wiper plugs

14 June 2019 colleagues
I have been trying to find (API) Standard for design of cement wiper plugs to no avail. The closest I get to was API TR 10TR6. Unfortunately this TR only dealt with the testing wiper plugs. It seems that manufacturers of cement wiper Plug each have their own design. For example the largest Fin OD for 7" csng -26 # of one manufacturer oversize the ID of the casing by 6.6%. Another manufacturer had other oversize.
On a recent 400 m long 4.5" Liner cement job the operator had to mill cement all the way fr the Liner Top to the Lndg collar despite that the cementing job went text book, i.e. shearing the bottom and Top Wiper plugs w the bottom and top darts respectively then bumping the plug and testing the floats ok. In this case a cement sheat clinging to the ID of the liner was preventing the bit to freely run in entire length of the liner. The fins may have been of wrong design of substandard rubber (duro harndness) was used.
On another Liner job there was no evident of the top Wiper Plug launching despite that the dart activated the flag on surface OK. Cement was displaced without bumping the plug even after o/displacing 50% of the shoetrck. On POH the RT it was evindent the Top Wiper plug was still attached to the RT. Days later the dart was found in the TJ of the stnd below the cmt head. It is apparent the dart fins let cement bypassing it freely.
Maybe our friend fr Sudelac could enlighten us the design criteria for wiper plugs and darts ??

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