Conditionals / type 1 (only) 1) not only the cleaning process (in involve) labor costs, it may require special equipment, particularly if chemical cleaning (to involve)
2) fresh deposits (to form) only if the deposit bond resistance (to be) greater the prevailing shear forces at the solid-fluid interface
3) dissolution (to occur) only if there (to be) a change in the properties of the deposit
4) if the temperature of the heat exchanger surface on the water side (to be) at or below 0, then a layer of ice (to form) on the surface
5) if the skid (to be) on the shell side, it (to be) impossible to remove the tube bundle
6) if the total thermal resistance (to increase) the amount of heat transferred throughout the surface (to decrease)
7) if the layer of insulating material (to have) a high thermal resistance, higher than any other part of the heat exchangers, the total thermal resistance ( to increase)

The operation of trains. To simplify the problem of running trains all railroads are divided into divisions. A division may be three or four hundred miles long or it may be thirty or forty miles long. Each division is operated as a small railroad. The train  with a long run may change locomotives and crews several times before it arrives at the station of its destination. Each railroad has regular trains and extra trains. A regular train is a train running according to time-table. Regular trains have definite times of leaving and definite times for arrival at the station where they complete their run. Extra trains are not common on our railroads. They are usually work trains ТВ wreck trains.
Работа поездов. Для упрощения задачи управления поездами, все железные дороги делятся на участки. Участок может быть длиной триста или четыреста миль, но может быть и тридцать или сорок миль. Каждый участок эксплуатируется как небольшая железная дорога. Поезд дальнего следования может несколько раз менять локомотивы и экипажи, прежде чем он достигнет станции своего назначения. Каждая железная дорога имеет регулярные и дополнительные поезда. Регулярный поезд - тот, что идёт по расписанию. Регулярные поезда отправляются и  прибывают на конечную станцию в определенное время. Дополнительные поезда не являются обычным явлением на наших железных дорогах. Это, как правило, служебные и аварийно-ремонтные поезда.

Mr. Mills asked James if he had already written to the University of Madrid. James apologized and added that he hadn't had time.
Mr. Mills said there was no point in apologizing to him.
He added that James had to apply early because they filled their places very quickly.
James explained that he was afraid he wouldn't pass his Spanish exam.
Mr. Mills wanted to know if James had been working hard.
James affirmed it and added that he was much better at French and he had hoped to apply to Paris.
Mr. Mills agreed that James was better at French and wondered if he put his name down for Sorbonne whether James would write that night.
James promised to write as soon as he got home.