Valves fast response

Several mercury electrodes combine the features of the DME and HMDE. In particular, one employs a narrow-bore capillary that produces DMEs with drop lives of 50-70 s (14). Another involves a controlled-growth mercury drop (15). For this purpose, a fast-response valve offers a wide range of drop sizes and a slowly (step-by-step) growing drop. 

Metrohm and BAS have also introduced improved DME models capable of operating in the SMDE mode. The Metrohm electrode (Fig. 14.6b) has a needle valve and small-bore capillary. Much of it is pneumatically controlled. The BAS version (Fig. 14.6c) is called the controlled growth mercury electrode (CGME). It is based on the work of Kowalski, Osteryoung, and coworkers [30]. Its features include a low-resistance electrical contact to the mercury thread in the capillary via a stainless steel tube and a fast response valve. The fast valve has allowed unique experiments to be performed where precise control of mercury drop growth during the experiment is desirable [31-33]. The BAS (Fig. 14.7), EG G Princeton Applied Research (Fig. 14.8), and Metrohm (Fig. 14.9) electrodes offer this easy and reproducible drop renewal in fully equipped cell stands. 

The solvent consumption appears to be in conflict with the corresponding optimum flow rates. Substances with high (a) values have a very high optimum flow rate (over 11 per min. for (a=1.2) and the column diameter is over 6 mm which would indicate a very large solvent consumption. However, because the separation is simple, a very rapid separation is achieved with analysis times of less than a second. As a consequence, only a few ml of solvent is necessary to complete the analysis. The apparatus, however, must be designed with an exceedingly fast response and very special sample valves would be necessary. In contrast, a very... 

Fast-Acting Valve A valve that closes a path of deflagration propagation in a pipe or duct in response to upstream detection of a deflagration. 

The p-jump unit produced by Hi-Tech Limited (PJ-55 pressure-jump) is based on a design by Davis and Gutfreund (1976) and is shown in Fig. 4.7, with a schematic representation in Fig. 4.8. A mechanical pressure release valve permits observation after 100 /us. There is no upper limit to observation time. Changes in turbidity, light absorption, and fluorescence emission can be measured in the range of 200-850 nm. The PJ-55 is thermostated by circulating water from an external circulator through the base of the module. The temperature in the cell is continuously monitored with a thermocouple probe. A hydraulic pump assembly is used to build up a pressure of up to 40.4 MPa. A mechanical valve release causes the pressure build-up to be applied to the solution in the observation cell. The instrument has a dead time of 100 /us. A fast response UV/fluorescence... 

It was to be a fast-operating valve located as close to the nozzle as practical. Automatic Sprinkler had such a valve that was built into the nozzle. This would provide a wet system in close proximity of the fire initiation point. It would be pilot-operated for fast response. 

Before the third series of tests was made, additional research was required to find or develop an ultra-fast opening valve. This was the only major component that could be replaced to further reduce the response time. Information from Detector Electronics Corporation introduced us to a valve manufactured by Grinnell, called the Primac valve, which seemed to fit the bill. The valve uses a primer detonating device with redundant detonators to blow the valve open. The same electrical signal initiated by the ultraviolet sensor could now be used to actuate the detonators, thus further reducing lost motion. 

Rupture disks are often used upstream of relief valves to protect the relief valve from corrosion or to reduce losses due to relief valve leakage. Large rupture disks are also used in situations that require very fast response time or high relieving load (for example, reactor runaway and external fire cases). They are also used in situations in which pressure is intentionally reduced below the operating pressure for safety reasons. 

The pressure of the vessel is controlled by a bypass valve that recirculates exhausted gas to the suction side of the vacuum source, giving the fast response that is required of the pressure loop to compensate for the varying vapor load to the condenser. Nevertheless, the contents temperature responds more slowly to pressure changes due to the time required to mix the surface with the vessel contents and the capacitance of the vessel. To decrease the response time, the contents temperature can be controlled by cascading the temperature to the pressure loop. The master temperature loop will then adjust the pressure set point at a rate commensurate with the temperature process response while maintaining the solution at the surface within the metastable zone the slave pressure loop will react to the pressure fluctuations during boiling. 

