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ASEPCO Sterillite Valves – Dead Legs Be Gone!

Our ASEPCO Radial-Diaphragm™ Sterillite™ Valve design offers contamination-sensitive industries, yet another significant advance in valving. The Sterillite Valve is a radial diaphragm valve seating directly on the body of a host ASEPCO valve (see Drawing #1).

This configuration ends a very troublesome source of dead legs—those small dead ends that occur when piping systems require nonflush ports, for example.

Drawing #1 In earlier ASEPCO newsletters, we showed how advanced piping configurations used ported ASEPCO valves to permit steam-in-place (SIP) behind the valve seat, while the valve is closed.

The ASEPCO Sterillite Valve controls the port while seating flush to its host valve, eliminating dangerous dead legs that can occur when weir valve bosses are tapped with ports.

Just what are dead legs?

A dead leg is a length of pipe in a system in which the process fluid is stagnant. A typical occurrence of a dead leg would be at a tee (see Drawing #2).


Dead legs can occur at any place where the main process flow isn’t moving through piping, but rather goes past an intersection with a dead end.

Dead legs are measured by taking the ID of the pipe and counting how many of these intersection with the main piping system.

ASME Bioprocess Equipment Standards state that a dead leg should be 2:1 pipe diameters or less, which is achievable in most processes with today’s equipment designs.

Why should dead legs be avoided in aseptic systems?

At a minimum, it takes much longer to clean, rinse, and steam dead legs, because the rate at which the liquid in the dead leg is exchanged with the main piping system is very slow.

Lengthy (and costly) cycles are not the only reason to worry about dead legs. Plugs of product form in these areas and can resist removal with standard CIP procedures. The material is baked on by the heat instead of being removed. Then you can get bacterial undergrowth in the area sheltered by the crusted product.

In addition, dead legs can lead to the build up of condensate during SIP procedures. Where there is condensate, there is insulation from the killing heat of the steam, and a good chance that kill temperature won’t be reached. This can leave behind live organisms, ready to grow in the stagnant condensate pool. It’s important to engineer these out of the system.

Every year, advances in process equipment reduce dead legs, but this is an elusive goal. Getting there requires manufacturers to rethink process component design.

The ASEPCO Sterillite Valve design brings an end to the dead legs that occur again and again in systems at the point where weir diaphragm valves are ported or where they have their bosses tapped (see Drawing #3).

What makes the ASEPCO Sterillite Valve design different? The seat of the Sterillite Valve is machined into the body wall of the host valve. The Sterillite Valve body is machined from bar stock like all ASEPCO valves. It is then welded onto the body of the host valve.

Note that in Drawing #1, the Sterillite diaphragm is longer, allowing the diaphragm to seat right at the wall of the host valve, eliminating the dead leg. When the Sterillite Valve is closed, the host valve doesn’t even know there’s a valve attached!

This valve design is possible because of the advanced manufacturing process unique to ASEPCO valves.

The ASEPCO Sterillite Valve can be mounted on valves ranging from 1.0 to 4.0 inches.

ASEPCO’s Sterillite Valve can be used wherever steam ports on valves are needed and dead legs threaten to sabotage your process.

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