Transfer pipework

Unlike reactor vessels where both hot- and cold-shell designs are extant, all CRU transfer pipework operates in hot service in a temperature range of approximately 400-530 °C. Parent material is generally of l-lV4CrV2Mo... 

Particular attention must be given to transfer pipework where seam-welded pipe runs are used. In such cases, experience from the American power industry steam reheat line catastrophic failures should be borne in mind. The critical factors identified are weld geometry, weld metal and flux compositions and pipe ovality. Generally, older CRU units utilise seamless pipe in this service but some instances are known, particularly in larger capacity units, where seam-welded pipe is in service. Where necessary, this factor can be taken into account in the assessment procedure described below. Seam welds are subject to the full pressure hoop stress, as well as to many of the system loads. Failure of such a weld is likely to lead to a full-scale rupture, rather than a leak. Accordingly, they must be treated as critical items for assessment, and replacement, rather than repair, should be considered the ultimate outcome. 

Plant assessment technology can provide guidance at this stage by prioritising the high risk of failure areas on transfer pipework systems, thus enabling targeted inspection. 

As stated earlier, the same approach can be applied to reactors. However, the assessment costs involved relative to inspection costs for reactors and pipework makes it much more cost beneficial in the case of the latter. The approach can thus be used for both component types, although the example given below is for CRU transfer pipework. 

Due to some areas of uncertainty in the input data, the results, (Fig. 2.19) should be viewed on a relative, as opposed to an absolute, basis. Nevertheless, when the described combined approach is applied it provides an enhanced input to the inspection decision-making process (Barrien, 1998 Barrien, Jarvis and Townsend, 1997). The ability to inspect critical as opposed to all locations on the transfer pipework system has significant cost benefits. 

Material transfer requires pipework, valves, pumps, and compressors. Fugitive emissions occur from pipe flanges, valve glands, and pump and compressor seals. 

Many initiators attack steels of the AISI 4300 series and the barrels of the intensifiers, which are usually of compound constmction to resist fatigue, have an inner liner of AISI 410 or austenitic stainless steel. The associated small bore pipework and fittings used to transfer the initiator to the sparger are usually made of cold worked austenitic stainless steel. The required pumping capacity varies considerably from one process to another, but an initiator flow rate 0.5 L / min is more than sufficient to supply a single injection point in a reactor nominally rated for 40 t/d of polyethylene. 

At the completion of the transfer of dangerous liquids the berth operator should render pipework, valves and associated equipment safe valves and tanks should be closed and shore pipeline blanked off. 

Some hot (370°C) pipework was supported by spring hangers to minimize stress as it was heated and cooled. The atmosphere was corrosive, and the spring hangers became impaired. They were removed, and the pipework was left solidly supported. It could not withstand the stress, and a condenser fractured hot heat-transfer oil was released and caught fire. 

Plates are available with effective heat transfer area from 0.03 to 3.5 m and up to 700 can be contained within the frame of the largest plate-type heat exchanger, providing over 2400 m of surface area. Flow ports and associated pipework are sized in proportion to the plate area and control the maximum liquid throughput. 

The operational duties of these smaller boiler systems vary widely, and for HW closed-loop heating systems, where the boiler is periodically offline, or in indirect heating systems where pipework, valves, or final heating units are exposed to chilly winds or icy conditions, some boiler winterization may be necessary. This is usually provided by replacing some of the water with glycols or other heat transfer fluids. 

Pipework and transfer hoses should be as short as possible, free from sharp bends and deadspots and routinely cleaned and sterilised with a biocide solution. Hoses should be stored in such a way (Figure 13) as to allow them to drain and avoid becoming a source of infection. 

Regenesys uses DuPont s Nafion (Section 6.1.7) as the perm-selective sodium ion transfer membrane, separating the two half cells. Figure 2.1. Diffusion of sodium ions in the concentration difference across the Nafion membrane is one of the irreversibilities of the system. The low-cost plastic (e.g. polyethylene) tanks and pipework are treated with fluorine to provide bromine resistance, and are able to operate with, and contain, both electrolytes at ambient temperature. 

Aseptic systems are used to transfer the inoculum to the vessel, to allow the removal of routine samples during fermentation, for early harvesting of aliquots when the vessel becomes full as a consequence of the media additions and to transfer the final contents to the extraction plant when fermentation is complete. Asepsis is assured by engineering design and by steam, which must reach all parts of the vessels and associated pipework. Any pockets of air or rough surfaces that steam does not penetrate could act as reservoirs for foreign growth. 

As we move toward fermentation it is essential that the integrity of the system is maintained and that all raw materials and adjuncts are appropriately stored and transferred under sterile conditions. The first challenge for the microbiologist is to ensure that all vessels and pipework are tested. 

A pressure relief system is normally required on all bioreactors and pressurised tanks as a safety feature to comply with pressure vessel design regulations. In a few cases, some companies appear to have overcome the need to use a pressure relief system on the vessel either by ensuring pressure relief is provided on relevant pipework to the vessel and/or ensuring there are no pumps transferring material which could lead to a build up of pressure if the outlet pipework were closed. The absence of pressure relief on the vessels can considerably simplify the process plant. The safety and regulatory requirements, as well as insurance inspection requirements, for pressure relief is currently a confused area. 

The mass balance calculations outlined in section 15.5 assume that the mass transfer of the solubles from the solids into the suspending liquid is complete. This is reasonably trae if the solids are non-porous and if enough time and shear are provided in the pipework, in the separator or in its feed sump for the mass transfer to take place before the solids leave the unit with the underflow. 

---