When to Replace Flat Slings: A Guide to Frequent and Periodic Inspection Criteria

A flat sling is used in a daily lifting operation. It looks fine—no visible cuts, no fraying. But six months later, during a periodic inspection, a qualified inspector discovers internal fiber damage that could have caused failure at any time. The sling is immediately removed from service.

This scenario highlights the critical difference between frequent and periodic inspections. Frequent inspections catch obvious damage before each use. Periodic inspections find hidden degradation that visual checks alone cannot detect. According to Wikipedia's entry on sling (rigging) , slings must be inspected regularly to ensure they are safe for use, and inspection frequency depends on service conditions. ASME B30.9 requires both frequent and periodic inspections for all slings in service.

Lishenflex has been manufacturing synthetic flat slings for over two decades, and our field data show that many rigging failures occur in slings that passed frequent inspections but failed periodic inspections. Understanding both levels of inspection is essential to maintaining a safe sling inventory.

Frequent Inspections: Daily Pre-Use Checks

Frequent inspections are performed daily or before each use, depending on the sling's service conditions. According to ASME B30.9, frequent inspections are visual examinations conducted by the user or operator to identify obvious damage that could affect safe use.

What to Check During Frequent Inspections

Per ASME B30.9 and EN 1492-1, a frequent inspection of a flat sling should include:

• Identification tag—is it present and legible?

• Cuts, tears, or snags—inspect the entire length of the webbing

• Abrasive wear—check for excessive wear that exposes core yarns

• Broken or worn stitching—especially in load-bearing splices and eyes

• Chemical or heat damage—look for discoloration, stiffness, or charring

• UV/sunlight damage—check for fading, bleaching, or stiffness

• Fittings and hardware—check for pitting, corrosion, cracks, or distortion

• Knots—ensure the sling is not knotted or twisted

• Grommets or eye protection—if present, check for damage

ASME B30.9 requires that frequent inspections be documented and that any damaged sling be removed from service immediately.

Frequent Inspection Frequency

Source: ASME B30.9

Critical note: Frequent inspections are the operator's first line of defense. According to Wikipedia's "Sling (rigging)" entry, visual inspection is the primary method of detecting damage before use.

Periodic Inspections: In-Depth Evaluation

Periodic inspections are more thorough than frequent inspections and are conducted by a qualified person at regular intervals. According to ASME B30.9, periodic inspections include all the elements of frequent inspections plus additional checks for internal damage, hidden degradation, and historical performance .

What to Check During Periodic Inspections

Per ASME B30.9 and EN 1492-1, a periodic inspection of a flat sling should include:

Visual Examination:

• All frequent inspection items

• Discoloration or stiff areas that may indicate chemical, UV, or heat damage

• Evidence of internal damage (bending the sling to check for crackling sounds)

• Reduced width from abrasive wear (the 1/10 rule)

• Splice condition—check for broken or worn stitching, pull-out, or distortion

• Eye condition—check for distortion, wear, or damage

• Tag legibility—confirm the tag is still readable

Record Review:

• Service history—number of lifts, load magnitudes, and environmental exposure

• Previous inspection reports—compare current condition to previous findings

• Maintenance records—cleaning, storage, and any repairs

Tactile Inspection:

• Bend the sling—listen for crackling sounds indicating internal fiber breakage

• Compress the webbing—check for soft or uneven areas indicating internal damage

• Feel for stiffness or brittleness—may indicate chemical, UV, or heat damage

Periodic Inspection Frequency

Source: ASME B30.9

ASME B30.9 requires that periodic inspection records be maintained by the employer. The records must include the date of inspection, the inspector's name, the sling identification, and the findings.

Retirement Criteria: When to Replace a Flat Sling

Both frequent and periodic inspections use the same retirement criteria. Per ASME B30.9 and EN 1492-1, a flat sling must be removed from service when:

Damage Requiring Immediate Retirement

The 1/10 Rule

According to EN 1492-1, when abrasive wear reduces the webbing width by one-tenth or more of the original width, the sling must be removed from service. This is a mandatory retirement criterion for flat slings.

Application of the 1/10 rule:

Inspection Documentation and Recordkeeping

Proper documentation is essential for both frequent and periodic inspections.

Frequent Inspection Records

ASME B30.9 requires that frequent inspections be documented, but does not specify a format. Many companies use:

• Daily inspection checklists

• Electronic logging systems

• Sling tracking software

Periodic Inspection Records

ASME B30.9 requires that periodic inspection records include:

• Date of inspection

• Inspector's name and signature

• Sling identification number

• Findings and condition

• Actions taken (passed, repaired, retired)

• Next inspection due date

Records must be retained for at least the service life of the sling and be available for review by regulatory authorities.

Training and Competency

ASME B30.9 requires that periodic inspections be conducted by a qualified person—someone who is knowledgeable about sling types, inspection criteria, and the effects of damage on sling capacity. Lishenflex recommends that:

• Operators performing frequent inspections receive basic training on identifying damage

• Inspectors performing periodic inspections receive comprehensive training on ASME B30.9 and EN 1492-1 standards

• Both groups receive refresher training annually

Summary and Practical Recommendations

Knowing when to replace flat slings requires understanding both frequent and periodic inspection criteria. Frequent inspections catch visible damage before each use, while periodic inspections detect hidden degradation that could lead to catastrophic failure.

Key takeaways:

1. Frequent inspections are daily—conducted by operators to catch obvious damage

2. Periodic inspections are in-depth—conducted by qualified persons to detect hidden degradation

3. Retirement criteria are the same—once damage reaches specified limits, the sling must be removed

4. Documentation is mandatory—records must be maintained per ASME B30.9

5. Training is essential—both operators and inspectors must be competent

Lishenflex manufactures polyester flat slings to EN 1492-1 and ASME B30.9 standards, with clear color-coded capacity markings and inspection guidance. We offer training programs to help your team conduct effective frequent and periodic inspections.

If you need assistance establishing an inspection program for your flat sling inventory—or need help determining whether your current slings meet retirement criteria—please send an email to sales@lishenflex.com, and our technical team will provide one-on-one support.