Pros/cons for each of the above?
Each of the methods have a place and in that place, are the best method. One of the real problems of correct pipe splicing is to determine which method of pipe splicing is most appropriate for a specific circumstance.
a. Welding end to end,
butt splice: Good for pressure applications where the pipe contains a gas or fluid, or in a visual structural application where high strength 90 degrees to the pipe axis is not critical.
b. Threading and couplers. Good for pressure applications where the pipe contains a gas or fluid. Also good for pipes used as a bottom weight for drops and scrims. Not suitable for any application where the pipe experiences loads perpendicular to it's axis. Extremely weak and prone to failure at the
point where threads start when subjected to bending moments.
c. internal spline. The strongest and most suitable method of joining pipes used as a structural, weight bearing member such as
stage rigging battens. Most common length of splice sleeve is 18". Common methods of joining all involve two fasteners on each side of the joint, usually at 90 degrees or "cross bolted" to each other. Fastening methods include bolts,
plug welds,
blind rivets or hardened
roll pins. Bolts are the fastest, cheapest and easiest method but protrude and can catch instruments, tools and hands.
Plug welds require welding and proper precautions, on
stage but are smooth and very strong. The disadvantage is that they can not be "undone" or disassembled for any reason and must be cut apart if needed.
Blind rivets or
roll pins (my choice) are actually stronger than bolts but about twice the cost in both materials and labor for installation. The advantage is they can be easily removed if needed and are flush and do not catch or
block "C" clamps, tools or hands.
d. Expanding splice: Very good for temporary joints. Not allowed by many architects, consultants and
AHJ for permanent installations. Does require access holes to be drilled in the pipe.
e. Exterior sleeve, such as
Kee Klamp #14-Straight Coupling: Very good for
hand rails, scaffolding and materials racks and storage structures. Often used for temporary light hanging structures such as
drop down ladders, wall mount brackets and other structures. Not suitable for
stage rigging battens.