Support pipes

Over long runs, between buildings and equipment, pipes are usually carried on pipe racks. These carry the main process and service pipes, and are laid out to allow easy access to the equipment. 

Various designs of pipe hangers and supports are used to support individual pipes. Details of typical supports can be found in the books by Perry et al. (1997) and Holmes (1973). Pipe supports frequently incorporate provision for thermal expansion. 

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SMITH, VAN LAAN Piping and Pipe Support Systems STOCK AI in Process Control... 

As a vessel is loaded, it moves downward because of deflection of the load cells and support stmcture. Pipes rigidly attached to a vessel restrict its free movement and assume some portion of the load that cannot be measured by the load cells. This is very detrimental to scale accuracy. Deflection of the load cell is unavoidable deflection of the vessel support stmcture should be minimized. Anything which increases vessel deflection, eg, mbber pads used for shock protection, must be avoided. The total number of pipes should be minimized and be of the smallest diameter, thinnest wall possible. Pipe mns to weigh vessels must be horizontal and the first pipe support should be as far as possible from the vessel. Alternatively, a section of mbber hose or flexible bellows should be used to make the final connection to the vessel. The scale should be caUbrated using weights, not by means of an electrical simulation method, which cannot account for the effects of the piping or test the correct functioning of the scale. 

Piping supports, guides, and anchors increase local stresses on the pipe wall at the point of attachment. These stresses derive from continuously acting loads owing to the weight of the piping system carried at these points (pipe, contents, insulation), the pressure in the pipe, and any other loads such... 

High temperature lines that grow due to thermal expansion are supported by shoes welded or strapped to the bottom of the pipe at the pipe support locations. Insulated lines must have insulation breaks at the support or be supported by shoes. Large-diameter lines are often used to support smaller lines at locations in between the supports by miming a support beam attached to two larger-sized lines below the smaller lines. 

FIG. 10-174 Typical pipe supports and attachments. (From Kellogg, Design of Piping Systems, Wiley, New York, 1965.)... 

Pipe hangers are essentially frictionless but require taller pipe-support structures which cost more than structures on which pipe is laicT Devices that reduce friction between laid pipe snbjec t to thermal movement and its supports are used to accomplish the following ... 

Figure 15.19 Examples of crack patterns due to stress-corrosion cracking and corrosion fatigue in branch connections and vessel or pipe support attachment welds. (Reprinted with permission from Helmut Thielsch, Defects and Failures in Pressure Vessels and Piping, New York, Van Nostrand Reinhold, 1965.)...

Pipe strain is normally caused by misalignment between the piping and the pump nozzles, improper pipe supports, or thermal expansion in the system. 

Figure 5.1-5 shows a perspective view of one loop of the system. Note that in this system, kinematic constraints in the form of pipe supports, anchors, and hangers are minimal. Only the pumps are laterally braced by the suppressors. The pumps in this system are supported by hangers from above. 

Mechanical vibration of pipe is handled in the same manner as for reciprocating pumps (Volume 1, Chapter 12). Normally, if the pipe support spacing is kept short, the pipe is securely tied down, the support spans are not unifoiTn in length, and fluid pulsations have been adequately dampened, mechanical pipe vibrations will not be a problem. It is good practice to ensure that the natural frequency of all pipe spans is higher than the calculated pulsation frequency. The pulsation frequency is given by ... 

Proceed with design of pipe supports and stress analysis, if required. 

Rohren-halter, m. tube (or pipe) holder, tube (or pipe) clamp, -kassie, /. pur ng cassia, -kleuune, /. tube clamp, -kiibler, m. tubular condenser, tube condenser tubular cooler, -libelle, /. spirit level, air level, -lot, n. pipe solder, -manna, /. flake manna, -nudeln, /.pi. macaroni, -ofen, m. tube furnace (for heating tubes liable to explosion) pipe still, -pulver, n. (Expl.) perforated powder, -struktur, /. tubular structure, -substanz, /. (Anat.) medullary substance, -trager, m. tube (or pipe) support, -wachs, n. petroleum ceresin. -werk, n. tubing piping tube mill, -wischer, m. tube brush, -wulst, n. tubular tore, doughnut , -zelle, /. tubular cell, specif. (Bot.) tracheid. 

Compressible fluid flow occurs between the two extremes of isothermal and adiabatic conditions. For adiabatic flow the temperature decreases (normally) for decreases in pressure, and the condition is represented by p V (k) = constant. Adiabatic flow is often assumed in short and well-insulated pipe, supporting the assumption that no heat is transferred to or from the pipe contents, except for the small heat generated by fricdon during flow. Isothermal pVa = constant temperature, and is the mechanism usually (not always) assumed for most process piping design. This is in reality close to actual conditions for many process and utility service applications. 

Figure 13-23. Recommended pulse level for acceptable pipe vibration (assumes adequate pipe support and anchors). (Used by permission Everett, W. S. Hydrocarbon Procession and Petroleum Refiner, V. 43, No. 8, p. 117, 1964. Gulf Publishing Company. All rights reserved.)...

Pipe supports shall be provided throughout the length of the pipe and in such a way as to allow thermal movement... 

Design of vessel and vent line pipe supports is very important because very large forces can be encountered as soon as venting begins. Figure 4 shows the equations and nomenclature to calculate forces on pipe bends. The authors have heard of situations where vent line bends have been straightened, lines broken off, or vent catch tanks knocked off their foundations by excessive forces. For bends, the transient effects of the initial shock wave, the transition from vapor flow to two-phase flow, and steady state conditions should be considered. Transient conditions, however, are likely to be so rapid as to not have enough dura-... 

Overhead pipes in all manufaeturing areas should be sited away from equipment to prevent eondensation and possible eontaminants from falling into the produet. Unless negleeted, stainless steel pipes support little mierobial growth, but lagged pipes present a problem and unless they are regularly treated with a disinfectant they will support mould growth. 

Layout spacings are also affected by other factors than safety. The space requirements of maintenance, repair works and proper performing of process operations has to be included into the process layout. Proper spacing around equipment is required to allow easy operation. Enough room should be provided for pipes, supports and foundations as well. 

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