This is a useful suggestion Jack. For this reason, and also to inspect that residue is cleared from the transition region between the vertical body of the silo and the converging hopper section, it is useful to incorporate a small inspection port. This should be of minimum 100mm diameter, and located just above the transition ‘hip’ of the silo. A short ‘plug’ should be fitted to the removable flange, so that the inner face of the silo wall does not have a pocket to retain product.

Visual access potential at this point is also invaluable for the investigation of ‘quaking’ problems, should they arise. A guide to the fundamental causal mechanism is provided if it can be established whether the mass movement of material is continuous or intermittent at this point. The port could also be used to mount a level detection probe, if this is appropriate.

This point also emphasises the value of including sufficient inspection, access, instrumentation facilities and even retrofit potential at the design stage, rather than provided after fabrication. Considerable time and money can be saved when under the pressure of service or operating problems if facilities are in place to conduct a definitive investigation should problems arise in service. It is almost invariably a false economy to neglect these provisions. ■