Guideline to trouble prone piping

Below is some of the guideline and fallacies related to some vulnerable or trouble prone process piping written by O.P. Goyal who works for Jacobs H&G Ltd.

According to him, piping accounts for a large number of failures in the hydrocarbon proceesing industry. Wrong designs, use of incorrect size and/or underated fittings an stop-gap arrangements have cause failures reuaslting in production loss, plant shutdowns.

Pressure drop and flow estimation. When a specific delta P in a pipe for a particular diameter is known at a given liquid flow rate, then at the same flowrate and other given parameters for turbulent flow - which is normally the case - the delta P in another pipe oof different dia can be quickly estimated as inversely proportional to the diameter raised to the power of five. For example, if the pipe dia is halved, the pressure delta P will be nearly 32 times. Many people instinctively have imagined it to be 4X or 8X and have amde wrong decision during troubleshooting.

Two-Phase Flow lines. Minimized pipe lenghts. Avoid elbows and downflow  vertical piping.
Steam and condensate lines. Install steam traps or condensate pots at suitable locations,otherwise design for trapless piping. Provide expansion bends. Avoid situation that cause water hammer. pH monitoring is necessary to avoid O2/CO2 corrosion. Compressor usction/discharge line. Sizing must be right. Stress and vibration analysis must be done. Valve should be butterfly type. Install surge vessels on outlet of reciprocating compressor to dampen pulsation.
Process furnace piping. Dont insulate flange joints. Hydrocarbon soaked insulation can cause fire. Fuel and atomizing lines should be designed to be serviceable. Thermal expansion must be accounted for. Steam traps. Trap oversizing is the most common mistake. Misconception is that trap size is dictated by the diameter of the line. In reality the trap should be sized according to the amount of condensate being drained and the line pressure. Installed test-tees to visually inspect discharge from traps and provide strainer where dirt conditons are bad. Received on Thu Jul 26 19:17:00 2001