PULSAIR's HT-2 System is an adaptation of the single horizontal tank HT-1 System, with one very important difference: the HT-2 will operate two separate tanks with one controller. This dual control capability is a feature that no other mixing or blending machine on the market can offer. Customers can’t just move a large mechanical mixer from one tank to another when they need to mix the other tank. With an HT-2, they simply throw the switch to select whichever tank they desire to mix.

Tanks mixed using an HT-2 Controller do not have to be the same size.For that matter, one tank can be horizontal the other a V or cone bottom tank (requiring only one accumulator plate). In the latter case, the pulse rate may have to be increased because there is only one plate that is pulsing in the cone tank. The HT-1 is best utilized when the two tanks are of similar size and shape. However, having two different tank configurations does not pose any great engineering difficulty for PULSAIR. See Shell Oil, Hong Kong

The HT-2D System

PULSAIR offers HT-2D version of the HT-2. Features of this model increase the HT-2's capability so that both tanks can be mixed simultaneously. The HT-2D was designed to meet the needs of customers wanting to operate two tanks simultaneously from one controller. Because the tanks could have different liquid levels, the system is configured to operate two pressure regulators, one for each tank. The operator can set different injection pressures to meet the changing conditions inside either tank. Both tanks share a common (dwell) control. The HT-2D will operate both tanks simultaneously at the same injection frequency, with two different injection pressure settings.

Because there are two injection pressure settings on the HT-2D, the system comes with two regulators. When both tanks are pulsing, this system uses air at twice the HT's rate of consumption. Therefore, the supply lines and filter are larger than the HT-2 system.

The controller sends an air signal (pilot signal) that acts on the spool inside the injection valve causing it to move into the open position. Once open, the valve allows air to flow to the accumulator plate(s). The pilot signal is then vented to the atmosphere. As pressure is lowered, the injection valve closes, cutting off the flow of air to the accumulator plate(s).

The Injection Time control determines how long the pilot signal is on. The longer this signal is on, the longer the valve will stay in the open position. The Dwell control determines the amount of time between injection pulses.

Note: the distance between the injection valve(s) and the controller also affects the amount of time that the valve will remain open. Air is elastic. If the injection valve is a long distance from the controller then a longer pulse signal is required to open the valve because the volume inside the tubing must be filled with air before there is sufficient pressure to open the injection valve. The pilot signal must fill the tubing and increase the pressure from zero to the injection pressure before the valve will open. Conversely, to close the valve the air must be exhausted from the tubing. The longer the tubing the longer it takes to exhaust the air. The net effect of excessive distance (more than 20 feet), between the valve and controller will make the injection valve’s on- off cycle slow, sluggish and diminish it effectiveness.

PULSAIR installation manuals recommend that the controller and injection valves be located next to each other. This allows for a shorter pilot signal tubing and therefore a very responsive injection valve. A quick acting injection valve produces a sudden burst of air under the accumulator plate. This burst of air causes a shock wave that excites all the liquid molecules in the tank. One of Newton’s laws states that "things in motion tend to stay in motion". Therefore, when the bubble starts to rise in the liquid it is working with liquid that is already in motion because of the initial shock caused by the bubble’s formation. The combination of the shock and vertical motion is why PULSAIR is so effective. It is also why the entire contents of a tank are in motion after only one to two pulses. (See Intermittent Mixing)

See Also: PULSAIR System Model Numbers