The supply rates of the liquid were eontrolled in the range from 0.05 to 1 g/h by a so-called p-Flow mass-flow meter (Bronkhorst, High-Teeh B.V.). At room temperature, the liquid was drawn from a pressurised container with an inert gas blanket and measured by the liquid mass-flow meter. The required flow rate was controlled to the set-point value by a control valve (C), forming an integral part of the liquid flow and earner gas mixing valve (M). The formed mixture was subsequently led into the evaporator to achieve total evaporation (E). This explains the abbreviation of CEM , shown in Fig. 1, viz. Controller-Evaporation-Mixing, the three basic functions of the liquid delivery system. The main features of this liquid delivery system are a) accurately controlled gas/liquid mixture, b) fast response, c) high reproducibility, d) very stable vapour flow, and e) flexible selection of gas/liquid ratio. 

This chapter provides an overview of the structure and function of mechanical ventilators. Mechanical ventilators, which are often also called respirators, are used to artificially ventilate the lungs of patients who are unable to breathe naturally from the atmosphere. In almost 105 years of development, many mechanical ventilators with different designs have been manufactured (MacIntyre and Branson, 2009). Very early devices used bellows that were manually operated to inflate the lungs. Today s respirators employ an array of sophisticated components, such as microprocessors, fast-response servo valves, and precision transducers to mechanically ventilate the incapacitated patients. Large varieties of ventilators are now available for short-term treatment of acute respiratory dysfunction as well as long-term therapy for chronic respiratory conditions. 

The CL (maximum at 450 nm) is conveniently detected with a photomultiplier tube (PMT). As shown in Figure 2A, a commercially available analyzer consists of a reaction chamber, flow control valves, and flowmeters for sample air and ethene. A coaxial double tube is used as a mixing jet in the reaction chamber. Sample air and ethene flow out from the inner tube at 0.3-1.51 min and the outer tube at 20-30 ml min respectively. Ethene is supplied from a high-pressure cylinder and unreacted ethene is removed with a catalytic converter to prevent it from polluting the environment. The ethene CL method has good selectivity and fast response, and is convenient for continuous air monitoring. However, fluctuations in the sample flow rate directly affect the measurement and care must be taken in the handling of ethene. Some instruments use ethene at a lower concentration than the flammability limit (<2.75%) to prevent possible accidents. 

A simple feedback system can control the process pressure if a throttling valve is installed in the suction line between the process and the pump, as shown in Figure 23-21. The main problem with this system is that the reponse time is directly tied to the system leakage rate. If the leakage rate is high, response if fast but if the leakage rate is low, the response time will be very slow. Unfortunately, low leakage rate and fast response time is the most desirable combination. 

A fast response, modulating-type valve, controlled by the steam bypass pressure regulator system, is used to perform three basic functions. The primary function is to reduce the rate of rise of reactor pressure when the turbine admission valves are moved rapidly in the closing direction. To perform this function, the bypass valve needs about the same speed of response as the turbine admission valves to prevent a pressure-induced reactor scram from high neutron flirx when the turbine load is suddenly reduced by partial or complete closure of the turbine admission valves. 

Modern high-speed GC systems are able to separate some light hydrocarbons within a second [117, 118]. This approach requires special sampling valves, narrow-bore columns (diameter = 0.005 cm), and detectors with a fast response. However, in EGA these fast separations are not necessary. Taking samples on-line from the reactor and separating them within 1 minute is frequently satisfactory in order to better understand degradation kinetics. The apparatus for this approach can be constructed of commercially available parts. 

The DHF effect seems to be successfully competing with the Clark-Lagerwall effect in such applications as Light Valves or Optically Addressed Light Modulators, operating at low controlling voltages with a suflSciently fast response time [98-100, 104]. Recently bistable states were found in FLC with the small values of helix pitch [177]. 

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