Dairy Establishment Inspection Manual – Chapter 17 - Higher Heat Shorter Time (H.H.S.T.) Processing and Extended Shelf-Life (ESL) Dairy Products
1.17.03 Constant Level Tank (C.L.T.)

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The constant level tank (C.L.T.) is a reservoir for supply, at atmospheric pressure, of raw product to the pasteurizer to permit continuous operation of the H.H.S.T. system. The constant level tank is located at the start of the H.H.S.T. system. The constant level tank controls the milk level and provides a uniform head pressure to the product leaving the tank. General Conditions

The tank shall be constructed of stainless steel and be in good mechanical and sanitary condition. The tank's design features will be assessed under the subsequent tasks. Design

The tank shall be of such design and capacity that air shall not be drawn in the pasteurizer with the product when operating at the maximum sealed capacity of the flow control device. The constant level tank shall therefore be fabricated so that the raw product will drain to the outlet before the outlet becomes uncovered. One method of complying with this requirement is to have the bottom of the tank pitched to the outlet at a minimum downward slope of at least 2% (0.2 cm per 10 cm) and the top of the outlet pipe lower than the lowest point in the tank (see Appendix 19-3). Cover

The tank shall be fitted with a removable cover, or an inspection port with a removable cover, of suitable design to maintain atmospheric pressure and to minimize the risk of contamination. The cover shall be pitched to an outside edge to provide drainage. All openings in the cover shall be flanged upwards and covered. Pipelines entering through the cover (excluding directly clamped lines) shall be fitted with a sanitary umbrella deflector that overlaps the edges of the opening and is located as close to the tank cover as practical. The cover shall be used during processing. Airspace and Overflow

Any product divert lines, recycle lines and water lines coming into the constant level tank (C.L.T.) must be installed in a way that prevents the siphoning of raw milk or cleaning products into finished product or potable water lines (a cross connection). This is accomplished by having an overflow outlet at least twice the diameter of the largest inlet to the constant level tank, and ensuring that the divert, recycle, water lines terminate and break to atmosphere at least two times the diameter of the largest inlet above the maximum overflow point of the C.L.T. Level Control Device

This device is required to control the flow of milk to the C.L.T. and therefore provide constant head pressure to the product leaving the tank.

The constant level tank shall be equipped with an automatic device of sanitary design and construction to control the raw product level.

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