the
push-button switch to operate the pressure/vacuum pump. The base plate (19) serves to
mount the pressure chamber. As an alternative a
cabinet (model 8720) can be used (see dimension
sketch page 4).
The pressure/vacuum pump is located inside the
chamber base.
Pressure chamber with base and cabinet are covered with a protective coating of blue varnish RAL
5009 (the inside of the pressure chamber is
white). Connecting nozzles and handwheels are
made of chrome-plated brass resp. steel.
8710.0000 BG
Pressure Chamber
small size
Mechanical design
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8710.0000 BG
Pressure Chamber
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small size
(For further technical data refer to operating instructions on "Rotary Vane Pumps", model 8750).
Technical Data
Pressure chamber:
Operating range:
700...1100 hPa
Volume of chamber:
approx. 65 l
Air inlets:
2 ea. NW 10
Electric feed-through
connections:
6 ea. terminals, Ø 4 mm
Power supply:
230 V AC
Dimensions:
refer to dimension sketch
page 4
Weight:
approx. 107 kg
Acrylic glass hood:
Dimensions:
refer to dimension sketch
page 4
Weight:
approx. 5.5 kg
Cabinet:
Dimensions:
refer to dimension sketch
page 4
Weight:
approx. 55 kg
Mounting support for standard barometer:
Lighting system:
fluorescent lamp, 16 W
Power supply:
230 V AC
Dimensions:
1300 x 170 x 120 mm
Weight:
approx. 1.7 kg
Vibrating table:
Power consumption:
1.2 W
Power supply:
12 V DC
Dimensions:
approx. 300 x 515 mm
Pressure/vacuum pump:
Nominal air intake
capacity:
2.4 m³ / h
Nominal motor rating: 0.22 kW
Weight:
12.5 kg
8710.0000 BG
Pressure Chamber
small size
Accessories
2 pce
rubber tube, red
length 1 m, completed with rubber hose
and additional tube clamp.
AS ALTERNATIVE MAY BE USED:
Twin-piston vibration pump:
Nominal air intake
capacity:
2.3 m³ / h
Nominal motor
rating:
50 W
(For further technical data refer to operating instructions "Reciprotor-pump", model 8760).
Remote vernier control:
Dimensions:
Control unit 8742:
135 x 71 x 45 mm
Control desk:
120 x 120 x 60 mm
Weight:
Control unit 8742:
approx. 0.3 kg
Control desk:
approx. 0.5 kg
Ordering Code
Pressure chamber c/w base, fittings,
controls and crossbar mount:
8710.0000
Hood (for mercury barometer) made
of acrylic glass c/w crossbar for suspending Hg-barometer
8711.0000
Vibrating table
8712.0000
Cabinet
8720.0000
Base plate
8721.0000
Mounting support for standard
barometer c/w fluorescent lamp,
16 W
8740.0000
Remote vernier control:
Control desk
Control unit
8741.0000
8742.0000
Pressure/vacuum pump
8750.0000
Twin-piston vibration pump
8760.0000
Control unit for Fortin-Barometer
8745.0000
Lighting set
9000.0112
For a suitable standard barometer: refer to our
catalogue group 5!
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8710.0000 BG
Pressure Chamber
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Dimension sketch
with cabinet type 8720
685
840
1240
510
760
700
2355
150
1500
8710.0000 BG
Pressure Chamber
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Operating instructions
Installation:
The pressure chamber shall be placed either on
the cabinet (8720.0000) or on a suitable table.
The mains connection to a 230 V, 50 Hz socket
has to be made.
If the mountable hood (8711.0000) is used the top
plate must be exchanged for it. For this purpose 8
ea. Flange nuts (M8) have to be removed, the
plate taken off and the hood must be positioned
correctly. In order to avoid putting undue strain on
the glass hood -bolting it down should be done
exactly in the below recommended sequence.
1. Put washers on bolts and screw on nuts by
hand.
is already equipped with suitable vacuum hoses
at the factory. These are only drawn up onto the
nozzles at the rear of the chamber base. The
hoses are marked as follows: V = vacuum, this
hose is connected to the nozzle on the left. "A"
means exhaust or pressure hose. This one is
connected to the nozzle on the right (ref. to drawing).
