Cartridge Bubble Point Tester
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Description
The cartridge bubble point tester accommodates cartridges having a wide range of sizes, facilitates quick and easy loading and unloading of cartridges, performs speedy high volume testing, measures pores on all sides of the cartridge, conserves the wetting liquid by circulating from a storage tank, and ventilates the sample chamber. It has many applications throughout the filtration industry.
Principles of Operation
A wetting liquid spontaneously fills the pores of a porous material, because the surface free energy of filtration media with wetting liquids is less than the surface free energy of the filtration media with air and the filling process is accompanied by a decrease in free energy. The wetting liquid cannot spontaneously come out of the pores. It can be removed from the pores by increasing differential pressure of a nonreacting gas on the sample. The testing technique involves measurement of gas flow rates through a wet sample as a function of differential pressure. The gas pressure needed to displace a wetting liquid from a pore is related to the pore diameter.
where, p is differential inert gas pressure on the wetting liquid in the pore, γ is the surface tension of the wetting liquid, θ is the contact angle of the wetting liquid with the pore of the filtration media, and D is pore diameter [1].
The diameter of a pore can change along pore path and a pore can have many diameters. The presence of a pore is detected by this technique only when the differential gas pressure is able to completely empty the pore to permit gas flow through the pore. The differential pressure capable of completely emptying a pore is the differential pressure needed to displace the wetting liquid from the pore throat. Therefore, the pore diameter computed from the measured differential pressure yields only the through pore throat diameter (Figure 1). No other diameter of the pore is measured.
Figure 1
Figure 2
The gas flow through the wet sample is zero at the beginning and does not increase with increase in differential pressure, because all the pores are filled with the wetting liquid (Figure 2). The first pore to be emptied at the lowest pressure is the pore with the largest throat diameter (Equation 1). The differential pressure that initiates gas flow through a wet sample yields the bubble point pressure and the largest through pore throat diameter (Figure 2). A special technique is used to accurately detect the bubble point pressure [2].
Unique Features
- Multiple Sample Chambers
- Accomodation of a Wide Range of Cartridge Sizes - movable cartridge clamping head accomodates cartridges having a wide range of lengths and diameters (Photo 1)
- Quick and Easy Loading and Unloading of Cartridges (Photo 2)
- Cartridge can be quickly and easily loaded in the sample chamber simply by using the two levers
- Horizontal lever is used to move the clamping head backward or forward to clamp the cartridges having a wide range of lengths
- The rotating lever is used to lock the cartridge
- Automatic Filling and Draining of Wetting Liquid from Sample Chamber (Photo 3)
- Automatic filling of sample chamber with test liquid through inlet tubes provided in the sample chamber
- Automatic draining of wetting liquid from the chamber through the opening at the bottom of the chamber
- Rotating Cartridge to Expose Pores on all sides of the cartridge for Testing (Diagram 1)
- When the cartridge is submerged in the wetting liquid, the bottom side of the cartridge is at a depth below the liquid surface equal to the outside diameter of the cartridge. Therefore, the outside pressure on the cartridge is higher on pores at the bottom of the cartridge and the differential pressure on these pores is lower. Consequently, the measured diameters of pores at the bottom side of the cartridge are lower
- This problem is eliminated by rotating the cartridge so that all pores are brought to the surface to be tested under the same conditions
- The speed of rotation is operator adjustable so that the speed may be adjusted depending upon the cartridge characteristics such as size, pore size & pore distribution
- Storage and Circulation of Wetting Liquid
- For conservation of wetting liquid and improve economy of volume testing, the wetting liquid is stored in a storage tank and circulated
- The level of wetting liquid in the tank is observable in front panel of the instrument and tank is easily accessible for refilling of wetting liquid
- Ventilation of the Test Chamber
- A transparent door is provided in front of the sample chamber so that the test in progress can be observed while trapping any vapor of the wetting liquid in the chamber
- A ventilation fan constantly removes vapor of the wetting liquid from the sample chamber
- The operator is prevented from inhaling the vapor of wetting liquid
- The laboratory is also not contaminated with the vapor
Specifications
For more information see our Bubble Point Test Brochure, Porometers Brochure, and Characterization of Pore Structure Brochure.
