13.3 SNT-TC-1A vs CP-189 Comparison

13.3 SNT-TC-1A vs CP-189 Comparison

Quick Answer: SNT-TC-1A = recommended practice (guidelines, should/may character, Written Practice tailoring). CP-189 = ANSI standard (shall language, mandatory minimums once invoked). Both keep the employer as certifying authority and both require a written program. CP-189 is not “SNT for nuclear only,” does not eliminate the Written Practice, and does not automatically equal ASNT Central Certification. For Basic after 1 January 2026, both references are the 2024 editions. When in doubt on a standards item, ask: Is this soft guidance or a non-reducible shall?

This section is the highest-yield standards comparison on the Basic exam. If you can deploy the table below under time pressure and then solve short scenarios, you will convert many Domain 1 points that method-physics specialists still miss.

Master Comparison Table

Memorize the table’s spine in one line: recommended practice vs standard; should vs shall; tailor vs do-not-reduce; experience-possible recert stories vs re-examination required; employer still certifies under both.

Nature: Recommended Practice vs Standard

SNT-TC-1A was built so employers could build a sensible local program using ASNT’s guidelines. That flexibility is a feature, not a bug—but it means two “SNT-compliant” shops can look different at the edges.

CP-189 was built so a purchaser can write a specification that locks a floor. When CP-189 is on the contract, an auditor is not merely asking “did you think about the guidelines?” They are asking “can you show you met the standard’s requirements?”

Exam wording cues:

• “guidelines,” “recommended,” “should,” “Written Practice may specify” → SNT-TC-1A flavor
• “shall,” “requirements,” “shall not be reduced,” “mandatory when invoked” → CP-189 flavor

Written Practice vs Certification Procedure (Same Job, Different Force)

Do not invent a false dichotomy that only one document name is legal. Employers may title the controlling document a Written Practice, certification procedure, or similar. The exam cares that:

1. A controlling employer document exists
2. It implements the chosen reference (SNT and/or CP-189 as invoked)
3. Under CP-189, that document cannot undercut the standard’s mandatory minimums

If a question says “CP-189 eliminates the need for a written practice,” mark it wrong.

Flexibility and Tailoring

Examination Requirements Character

Both systems expect meaningful general, specific, and practical evaluation for Level I/II paths. The Basic differentiator is force and control:

• SNT-TC-1A: Level III develops, administers, or approves exams and protects integrity; recommended grading schemes (e.g., each exam at least about 70% with composite about 80%) appear as recommendations to confirm in the current edition and Written Practice.
• CP-189: Examinations shall be administered or approved by a Level III with documented records—a cleaner “mandatory control” hook for multiple-choice stems.

Scenario practice: a Level II scores the practical for a peer and files no Level III approval trail. That is a program failure under either serious employer system—and an almost automatic CP-189 fail on exam items that mention mandatory Level III administration/approval.

Level III and Outside Agency Use

Both frameworks recognize that not every employer keeps a full-time Level III on payroll for every method.

Shared truth:

• Outside Level III support is a documented relationship, not an informal favor
• The employer remains the certifying authority
• Responsibilities (who writes procedures, who builds exams, who signs certifications) must be clear

CP-189 exam stems often add the explicit pair: qualified person + documented written-practice arrangement.

When Employers Choose Which

Use this decision framing on scenario items:

Lean SNT-TC-1A when:

• Contracts accept recommended-practice language
• The industry sector historically runs employer programs to SNT
• The shop wants guideline flexibility while still running a credible Written Practice
• No customer/code has imposed CP-189

Lean CP-189 when:

• Purchase orders, nuclear or other high-spec work, or client quality manuals invoke CP-189
• Stakeholders want enforceable minimums that local managers cannot bargain away
• Auditors expect shall-based evidence of training floors, Level III exam control, and recertification by exam
• The organization wants a single “standard compliance” claim rather than “we tailored a recommended practice”

Hybrid reality (common in industry, useful on exams):

• An employer Written Practice may state it meets SNT-TC-1A and also meets CP-189 for work requiring the standard
• Personnel performing CP-189-invoked work must meet the stricter applicable requirements
• Holding ASNT Central Certification may be recognized inside either program, but it does not automatically replace employer certification unless the written program says how recognition works

Scenario Drill (Level III Thinking)

Work these mentally before exam day:

1. Contract says “qualify personnel to ANSI/ASNT CP-189.” Manager wants to keep last year’s looser SNT hours that undercut CP-189 minimums.
   → Not acceptable for that work. Meet CP-189 floors; update written practice and records.

2. Shop claims CP-189 compliance but has no written practice.
   → Fundamental failure. Standard still requires a local controlling document.

3. Recertification packet has only attendance sheets and a supervisor “still good” email—no re-exam under a CP-189 program.
   → Fails CP-189 recertification character. Experience alone is not enough.

4. Outside Level III grades exams; contract is silent; written practice never names the outside agency.
   → Documentation failure under CP-189 (and poor practice under SNT).

5. Candidate confuses “I passed ASNT NDT Level III Basic and UT method” with “I am certified under the employer’s CP-189 UT Level II.”
   → Different authority models. Central credential ≠ automatic employer certification.

6. Question stem: “Which differs most clearly?”
   → Answer family: mandatory requirements vs recommendations / shall not reduce minimums.

7. Stem claims CP-189 is only nuclear.
   → Reject. Nuclear often uses it; the document is not limited to that sector by Basic-level characterization.

High-Yield Traps for the Comparison Block

• Swapping labels: calling SNT a standard or CP-189 a recommended practice
• Believing CP-189 makes ASNT the everyday shop certifier
• Believing either document is a method acceptance code
• Forgetting both need a written employer program
• Treating 2020 as current Basic default after the 2024 switch date
• Using CP-105 as a synonym for CP-189 (CP-105 = training topical outlines)
• Assuming “stricter customer requirements” somehow allow cutting below CP-189 when CP-189 is invoked (stricter is allowed; looser is not)

Closing the CP-189 Arc

Across Chapter 13 you should now defend:

1. What CP-189 is — ANSI/ASNT standard with mandatory requirements for employer-based NDT personnel qualification/certification when invoked
2. What controls the local program — the employer’s written practice/procedure implementing those requirements
3. What cannot be reduced — mandatory training/experience/exam/vision/recertification floors
4. Who owns exams — Level III administers or approves with records; outside Level III only when qualified and documented
5. How it differs from SNT-TC-1A — recommended practice vs standard; should vs shall; flexible vs non-reducible
6. Edition for Basic after 1 Jan 2026 — 2024

Chapter 14 moves to CP-105, the training topical-outline companion that feeds the training content side of both SNT-TC-1A and CP-189 programs. Keep the standards hierarchy clean: SNT = guidelines, CP-189 = mandatory standard when invoked, CP-105 = what to teach.