we make zealsŪ

Since 1962


  

 

CATALOG 2000

DESIGN INFORMATION

What is a Diaphragm Seal?

A diaphragm seal is a device consisting of a diaphragm firmly clamped between two suitable flanges and properly gasketed to prevent leakage of liquid or gas. In this type of device a diaphragm, which is a "dividing membrane or a thin partition", acts as a barrier to a liquid or gas that may tend to clog or corrode the sensing element in a pressure instrument and therefore render the pressure instrument useless. This type of device is sometimes called a Chemical Seal or a gauge Protector.

Our Diaphragm Seal, made by The Zavoda Manufacturing Co., Inc. is called a ZealŪ. ZealŪ is short for Zavoda Diaphragm Seal and is our registered trademark.

Series


What is a Diaphragm Seal?
Series
Continuous Type
Cleanout Type
Non-Cleanout Type
Fill/Bleed Port
Type W
Type M
Type V
Type T
Teflon Wetted Parts
Liquid Fill
Pressure
Vacuum
Materials

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 - Teflon Diaphragm

The Teflon 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. 

Teflon 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 Teflon is becoming more and more common, due to its compatibility with practically all gases and fluids. Because Teflon can be used in so many applications, now mostly reserved for high priced metals, we are offering our ZealsŪ using Teflon 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 Teflon for the Adapter Ring. The material designation for this method is 'Teflon'. The second method is to use two pieces for the Adapter Ring. the inner wetted part is made of Teflon and is fitted into an outer non-wetted metal shell. The material designation for this method is 'Teflon Lined'.

The one disadvantage of using Teflon is the "Cold Flow" tendency that is inherent in this material. in the 'Teflon' 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 Teflon to 'cold flow' somewhat the same as if the Adapter ring was made of rubber.

In the 'Teflon Lined' construction the Teflon 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 Teflon 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 Teflon'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 Teflon and 'L' for Teflon 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 Teflon 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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ZAVODA MANUFACTURING CO., INC.

5848 Hwy. 71 West * P. O. Box 506 * La Grange, Texas 78945
Phone: (979) 242-3300 * Fax (979) 242-3353

DIAPHRAGM SEALS

 
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