ISA CCST Level II flashcards

33 cards. Read the term and the definition here. The deck at the top of this page is optional.

Calibration error formula

Error equals indicated value minus true reference value. Report it as percent of span, percent of reading, or percent of upper range value, and always state which basis was used.

Five-point calibration check

A check at 0, 25, 50, 75, and 100 percent of span, run both upscale and downscale. It reveals hysteresis, deadband, and linearity in a single pass.

Hysteresis versus deadband

Hysteresis is the difference between upscale and downscale indication at the same input after a full-range excursion. Deadband is the largest input change that produces no measurable output change.

Live zero purpose

A 4–20 mA signal uses 4 mA at the lower range value, so a true zero reading is distinguishable from a broken wire or dead instrument.

Milliamp to percent conversion

Percent of span equals (mA minus 4) divided by 16, times 100. So 8 mA is 25 percent, 12 mA is 50 percent, and 16 mA is 75 percent.

Test uncertainty ratio

The reference standard should be at least four times more accurate than the device under test. This ratio keeps the standard's contribution to test uncertainty small.

As-found versus as-left

As-found data records drift before any adjustment and shows whether the device was in tolerance. As-left data proves the instrument was returned within tolerance after calibration.

Zero then span rule

On most analog transmitters, set zero at the lower range value first, then span at the upper range value. Re-check zero afterward on non-interactive designs.

Manifold equalize sequence

Equalize before opening the low side, and close the equalize valve before returning the transmitter to service. This protects the sensor from overrange differential pressure.

Impulse line slope rule

Gas and liquid impulse lines slope at least one in twelve. Steam lines are filled with condensate using a condensate pot, and lines are blown down before commissioning.

Loop burden budget

Total loop resistance, including receiver, wiring, and barriers, must stay below the transmitter's rated maximum load at the available supply voltage.

Intrinsic safety maintenance rule

Keep the hazardous-area device, barrier, and cable parameters within the entity or system approval. Never substitute uncertified parts, because that voids the safety certification.

Ground loop diagnosis

Noise, offset, and drifting readings often come from multiple earth connections. Ground cable shields at one end only and isolate the signal from earth elsewhere.

Valve seat leakage class

Seat leakage is specified by class, such as ANSI/FCI 70-2. Verify leakage against the specified class during maintenance, not simply that the valve closes.

Preventive maintenance drivers

Maintenance intervals are set by criticality, environment, and manufacturer recommendation. Instrument air quality, meaning dew point, oil, and particulate, drives many pneumatic failures.

Split-the-loop troubleshooting

Verify the symptom at the indicator, then divide the loop into field device, wiring, I/O card, controller, and HMI. Testing each half halves the search space.

Signal substitution test

Drive the loop with a milliamp source at the marshalling terminal. If the system responds correctly, the fault is field-side; if not, it is system-side.

NAMUR NE43 fault band

Values below 3.6 mA or above 21 mA are reserved for fault signalling on 4–20 mA devices. Check the configured fault direction before assuming a process change.

Valve fails to stroke

Check supply pressure at the actuator, then positioner output, then actuator diaphragm integrity, then stem or packing seizure. Work outward from the air supply.

Repair record content

A repair record states root cause, parts replaced, calibration as-left values, and any temporary workaround still in place. It supports later failure analysis.

Intermittent signal causes

Loose terminal torque, corrosion, and shield drain faults cause a large share of intermittent signals. Check terminations before condemning the instrument.

Commissioning sequence

Mechanical completion, leak test, instrument air blowdown, power-up, loop check, functional test, then first line-up and start-up. Each stage gates the next.

Loop check definition

A loop check verifies continuity from field device through marshalling, I/O card, controller tag, and graphic. One device, one tag, correct direction and scaling.

Cold versus hot loop check

A cold loop check verifies wiring and signal path only, with no process. A hot loop check is performed with process or simulated process at operating conditions.

Cause-and-effect matrix test

Each row of the cause-and-effect matrix is tested individually to prove that interlocks and shutdowns act as designed. Every row is signed off.

SIF proof test scope

A safety instrumented function proof test must demonstrate the full function including the final element, not only the sensor, and record detected and undetected failures.

Punch list categories

Category A prevents start-up, B must close before handover, and C may close after handover. Each item closes with documented evidence.

Instrument index role

The instrument index is the master register of tags. The I/O list must reconcile to it, and the difference count measures documentation quality.

ISA-5.1 tag consistency

The tag format of area, loop number, and function letters must be identical across the index, drawings, database, and field labels. Mismatches cause start-up trips.

Work breakdown structure

The work breakdown structure decomposes scope into installable packages. The schedule links them with dependencies and milestones such as mechanical completion and loop check complete.

Turnover package contents

The turnover package includes as-built drawings, calibration records, loop folders, vendor manuals, and training records. It transfers documented evidence to the owner.

Earned value indices

Cost performance index equals earned value divided by actual cost. Schedule performance index equals earned value divided by planned value. Below one means over budget or behind schedule.

Contract risk allocation

Lump sum shifts quantity risk to the contractor. Reimbursable or time-and-materials shifts it to the owner. Unit price shares quantity risk between both parties.