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The Zavoda Diaphragm
Seal (ZealŪ) is available in two basic sizes - a "Small
Size and a "Large Size". The small size is the 5 series
and the large size is the 6 series.
The difference between
the two series is that the effective diaphragm area used
in the 6 series ZealŪ is double that of the effective
diaphragm area used in the 5 series ZealŪ. Therefore,
the series 6 ZealŪ should be the choice for all
sensitive and low pressure applications.
Continuous Type
All ZealsŪ are the
continuous type for safety. This is especially important
when a diaphragm seal is used in a hazardous
application. With this type of construction, the
diaphragm will aid in containing the process media
should the pressure instrument be accidentally broken or
removed. This is very important, should the process
media be either a corrosive or a harmful gas. This also
allows the process operation to continue to run until a
convenient time to shut down the process line and
replace the damaged pressure instrument.
Cleanout Type
All ZealsŪ are of the
cleanout type except for the styles 10 and 11. (Example:
Model M511). The bolts of the cleanout type can be
removed and separated at the flanges for cleaning,
liquid filling, calibrating, welding, or other purposes,
without the loss of the Liquid Fill fluid.
Non-Cleanout Type
The bolts of the
Non-Cleanout type ZealŪ (Styles 10 and 11) MUST NOT be
removed. Loss of Liquid Fill fluid will result, as the
diaphragm is NOT held in the instrument flange.
Fill / Bleed Port
All ZealsŪ come
standard with a Fill / Bleed Port. This tapped hole in
the instrument flange gives access to the fill area
above the diaphragm. this port is used for filling the
pressure instrument / seal combination and for bleeding
excess fluid from the system.
Type W - Welded
Metal Diaphragm.
In this type of ZealŪ
the metal diaphragm is welded at is periphery to the
instrument flange. The advantage of using this type of
ZealŪ is that it will retain the liquid fill fluid with
less danger of leakage. It is very popular because of
this feature and is usually the lowest in cost. This
type of ZealŪ is classified as a throw away type because
it cannot be repaired if the diaphragm is damaged or
worn out; therefore, it must be replaced with a new
Diaphragm Seal.
Type M - Metal Diaphragm
In this type of ZealŪ
the diaphragm can be replaced if worn our or damaged.
The ZealŪ can be rebuilt many times thus restoring it to
a "like new" condition and lowering cost. This type of
ZealŪ is the cleanout type in all models and series
except styles 10 and 11, which are the non-cleanout
type.
Type V - Viton Diaphragm
Viton Diaphragms are
suitable for use with extremely low pressures and high
vacuums. In the cleanout style the diaphragm is bonded
to the instrument flange. In the non-cleanout style the
diaphragm is clamped between the flanges.
Type T - PTFE
Diaphragm
The PTFE Diaphragm
Seal is truly the top of the line of Diaphragm Seals
regardless of manufacturer and many nave discovered that
the ZealŪ is superior. This type of ZealŪ is very
forgiving due to abuse or error. The list of advantages
and features is very impressive.
PTFE Wetted Parts
The Diaphragm and all
other parts of the ZealŪ in contact with the process
media (gas or fluid), are referred to as "Wetted Parts".
The wetted parts must be of a material selected to be
reasonably immune to attack from, and compatible with,
the process media. Selection of the material is the sole
responsibility of the buyer and / or the user.
The use of PTFE is
becoming more and more common, due to its compatibility
with practically all gases and fluids. Because PTFE
can be used in so many applications, now mostly reserved
for high priced metals, we are offering our ZealsŪ using
PTFE for the wetted material instead of very expensive
metals and even Stainless Steel.
Two methods of
construction are offered for the Adapter Ring, which is
the wetted part used in the Flanged Type ZealŪ. One
method is to use a solid piece of PTFE for the Adapter
Ring. The material designation for this method is
'PTFE'. The second method is to use two pieces for the
Adapter Ring. the inner wetted part is made of PTFE
and is fitted into an outer non-wetted metal shell. The
material designation for this method is 'PTFE Lined'.
The one disadvantage
of using PTFE is the "Cold Flow" tendency that is
inherent in this material. in the 'PTFE' construction
the clamping flanges must be bolted up evenly and gently
with the bolts being just tight enough to contain the
process media, otherwise the tightening pressure of the
bolts will cause the PTFE to 'cold flow' somewhat the
same as if the Adapter ring was made of rubber.
In the 'PTFE Lined'
construction the PTFE is prevented from cold flowing
by being contained in a metal shell. Installation is
virtually foolproof because of this patented plastic
lined pipe system, especially where expensive materials
are required.
