Cold trap/condenser

01

Choose trap temperature, cooling and capacity

Thermo Scientific describes its Savant refrigerated vapour traps as collecting solvents removed during vacuum evaporation, with vapours condensing in a collector so they do not reach and degrade the oil pump. The RVT450 cools from ambient to −50 °C for water and non-aggressive organic solvents; the RVT5105 cools to −105 °C for organic and highly volatile solvents such as methylene chloride, acetone, hexane and chloroform, acids, water and low- and high-boiling solvents. Both hold 4 L and use HCFC-free refrigeration. [1]

The RVT5105 uses two 1/3 hp compressors to reach −105 °C in under 40 minutes and has a 4 L stainless collector with a stainless drain port and nylon valve; it weighs 68 kg (150 lb) and measures 61 × 61 × 47 cm, against 32 kg for the RVT450. Both come in 115 V/60 Hz and 230 V/50 Hz versions. [1]

Weizmann Institute safety guidance says a cold trap safeguards vacuum lines and pumps by condensing solvents and volatile liquids and recommends one to keep a vacuum pump working at lower pressures; it describes traps cooled by placing them in a dewar of liquid nitrogen. [2]

DigiVac's 4-inch liquid-nitrogen cold trap uses a "cold thimble" design: the thimble holds liquid nitrogen, which DigiVac gives as −187 °C, and its outer surface, exposed to the vacuum system, condenses molecules in the vapour phase. DigiVac lists a water-vapour pumping speed at the trapping surface of 95 L/s per square inch and a "theoretical" water-vapour pressure at the thimble of 10⁻²¹ Torr. The trap is electropolished 304 stainless steel with an easily removable thimble and comes with an NW16 or NW25 port. [4]

Give the supplier the vapours and their amounts per run, the lowest temperature needed to condense them, vacuum level and pump size, cooling method (refrigerated or liquid nitrogen), collector capacity and drain arrangement, materials for corrosive vapours, electrical supply, and installation (bench, inline, skid).

02

Operate, drain and clean the trap safely

For liquid-nitrogen traps, the Weizmann guidance warns that liquid oxygen (blue) can form in nitrogen-cooled vessels and may cause a serious explosion, so the trap must always be removed from the liquid nitrogen before the vacuum is turned off. It also says to close the valve between vessel and pump before stopping the pump and to release the vacuum immediately after shutdown to avoid sucking pump oil into the system. [2]

The guidance says to let the trap warm to room temperature before disposing of collected solvents, to leave traps that may hold toxic or corrosive condensate in a fume hood overnight before washing, and to wear safety glasses, lab coat, closed shoes and gloves, plus a full face shield and cryogenic gloves for liquid nitrogen. [2]

Editorial calculation: the RVT5105's −105 °C is 55 K colder than the RVT450's −50 °C. [1]

03

Compare trap temperature grades and pull-down time

Labconco's CentriVap cold trap product page lists three collector temperature grades sharing a 4-litre stainless steel collector, a stainless steel drain port with polypropylene valve, a lid with two quick-disconnect fittings for 1/2 in ID hose, and an HCFC/CFC-free refrigeration system. A temperature graph lights green when the collector coil reaches its operating temperature. [3]

The page links a boiling point calculator for choosing the grade against the solvent, and the colder grades use two compressors. Compare collector volume, the lowest temperature and the pull-down time with the vapour load of your evaporator or vacuum process, alongside the safe-operation points above for liquid-nitrogen traps. [3] [2]

Editorial calculation: the −105 °C grade is 55 °C colder than the −50 °C grade but more than doubles the unit weight (68 kg against 32 kg).

State the solvents and their freezing points, vapour load per run, required trap temperature and collector volume, and ask for pull-down time, drain arrangement and hose connection size.

04

Pull-down, condensing capacity and drain method: what to ask before buying

Ask any supplier for lowest trap temperature and pull-down time, condensing capacity and collector volume, compatible solvents and acids, wetted materials, pump size it suits, refrigerant, power supply, drain and defrost method, dimensions and weight.

05

Collector, LN2 thimble, refrigeration and the shutdown valve

Two cooling routes share this list: a refrigerated collector or a liquid-nitrogen thimble. The isolation valve row matters for the shutdown order the Weizmann guidance sets out. [4] [2]

06

Refrigeration, temperature, supply and material values found so far

Surface area, coolant flow, accuracy, pressure drop, power draw and IP rating have no published figure in the sources reviewed; the lowest temperature and pull-down rows are the ones that decide which grade condenses your solvent. [3]

07

Send the vapour, vacuum and site data together

Paste it into your enquiry below or into an email to a maker, then replace every bracket.

Vapours: [solvents; acids; water; amount per run]
Temperature: [lowest needed]
Vacuum: [level; pump size]
Cooling: [refrigerated; liquid nitrogen]
Capacity: [collector litres]
Materials: [stainless; corrosion-resistant]
Supply: [voltage; frequency]

See manufacturer records Send an enquiry through CNFX