LEFF stands for Low Emission Flip Flop. The LEFF® function is integrated in the T.VIS® A-15 valve control head and can be easily activated. The intermittent movement of the valve disk significantly improves cleaning efficiency. GEA VARIVENT® Mixproof Valves and thus the LEFF® technology are used in hygienic beverage and dairy processes and even meet the strict requirements of the Pasteurized Milk Ordinance (PMO). Staggered CIP cleaning of the individual housings means these valves can be used around the clock, without ever having to entirely shut down production.
Optimum cleaning of the valve seats and the valve chamber
Cleaning the cavity of the VARIVENT® Mixproof Valve takes place while product is present in the opposite valve housing. There is never a worry of intermixing. Accurate control of valve seat lift position is made possible by LEFF®, so only a narrow opening between the valve disk and seat is created during cleaning. This narrow opening causes the CIP liquid velocity to increase, producing an optimum cleaning burst in the seat area and vent cavity. The result is superior cleaning using a minimal amount of CIP media. To use the LEFF® function, no complicated programming in the higher-level control (PLC) is required. The LEFF® function works independently of process run times and product pressures. There is automatic monitoring of the lifting functions. With double-seat valves, only the standard feedback units are used. No special components are required. The rectilinear configuration with two push-buttons on the T.VIS® bonnet allows separate activation of the LEFF® function at any time when setting the valve. Activation of the upper seat function requires an external proximity switch.
Shear forces optimally exploited
Sealing zones on the valves can be cleaned separately by LEFF® with their sealing function entirely retained. This means that they can work around the clock, regardless of process run-times and product pressures, without interrupting production for CIP. “The principle is based on a flip-flop movement of the valve discs,” explains Bernd Porath, Product Manager for Hygienic Valve Technology at GEA. “At the moment when the valve disc lifts from the seat and opens up a cleaning gap, the cleaning medium flows in. That’s when the shear forces are at their greatest and they clean most effectively. We leverage this principle,,and the closing and opening of the valve discs, in a very specific manner.”
No additional system planning and programming
LEFF® is integrated as standard in the T.VIS® A-15 control head. Path-controlled electronics pulse-control the moment and degree of opening the valve disk with absolute precision. The electronic function monitors and controls the stroke of the valve seat via the valve’s path measurement system, independent of PLC scan times and line pressures. Since the electronic processing takes place only in the T.VIS® A-15 control top and not via the PLC, the signal speed is much faster. The LEFF® function can be easily enabled with the control top T.VIS® A-15. Activation of the function for the upper seat requires an external proximity switch.
Green light also from PMO Regulation of US Food and Drug Administration
While low emission flip-flop has already become standard in Europe for a number of major processing operations, the function had not been approved in the control head of mixproof valves in the USA. This approval has now been granted to GEA.
GEA engineers with great flexibility
GEA engineers have now redesigned the double-seat valves for milk processing in line with the PMO specifications and eliminated the risk with a special under pressure in the leakage space suctioning up any cleaning medium that may have overflowed, thus pressure cannot build up on the valve disk. This means that if a line and its sealing points are being cleaned, the other line can continue to conduct product.
GEA is the first manufacturer of double-seat valves to meet the strict requirements of the PMO. The approval of Low Emission Flip Flop for the USA is a great success: “Water shortage is a critical issue especially in California. We are pleased to be able to help our customers in the USA with LEFF® by lowering water consumptions alleviating other cost pressure in their operations,” summarizes Bastian Tolle, Head of Product Group Management Flow Components at GEA.
Good news for existing customers in the United States as well: LEFF® is already integrated in the T.VIS® A-15 control head of the VARIVENT® 24/7 PMO 2.0 and only needs to be switched on to be used in existing applications. Additional system technology and programming are not required.