The key points to be considered for an air chamber were the following:

• (1)
  Regular supply of air is required. (Including issues related to high pressure)

  • a)
    Keep the air pressure at or below 0.5 MPa whenever possible.
  • b)
    Air chamber cannot be used with any liquid affected by air.
• (2)
  Throttle valve needs re-adjustment every time the pump's discharge volume is changed.
• (3)
  Delayed discharge occurs when pump is started and liquid drips when pump is stopped.

Accumulators are used to deal with requirement (1) above.

• *
  Using an accumulator does not fulfill (2) or resolve (3).

As shown in Fig. 1, imagine that an elastic diaphragm is placed inside the air chamber so as to keep the air from coming into direct contact with the liquid.
In the actual accumulator, a bladder--which is something like a rubber balloon--is installed, filled with gas (generally nitrogen gas) compressed to the given pressure. The principle of reducing pulsation is the same as the air chamber.
When you use an accumulator, because air (gas) does not come into direct contact with the liquid, air does not dissolve into the liquid or the liquid does not oxidize and deteriorate. This is particularly effective at operating pressures above 1.0 MPa.

Problems With Accumulators

While an accumulator is an excellent piece of equipment to use to reduce the pulsation of a diaphragm pump, it has its own limitations. The following two precautions are common to both air chambers and accumulators:

• (1)
  In principle, the throttle valve needs re-adjustment every time the pump's discharge volume is changed.
• (2)
  Delayed discharge occurs when the pump is started and liquid drips when the pump is stopped.

The reasons for the above are exactly the same as for air chambers. (4-4. Precautions for Using the Air Chamber (2/2)) As a point to consider that is specific to accumulators, there is the issue of corrosion resistance due to the bladder (rubber membrane inside) being made of rubber. Particular care must be taken when transferring organic solvent.

TACMINA's Smoothflow Pump can provide continuous metered transfer without an air chamber. No need for burdensome air chamber recharge--eliminate the risk of chemical splattering from air chamber bursting or leakage from piping vibrations.
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