Leakage measurement

For the tandem arrangement gas seal, a primary seal vent must be pro vided to vent the leakage across the process side seal. This vent ma> lie to flare or other suitable gas disposal point. The back pressure under nor mal conditions should be kept to a low value. A small amount of back pressure is recommended to keep a positive differential across the see ondaiy seal. Leakage measurement may be provided in the vent line to provide health monitoring of the primary seal. Unfortunately, the rotameter, which would be the obvious choice, should not be used because of its lack o reliability. If an orifice or needle valve is used to set the back pressure to the seal vent, pressure upstream of the restriction can be measured for a relative flow measurement. This type of reading does provide trend data that may be used to judge the seal s performance. 

In some texts guidance is given to estimate and evaluate the leakage of buildings and building components. The multizone airflow model can also be used to adjust the assumed conductances to an overall building leakage, measured by blower door technique, for example. 

When Valve Seat Leakage Measured During and After Test During Test After Test After Test After Test... 

When ozone is turned-off at some point during this rapid loss period, the high rate of Rb leakage ceases within 2-3 min and returns to the control leakage rate. Thus, this permeability change, measured by efflux, appears to be reversible, as is net K+ leakage measured with the cation electrode. ... 

Figure 3.14 Current response and integration range for a leakage measurement.

Lagus, P.L. "Air Leakage Measurements by the Tracer Dilution Method - A Review" ASTM STP 719 Hunt, C. King, J. Trechsel,... 

Air leakage measurements use a system of controlled negative pressure in which air is pumped out of the respirator to create a fixed negative pressure (usually 1 in water gauge) and the airflow need to maintain this pressure is measured. The airflow is taken as the same as the leakage rate into the respirator. The method requires wearers to hold their breath and the filter canister to be blanked off (otherwise, air will leak through the filter). 

Earth leakage. Measures any current that leaks onto the equipment enclosure and to a person or ground (3.5 mA maximum for movable products). 

Obviously, each containment is a particular case and the best way to establish a realistic yet conservative value of the leak rate for safety analyses would be to observe the behaviour of the containment with time and the amount of the leakages measured either in the as found conditions (that is before having performed maintenance to the sealing parts) and in the as left conditions (that is after maintenance). Unfortunately, however, at the time of the design and of the initial safety analyses this experience is not available and therefore reasonable preventive estimates have to be done, which should be confirmed during the operation. 

In the case of test specimens representative of full sized containment systems, direct leakage measurements can be made on the test specimen. 

Johansson, E., Lyngfelt, a., Mattisson, T. and Johnsson, F (2003) Gas leakage measurements in a cold model of an interconnected fluidized bed for chemical-looping combustion. Powder Technology, 134, 210-217. 

These faradic leakage measurements are also dependent upon temperature (log I vs. j) where the slope is determined by the activation energy of the mechanism. As a result faradic leakage currents can have important impacts on high temperature performance. 

The pol3mierization behaviour of these membrane systems can be characterized in monolayers and liposomes using surface pressure-area diagrams or DSC investigations respectively. Decreased membrane permeability and improved stability towards the addition of detergents of pol3nnerized vesicles can be verified by leakage measurements of entrapped 6-carboxyfluorescein. 

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