Question 2 of 7: Cumulative Trauma Disorders and Machine Guarding
Nivaar worked solution (AI-drafted; not reviewed by a licensed engineer)
Notes on this paper
National Exams — December 2013 — 11-CS-2 Engineering in Society: Health and Safety. Closed book; approved calculator permitted. Any five of the seven questions constitute a complete paper; all questions are of equal value. Answers are written in point form but fully, as instructed. Complete answers to all seven questions follow.
Cumulative trauma disorders (CTDs), also called repetitive-strain injuries, are musculoskeletal injuries that develop gradually from repeated micro-trauma to muscles, tendons, nerves and joints—no single event causes them.
Causes/risk factors: high repetition, forceful exertions, awkward or sustained (static) postures, mechanical contact stress, vibration, and cold, especially in combination and over long durations without adequate recovery.
They typically affect the hands, wrists, arms, shoulders, neck and back; symptoms progress from discomfort/fatigue to pain, weakness, numbness and loss of function.
(ii) Typical Disorders
(a) Trigger finger — inflammation/thickening of a flexor tendon or its sheath in the finger, so the tendon catches as it slides; the finger locks in a bent position and snaps ("triggers") when straightened. Caused by repeated gripping.
(b) Carpal tunnel syndrome — compression of the median nerve where it passes through the carpal tunnel at the wrist, from swelling of surrounding tendons due to repetitive/forceful wrist motion or bent-wrist postures. Causes numbness, tingling, pain and weakness in the thumb and first fingers.
(c) Tenosynovitis — inflammation of a tendon and its surrounding synovial sheath, causing pain, swelling and restricted movement; results from repeated or forceful tendon movement (e.g., repeated wrist/forearm motion).
(iii) Basic Principles of Machine Guarding
Prevent contact — the guard must keep any body part from reaching the danger zone (point of operation, nip points, rotating and power-transmission parts).
Be secure and durable — fixed in place, tamper-resistant, not easily removed or defeated, strong enough for the environment.
Create no new hazard — no shear/pinch points, sharp edges or entrapment.
Not interfere with the work — allow the job to be done without removing the guard; otherwise it will be bypassed.
Allow maintenance — permit lubrication/servicing without full removal (or use interlocks).
Interlock where appropriate — machine stops if the guard is opened; combine with lockout/tagout for servicing.
