5) Which gas is used to heat the torches in gas heated operated type welding?

6) Which 'time parameter' for joint to get cooled and free from physical stresses in poly fusion welding?

7) Which fitting is used to connect one length to another for continuation of the PVC pipe?

8) Which has an exterior pipe thread end and used for fitting in the socket?

9) What is the name of joint that has threads on both sides of the central piece?