Extension spindles serve to operate shut-off valves in the field of underground pipeline construction. Telescopic extension spindles permit the continuous adaptation to the existing pipe cover depth.
Via the round threaded cover (for gate valves DN 50 - DN 200) the extension spindle is screwed clockwise onto the round thread (round thread adaptor) of the shut-off valve.
This has the advantage that the torque is transferred from the coupling socket to the spindle square, making the additional pinning of the coupling socket of the extension spindle and the spindle of the shut-off valve unnecessary.
Especially in case of cohesive soils care shall be taken that the valve and the extension spindle are properly back-filled with sand to ensure frost resistance.
For operation, operating keys are suitable. Extensions and similar must not be used.
For "rigid" extension spindles see model no. 900-00, 900-01.