Peak flow

Because of large equipment and land requirements, capital costs for wastewater-treatment plants are high. A collection system that conveys both sanitary and storm flows must be designed to deal with high peak flows at the treatment plant detention basins are usually provided in order to smooth the flow into the plant and reduce the sudden peak flow. In the absence of such precautions, it may be necessary to by-pass a portion of the flow. 

The so-called flow temperature cannot be considered to be either the processing temperature or the maximum service temperature. It is obtained using the highly arbitrary Rossi-Peakes flow test (BS 1524) and is the temperature at which the compound is forced down a capillary of fixed dimensions by a fixed load at a specified rate. It is thus of use only for comparison and for quality control purposes. Since the rates of shear and temperatures used in processing are vastly different from those used in this test, extreme caution should be taken when assessing the result of flow temperature tests. 

Figure 23.18. Dependence of the extent of flow on temperature for a general purpose phenolic resin. Curves of this type may be obtained from measurements made on widely different pieces of equipment, e.g. the Rossi-Peakes flow tester and the flow disc. Thus no scale has been given for the...

There is no entirely satisfactory way of measuring flow. In the BS 2782 flow cup test an amount of moulding powder is added to the mould to provide between 2 and 2.5 g of flash. The press is closed at a fixed initial rate and at a fixed temperature and pressure. The time between the onset of recorded pressure and the cessation of flash (i.e. the time at which the mould has closed) is noted. This time is thus the time required to move a given mass of material a fixed distance and is thus a measure of viscosity. It is not a measure of the time available for flow. This property, or rather the more important length of flow or extent of flow, must be measured by some other device such as the flow disc or by the Rossi-Peakes flow test, neither of which are entirely satisfactory. Cup flow times are normally of the order of 10-25 seconds if measured by the BS specification. Moulding powders are frequently classified as being of stiff flow if the cup flow time exceeds 20 seconds, medium flow for times of 13-19 seconds and soft flow or free flow if under 12 seconds. 

A variation for one vendor is shown in Figure 26. The design and control of the system takes into consideration the following parameters flow rate, water temperature, waste characteristics, chemical pretreatment options, solids loading, hydraulic loading, the air to solids ratio. Units are designed on the basis of peak flow rate expected. 

Flow equalization system A device or tank designed to hold back or store a portion of peak flows for release during low-flow periods. 

When analyzing such individual control valve failures, one should consider the action of other control valves in the system. In the first two cases above, credit may be taken, where applicable for the reduction in pressure of a high-pressure source due to net inventory depletion during the period that the downstream equipment pressure is rising to relieving pressure. However, the pressure relieving facilities must be sized to handle the calculated peak flow conditions. 

Settlement/storage areas for effluent need to be sized not just for average flow but also for peak periods. Where production is based on a shift system, peak flows created during holiday periods (shutdown, major maintenance, etc.) should be considered. 

Maximum recommended airflow (l/s free air) through medium series steel pipe for branch mains not exceeding 15 meters in length (see BS 1387). The flow values are based on maximum recommended peak flows. Normal steady air consumption should not exceed 80 per cent of these figures in pipe sizes 20 mm nominal bore and above. 

Patients receiving bronchodilators or antiasthma drugs otten need to monitor their lung function at home with a peak flow meter. Doing so provides the patient and the physidan with valuable information about the status of the patient s condition and the effectiveness of therapy. Otten, trends in the readings can detect changes in the patient s airway and airflow even before any signs and symptoms are experienced. This allows possible intervention before a major problem arises. 

Because a variety of meters are oommerdally available, the nurse explains about the type of meter that will be used, how often the peak flow should be checked, and the ranges for the readings along with instructions on what to do for each range. The nurse uses the following steps to instruct the patient on the use of the peak flow meter ... 

Watch the indicator rise on the scale, noting where it stops. The number below the indicator s position is your peak flow reading. Repeat the procedure two more times. 

Measure the peak flow rate dose to the same time each day. (Your physidan may provide you with a suggested time. Some patients measure the peak flow rate twice daily between 7 and 9 am and between 6 and 8 pm. Others measure the peak flow rate before or after taking their medication.)... 

Many primary care health providers recommend a three-zone system. This system is based on your personal best peak flow rate-the highest peak flow measurement you can achieve on a day when your asthma is under good control-and it divides peak flow readings into three zones. The green zone ranges from 80% to 100% of your personal best. The yellow zone, from 50% to 80%. And the red zone is anything below 50%. ... 

Red means stop This is a danger zone. Notify the primary care health provider immediately. Use the medication prescribed when peak flow readings indicate that asthma is not in good control. 

The primary care health provider will adjust the color-coded zone indicators on your personal best peak flow meter to remind you of your red, yellow, and green zones, as well as fill out your action plan with your medication instructions. 

If your symptoms (and peak flow, if used) return to GREEN ZONE after 1 hour of above treatment IQ Take the quick-relief medicine every 4 hours for 1 to 2 days. 

Two major rivers in California influenced by a Mediterranean climate are the Sacramento River and the San Joaquin River. The Sacramento River drains 72,132 km with a relief of 4,317 m. Mean discharge is 650 m /s with peak flows in the winter and early spring and with minimum flows in the late summer and early fall. The San Joaquin River drains 83,409 km with a relief of 4,418 m. Mean discharge is 130 m /s with peak flows in spring and low flows in late summer and fall. Population density is 24 people/km in the Sacramento River basin and 29 people/km in the San Joaquin basin. Agriculture in the Central Valley of California that encompasses parts of both basins is the primary user of water in both basins [1]. 

It is difficult to predict if a neurologically injured patient will successfully be extubated. Salam et alstudied 88 patients prospectively, measuring cough peak flow (CPF), endotracheal secretions, and the ability to complete four simple tasks prior to extubation. In patients who failed extubation, they had a lower CPF p = 0.03), higher amount of secretions (RR 3.0, 95% Cl 1.0-8.8), and diminished ability to complete the four simple tasks (RR 4.3, 95% Cl 1.8-10.4). 

Review peak flow meter and inhaler technique... 

Educate patients on the use of inhaled drug delivery devices, peak flow monitors, and asthma education plans. 

Demonstrate the appropriate use of drug delivery devices and peak flow meters then have the patient perform these activities for you. If the task is performed incorrectly, demonstrate the skill again, emphasizing the incorrect step and have the patient re-demonstrate the skill. 

Objective measurements of airflow obstruction with a home peak flow meter may not necessarily improve patient outcomes. The NAEPP advocates use of PEF monitoring only for patients with severe persistent asthma who have difficulty perceiving airway obstruction. 

Spirometric tests are recommended at initial assessment, after treatment is initiated, and then every 1 to 2 years. Peak flow monitoring is recommended in moderate to severe persistent asthma. 

Patients at risk for acute severe exacerbations should monitor morning peak flows at home. 

Lung function, either spirometry or peak flows, should be monitored 5 to 10 minutes after each treatment. 

---