Pipe routing: below point to consider while doing the pipe routing
Piping shall be routed such way that the optimum piping layout is achieved in terms of process requirements, ergonomics, operation, inspection and maintenance. Having considered these factors, the number of flanges, fittings, valves and welds shall be minimized which helps to reduce the cost of the project.
All 90 deg elbows shall be long radius. If there is somewhere impractical to use long radius elbow, the application of short radius elbows shall be clarified with projects.
In situations where in-line equipment (e.g. control valves) with a higher ASME rating class than the run pipe is fitted, the connecting flanges shall have the same rating as the in-line equipment.
In a pipe rack the heaviest and or the hottest pipes should be located at the sides of the pipe rack to provide space for expansion loops and to reduce the moments in the beams caused by the weight and thermal expansion of the pipes.
Elevation of pipes should be determined considering the height of pipe shoe, cradle, saddle height, HSE, Operability etc.
In process units where the layout requires that main unit pipe racks intersect, different elevations shall be established for lines running north-south and east-west. Pipe should change elevations where entering and leaving the pipe way and, where feasible, at each change of direction of the piping to avoid interference with the routing of future lines or additions to the pipe way. Changes in elevation should be made with 90 degree elbows and vertical legs 45 degree elbows should not be used it their use interferes with the future space.
Piping shall be arranged to allow the removal of equipment without removing the block valve adjacent to the equipment and large quantities of associated equipment of piping. Put the break up flange while pipe connecting to equipment.
Pockets shall be avoided in process lines, flare lines, lines carrying caustic, acid, or materials that may congeal or freeze or in lines containing solids that may settle out. Pockets shall also be avoided in piping in which corrosive condensate may form.
If a piping system operating above 0º C is connected to a system operated at 0º C or below, the first 50 times of pipe diameter (with a maximum of 10 m) long part of the former shall be designed according to the specifications of the lower temperature system.
Both Insulated and uninsulated lines passing through concrete such as walls, decks, and paving shall be installed with insert pipes or sleeves. Both the insert pipe and the sleeve shall be coated for corrosion protection as well as penetrating pipe. Each end of the sleeve shall be sealed with a material having the appropriate fire rating.
Austenitic stainless steel piping shall be protected against zinc embitterment which may result from molten zinc dripping from galvanized steel on a design condition (except fire condition). This may be done either by not locating the austenitic stainless steel piping underneath zinc-containing items or by installing protective shields (for austenitic stainless steel piping which is insulated, the cladding is considered to be sufficient protection).
A piping system shall be designed for the most severe conditions to which it may be subjected. The following may determine the design conditions:
- Steaming-out pressure and temperature
- Surge pressure
- Pump shut-off pressure
- Static pressure
- Pressure drop
- Vacuum caused by cooling and possible condensing of trapped medium
Pipe routing for critical lines shall be confirmed and fixed at the early design stage. The execution procedure shall be confirmed with project at the job stage. Pipe routing should be follow the Piping and instrument diagram ( P&ID) and equipment layout, piping material specification etc.