Closed-Loop & Packaged Liquid Ring Vacuum Systems
Complete liquid ring vacuum units and closed-loop systems for processes that need continuous, reliable vacuum with no water or sealing-liquid waste.
We supply two engineered configurations in addition to bare pumps:
- Closed-loop (recirculating) systems — pump with separator, heat exchanger, piping and work-liquid circulation. Sealing water is reused; no continuous discharge.
- Air-cooled closed-loop units — no site cooling water required; suited to outdoor or water-scarce plants and cold climates (anti-freeze options).
Typical duties: distillation and solvent recovery, paper-machine vacuum, condenser evacuation (power), sugar crystallization, chemical and general industry. The unit is assembled, leak-tested and run at the factory before dispatch; drawings, P&ID and spare-parts list are provided with the quotation.
Tell us the process (gas, vacuum level, capacity, available utilities) — we size the pump and the system.
Once-through, partial-recovery or fully closed loop
The seal liquid is what decides the system layout. Three arrangements cover almost every enquiry we receive:
- Once-through. Fresh water in, warm water out. Cheapest to build, highest running water cost — normally only acceptable where water is abundant and uncontaminated discharge is allowed.
- Partial recovery. A separator returns most of the liquid; a controlled make-up stream carries away heat and dissolved contaminant. A middle option when process gas dirties the liquid slowly.
- Fully closed loop. Separator plus heat exchanger, with the liquid recirculated by pump or by the vacuum pump's own discharge head. No continuous discharge, so the process can run where water is metered or effluent is regulated.
What a packaged unit contains
A skid is quoted from your duty point, not from a fixed part list, but a closed-loop liquid ring set normally includes: the pump and motor on a common baseplate; an inlet separator or knock-out pot; a discharge separator with level control; a plate or shell-and-tube heat exchanger sized for the heat the pump adds to the liquid; work-liquid circulation piping with strainer, sight glass and drains; a cavitation-protection or non-return line; instrumentation for vacuum, liquid level and temperature; and a control panel with starter or VFD when the vacuum has to be held against a varying load.
Roots-boosted sets for deeper vacuum
A liquid ring pump alone is limited by the vapour pressure of its seal liquid. When the process needs a lower absolute pressure than that, a Roots booster is fitted ahead of the liquid ring pump — this is the JZJ arrangement, with the booster raising both attainable vacuum and pumping speed at low pressure while the liquid ring stage handles the discharge. Chilled or glycol seal liquid is the alternative route to a lower base pressure and is sometimes cheaper to run than an extra stage.
Air-cooled units where cooling water is the constraint
Where no cooling water is available, the heat exchanger becomes an air-cooled radiator with fan. This raises the seal liquid temperature relative to a water-cooled loop, so capacity at deep vacuum is derated — we size the pump for the summer ambient at your site rather than for a nominal 15 °C water temperature. Anti-freeze charging is available for outdoor installations in cold climates.
What we need to quote a system
Suction pressure and required capacity at that pressure; the gas composition and whether it carries condensable vapour, solids or corrosives; available cooling water temperature and flow (or confirmation that the unit must be air-cooled); ambient and site elevation; power supply and frequency; and any zone or explosion-proof requirement. With those we return a system schematic, the pump selection with its curve, a utility list and an outline drawing — the same drawing-first process we use for bare-pump replacements.
Multi-pump sets we have built
2BW-type sets: several liquid ring pumps on one skid with the separator and plate heat exchangers sized for the combined load. Sizing depends on your cooling water, so send the duty.
- 2BW5-2070-2 — 2 liquid ring pumps, separator, 4 plate heat exchangers, magnetic turnover
- 2BW5-2070-4 — 4 liquid ring pumps, separator, 8 plate heat exchangers, magnetic turnover