The flatolet is basically “olet” to be used on flat surface or on the very large run sizes (where the difference of curvature becomes less and less significant.The basic design of a flatolet is same except the flat base. The weldolet for run sizes larger than 36″ (DN 1800) will be considered as flatolet.
A run pipe having a branch connection is weakened by the opening made in it. The branch connection must reinforce the opening and restore the original strength of the run pipe. It is the intent of this Standard Practice that these integrally reinforced branch outlet fittings and the deposited weld metal used to attach the fittings to run pipes contain all the reinforcement required by the applicable piping codes without the addition of saddles or pads.
The adequacy of the design of branch connection fittings may be established by mathematical analyses contained in pressure vessel or piping codes, or, at the manufacturer’s option. Records of design or proof tests shall be available at the manufacturer’s facility for inspection by the purchaser.