Heat exchanger sealing

Standard components for a bioreactor comprise the vessel, the agitator and impeller, heat exchangers, seals, and valves. Other components include utilities such as clean-in-place (CIP), and steam-in-place (SIP) systems, auxiliary tanks, pH and foam control, inlet tubes,... 

Figure 4.3 Floating-head heat-exchanger seal designs. From Ref.16 with permission. 

Figure 10.8 lOkW counter-flow heat-exchanger sealed by laser welding (source IMM). 

In other useful appHcations, siHcon nitride bearings have been found to offer exceUent performance siHcon nitride cutting tool inserts are a commercial product wear parts such as sand blast nozzles, seals, and die liners are also commercially produced the superior performance of heat exchangers has been demonstrated and there are also military appHcations. 

With a batch process, such as hot isostatic compaction (HIP), heat exchange as used in a continuous reactor is not possible, and it is common practice to provide a furnace within the pressure vessel which is thermally insulated to ensure that the temperature of the vessel does not rise above 300°C. Most HIP operations involve gas pressures in the range 70—200 MPa (10—29,000 psi) and temperatures of 1250—2000°C, occasionally 2250°C (74). The pressure vessel may have a bore diameter from 27 to 1524 mm (75) and is nearly always provided with threaded closures sealed with O-rings made of elastomer provided the temperature is low enough. 

Some toll processes lend themselves to test runs in the pre-startup phase. Actual materials for the toll may be used in the test or substitute materials, typically with low hazard potential, are often used to simulate the charging, reaction, and physical changes to be accomplished in the toll. Flow control, temperature control, pressure control, mixing and transferring efficiency can be measured. Mechanical integrity can be verified in regard to pumps, seals, vessels, heat exchangers, and safety devices. 

The heat exchanger i.s good for controlling temperature in the seal chamber utilizing the same pumped product. This method doesn t dilute the product. 

Inert gas-filled motors can also be used in refineries and chemical plants, but their applications are limited. They have tightly fitted covers and oil seals around the shaft to minimize gas leakage, are continually pressurized with an inert gas or instrument air, and are equipped with an internal air-to-water heat exchanger. Inert gas-filled motors are suitable for any hazardous location but require auxiliaries such as cooling water, gas pressurizing system, and control accessories. 

Add insulation to walls Raise compressor efficiency Add insulation to ceiling Switch to demand defrost Improve controls Improve heat exchanger Improve door seals... 

Bayonet heat exchangers are modified shell and tube types. The tubes are concentric with the outer tube, being sealed closed at one end, although the shell in its entirety is not always used or needed, see Figure 10-165. A helpful article describing this type of unit is by Corsi. ... 

The plate heat exchanger consists of a frame in which closely spaced metal plates are clamped between a head and follower. The plates have corner ports and are sealed by gaskets around the ports and along the plate edges. A double seal forms pockets open to atmosphere to prevent mixing of product and service liquids in the rare event of leakage past a gasket. 

Design faults in two-pass condensers and heat exchangers that can cause corrosion include poor division plate seals allowing the escape of water at high velocity between the passes, and flow patterns that produce stagnant zones. 

These alloy coatings have advantages over tin in atmospheric exposure where there is heavy pollution by oxides of sulphur. They are cathodic to steel and anodic to copper. In industrial atmospheres, however, formation of a layer of lead sulphate seals pores and produces a generally stable surface and terne-plate has been used extensively as roofing sheet, especially in the USA. It is easily and effectively painted when additional protection is required. Copper heat exchangers in gas-fired water-heaters may be coated by hot dipping in 20% tin alloy . 

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