A system for on-line pigging, which comprises: a first tubular assembly having a first passage, a second passage and a third passage, wherein the first passage of the first tubular assembly is connected at one end to a first end of a tubular segment and each passage (104, 106, 108) includes a respective valve (104a, 106a, 108a) for controlling fluid communication through each passage (104, 106, 108) and the tubular segment; a second tubular assembly having a first passage, a second passage and a third passage, wherein the first passage of the second tubular assembly is connected at one end to a second end of the tubular segment and each passage includes a respective valve (116a, 118a, 120a) for controlling fluid communication through each passage (116, 118, 120); a pig for traversing the third passage of the first tubular assembly, cleaning the tubular segment during normal operation of the tubular segment and traversing the third passage of the second tubular assembly when the pig is carried by a fluid under pressure; and wherein the pig comprises a plurality of wooden discs and a plurality of ceramic cloth discs joined together, or a tightly wound rope, wherein a diameter of the pig is greater than an inside diameter of the third passage of the first tubular assembly, the tubular segment and the third passage of the second tubular assembly, wherein the first passage and the third passage of the first tubular assembly and the first passage and the third passage of the second tubular assembly are parallel for most of a respective length of each, wherein the second passage of the first tubular assembly connects the first passage and the third passage of the first tubular assembly upstream from the valve for the first passage and the valve for the third passage of the first tubular assembly, wherein the second passage of the second tubular assembly connects the first passage and the third passage of the second tubular assembly downstream from the valve for the first passage and the valve for the third passage of the second tubular assembly. a first tubular assembly having a first passage, a second passage and a third passage, wherein the first passage of the first tubular assembly is connected at one end to a first end of a tubular segment and each passage (104, 106, 108) includes a respective valve (104a, 106a, 108a) for controlling fluid communication through each passage (104, 106, 108) and the tubular segment; a second tubular assembly having a first passage, a second passage and a third passage, wherein the first passage of the second tubular assembly is connected at one end to a second end of the tubular segment and each passage includes a respective valve (116a, 118a, 120a) for controlling fluid communication through each passage (116, 118, 120); a pig for traversing the third passage of the first tubular assembly, cleaning the tubular segment during normal operation of the tubular segment and traversing the third passage of the second tubular assembly when the pig is carried by a fluid under pressure; and wherein the pig comprises a plurality of wooden discs and a plurality of ceramic cloth discs joined together, or a tightly wound rope, wherein a diameter of the pig is greater than an inside diameter of the third passage of the first tubular assembly, the tubular segment and the third passage of the second tubular assembly, wherein the first passage and the third passage of the first tubular assembly and the first passage and the third passage of the second tubular assembly are parallel for most of a respective length of each, wherein the second passage of the first tubular assembly connects the first passage and the third passage of the first tubular assembly upstream from the valve for the first passage and the valve for the third passage of the first tubular assembly, wherein the second passage of the second tubular assembly connects the first passage and the third passage of the second tubular assembly downstream from the valve for the first passage and the valve for the third passage of the second tubular assembly.