Casing float collar

When the bottom wiper plug reaches the float collar there is a brief sharp rise in pump pressure. The pump pressure increase breaks the diaphragm in the lower wiper plug. Once the diaphragm is broken the spacer and the cement slurry flow through the float collar into the final joint or two of the casing... 

The internal volume of the casing string above the float collar is Internal volume = 13,800(0.2086)... 

Therefore, the mud pumps are used to fill the remainder of the casing string at a rate of 300 gal/min. Thus, the additional time T, to get the bottom plug to the float collar is... 

Equation 4-331 is valid for a back-flow valve at the bottom of the casing string such as a float collar. It is also valid for a back-flow valve located at the top of the casing string. 

Floating-rate notes can include additional features. One example is the inclusion of cap, floor and collar clauses. A floater with cap feature means that the reference rate cannot overcome the threshold rate defined in the indenture. Usually the threshold is expressed in terms of coupon, that is after a coupon threshold (e.g. 6%, reference rate plus quoted margin) the investor receives at maximum the cap level. In this case, the floater is not completely covered by rising interest rates, in which after the threshold the floater trades as a conventional bond. In contrast, a floater with a floor feature represents the minimum coupon level that an investor can receive, hedging to the downside risk of interest rates. If the bond includes both cap and floor, this feature is known as collar or collared floating-rate note. The bond can include also a drop-lock feature that after a threshold it ceases to float. 

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