The pneumatic sealing tube is pumped up (to 0.5 bar) with a small hand pump rather like a bicycle tyre pump.
When the sealing tubes are new they are a very tight fit, difficult to stretch around the lid. With use they stretch gradually and become progressively easier to fit.
A list of tube sizes and prices.

Volume calculations, measurements should be accurate to 0.1 cm :-
1. Before first using a tank:-
a. calculate the volume in litres per cm height = surface area (π r², where π = 3.14159, r = radius in cm) divided by 1000.
b. calculate the total volume in litres = internal height at the side of the tank (in cm) x the volume in litres per cm height; plus (if the tank has a concave base) the volume of the concave base, measured by pouring in water from a measuring jug.
2. Calculating the volume of liquid in the tank:-
use a tape measure (with the end lowered to touch the liquid surface) to measure the height of the liquid surface below the top of the tank. Measure down on two opposite sides, and take an average of the two heights, as the tank may not be standing quite horizontally. Multiply this average height by the volume in litres per cm height, and subtract the result from the total volume.

Note: cleaning the tanks.

New Variable Capacity tanks:-

Vertical cylinders with flat bottom or concave bottom; flat bottom tanks can be placed on a small pallet, which can be moved around with a pallet-truck.
Internal cooling can be fitted through the lids of all types:-

with three stainless steel welded-on legs, a DIN40 male-thread racking outlet, a concave bottom with V-channel to DIN40 male-thread final-drain outlet, and with a level/sight gauge and sampling tap. Also a crane to lift the lid (adds 350 mm to the height) with 1000 litre and 1250 litre:-

       530 litres (770/750 mm diameter, 1720 mm high),  £1026
    1000 litres (960/940 mm diameter, 1970 mm high),  £1876
    1250 litres (1020/1040 mm diameter, 1970 mm high),  £2115