Can I use ordinary silicone tubing for high vacuum?

Not for anything below about 10⁻³ mbar. Silicone is flexible and cheap, but it permeates water vapour and atmospheric gases and outgasses progressively under pumping, so a silicone line will hold a rough vacuum and no better. Below 10⁻³ mbar use thick-wall PTFE, stainless braided flexible line or rigid stainless tubing, and keep elastomer sections as short as possible.

What bore size should a vacuum line be?

Size for conductance rather than for the pump inlet. As a working rule keep the hose bore at least the diameter of the pump inlet and no smaller than the port it connects to, and keep the run under one metre. A 6 mm bore line one metre long has roughly one tenth the conductance of a 10 mm bore line of the same length, which is enough to halve the effective pumping speed at the chamber.

How do I stop vacuum hose from collapsing?

Use a hose with a helical wire reinforcement or a braided stainless overbraid, and avoid sharp bends. Standard unreinforced silicone will flatten at about 100 mbar differential if the bend radius is tight. Support long runs with clamps every 500 mm and fit a hose barb or KF adapter rather than stretching the hose over a glass spigot.

Vacuum Tubing and Hose Singapore

Q: Does JWRESEARCH supply vacuum tubing in Singapore?

Yes. JWRESEARCH supplies silicone, PVC, PTFE and braided stainless vacuum tubing and hose in laboratory bore sizes, together with hose barbs, KF adapters, worm-drive and spring clamps, and cut-to-length service, delivered across Singapore with advice on material and bore selection.

Published: {{NEW_ARTICLE_DATE}} | By JWRESEARCH | Category: Laboratory Consumables

A vacuum line is the part of the system nobody specifies. It is bought at the last minute, cut to reach, and pushed over whatever spigot is available. Then the pump performs below its datasheet, the chamber takes twice as long to reach base pressure, and the pump is blamed for a problem that lives in a metre of tubing.

At JW RESEARCH SUPPLY, we supply vacuum tubing and hose to Singapore laboratories in silicone, PVC, PTFE and braided stainless constructions, with the barbs, KF adapters and clamps that make a line leak-free. This guide covers material choice, bore sizing, clamping practice and the limits of each type.

Material Selection by Vacuum Range

The single decision that matters most is the material, because each polymer has a different permeation and outgassing behaviour. Elastomers are convenient at rough vacuum and become a liability at fine vacuum.

Material	Practical Vacuum Range	Flexibility	Typical Use
Silicone (platinum cured)	Atmospheric to 10⁻³ mbar	Excellent	Filtration manifolds, aspirators, peristaltic lines
PVC (clear, food grade)	Atmospheric to 10 mbar	Good	Water aspirators, low-cost rough lines, drainage
PTFE (thick wall)	Atmospheric to 10⁻⁶ mbar	Limited, stiffens when cold	Solvent lines, corrosive vapours, rotary evaporator
Braided stainless flexible hose	Atmospheric to 10⁻⁸ mbar	Moderate, fixed bend radius	Turbo pump inlet, chamber connections, vibration isolation
Rigid stainless tube (welded)	To 10⁻¹⁰ mbar	None	UHV manifolds, permanent installations

Specification Reference

Parameter	Typical Value	What It Affects
Bore (ID)	3, 5, 6, 8, 10, 12, 16, 19, 25 mm	Conductance and therefore effective pumping speed
Wall thickness	1.5 – 6 mm	Resistance to collapse and permeation rate
Working pressure (internal)	Full vacuum to 3 – 10 bar	Whether the same hose can be used for pressure transfer
Temperature range, silicone	−60 to +200 °C	Autoclave and hot-plate adjacent runs
Temperature range, PTFE	−200 to +260 °C	Oven and cryogenic connections
Bend radius, braided hose	4 – 6 × nominal bore	Routing in a crowded fume hood or pump cabinet
Permeation (water vapour, silicone)	High; roughly 10 – 100 × PTFE	Base pressure achievable on humid Singapore days
Clamp options	Worm drive, spring band, KF 16/25/40 centring ring	Leak-tightness and whether the joint can be remade quickly

Sizing for Conductance, Not for Convenience

A long thin hose throttles the pump. Conductance in the molecular regime scales with the cube of the diameter and inversely with length, so a small change in bore has a large effect. Doubling the bore multiplies conductance roughly eightfold; doubling the length halves it. That is why a 1 m length of 6 mm tubing can turn a 60 L/min pump into something that behaves like 20 L/min at the chamber.

Keep the run short, keep the bore equal to or larger than the pump inlet, and avoid unnecessary elbows. Where a flexible section is essential — at a turbo pump inlet, for instance — use a braided line of the full inlet diameter and support it so the weight does not hang on the flange.

Fittings, Clamps and Leak-Free Joints

Most vacuum leaks in a laboratory are at joints, not in the tube. Push the hose fully onto a barb of the correct size; a barb that is one size small will stretch the elastomer, thin the wall at the tip and seep. Use a spring band or worm-drive clamp behind the barb's shoulder, not on the taper. For anything below 10 mbar, replace the barb with a KF adapter and a centring ring with a fresh O-ring.

Cut tubing square with a sharp blade, not scissors, and inspect the cut edge. A ragged edge will not seal against a barb or a compression ferrule, and the leak it creates is small enough to be invisible and large enough to spoil a pump-down curve.

Practical Notes for Singapore Conditions

Ambient humidity above 80 per cent is normal here, and water vapour is the dominant residual gas in any unbaked polymer line. A silicone hose that has been sitting on a shelf absorbs moisture and will release it for hours under vacuum. If a system must reach 10⁻⁴ mbar, keep the elastomer section as short as possible, prefer PTFE or stainless for the rest, and allow a longer pump-down on wet afternoons.

Replace tubing that has hardened, discoloured or taken a permanent set at a bend. Silicone that has been autoclaved repeatedly loses elasticity and begins to crack at the barb, which produces a leak that appears only when the line is moved. Keep a stock of the two or three bore sizes actually used on site rather than a drawer of near-misses.

Frequently Asked Questions

Can I use the same hose for pressure and vacuum?
Only if it is rated for both. A hose rated for full vacuum may have a modest positive pressure limit, and a pressure hose may collapse under vacuum. Check both figures on the datasheet.

How often should vacuum hose be replaced?
Inspect at every pump service. Replace any section that is hard, cracked, flattened or discoloured, and replace all elastomer sections in a fine-vacuum system annually as a baseline.

Does tubing length really matter that much?
Yes. In the molecular regime conductance falls linearly with length, so a 2 m run delivers half the pumping speed of a 1 m run of the same bore. Move the pump closer before buying a bigger one.

Does JWRESEARCH supply vacuum tubing in Singapore?
Yes — silicone, PVC, PTFE and braided stainless vacuum tubing and hose, plus barbs, KF adapters and clamps, delivered across Singapore with advice on bore and material selection.

Contact JWRESEARCH

JW RESEARCH SUPPLY — laboratory equipment and consumables, Singapore.
Tel / WhatsApp: +65 8039 3660
Email: SINGAPORE@JWSHY.COM
Website: www.jwresearch.cn