Overview This procedure is used to measure the volume of a pressure vessel. Because pressure vessels can stretch while pressurised the volume also changes. The change in volume is important for design purposes and estimating the expected altitude.

Caution

Due to pressures involved, this experiment should be carried out behind a safety barrier.

Equipment

• Air source. This includes pumps, tanks, compressors etc.
• Pressure gauge
• Volume and dimension measuring stand
• Scale with 1 gram resolution.

Procedure A - Unpressurised

This procedure measures the volume of an unpressurised pressure vessel. The labelled value on a bottle is not the exact capacity.

1. Place the pressure vessel on the scale, and zero the reading.
2. Completely fill the bottle with water.
3. Record the reading on the scale. (1 gram = 1 mL).

Procedure B - Pressurised

This procedure describes how to measure the increase in volume of a pressure vessel as it stretches under pressure. This information can be used when simulating the flight of the rocket. The description below is for a PET bottle, but is equally applicable to other pressure vessels.

1. Fill the bottle with water all the way to the neck and stand bottle vertically.
2. Mark a line on the bottle representing the meniscus.
3. Connect air supply to pressure vessel.
   NOTE: You should have performed the burst test on the bottle prior to this test in order to not exceed the burst pressure.
4. Slowly increase the pressurise to the desired amount.
5. Mark a line on the bottle representing the new meniscus level.
   NOTE: Because this step requires you to approach the pressurised bottle, appropriate protection should be worn .
6. Depressurise the bottle.
7. When the bottle is depressurised empty enough water until the meniscus lines up with the pressurised mark.
8. Place the bottle with water on the scale.
9. Zero the scale.
10. Add water to the bottle until it reaches the original mark.
11. Take the reading on the scale. This represents the volume increase of the bottle at the particular pressure.

Notes

1. Caution should be exercised when performing this experiment. Alternatively one can place a scale on the side of the bottle and record the change in meniscus levels remotely.