Most plant steam systems are designed to distribute steam at higher pressures which means that smaller sized steam lines can be used to transmit a given steam flow to an area of your facility.

Higher pressure steam has a lower specific volume compared to low pressure steam which is the reason why steam line sizes can be reduced. Low pressure steam has a greater heat of enthalpy of evaporation which means it can provide more BTUs per pound.

Steam at 100 psig has a temperature 338 F, a heat of evaporation of 880 BTUs per lb, and a specific volume of 3.89 cubic feet per pound. Steam at 15 psig has a temperature of 250 F, a heat of evaporation of 945 BTUs per pound, and a specific volume of 13.9 cubic feet per pound.

Although 15 psig is some 88 F cooler, it contains 7.4% more BTUs per pound of steam when condensed. A good rule of thumb is to have the steam temperature about 50 F hotter than the product you are trying to heat.
As an example, let assume we are trying to heat a product to 180 F using steam at 100 psig. Using our 50 degree difference rule of thumb means the steam temperature should be 230 F. From a steam table, steam pressure required to produce 230 F steam is 6 psig. Steam at 6 psig has a heat of evaporation of 959 BTUs per pound or 9% more than steam at 100 psig. Translated this means steam flows would be reduced by 9% just by reducing the pressure!

Lower pressures also generally mean less wear and tear on equipment which further reducing operating costs. Self contained and pilot operated pressure reducing valves are generally inexpensive and with much higher energy costs, reducing steam pressures in your plant can result in energy reductions of 5-10% with little effort or expenditure on your part.

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