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Features
• Proprietary design helps prevent over-tightening that can cause glass breakage.
• Piston design allows quick and safe removal, eliminating the cleaning and assembly problems
associated with other stopcock styles.
• Glass-filled PTFE piston minimises the differential expansion between piston and reaction vessel, and
removes the danger of the piston fracturing the vessel due to over-tightening followed by piston
expansion. The piston also reduces the differential contraction between vessel and piston when
operating at temperatures down to -60°C.
• Interchangeable between vessels, with a full range of replacement parts and FEP O-rings.
• The large 15mm bore minimises sample hold-up and is ideal for slurries (25mm available on request).
• Features a double O-ring seal at the top of the piston to further improve the sealing of the vessel
stopcock, which is particularly useful at extremely low temperatures.
The Reactor-Ready V4 ZDS stopcock should only be operated by hand and not with the use of
tools. If the piston cannot be inserted or removed easily, do not force it. If the piston becomes
stuck please contact your local distributor or email sales@radleys.co.uk for technical advice.
When closing the V4 ZDS stopcock, the piston will reach the closed position whereupon you will feel
resistance. The piston does not need to be tightly closed to provide a seal – in fact, this can lead to
breakage of the glass thread and should therefore be avoided. Once the piston is fully closed, gently
(with fingers only) unscrew the cap by a ¼ turn to prevent stressing the thread.
→ Reactor-Ready filter vessels feature the same V4 ZDS stopcock design as reaction vessels,
however, the piston assembly is longer in order to allow the filter vessel to accommodate the
additional length of the outlet of the filter vessel base.
→ Pistons are not interchangeable between reaction vessels and filter vessels, so care should be
taken to ensure the correct piston is being used for your application.
Minimising weeping at low temperatures
Care must be taken with the piston seals, particularly when operating at extreme low temperatures, as
below -50°C there may be some weeping from the stopcock. (Some minimal weeping at low
temperatures is commonplace with most reaction systems with conventional-style stopcocks.)
The occurrence of weeping may vary from experiment to experiment and from vessel to vessel.
The performance of the piston and O-rings, particularly when operating at low temperatures, will be
reduced by the following factors:
• Low temperatures – will cause the FEP encapsulated O-rings to harden and become brittle during
use, which reduces the elasticity of the polymer and potentially the effectiveness of the seal.
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