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ITT Pure-Flo Block Body Diaphragm Valves: ZSBT vs ZSBBT- What’s the Difference?

October 28, 2014
The ITT ZSBBS Body

ITT Pure-Flo Zero Static Valve Body with Sampling Port

Even at Holland, where we’re all sanitary process experts, occasionally we can get confused. One issue that came up recently is the difference between ITT Pure-Flo’s ZSBT and ZSBBT valve. We’re going to take this post to review the functionality of a zero static point of use diaphragm  valve and clarify the difference between the ZSBT and ZSBBT zero static valve.

To begin, zero static use points are some of the most critical valves used in the biopharmaceutical industry. A point of use valve allows fluids to be transferred, sampled, drained, or diverted. Zero static valves help us comply with ASME BPE’s L/D dead leg requirements of 2:1. A dead leg is basically a one way water system. Dead legs result in process system that are difficult to clean. Stagnant fluid can also harbor process compromising bacteria.

While the FDA had historically required dead legs not to exceed 6 diameters of unused pipe, the BPE, finding this rule not sufficient to assure sterility, imposed even more stringent requirements. In 1997 the ASME addressed these problems by strongly suggesting (stopping just short of mandating) that the length of a dead leg shall not exceed two times the pipe diameter.

With these stringent requirements, you can see why putting a valve on the branch of a tee could be problematic. As a response to this requirement, the zero static point of use valve has been widely adopted throughout the pharmaceutical process industry. A zero static point of use valve incorporates the outlet valve weir into the main run. Fluid can then be drawn off the main line in a much “cleaner” fashion.

Several variations of the standard zero static diaphragm  valve have also developed, including the zero static sample valve and zero static valve with downstream purge. These block body valves incorporate an integral valve onto the back of the valve assembly that provides access either to fluid upstream of the valve weir (Sample), or access to the process downstream of main valve weir (purge). These integral valve assemblies greatly reduce contact surfaces, hold up volume, and possible dead legs.

So now that we know what a zero static valve does, what is the difference between the ZSBT and ZSBBT valve? The answer is shockingly simple- not much. When ITT originally debuted the ZSBBT valve, they used a faceted body that helped in situations with tight space constraints.

Over time, the market started asking for a more economical zero static valve that could be used in applications without space concerns. To answer this, ITT debuted the ZSBT non-faceted zero static tee. This valve has a squared block body that requires fewer machining steps to make. All other critical dimensions are identical between the ZSBT and ZSBBT valves. All MOC’s and actuation options are the same as well. The only difference are the aesthetics.

So there you have it- the mystery of the ZSBT solved. So the next time you’re looking to replace a legacy ZSBBT valve and you get a quote for a ZSBT, rest assured you are getting a drop in replacement for your legacy valve. For any additional questions about your next sanitary diaphragm valve application, contact a Holland Sales Engineer today.

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