Abstrict In a liquid fitting for corrosive liquids under pressure, such
as a liquid flow meter having an outer pressure resistant housing
in which a measuring chamber housing with a movable measuring element
is arranged, the space between the outer housing and the measuring
chamber housing is filled with the liquid to be measured with the
outer housing provided with a thin walled elastic lining at its
inside surfaces forming a hollow wall, and the hollow wall filled
with a noncorrosive medium.
Claims What is claimed is:
1. In a liquid fitting for corrosive liquids under pressure, comprising
a pressure resistant outer housing, an inner housing and a space
filled with a liquid to be measured between the outer and the inner
housings, the improvement comprising:
a. a thin walled corrosion resistant elastic lining, forming a
hollow wall attached to the inside surfaces of the outer housing,
and
b. a noncorrosive liquid medium filling said hollow wall.
2. Apparatus according to claim 1 wherein said fitting is a liquid
flow meter for measuring a corrosive liquid under pressure in which
a measuring chamber housing with a movable measuring element is
arranged forming said inner housing.
3. Apparatus according to claim 1 wherein outer housing is divided
into two parts and wherein said lining is fastened to the parts
of the housing in the region of the mating surface forming a tight
seal of the hollow wall.
4. Apparatus according to claim 1 wherein first surfaces of said
thin walled lining are provided with corrugations for increasing
elasticity.
5. Apparatus according to claim 1 and further including at least
one bellows in said thin walled lining.
6. Apparatus according to claim 1 wherein said outer housing contains
connection stubs and wherein said thin walled lining is of a cylindrical
shape in said connection stubs and is firmly attached to the parts
of the housing at the respective outer end of the connection stubs,
and is resiliently connected to the remaining part of the thin walled
lining in the interior of the outer housing.
7. Apparatus according to claim 5 wherein said thin walled lining
in said connection stubs is formed by corrugated tubes.
8. Apparatus according to claim 1 wherein said thin walled lining
is attached to the outer housing by a weld.
9. Apparatus according to claim 1 and further including an indicator
for checking the chemical composition of the noncorrosive medium
protruding into the medium contained in said hollow wall.
Description BACKGROUND OF THE INVENTION
The invention relates to liquid fittings for corrosive liquids
under pressure in general and more particularly to an improved fitting
such as a liquid flow meter for measuring corrosive liquids under
pressure.
Liquid flow meters for measuring liquids under pressure must be
designed so that their parts which are important to the measuring
process, i.e., in particular, the measuring chamber which is machined
to close tolerances, are either not deformed or only slightly deformed
under the pressure of the liquid. Otherwise the functioning, or
at the every least, the measuring accuracy of the equipment would
be adversely affected to a large extent.
To satisfy these requirements in known commercially available liquid
flow meters of the type having a pressure resistant outer housing
in which a measuring chamber housing with a movable measuring element
is arranged, and a space filled with the liquid to be measured between
the outer and the measuring chamber housing, the space between the
outer and the measuring chamber housing is filled with the liquid
to be measured under pressure. As a result, the pressure outside
and inside the measuring chamber housing is practically the same
and no mechanical pressure is then exerted on the measuring chamber
housing, so that there is no adverse effect on the measuring accuracy.
If chemically corrosive media are to be measured with the known
liquid flow meters, which is quite often the case, then the outer
housing must also be made of high quality material because of the
required corrosion resistance. Since the outer housing must be able
to withstand the pressure of the liquid to be measured, it must
be made appropriately strong, which requires a relatively large
amount of valuable material.
To reduce the required amount of valuable material needed for the
outer housing, there have been attempts to provide the outer housing
with a corrosion resistant plastic lining. However, this presents
great difficulties, among other things, with respect to dimensional
compatibility, since accurate fitting of the plastic lining into
the outer housing is necessary, so that the pressure prevailing
within the outer housing is transmitted to the outer housing without
damaging the plastic lining. The range of application for using
a plastic lining, furthermore, is relatively narrow, for instance,
because of the temperatures permissible for plastic.
In another attempt to solve the problem, a liquid flow meter which
can be manufactured inexpensively even in a design for measuring
corrosive liquids under pressure, has been proposed. In such device
the space between the measuring chamber housing and the outer housing
is tightly separated from the liquid to be measured and is kept
in pressure equalizing connection with the liquid to be measured
by means of at least one element which is movable by pressure.
SUMMARY OF THE INVENTION
The present invention provides an improved solution to this problem.
In accordance with the present invention the outer housing is provided
with a thin walled elastic lining at its inside surfaces, forming
a hollow wall, and the hollow wall is filled with a noncorrosive
medium.
The advantage of the liquid fitting according to the present invention
is in particular that only a thin walled lining of high quality,
corrosion resistant material needs to be fabricated, for which the
cost is relatively small. A less expensive material can be used
for the pressure resistant, thick walled outer housing, since the
latter is not exposed to corrosive media.
In the liquid fitting according to the present invention, the lining
is fastened, if a divided outer housing is used, at the parts of
the housing in the area of the respective mating surfaces forming
a tight seal for the hollow wall. The hollow wall itself is then
filled with the noncorrosive medium.
In order to ensure that the thin walled lining can adapt itself
well to the pressure changes of the liquid to be measured, the flat
surfaces of the thin walled lining of the liquid fitting according
to the present invention are advantageously provided with corrugations
to increase their elasticity.
In lieu of such corrugations or possibly, as a supplement thereto,
it may be advantageous to provide the thin walled lining with bellows,
whereby the ability of the thin walled lining to "breathe"
becomes particularly high.
