TAV 'Checkable' Level Switches
User safety checks and switch testing
1. Identification of switches.
These physical checks and test procedures should be applied to
models of "TAV Engineering" level switches that are prefixed
with the following numbers:
Type A: F150, F160, F171, 155, 156, 157, 170 (May 1987 - December
Type B: B14-, B17-, F15-, F16-, S14-, S17- (December 1996 - 2006)
This prefix should be readily identifiable on the manufacturer's
label fitted to the device e.g. F150 or F16-123-123 etc.
If you have any doubts about the applicability of the 'checkable'
switches fitted to vessels under your control, the switches may be
identified by reference to the following descriptions of the check
Devices that are fitted with a small plate fixed to a shaft that is
located within the main body of the switch assembly. The plate is able
to pivot out of a slot in the body of the switch (the 'home' position)
through an angle of approximately 90°. This enables it to be moved in
the vertical plane and hence raise or lower the shaft. The plate has a
hole drilled in its centre that will allow it to be locked or fixed to
the main body of the switch when in the 'home' position.
Devices that are fitted with a pivoting lever that protrudes out of
the side of the switch assembly and can be moved in the vertical
plane. These levers may be fitted with a red sleeve. The levers have a
pivot point located in a flange on the opposite side of the switch
body. This flange also has a hole drilled in it that will allow the
lever to be locked or fixed in a position where the lever is at 90°
(perpendicular) to the main body of the switch.
If you are still unable to identify if your switch is affected,
advice should be immediately sought from the manufacturer / supplier
of the device.
2. Interim tests that should be undertaken.
It is important that all relevant switches have an interim test
performed to ensure that they will activate the appropriate alarms,
emergency shut down systems etc. in addition to ensuring that the
check lever is correctly replaced and secured in the normal operating
To test that the switch is working correctly the lever / plate
fitted to the head of the switch should unlocked or any fixing devices
removed (should they be fitted) and then the lever / plate raised
vertically to its highest position thereby simulating a high level in
the tank (note - the plate operated mechanism will need to be rotated
by approximately 90° to facilitate this). If the switch is working
alarms and / or trip devices connected to the switch should operate.
In the event of any switch failing the above interim test
procedure, appropriate steps should be taken by other means to secure
the safety of the related tanks.
This interim test does not negate the requirement for further, more
thorough, proof testing and examinations of the alarm / trip system at
the next practicable opportunity.
3. Returning the switch to the normal operating position.
It is critical that after carrying out this test the lever
or plate is put back into the correct operating position and is then
padlocked or fixed firmly in place. Failure to do this can render the
switch inoperative and hence overfill protection may be negated.
With reference to the two switches noted previously the following
procedure should be used:
Move the plate vertically until it is in a position level with
the slot in the body of the switch assembly and then rotate the
plate until it is fully seated within the slot. Following this
action, secure the plate to the switch body by using a suitable
padlock or fixing device  placed through the holes in the plate and main switch body.
Move the lever vertically so that it is at approximately 90°
(perpendicular) to the main switch body. This will align a hole in
the handle with the hole located in the plate adjacent to the
lever's pivot point. Following this action, secure the lever in
position by using a suitable padlock or fixing device 1,  placed through the previously aligned holes in the plate and lever.
There should only be minimal free-play when moving the handle in the
 Any temporary padlock or
fixing device installed whilst awaiting manufacturers equipment should only
be removable with a key or tool.
 As an interim measure a
5mm diameter shackle / pin secured by a padlock or chain should hold the
handle in the correct place whilst awaiting the manufacturers equipment