The 90 degree elbows are used to connect tubes at a 90° angle. As the name suggests, the elbow is always a right-angle in shape. Such type of elbow is also known as "90 bends or 90 ells". This is a pipe fitting device that is bent in such a way to produce a 90° change in the direction of flow of the fluid/gas in the pipe. The elbow is used to change the direction in piping and is also sometimes called a "quarter bend
http://www.zhijusteel.com/elbow/90-degree-elbow/

Bismuth-based: Bismuth alloys will have a composition that is less of a ductile characteristic than tin, as it can become brittle. Manufacturers use bismuth due to its expansion qualities when it melts and then solidifies as it can expand to up to 3.3%. The more bismuth is in an alloy, the more it expands. It is less expensive than other alloys that are featured and the least toxic as it can be used in applications where there is drinking water present.
http://www.wocmetal.com/low-me....lting-alloys/bismuth

A properly functioning HVAC system is essential to a comfortable home. While many people know how to operate their AC system, very few people know how it actually works. Your AC’s return air vent is a critical component of an HVAC system and serves several purposes. Not only do return air vents maintain your home’s air pressure and filter out debris, but they can also serve to save you on energy costs and expenses.
http://www.sxcanreal.com/return-air-vent/

A PP suspended floor is a ground floor with a void underneath the structure. The floor can be formed in various ways, using timber joists, precast concrete panels, block, and beam systems, or cast in-situ with reinforced concrete. However, the floor structure is supported by external and internal walls. Supports underneath the floor are permanent and include sleeper walls or timber props placed at regular intervals.
http://www.sjzwlplastic.com/pp-suspended-floor/

Piano hinges, also known as ‘continuous hinges’, represent one of the many types of hinges where 6, 7, and 8-foot lengths are not uncommon. One big difference between piano hinges and other hinge types is the fact that piano hinges will run the full length of the surface they serve – hence, the name ‘continuous’. Piano hinges are available in various thicknesses, pin diameters, widths, finishes, and customized designs.
http://www.sihaimetal.com/piano-hinge/