Flush sample

Couplings are handy to have on the process inlet and outlet nozzles on both the tube and shell sides. These may be used for flushing, sampling, or thermometer wells, thermocouple bulbs, or pressure gages. 

A qualitative measure of the corrosion rate can be obtained from the slope of the curves in Fig. 2. Z INT is given in units of s ohm" . Owing to the presence of the uncompensated ohmic resistance and lack of values for Tafel slopes [Eq. (2)], data in Fig. 2 should be viewed as indicative of significant changes in corrosion rates. Corrosion loss remained low during the first 2 months, followed by a large increase for both flushed samples and controls. The corrosion rate increased when the surface pH reached values of 1 or less. Total corrosion loss as determined from integrated Rp data was less for the control than for the flushed sample. 

Figure 2. Cumulative corrosion loss Y. INT for mild steel sensors embedded in concrete and exposed to a sewer bypass (a) control sample, (b) flushed sample. (Reprinted from Ref 6 with permission from NACE International.)...

Figure 13. Steps in the electrokinetically-controlled immunoassay. Arrows indicate flow direction. Solid arrows stand for major flows, and dashed arrows, minor flows, (a) Loading and incubation of samples. Sample solutions were dispensed from the sample weUs to the reaction region and discharged into the waste well, (b) Washing of samples. Buffer solution flushed sample solutions from the reaction region back into the sample wells, (c) Second washing of samples. Sample solutions having entered the antibody channel during the previous three steps were flushed into the waste well, (d) Loading and incubation of detection antibody, (e) Washing of detection antibody.

Time to flush sampling tube and sample loop. When injecting different samples, it wfll be necessary to flush the previous sample completely from the sampling tube and the injection loop. Determine the time required to just... 

NOTE A sample taken by the consumer cannot be considered a true random daytime sample, as the consumer is likely to take a sample with extreme stagnation time (either a first draw sample or a fully flushed sample). 

Fully flushed sampling (FF) is defined as a sample taken at the consumers tap after flushing the plumbing system for at least three pipe volumes. The 90 % prediction range of FF at a COMP level of 10 ug/l is 12 6 igl. Furthermore FF enables detection of only 45 % of problem properties, whereas it results in 4 % false positives. FF is very cost effective, practical and acceptable to consumers. 

Flushing the tap before use is an effective measme to reduce considerably the lead concentration at the consmner s tap. However, flushing does not guarantee that the lead level will be below 10 This study shows that in 50% of properties where the composite proportional sample exceeded 10 (xg/1, the fully flushed sample was less than 10 (xg/1. For 70 % of properties where lead exceeded 25 (xg/1, the lead concentration after flushing was less than 25 ig . ... 

Corrosion losses remained low during the first two months followed by a large increase for both the flushed sample and control. Increased corrosion rates of embedded steel electrodes occurred when surface pH reached values of 1 or less due to accumulation of sulfuric acid (H2SO4). 

Do YOU USE THE WATER IMMEDIATELY OR DO YOU LET THE WATER RUN FOR AWHILE FIRST (If water lead levels are elevated in the FIRST FLUSH, BUT LOW IN THE FLUSHED SAMPLE, RECOMMEND FLUSHING THE WATER AFTER EACH PERIOD THE WATER HAS REMAINED STANDING IN THE PIPE FOR MORE THAN 6 HOURS.)... 

Test water (first-draw and flush samples). 

A FLUSH sample (also referred to as purged-line or second-draw) should be taken after letting the water run 5 minutes, until there is a noticeable change in its temperature. This will tell you whether the town water is contaminated before it even gets into your home. 

The main value of a fuUy flushed sample is to confirm the absence of lead in the distribution system prior to contact with domestic pipe-work. Lead residuals should normally be below 1 pg/1 in a fully flushed sample from a consumers tap. If not, there are a number of possible reasons (i) flushing has not been sufficient, particularly with very long lead pipes, (ii) there is lead in the distribution network from a lead water main (rare but possible), or (iii) particulate lead problems are being experienced. Fully flushed samples have no role to play in determining compliance with standards at consumers taps. 

In urban areas, sampling strategies for storm water runoff from industries and municipalities are of specific importance. The United States Federal Storm Water Regulations of 1990 specify protocols for such storm water nmoff sampling. These regulations define two separate samples that must be collected when a storm occurs. A first-flush sample is to be collected during the first 30 min of the storm event. A flow-weighted composite sample must be collected for the entire storm event or at least the first 3 h of the event [8]. 

The first-flush sample and the flow-weighted composite sample must be analyzed for the pollutants listed in Table 1.3. In general, the sample volume required for laboratory analysis depends on the particular pollutants being monitored and varies for each application. As a general rule, a 3 L sample volume for both first-flush and flow-weighted composite sample usually is sufficient for the majority of applications [8]. 

Direct the autosampler probe to sample vial, switch on the peristaltic pump, rotate clockwise at 70% for 40 s to propel sample and flush sample tubing. 

Rinse or flush sample containers with product and allow it to drain before drawing the sample. If the sample is to be transferred to another container (for testing other than DVPE), the sampling apparatus also is rinsed with some of the product and drained. When the sample is emptied into this container, upend the sampling apparatus into the opening of the sample container. 

Flushing Intermediary Post flush Sampling Period... 

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