Portable Autoclaves - Safety Valve Adjustment

The illustration to the right shows the safety valve currently fitted. If your safety valve does not resemble this illustration please contact us to acquire a current safety valve.

Note: The thread fitting on the Safety Valve is 1/4" BSP. On some older models it may be necessary to retap the hole in the lid to suit.

Note: This Safety Valve is only suitable for use on the models of Dixons Portable Autoclaves as detailed below. It must not be used on any other equipment. Do not excede any of the pressure settings detailed below.

The models ST 18, ST 19, ST 20, ST 21, ST 22 and ST 23 all use the safety valve to control their operating temperature by controlling their operating pressure. Older versions of all thermostatic models (those with external thermostats) also use the safety valve to control their operating temperature by contolling their operating pressure. These models should have their safety valves adjusted as follows:

1. Unscrew the top cap and loosen the M3 locking socket grub screw with a hexagon key.
2. Set a gap of about 4mm between the slotted adjuster and the top of the body.
3. Bring the Autoclave up to working pressure.
   Warning - The Safety Valve will be hot at this point!
4. The pressure at which the Safety Valve releases steam can now be adjusted by turning the slotted adjuster. To raise the pressure (and therefore the temperature) turn the slotted adjuster clockwise, and to lower the pressure (and therefore temperature) turn it anti-clockwise. The Autoclave should be left to settle for about two minutes after each adjustment.
5. When the desired pressure (and therefore temperature) setting is reached, tighten the M3 grub screw back up to prevent the slotted adjuster moving and replace the top cap.

The maximum settings allowed are as follows:

ST 18, ST 19, ST 19 T (external thermostat)	121șC - 1.0 bar (15 psi)
ST 20 / ST 22, ST 21 / ST 23, ST 21 T / ST 23 T (external thermostat)	121șC - 1.0 bar (15 psi)

The models ST 19 T (with internal elements), ST XX28, VARIO 19, and VARIO XX28 use the safety valve purely as a safety precaution. These models should have their safety valves adjusted using a test rig to the following settings:

ST 19 T, VARIO 19	1.3 bar (18 psi)
ST XX28, VARIO XX28	1.3 bar (18 psi)

Maintenance (All Models)

1. Remove the top cap, undo the lock screw and unscrew the slotted adjuster as above.
2. Remove the spring and spindle to expose the silicone seal.
3. Clean all parts and check the silicone seal for wear. Replace if necessary.
4. Reassemble using a small smear of Autoclave grease on the spindle and threads.
5. Set the Safety Valve to the desired setting as described in the relevant section above.