Flovarem - the new flow-through expansion vessel

A solution that improves the performance of systems equipped with electronic pump controllers

Since its launch in recent years, the electronic pump controller has carved a considerable niche on the market; this device is designed to control pump start-ups based on the requests for withdrawal in potable water distribution and pumping systems. It has also been designed to prevent the pump from running dry, hence avoiding damage if the water supply is absent.

This is without doubt an interesting innovation, due to its limited overall size and ease of installation, so much so that it has enjoyed widespread distribution in times in which space has become increasingly precious and must necessarily be optimized.

This device has partly replaced the use of conventional expansion vessels, which are bulkier and heavier, substituting its function of water reserve and pressure stabilizer with a different approach, i.e. causing the pump to start-up each time there is a request for water.

However, the electronic pump controller has not dealt with all the typical functions performed by the expansion vessel; the water reserve normally contained is too small to be able to form a hydrodynamic flywheel in the case of small withdrawals or, even worse, micro leaks, in these cases causing abnormal pump operation subject to numerous and frequent starts and stops. This leads to a shorter useful life of the pump, as it has to deal with a large number of cycles in a short space of time, and therefore a significant increase in power consumption. Instead, in the case of long withdrawals, but with a low flow rate, the electronic pump controller always controls the pump (which therefore operates with maximum head); due to its pressurized water reserve, the expansion vessel allows the pump to be used at the maximum flow rate to fill the vessel, which then acts as a water flywheel for withdrawals with a low flow rate.

The lack of an expansion cell also exposes the system to greater risks of sudden pressure peaks, or water hammer, which can compromise the seal of the system with unfortunate consequences linked to sudden and substantial water leaks.

To deal with these problems, electronic pump controllers with an integrated expansion vessel of small size (typically 3 litres) have been introduced to the market, thus obtaining a decrease in pump start-ups and dealing with the problems described above.

Instead, in systems equipped with electronic pump controller without a water reserve, and in with no expansion vessel installed, these critical points remain and can be the source of evident problems (breakages caused by water hammer), but above all hidden problems (shorter useful life of the pump and increased power consumption).

After having identified these shadow areas, Varem’s R&D department set to work to find possible solutions. The result was the production of a flow-through vessel, provided with membrane with double entry and exit hole and a perforated pipe that passes through the whole length of the tank. The initial nominal volume provided by the manufacturer is 3 litres, but expanding the options with larger tanks is currently being studied.

The Flovarem flow-through vessel

This is a patented innovation which, when applied to any electronic pump controller on the market, reduces the disadvantages and improves the efficiency of the system, also bringing benefits in terms of protection of the system and water quality.

The operating principles and the impact of adopting this product in a hydraulic system are set down below, comparing cases in which the through vessel connected to the electronic pump controller with cases in which it is not connected.

In a pressurization system designed with the use of an electronic pump controller this is normally applied directly to the pump, in the water outlet connection, and wired to control its supply. Therefore, the water passes through it and is delivered towards the various users of the hydraulic system. The pressure is detected inside and during withdrawal drops rapidly, causing the pump to start up; in this way, each time a user is activated (even at a low flow rate) the system is maintained in pressure by the pump, which ensures that pressurized water is available where required. After withdrawal, the pressure tends to rise rapidly, producing the impulse for the pump to shut down.

Finally, the presence of an integrated electronic pump controller detects the flow rate of the water with the aim of preventing the pump from running dry, which is dangerous and in a very short time would cause damage to or even breakdown of the pump.

However, in this configuration the pump operates at each withdrawal, whether the flow rate is substantial (i.e. taking a shower), minor (i.e. turning on a tap to wash hands) right down to small leaks in the system.

One of the objectives of the flow-through vessel is to reduce pump start-ups, due to a reserve of pressurized water; if in the first case (the shower), start up will be almost immediate, in the case of smaller and shorter withdrawals the pump will carry out a lower number of cycles than the number of withdrawals; this will have the positive result of extending pump life and simultaneously reducing power consumption for its operation.

Diagram of a system with electronic pump controller and flow-through vessel

Tests carried out in the Varem laboratories have shown just how much the efficiency of the system has improved from the viewpoint of consumption after fitting the flow-through vessel. 

Power consumption with and without flow-through vessel

Another advantage linked to the use of the flow-through vessel is that of providing a fundamental protective function of the system, which is otherwise covered by the conventional expansion vessel, namely offering a compensation chamber in the case of water hammer that might occur. In fact, the vessel is pressurized and absorbs even violent changes in pressure, which could have serious consequences on the system if it were absent.

Moreover, the presence of a through pipe inside the vessel has the dual advantage of allowing it to be emptied (with beneficial effects in terms of water quality) without interrupting the flow inside, guaranteeing the use of the product even if the pre-charge setting is inaccurate.

The internal pipe also has holes for water to pass through along the whole of its length; this construction ensures recirculation of water inside the vessel. The solution used with recirculation pipe and complete emptying offers a product designed with a view to preventing Legionella.

Section of flow-through vessel

Its construction with double hole membrane, blocked at both ends, together with its adequate sizing, ensures a product that has a very long useful life; in fact, elongation of the membrane is lower than that of conventional expansion vessels and consequently it is subject to less stress during operation. This aspect has the further advantage of eliminating limits for its positioning (vertical or horizontal).

Flovarem has been designed to be UNIVERSAL, suitable for all types of electronic pump controllers and easy to install, directly in line on the system; it has also been designed to allow installation IN SERIES, with the undoubted advantage of reducing the overall cross section if a larger water reserve is required. Assembly in series can also be appreciated as they offer one another “mutual assistance”, even in the event of incorrect pre-charge.

To conclude, in cases in which it is not possible to use a conventional expansion vessel (which is still the best solution to optimize operation of the pump and protect the system), the new flow-through vessel designed by Varem is without doubt a device that reduces the problems occurring in systems that only have an electronic pump controller.