7.8 Liquid table

Liquid table

Comments on the liquid tables on the following pages. The liquid table gives necessary data for pumping. The characteristics of liquids are not given to that degree of accuracy which, in special cases, may be required in order to specify other process equipment. Note that the monest liquids, water, oils and certain suspensions, are dealt with in more detail in specialized sections, 7.1 – 7.3.

Compressibility and speed of wave propagation are not included in the liquid tables. These characteristics are stated for a number of liquids in section 7 Properties of liquids for pumping

The liquid table contains the following data:

• Substance: The liquid properties are arranged in alphabetical order according to the name of the substance. The trade names with synonyms are given in Figure 7.8a. The letter D indicates a dangerous (inflammable or otherwise hazardous) liquid with the terms of the Petroleum (Inflammable liquids and other dangerous substances). The letter T indicates a high level of toxicity.
• Chemical formula: for identification of substance. In practice a substance can unfortunately not be assigned to a single formula because of contamination. Liquids containing contaminants which are insoluble or unmeltable have the worst pumping characteristics, often causing troublesome wear on pumps and shaft seals.
• Concentration in H₂O, i.e. the concentration of the substance in water expressed as percentage weight.
• Solubility in H₂O: Attention is drawn in the table to various diagrams referring to the solubility of the substance in water. The solubility is expressed as a concentration in percentage weight at varying temperatures. When pumping, precipitation often occurs when the concentration exceeds that stated by the solubility curve for the given temperature. Conversely, there will be precipitation if the temperature drops below the stated solubility temperature.
• Viscosity is stated in mm²/s (cSt) at + 20°C. Viscosity below 5mm²/s indicates that the liquid is so easy flowing that a closer investigation is of no interest as regards choice of pump. The liquid table also refers to diagrams showing dependence of viscosity on temperature. The viscosity will also be used for the determination of frictional losses in the pipe. This depends primarily on whether the flow is laminar or turbulent, see section 8. In the laminar region, the pipe frictional losses are proportional to the viscosity, whereas its effect can be neglected in the turbulent region for the internal roughness of pipes which occur in practice. Certain liquids are non-Newtonian and require special care when determining the equivalent (apparent) viscosity.
• Vapour pressure (absolute pressure) is stated in kilo-Pascals (kPa) at 20°C. See curves in Figure 7.8.4 which show the temperature dependence of vapor pressure. Note that boiling point at atmospheric pressure (101.3 kPa = 760 mm Hg) gives another point on the vapor pressure curve. The curves in Figure 7.8.4 are set out schematically and may deviate from the exact values. This is especially applicable to aqueous solutions, curve 13. All references to this curve apply to chemicals in solution in water. Liquid pressure near to the vapour pressure at the actual liquid temperature can cause cavitation in a pump or pipe.
• Density is stated in kg/m³ at +25°C. Reference is made to various figures for other temperatures and concentrations. The density is used among other things for conversion of pressure to head and for the calculation of the power required for the pump.
• pH region: is an expression of acidity of alkalinity and is grouped within pH regions 0-4, 4-6, 6-9 and 9-14. This group classification assists in the choice of pump material, the pH regions coinciding with commonly used pump material resistivity to corrosion.
• Melting point. Note that many contaminants gradually begin to break down at temperatures immediately above the melting point which can have a harmful effect on the function of the pump.
• Fire hazard class is stated in accordance with …. regulation to be attached.

Where there is no information in the liquid table, this means that the actual liquid property is not known and it does not mean that the information omitted is of no general interest in pumping.

Liquid trade names and synonyms

Figure 7.8a Liquid trade names and synonyms