The "A"-output of pump model 8750 is equipped
with an oil separator and a relief valve which
opens at an excess pressure of 0.5 bar. (Pump
model 8760 is limited to a max. excess pressure
of 0.85 bar by its design).
2. Tighten nuts somewhat in the sequence 1, 2,
3... etc. according to sketch below.
3. Tighten nuts further in the sequence 1, 2, 3...
etc. with a torque wrench. Recommended
torque: 10 Nm!
3
5
7
1
Plug
(Traverse)
(Cross bar)
Power
2
Pump
Pump
8
Light
6
4
Pressure
The supplied rubber hose is connected to the
reference barosensor and placed on one of the
two air inlets of the chamber. The second inlet
remains closed by a blind flange when not in use.
Vacuum
Mains
connection
Pressure chamber 8710, rear view
Attention must be paid to the operating instructions of the reference barosensor!
The pressure/vacuum pump is equipped with shock
absorbing rubber mounts and it may simply be
placed inside the chamber base. Refilling the pump
with lubricant etc. is described in detail in the operating instructions on "Rotary Vane Pumps". Please
read instructions carefully before starting up unit.
The vibration pump, model 8760 requires no lubrication. However - even for this unit - the instruction manual must be precisely followed. The
pump
Likewise two electric sockets are located at the
rear for connecting the pressure/vacuum pump
(top socket and one spare. After plugging in
power cable (230 V AC/50 Hz) the unit is ready
for use.
8710.0000 BG
Pressure Chamber
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Operation
Closing and opening the front door:
After closing the front panel door, close attention
should be paid to tightening the handwheels
"crosswise" - lightly at first, then firmly in the
same sequence. The handwheels are so dimensioned that no additional tools for clamping down
are needed. When the pressure chamber is
opened after measurements are completed - it
must be carefully watched that valve (17) is
opened and pressure is thereby equalized between chamber and ambient air.
Testing for leaks:
It is recommended to test the pressure chamber
for leaks before actually starting measurements.
The test is carried out by creating an excess
pressure as well as a subpressure of 50 to 100
hPa in the chamber and to compare readings of
the barometer with eachother. It must be noted
that at first a period of pressure deviations and
distribution is observed in the chamber when
pressure is not stable, yet. Only after approx. ½
hour measurements may be compared with
eachother! The stabilizing period can be shortened - after having gained some experience - by
increasing pressure above the desired level and
then letting air escape again through the pressure
equalizing valve. Similarly one may proceed with
vacuum measurements. When comparing the
readings of indicated pressure it must be noted
that the temperature may change during the observing period and a mathematical correction may
have to be applied. If an unwarranted high loss of
pressure or vacuum is observed, valves 16 and
17 must be checked for a tight fit and also the
position of the connecting hose to the reference
barosensor. Equally the four handwheels at the
front panel door must be checked for tightness. If
necessary it should further be examined if larger
dirt particles or any foreign matter may have become lodged in the O-seal of the front door or at
the top flange - which may impair sealing.
Testing of direct reading, analog or digital
instruments (e.g. aneroid barometers, barographs):
The instruments should be positioned or suspended (crossbar mount) in a way that correct
readings may be taken by avoiding errors of parallax. Regulating the chamber to the various pressure levels is done with valves 15, 16 and 17 as
previously described.
Testing of barometric sensors with electric
output:
Connecting the power supply as well as transmitter the measured values (e.g. to an external DVM)
can be done by using the 6 feed-through terminals. (Attention: Conducting voltages through
these terminals is allowed only up to max. 50 V
according to VDE specification.)
Testing of mercury barometers:
The barometer is hooked to the crossbar inside
the glass hood and hangs freely inside the pressure chamber. For remote control of the vernier
the unit 8742.0000 for station barometers is connected. (resp. 8745.0000 for Fortin-barometers)
The gear wheel of the control unit 8742.0000 is
attached to the knurled knob of the vernier. The
three setscrews in the gear wheel are tightened.
