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A steel guard can prevent a falling object from striking an instrument and still make its measurement unusable. Silo radar protection has two separate jobs: protecting the enclosure above the roof and keeping the antenna's view of the material clear. A cover that suits the first job may obstruct the second.
Keep weather covers outside the measurement path
A sun or rain cover over the electronics should leave room for the cable entries, display, cover removal and drainage. Its supports must not distort the instrument mounting. Avoid an arrangement that collects water at a gland or forces maintenance staff to remove the radar whenever the enclosure needs access.
A shield below the roof is different. Metal between the antenna and the material is a radar target, even when the opening appears large enough from above. Side plates, braces and deposits on the shield can add reflections. Review the complete assembly from the antenna reference plane, not only the clear opening at the silo roof.
Decide what the silo radar protection must withstand
| Exposure | Design question |
|---|---|
| Falling material | Can the mounting position be moved outside the stream before adding a shield? |
| Wind and vibration | Will the cover and its supports transmit movement into the antenna alignment? |
| Dust deposits | Where can material collect, and how can it be inspected without entering the silo? |
| Rain and sunlight | Does the enclosure cover protect the electronics without restricting drainage or access? |
If the antenna sits in the direct fill stream, treat relocation as a design option. A guard is not proof that the instrument can tolerate burial, repeated impact or abrasion. Its strength, attachment and effect on the silo structure also need assessment by the responsible mechanical designer.
The METRAVON MV-RD21 uses a 76 mm PTFE antenna with a published nominal 3-degree beam angle. These dimensions help assess the installation, but they do not define an approved shield clearance. A nominal beam outline is not a hard boundary beyond which all objects are invisible.
Check the arrangement before and after fitting
Where safe access and the operating plan permit, retain a known-condition reading and diagnostic record before adding protection. After fitting, compare at a similar material level and process state. Record any new fixed return, loss of tracking or change during filling. Do not erase a new obstruction from the configuration merely to make the display agree.
Include cleaning access in the drawing. A shield that gradually fills with powder can produce a different installation a month later. Do not add an air purge, drill the antenna assembly or change a pressure or explosion-protection boundary without documented approval for the supplied equipment.
Q1. Can a plastic cover be placed across the antenna?
Not on appearance alone. Material, thickness, moisture and deposits affect its behaviour. An approved protective window is different from an arbitrary sheet fitted in the field.
Q2. Does an IP rating cover falling bulk material?
No. Enclosure ingress protection does not specify resistance to process impact or abrasive particles. Those exposures require a separate mechanical assessment.
Q3. What should accompany a shield enquiry?
Provide a section through the antenna, shield and inlet, including dimensions, materials, support points and safe inspection access. Include photographs showing where material strikes or accumulates.
Summary
Protect the radar without creating another obstruction. Request an MV-RD21 installation review with the proposed cover and fill-stream drawings before fabricating a guard around the antenna.