In the threaded Style
ZealŪ, the 'cold flow' of PTFE is kept to a minimum by
supplying this style, and all of our ZealsŪ having
non-metallic (i.e. Plastics) process flanges, with a
thick metal ring under the hexagon nuts to prevent the
nuts from embedding themselves into the process flange.
In addition the metal ring helps spread the bolting
pressure over a wider area.
In summary, we feel
this design of ZealŪ would be well worth trying on any
particular process for your evaluation. It can offer
great savings, not only in the lower initial cost but
because of PTFE's forgiving nature to tolerate user
error. Also, in many applications, they outlast metal
diaphragm seals as much as three to one.
When ordering, be sure
to add the correct code letters in the order number: 'T'
for PTFE and 'L' for PTFE Lined. For ordering
information, see
How to
Order.
Liquid Fill
With a Diaphragm Seal
installed between the process media and the pressure
instrument, the process pressure acts on the diaphragm
which transmits the pressure to the sensing element in
the pressure instrument through a liquid. This liquid is
called the Liquid fill of the diaphragm Seal. Various
standard liquids are available. See Price List for
standard fill fluids. Other liquids are available on
special order. This liquid is usually an instrument oil.
It fills the cavities in both the sensing element and
the instrument flange on the instrument side of the
diaphragm. Selection of the fill fluid is the sole
responsibility of the buyer and / or the user.
Pressure
MAXIMUM recommended working pressure
for ZealsŪ in all series and on all types follow and are
arranged by style numbers:
- 05, 06, 10, 11, 15 and 16
threaded types - 2500 psi at 100°F
- 25, 26, 30 and 31 flange
types limited by the pressure rating of the ANSI
flange being used
- 35, 40, 45, 50, 55, 60 and 65
for "In-Line" and saddle types are limited by
the pressure rating of the pipe being used but
not to exceed 600 psi at 100°F
- Allowable working pressure is
300 psi at a maximum temperature of 140°F for
ZealsŪ with wetted parts made of non-metallic
material (e.g. Plastics)
MINIMUM recommended working pressure
for ZealsŪ is as follows: (arranged
by series number and ZealŪ type):
|
Series 5 |
Type W
and Type M is 20 psi |
| |
Type T
is 15 psi |
| |
Type V
is 5" of water column |
|
Series 6
|
Type W
and Type M is 10 psi |
| |
Type T is 8" of water column |
Vacuum
All ZealsŪ can be used for vacuum
service. Indicated vacuum ranges in instruments with
bourdon tube sensing elements are as follows: (arranged
by series number and ZealŪ type):
|
Series 5 |
Type W
and Type M between 0" and 21" Hg. Vac. |
| |
Type T
between 0" and 23" Hg. Vac. |
| |
Type V
between 0" and 29" Hg. Vac. |
|
Series 6
|
Type W
and Type M between 0" and 24" Hg. Vac. |
| |
Type T between 0" and 26" Hg.
Vac. |
For extremely difficult pressure and
vacuum applications consult with factory. The above
pressure and vacuum ranges apply only when ZealsŪ are
properly installed, operated and maintained.
MATERIALS
The following are standard materials.
Other materials are available on special order.
- Instrument flange -
(Non-wetted part) Nickel Plated. Carbon Steel.
- Wetted Parts - (Process
flange, adapter ring, etc.) Various standard
materials are available (See Price List) and must be
specified when ordering. Specify by calling out
proper material code letter in order number when
ordering. (See
Material Code Letter Chart). Selection of
material is the sole responsibility of the buyer and
/ or the user.
- Diaphragm - (Wetted Part)
Various standard materials are available and must be
specified when ordering. Specify by calling out the
proper material code letter in order number when
ordering. (See
Material Code Letter Chart). Selection of
material is the sole responsibility of the buyer and
/ or the user.
- Gaskets - Process flange
gaskets (wetted part) are made of PTFE and are
used in all the series and all the types of ZealsŪ.
Instrument flange gaskets (non-wetted part) are made
of Viton and are used in all ZealsŪ. Other materials
are available on special order.
- Fill Fluids - Various
standard fluids are available, and must be specified
when necessary for Zavoda Mfg. Co., Inc. to liquid
fill the assembly. Other fluids are available on
special order. Selection of the Fill Fluid is the
sole responsibility of the buyer and / or the user.
- Bolts - Supplied with
ZealsŪ, when required, are heat treated alloy steel
hexagon head cap screws, socket head cap screws, or
socket set screws. Other materials are available on
special order.
- Nuts - Stainless Steel
hexagon nuts supplied with above hexagon head cap
screws.
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