Class 4 (4th Engineer) MEP 📅 Oct 2022

Exam Question

With reference to multi-stage, single crank air compressors explain why:

(a) (i) 'Bumping' clearances are checked. (3)

(ii) Bottom end adjustment does not affect 'bumping' clearance. (3)

(iii) The clearance is not adjusted on one stage alone. (3)

(b) Describe how bumping clearances are corrected. (7)

Reference Answer

### (a) Explanation of Bumping Clearances
#### (i) Why 'Bumping' clearances are checked.
The bumping clearance, also known as the piston-to-head clearance, is the linear distance between the piston crown and the cylinder head when the piston is at Top Dead Centre (TDC). It is a critical parameter that is checked for two primary reasons:
1. **Mechanical Safety & Prevention of Damage:**

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