Two lashings serve for torque compensation and
are clamped to the barrel of the mercury barometer (ref. to drawing). The electric connection is
achieved through banana plugs and the feedthrough terminals in the wall of the pressure
chamber - to the external control desk.
Installing control unit 8742.0000
8710.0000 BG
Pressure Chamber
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The vernier control unit 8745.0000 for Fortin-type
barometers is already installed in a suitable table.
By loosening the set screw in the bushing the
height of the control unit may be adjusted for barometers of various lengths. The disk mounted on
the gear shaft moves through driving pins an adjustment ring which is held to the knurled knob of
the fortin-type barometer by tree setscrews (ref.
to drawing). Supply voltage can be fed to this
device via stationary terminals at the top of the
table. For starting operation they only have to be
connected to the feed-through terminals.
Vibrating table, type 8712 (working principle)
The control desk for the remote vernier control is
externally connected to the feed-through terminals by cables fitted with banana plugs. The same
connections are used for a corresponding powersupply or control desk for the vibrating table. The
control desk 8741.0000 features a power supply
230 V AC/12 V DC. On one side of it the On/Offswitch and the fuse are located and on the front
panel the connecting sockets are mounted and
also a pair of polarity reversal is achieved which
results in an upward or downward movement of
the vernier (ref. to fig.).
Using the vibrating table, type 8712:
The vibrating table is supplied completely assembled. This unit is equipped with four rubber
mounts and can be set up directly in the pressure
chamber.
The crossbar mount is screwed to the vibrating
table (two screws, M4). The supply circuit to the
vibrating motor consists of two electric sockets
mounted to the top plate of the vibrating table with
extension to the outside through use of banana
plugs and the feed-through terminals. A power
supply of 12 V DC at a power consumption of 1.2
W is required. It should have a push-button or
toggle switch. The vibrating table should only be
operated at intervals of 2 to 3 seconds which is
sufficient in order to loosen mechanism of instruments under test.
Control desk, type 8741.0000
Maintenance
Attention must be paid to the maintenance instructions in the operating manuals of the "Rotary
Vane Pumps" or the "Reciprotor Pumps" - especially the oil level check and the oil change for the
pump. The further equipment is maintenancefree!
After a long operating period the rubber hose and
the O-seals should be checked for cracks etc.
and should be exchanged if necessary.
8710.0000 BG
Pressure Chamber
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Pressure/vacuum diagram
Sperr- bzw.
Drosselventil;
Kammer-Pumpe
Sperr- bzw. Drosselventil;
Kammer-Außenluft
Druckkammer
Pressur chamber
Control valve
chamber/pump
Control valve
chamber/outside air
Ölabscheider *
Oil seperator *
Druckbegrenzungsventil *
Relief valve *
Druck/Vakuum
Pressure/vacuum
Druck-/Vakuumpumpe
Pressure/vacuum pump
*) nur bei Pumpe Typ 8750.0000 vorhanden!
*) with pumps model 8750.0000 only!
Working diagram, pressure chamber
Anschlußstecker
Plug
230 VAC
12 VDC
(Externe Versorgung über
Netzgerät, Drucktaster)
(External supply
with push button)
Rütteltisch
Vibrating table
M
(Druckkammerdurchführung)
(Feed-through terminals)
M
Pumpenschalter
Pump switch
Druck-/Vakuumpumpe
Pressure/vacuum pump
8710.0000 BG
Pressure Chamber
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Circuit diagram, vernier control
1A
Trafo
Transformer
Gleichrichter
12 V
Rectifier
B40 C1500
230 V/50 Hz
220 µF/40 V
510 W
510 W
Umschalter
langsam-schnell
Selection switch
slow-fast
Drucktaster für Umpolung
aufwärts/abwärts
Push button for upward/
downward movement
+
-
M
Verstellmotor
Gear motor
Technical data are subject to change!
THEODOR FRIEDRICHS & CO.
Meteorologische Geräte und Systeme GmbH
POB 1105 • D 22858 Schenefeld • Tel. (040) 839 600-0 • Fax (040) 839 600-18
Email: [email protected] • http://www.th-friedrichs.de