The thin walled lining in the connection stubs of the liquid fitting
according to the invention is advantageously of cylindrical shape
and is firmly attached to the outer housing at the respective outer
end of the connection stub and resiliently connected to the remaining
part of the thin walled lining in the interior of the outer housing,
so that the mobility of the thin walled lining cannot be affected
by the lining of the connection stubs. This objective can also be
reached advantageously by making the thin walled lining in the connection
stubs as corrugated tubes. If corrugated tubes are used, moreover,
manufacturing tolerances can be equalized better.
The thin walled lining can be fastened to the outer housing in
various ways. It is possible, to provide the lining with flanges
or extensions at suitable points and to attach them therewith firmly
to the outer housing with the interposition of a gasket. For production
reasons, it appears particularly advantageous to fasten the thin
walled lining tightly to the outer housing by welding.
Particularly if, for instance, poisonous liquids flow through the
liquid fitting according to the present invention or the liquid
flow meter according to the invention, it is desirable to monitor
whether the thin walled lining is still tight everywhere. This can
be achieved with relatively little effort in an advantageous manner
by providing an indicator for checking the chemical composition
of the noncorrosive medium projecting into the medium in the hollow
wall.
BRIEF DESCRIPTION OF THE DRAWING
FIG. 1 is a cross sectional view of a liquid fitting in the form
of a liquid flow meter according to the present invention.
FIG. 2 is a similar view of a further embodiment of the present
invention.
DETAILED DESCRIPTION OF THE INVENTION
The liquid flow meter shown in FIG. 1 contains an outer housing
1 which consists of an upper part 2 and a lower part 3. The upper
part 2 as well as the lower part 3 are made with relatively thick
walls and consist of a relatively low quality but pressure resistant
material. The upper part 2 and the lower part 3 of the outer housing
1 are each provided with flanges 4 and 5 with which they are clamped
together. The lower part 3 contains a connection stub 6 through
which the liquid to be measured flows in, in the direction of the
arrow 7; the upper part 2 has a connection stub 8 through which
the liquid to be measured leaves the liquid flow meter.
Inside the outer housing 1 a measuring chamber housing 9 is clamped
with a circular flange 10 disposed between the upper part 2 and
the lower part 3. Inside the measuring chamber housing 9 a ring
piston, for instance, may be arranged as a measuring element which,
together with the measuring chamber housing 9 forms a ring piston
meter known per se. The rotary motions of the measuring element
in the measuring chamber housing 9 are transmitted via a drive shaft
11 and a magnetic clutch 12 known per se, to the input shaft 13
of a counter mechanism, not shown.
Within the outer housing 2 a thin walled lining 14 of high quality,
corrosion resistant material is arranged. The thin walled lining
14 is welded to a circular flange part 15 in the upper part 2 of
the outer housing 1 as well as to the housing 16 of the magnetic
clutch 12 care being taken that the welds seal the hollow wall
17 formed by the outer housing 1 and the thin walled lining 14
from the remaining interior of the liquid flow meter. The lining
of the connection stub 8 is cylindrical and is provided at its outer
end 18 with a reinforcing flange 19 for welding to a connecting
flange 20. Inside the housing 1 the cylindrical lining is welded
to the thin walled lining 14.
In the same manner as in the upper part 2 the thin walled lining
14 is connected to a circular flange 22 in the lower part 3 by a
welded joint 21. The thin walled lining of the connection stub 6
to show a further possibility of a lining of the connection stubs,
is formed by a corrugated tube 23 which carries a fastening flange
24 at its outer end; the corrugated tube 23 is welded to the fastening
flange 24 which in turn is fastened by a bolted connection to the
connecting flange 26 of the connection stub 6 with the interposition
of a gasket 25. At its other end, the corrugated tube 23 is movably
supported in the longitudinal direction by means of ring parts 28
and 29 between which a seal is provided; this does not affect the
mobility of the thin walled lining 14. The ring parts 28 and 29
are connected to the thin walled lining 14 as well as to the corrugated
tube 23 by welding.
To increase its elasticity, the thin walled lining 14 is provided
with corrugations 30 and 31 in the upper part 2 as well as in its
lower part 3.
The noncorrosive medium is filled into the hollow wall 17 between
the thin walled lining 14 and the outer housing 1 through filling
holes 32 in the upper part 2 or 33 in the lower part 3 which can
be closed off by threaded plugs 34 and 35 respectively. Instead
of these threaded plugs 34 and 35 an indicator can be inserted
through the holes 33 which checks, for instance, via a conductivity
measurement of the noncorrosive medium, whether the hollow wall
is properly sealed against the space through which the liquid to
be measured flows. Openings 38 and 39 which can be closed off by
further screws 36 and 37 respectively, serve for proper venting
when the hollow wall 17 is filled.
The embodiment depicted in FIG. 2 agrees in substance with that
according to FIG. 1; it differs from the embodiment of FIG. 1 in
that the lining 40 in the upper part 41 of the housing 42 is provided
with a bellows 45 in addition to corrugations 43 and 44. The lining
in the lower part of the housing 42 may be similarly constructed.
However, it may also be sufficient, as shown by the example of
the lining 14 in the lower part 46 of the housing 42 in FIG. 2
to provide only bellows 47 in the lower and upper part instead of
corrugations.
To monitor the lining 40 for a tight seal against the interior
of the liquid fitting, indicators 50 and 51 are inserted through
openings 48 and 49 in the upper part 41 and the lower part 46 in
such a manner that they project into the bellows 45 and 47. These
indicators monitor the chemical composition of the medium in the
hollow wall.
With the present invention, a liquid fitting and in particular,
a liquid flow meter for measuring liquids under pressure is provided,
which is distinguished by the small amount of high quality material
required and by relatively low manufacturing costs. |