Experienced-Based Rules of Chemical Engineering

Storage Vessels

I. For less than 3.8 m3 (1000 gallons) use vertical tanks on legs

J. Between 3.8 m3 and 38 m3 (1000 to 10,000 gallons) use horizontal tanks on concrete supports

K. Beyond 38 m3 (10,000 gallons) use vertical tanks on concrete pads

L. Liquids with low vapor pressures, use tanks with floating roofs.

M. Raw material feed tanks are often specified for 30 days feed supplies

N. Storage tank capacity should be at 1.5 times the capacity of mobile supply vessels.

For example, 28.4 m3 (7500 gallon) tanker truck, 130 m3 (34,500 gallon) rail cars

Piping

A. Liquid lines should be sized for a velocity of (5+D/3) ft/s and a pressure drop of

2.0 psi/100 ft of pipe at pump discharges

At the pump suction, size for (1.3+D/6) ft/s and a pressure drop of 0.4 psi/100 ft of pipe

**D is pipe diameter in inches

B. Steam or gas lines can be sized for 20D ft/s and pressure drops of 0.5 psi/100 ft of pipe

C. Limits on superheated, dry steam or gas line should be 61 m/s (200 ft/s) and a pressure drop of 0.1 bar/100 m or 0.5 psi/100 ft of pipe. Saturated steam lines should be limited to 37 m/s (120 ft/s) to avoid erosion.

D. For turbulent flow in commercial steel pipes, use the following:

E. For two phase flow, an estimate often used is Lockhart and Martinelli:

First, the pressure drops are calculated as if each phase exist alone in the pipe, then

F. Control valves require at least 0.69 bar (10 psi) pressure drop for sufficient control

G. Flange ratings include 10, 20, 40, 103, and 175 bar (150, 300, 600, 1500, and 2500 psig)