( ( Heavy hydrocarbons ) ( ( ( are only ) ( required ( to ( be ( removed ( if ( they ( are ( ( significant enough ) ( in ( the ( gas ( to ( ( become liquid ) ( at ( ( ( high pressures ) and ) ( ( low temperatures ) ( experienced ( by ( the pipeline ) ) ) ) ) ) ) ) ) ) ) ) ) ) ) ) ) ) ) ) . ) )
(ROOT (S (NP (JJ Heavy) (NNS hydrocarbons)) (VP (VBP are) (ADVP (RB only)) (VP (VBN required) (S (VP (TO to) (VP (VB be) (VP (VBN removed) (SBAR (IN if) (S (NP (PRP they)) (VP (VBP are) (ADJP (JJ significant) (RB enough) (PP (IN in) (NP (DT the) (NN gas) (S (VP (TO to) (VP (VB become) (ADJP (JJ liquid)) (PP (IN at) (NP (NP (JJ high) (NNS pressures)) (CC and) (NP (NP (JJ low) (NNS temperatures)) (VP (VBN experienced) (PP (IN by) (NP (DT the) (NN pipeline)))))))))))))))))))))) (. .)))
Heavy hydrocarbons are only required to be removed if they are significant enough in the gas to become liquid at high pressures and low temperatures experienced by the pipeline.
(ROOT (S (NP (NNS Gases) (CC and) (NNS liquids)) (VP (VBP become) (NP (NNS solids)) (PP (IN at) (NP (JJ low) (NNS temperatures)))) (. .)))
Gases and liquids become solids at low temperatures.