Pressurereduction Valves

Pressure-reduction valves are incorporated into pipelines when it is necessary to reduce from a higher to a lower pressure, and be able to maintain the lower

Plug

Cap Handle

Adjusting screw Spring

Bonnet

Fig. 7.38. Section of a safety valve (Kemplay, 1980).

Plug

Cap Handle

Adjusting screw Spring

Bonnet

Spindle

Temperature equalising lantern

Cover Guide bush Guide piston Disc

Adjusting ring Body

Inlet nozzle

Fig. 7.38. Section of a safety valve (Kemplay, 1980).

liquid. Once the pressure falls below the value set by the tensioned spring, the spindle should return to its original position. However, the valve may stick open if waste material lodges on the valve seat and plant operators may interfere with the release pressure setting. Bursting/rupture discs may be used as an alternative and are of a more hygienic design than some valves (Leaver and Hambleton, 1992).

For GILSP operational categories, venting the escaping gas through the factory roof in emergencies would be satisfactory. At higher containment levels it would be necessary to treat the escaping gas. A kill tank with a HEPA venting filter is one possible solution, but not fully satisfactory.

It is also important to ensure that vessels do not collapse when vacuums occur. Vacuum release valves have been designed to cope with cold rinsing of a hot vessel or absorption of COz when cleaning with caustic solutions (Maule, 1986). Shuttlewood (1984) has discussed design pressure and vacuum pressure in relation to vessel thickness requirements for design codes for American and British standards of safety.

Steam traps

In all steam lines it is essential to remove any steam condensate which accumulates in the piping to ensure optimum process conditions. This may be achieved by incorporating steam traps, which will collect and remove automatically any condensate at appropriate points in steam lines. A steam trap has two elements. One is a valve and seat assembly which provides an opening, which may be of variable size, to ensure effective removal of any condensate. This opening may operate on an open/close basis so that the average discharge rate matches the steam condensation rate or the dimensions of this opening may be varied continually to provide a continuous flow of condensate The second element is a device which will open or close the valve by measuring some parameter of the condensate reaching it to determine whether it should be discharged (Armer, 1991).

The steam trap may be designed to operate automatically on the basis of:

1. The density of the fluid by using a float (ball or bucket) which will float in water or sink in steam (Fig. 7.39).

2. By measuring the temperature of the fluid, closing the valve at or near steam temperature and opening it when the fluid has cooled to a temperature, say 8° below the saturated steam temperature of the steam. The sensing element is often a stainless-steel capsule filled with a water-alcohol mixture which expands when steam is present and presses a ball into a valve seat or contracts when cooler condensate is present and lifts the ball from the seating. These are used in thermostatic and balanced pressure steam traps (Figs 7.40 and 7.41).

3. By measuring the kinetic effects of the fluid in motion. At a given pressure drop, low-density steam will move at a much greater velocity than higher density condensate. The conversion of pressure energy into kinetic energy can be used to control the degree of opening of a valve. This type of steam trap is not used vety widely.

Condensate Cooler Spirax Sarco
^ Inlet
Micro Organisams

Fig. 7.40. Balanced pressure steam trap (Spirax/Sarco, Cheltenham, England). (1) body; (2) end connection; (3) element; (4) Tri-Clover clamp; (5) Tri-Clovcr joint gasket; (6) ball seat.

Distillation Traps

Fig. 7.42. SBP 30 Sealed balanced pressure thermostatic steam trap (Spirax/Sarco, Cheltenham, England). (1) cover; (2) body; (3) element/capsule; (4) ball scat assembly; (5) strainer screen-' (6) inlet; (7) outlet.

Fig. 7.40. Balanced pressure steam trap (Spirax/Sarco, Cheltenham, England). (1) body; (2) end connection; (3) element; (4) Tri-Clover clamp; (5) Tri-Clovcr joint gasket; (6) ball seat.

Fig. 7.42. SBP 30 Sealed balanced pressure thermostatic steam trap (Spirax/Sarco, Cheltenham, England). (1) cover; (2) body; (3) element/capsule; (4) ball scat assembly; (5) strainer screen-' (6) inlet; (7) outlet.

boiler, (b) used in a steam condensate line, (c) vented to waste or (d) piped to a kill tank in a containment location

Complete loss of contents from a fermenter

Armer (1991) thinks that balanced pressure thermostatic traps are the most suitable for autoclaves and sterilizers. Some can operate close to steam-saturation temperature with little back up of condensate. Sarco Ltd (Cheltenham, U.K.) make a hermetically sealed balanced pressure steam trap (Model No. SBP 30; Fig. 7.42) which has been used with a high containment level pilot-plant fermenter (Hambleton et al., 1991).

Any steam condensate may be (a) returned to the

Thermostatic Traps
Fig. 7.41. Stainless steel thermostatic steel trap (Spirax/Sarco, Cheltenham, England). (1) inlet; (2) outlet; (3) body; (4) ball seat; (5) element.

Leaver and Hambleton (1991) have suggested building a wall or dyke around a fermenter which would retain the entire contents were they to leak out. The escaping fluid would then be pumped into a suitable vessel for sterilization. The floor should be covered with an impervious epoxy based surface and coved up the walls (Kennedy et al., 1990).

Testing new fermenter*

When a new fermenter (10 dm3 or larger) has finally been assembled in a factory it must be hydraulically pressure tested and checked by independent inspectors using nationally approved test procedures. A vessel which has passed the approved tests is given a certificate which is recognized by insurance companies which will allow it to be operated in a laboratory or factory. If any subsequent modifications are made to a vessel in this size range it must be retested and certificated before it can be legally used. Thus a number of fermenter manufacturers cut extra 'O' ring grooves and steam traces in head plates or ports to satisfy higher containment-level needs so that the vessels will not have to be modified subsequently and to avoid extra pressure checks.

Vinegar For Your Health

Vinegar For Your Health

A resource for the many ways you can use Vinegar to improve your health! In today's society of miracle medicine, we often overlook things that have been around hundreds of years! Things like Vinegar!

Get My Free Ebook


Post a comment