Unit 13 · CVT & Assessment · Summary
CVT Assessment Preparation
The CompEx Competency Validation Test (CVT) assesses practical competency on physical Ex equipment rigs. This unit covers the format of CVT EX01–EX04, PTW completion, installation sequences, inspection report requirements, and the most common errors to avoid.
Learning Objectives
- Describe the four CVT assessments EX01–EX04 and their time limits
- Complete the PTW and Gas Free Certificate forms correctly for a CVT scenario
- Perform an Ex d installation in the correct sequence
- Carry out Visual, Close, and Detailed inspection of a pre-faulted rig
- Complete an inspection report with fault, grade, category, IEC reference, and remedial action
- Identify the most common CVT errors and how to avoid them
CVT Format
| CVT | Assessment | Time |
|---|---|---|
| EX01 | Preparation and installation of Ex d, Ex e, and Ex n equipment | 3h 35min |
| EX02 | Inspection of Ex d, Ex e, and Ex n installations | 1h 30min |
| EX03 | Preparation and installation of Ex i (IS) system | 3h |
| EX04 | Inspection of Ex i installation | 1h 30min |
All CVTs conducted in simulated hazardous area training bays. PPE mandatory throughout. All work controlled by PTW.
PTW — Seven Sections
- Work details — CVT ref, bay, tag number, job description, time
- Safety requirements — minimum PPE specification
- Safe isolation — isolation point, gas-free certificate, TEST-PROVE-reTEST, candidate signature
- Authorisation to proceed — assessor authorises; candidate accepts
- Final instrument testing — gas-free endorsed; isolation released (EX01/EX03)
- Clearance and de-isolation — work complete; de-isolation authorised and confirmed
- Permit closure — signed by authorised person
Installation Sequence — Ex d Junction Box
- Verify dataplate — zone/EPL, gas group, T-class, IP, ambient
- Select gland — barrier for SWA into Ex d; gas group ≥ area; thread matching entry
- Prepare cable — strip outer sheath, dress armour, strip cores
- Assemble gland — cable through body, armour into clamp, inner seal onto cable
- Install gland — ≥5 threads; no sealant on threads or flamepath
- Seal unused entries — certified Ex d stopping plugs, correct thread and gas group
- Terminate conductors — correct torque, ferrules, per wiring diagram
- Close enclosure — all bolts, correct grade, diagonal cross-sequence tightening
CVT EX02 — Inspection Approach
- Read the work order — zone, gas group, T-class, protection type
- Check the dataplate — verify against area specification first
- Check all entries — gland types, gas group, stopping plugs (Visual)
- Check fixings — all bolts present, no damage (Visual/Close)
- Check flamepath — no sealant, no corrosion, no damage (Close)
- Check earthing — earth tag on motors and GRP enclosures
- Record every fault — description, grade, category, IEC ref, remedial action
- Return rig to original state before submitting report
Top CVT Errors
Most Common CVT EX01 Errors
1. Non-barrier gland used for SWA into Ex d direct entry
2. Missing stopping plug or rubber bung on unused entry
3. Wrong gas group on gland or stopping plug (IIB in IIC area)
4. External earth tag not fitted on motor or GRP enclosure
5. Jointing compound or sealant on flamepath face
6. Fewer than 5 threads on gland or stopping plug
7. Wrong thread size for the enclosure entry
8. Inspection report missing category or IEC reference
9. PTW not completed correctly before starting work
10. Gas-free certificate not endorsed before final live testing
2. Missing stopping plug or rubber bung on unused entry
3. Wrong gas group on gland or stopping plug (IIB in IIC area)
4. External earth tag not fitted on motor or GRP enclosure
5. Jointing compound or sealant on flamepath face
6. Fewer than 5 threads on gland or stopping plug
7. Wrong thread size for the enclosure entry
8. Inspection report missing category or IEC reference
9. PTW not completed correctly before starting work
10. Gas-free certificate not endorsed before final live testing
Quick Check — 5 Questions
Test key concepts from this unit before moving on.
Q1Summary
At what two points is a gas-free certificate required during CVT EX01?
Two endorsements: (1) before the zero voltage test/isolation step; (2) before final instrument testing when the installation will be re-energised. Both required from the assessor (acting as authorised person).Ref: CVT EX01
Q2Summary
During CVT EX02, a loose cable gland is found. What must the inspection report include?
Every fault: description; inspection grade found at; deficiency category (X/A/B/C); remedial action; IEC standard reference. A loose gland = Category A — Close inspection grade.Ref: CVT EX02
Q3Summary
During EX01, you cannot find a certified IIC stopping plug for an unused M25 entry. You have an IIB certified M25 plug. What do you do?
Knowing when NOT to proceed is core competency. IIB stopping plug cannot be used in IIC area — flamepath dimensions are insufficient for IIC gases. Advise the assessor, explain the requirement. This demonstrates selection competency.Ref: CVT EX01 — Selection Competency
Q4Summary
What does TEST-PROVE-reTEST detect that a single voltage test cannot?
The reTEST (third step) confirms the instrument was working correctly after the test. A failure during or after step 1 would give a false "dead" reading at step 2 without detection — creating a live-working situation in the hazardous area.Ref: Safe Isolation — Sandwich Test
Q5Summary
After completing CVT EX02 inspection, what must be done before submitting the report?
Return rig to original condition (restore all faults found). The inspection report documents what was found — subsequent authorised remedial work is a separate activity.Ref: CVT EX02
EX Academy — independent CompEx-style preparation. Not official CompEx course materials.