My experience has been to install a ball valve both upstream and downstream of the globe valve, even in manual blowdown situations. mbt22 is correct that hydrates could interfere with getting a good seal on a downstream ball valve, and an extra valve in a blowdown line is likely a 2" or...
Quite right, AgSilver - the 3-way valve needs to be straight-thru in normal operation. When it is acting as a 90deg elbow, consider it as at very best a branch-flow tee (more likely a 1-cut miter elbow), while your pipe fitting will likely be a long-radius elbow, with much less pressure drop.
