CALCULATING TANK SETTLEMENT
- Calculate the value of d/H L (d = diameter of the tank, H L = the design maximum height of the liquid contents) and...
- Determine the values for the weight coefficients K w1 and K w2 from Figure 41. 1.0 0 2.0 3.0 4.0 5.0 6.0 7.0 8.0 0.2...
- Determine the value for the site amplification factor S from Figure 42. Rock of any...
Full Answer
How to calculate the number of settlement points in a tank?
In a tank, the number of settlement points around the periphery for external settlement measurement is given by the following formula N is the minimum required number of settlement measurement points. D is the tank diameter, in feet (ft).
What percentage of tank settlement should be considered in piping stress analysis?
Settlement at Edge of Tank. Then out of total settlement at Edge, 40% of total settlement is what we consider in piping stress analysis. Pipe routing guidelines (Fig. 2) to minimize effect of tank settlement:
Where to place the settlement of a tank?
The settlement is more at the centre of tank, and typically 50% at the edge of tank. Since our nozzles and tank roof are connected / supported on shell, that is on outer edge of tank, we need to consider the settlement at outer edge of tank.
How much differential settlement is acceptable across tank bottom?
"The columns shall be effectively....in the event of vertical movement of the columns relative to tank bottom of up to 3 in.".Par. 7.3.6.6 (hydro test)"...differential settlement greater than 1/2" per 32 ft. of circumference or uniform settlement of 2 in."...... Neither of these paragraphs address differential settlement across the tank bottom.
What is tank settlement?
Interceptors are settlement tanks which remove light, nonaqueous phase liquids (such as oil and gasoline) and, to a lesser extent, solids from wastewater.
What is tank settlement survey?
Tank settlement is one of the topics of the Body Of Knowledge for the API 653 exam. It is a very important subject for us tank inspectors, althought is also one of the most vague topics for a new inspector. In fact, the word “settlement” is mentioned more than 250 times in the API 653 standard.
TYPES OF TANK SETTLEMENT
Settlement in tanks can be of several types. API 653 talks about three types: uniform, planar tilt and out-of-plane settlement. [adToAppearHere]
THE COSINE CURVE
For the study of settlement (general settlement of the shell) let´s establish a common notation.
DETERMINING THE NUMBER OF POINTS FOR SETTLEMENT MEASUREMENT
In a tank, the number of settlement points around the periphery for external settlement measurement is given by the following formula
IMPORTANCE
Settlement measurement stations are to be used during hydrostatic test and operation of the tank; settlement measurements should be taken at a planned frequency, based on an assessment of soil settlement predictions (See Annex B of API 653)
How deep is a settling tank?
His tests proved that deep settling tanks were not ordinarily necessary. The use of tanks 2 or 3 ft. in depth was suggested. Later experiments demonstrated that the following principles of settling applied to Tigre pulp.
How does cohesion affect settling?
Cohesion plays an important part during all settling operations. In the free-settling zone it causes the slime particles to aggregate into flocs. In the first stages of thickening, it causes the flocs to draw together, thus developing tensile strains in the pulp which are relieved by cracks and channels (the clear liquid reaching surface through these avenues). During the final stages of thickening, especially in the presence of high lime, cohesion no longer causes closer union between slime particles, or between flocs; but it still strongly resists any force tending to change the shape of the flocs. This resistance reduces settling rate by opposing the compression, due to pulp depth, which would otherwise force the flocs to displace the liquid in the interfloccular spaces. The greater density attained by the deeper pulp columns in Table 3 can best be explained on this basis.
When pulp first leaves the feed column of a tank, are flocs entirely unformed?
When pulp first leaves the feed column of a tank, flocs are entirely unformed and the settling rates are low or nil. The dilute pulp spreads out laterally—over the top of the denser pulp in the bottom of the tank. As the lateral movement lessens, flocs begin to form and the settling rate increases correspondingly.
What is the boundary between dilute and thick pulp?
The critical dilution, or the boundary between dilute and thick pulp, in the application of the above principles, is the highest dilution at which channels form in the pulp; clear liquid reaching the surface through the channels.
What is the L:S ratio?
Dilution is expressed in terms of the ratio by weight of liquid to solids, and is termed, for short, “The L:S Ratio.” In tables, charts and formulas, the first factor only of the L : S ratio is used. Thus the figure 5 designates a dilution of 5 :1.
Is elimination of water in the thickening zone a function of time?
In the absence of channels, elimination of water in the thickening zone is a function of area and not of time. This fact is illustrated in Table 3.
Does stirring increase the capacity of the thickener?
Stirring would not increase the capacity of the thickener beyond the natural capacity for discharging pulp of the consistency at which the channels have just closed; on the contrary, the capacity should be slightly lower, due to the fact that the D in Mr. Mishler’s formula No. 3 becomes less and A, or required area, consequently becomes greater.
