Steam Retorts

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Steam Retorts

Still steam retorts are identified as vertical, in which the crates are lowered by hand or overhead hoist into the retort. or horizontal, in which the crates are pushed or conveyed into the retort; or crateless , in which the containers drop into cushion water in the retort.
Still steam retorts were one of the first types of retort systems used to pressure process lacf.

Steam under pressure provides a number of advantages for processing lacf products in metal containers:

1. It is an excellent medium for heat transfer

2. Its temperature is easily regulated

3. The steam pressure required in the retort in order to achieve the required processing temperature serves to counter-balance the pressure built up inside of the container during processing.

4. Steam can be easily manufactured and held in reserve for immediate use.

5. The stored energy property of steam makes it a superior heating medium as compared to water or steam-air.

When the steam condenses on the containers during processing this latent heat is given up to the container

It is important in the operation of still steam retorts to remove air from the retort prior to starting the process. Air in the retort acts as an insulator around the containers, preventing steam from contacting the container. Air in the presence of high heat may also cause the containers to rust. Small amounts or pockets of air in the retort can cause containers in those areas of the retort to be under processed.

Air may be supplied to the still steam retort to provide overpressure during the water cooling of containers in the retort. Considerable pressure is built up in the container during thermal processing. To prevent buckling (the container ends become permanently distorted) of the container overpressure from air or steam is provided during cooling.

Air overpressure is more easily controlled as the steam tends to collapse in the retort headspace. The overpressure must be controlled within limits, as too great a pressure or cooling for too long will panel (permanently distort the side panels) the containers. The air supply line must be equipped with a tight fitting valve (e.g. globe or ball) to prevent air leaking into the retort during thermal processing.