OSHA requirements are set by statute, standards and regulations. Our interpretation letters explain these requirements and how they apply to particular circumstances, but they cannot create additional employer obligations. This letter constitutes OSHA's interpretation of the requirements discussed. Note that our enforcement guidance may be affected by changes to OSHA rules. Also, from time to time we update our guidance in response to new information. To keep apprised of such developments, you can consult OSHA's website at https://www.osha.gov.

Jul 19 1988

SUBJECT: Load Testing of Synthetic Web and Other Slings

The questions posed by your memorandum of June 7, 1988, are answered as follows:

1. The proof testing of slings is the responsibility of the sling manufacturer or equivalent entity as delineated by the standard at 29 CFR 1910.184(e)(4), (g)(5), and (i)(8)(ii). The employer shall retain a "certificate of proof test" and shall make it available for examination by OSHA compliance officers.

It is believed that any proof load testing of workplace slings by other than the manufacturer or equivalent entity is an unacceptable loading and would necessitate that the sling be taken out of service unless written permission to test is obtained form the sling manufacturer. Users of slings must not exceed the sling manufacturer's specifications and requirements pertaining to use and loadings.

The requirements imposed by the Boeing Company upon their subcontractors to repeatedly proof test slings to two (2) times rated load is not a recognized inspection procedure under the OSHA standards and would be a violation of 29 CFR 1910.184 (c)(4). However, should the sling manufacturer provide written permission to test the slings on a regular basis to a load greater than the designated working load, OSHA could consider the violation de minimus. Of course the procedures for such testing would also need to comply with the manufacturer's recommendations.

The repeated testing of spreader bars and similar equipment seems to provide little more assurance of continued reliability than the visual inspections required by the various standards, including OSHA's. Properly conducted visual inspections together with the careful reporting of misuse and various damaging exposures will provide for the continued reliability of the lifting equipment. Should periodic load testing be desired, it is recommended that slings be returned to the manufacturer or equivalent entity for the conduct of detailed inspection and load tests.

2. 29 CFR 1910.184(c)(4) prohibits loading any sling beyond the rated capacity.

3. Only the manufacturer or equivalent entity are permitted to proof test and certify.

4. Certification is exclusively the right of only the manufacturer of new slings. Repaired slings may be certified by an equivalent entity who made the repairs.

June 7, 1988

  Directorate of Compliance Programs
THROUGH: LEO CAREY, DIRECTOR Office of Field Programs
FROM: BYRON CHADWICK Regional Administrator
SUBJECT: Load Testing of Synthetic Web and Other Slings

This is a request for an interpretation of the following items:

1. Can a prime contractor or other employer require frequent proof testing?

2. Is proof testing after manufacture controlled by lifting working loads in excess of 125 percent of the rated capacity?

3. Do slings have to be sent back to the manufacture or testing laboratory for testing or can the user proof test the slings at the work site?

4. If proof testing is allowed at the site, what would constitute proper procedures for field proof testing and certification?


cc: Neal H. Blooding, Owl Constructors John T. Chambers, Wyoming OH/S

May 19, 1988

U. S. Department of Labor (OSHA) Federal Office Building, Room 1576 1961 Stout Street Denver, CO 80294

Attention: Ethan Scott

Subject: Load Testing of Synthetic Slings

Dear Sir:

Per our telephone conversation on the subject matter, I would like to request of Federal OSHA a review of the enclosed documents and give me your comments on their requirements.

The Boeing Company is quoting out of the WYOSHA General Rules and Regulations, 1910 Chapter 14, Section 7, Paragraph (a) and (b) for the justification to load test synthetic web slings to 200% (2X rated load). This reference deals with repair of synthetic web slings. We do not do any repair on web slings. If they are bad the slings are removed from service and destroyed.

If you have any questions, please feel free to contact me at (307) 632-7975.


Neal H. Blooding Safety Engineers

Enclosure(s) - as noted


LOAD FACTOR AND INSPECTION FREQUENCY Metallic slings and chokers and synthetic web slings - conduct 200% (2 x Rating) proofload test before placing in service and every 90 days thereafter with comprehensive inspection every 90 days. (Handwritten next to the above - Here is what Boeing requires per the safety requirements document.) Non-metallic rope slings and chokers - conduct 100% (1 x Rating) proofload test before placing in service and every 90 days thereafter with comprehensive inspection every 90 days. Shackles, turnbuckles, eyebolts, swivel ring bolts, hoist rings, and other metallic hardware - conduct 200% proofload test before placing in service.

1009.4.4 Special lifting fixtures and accessories designed for lifting specific materials, assemblies, or equipment such as large lifting fixtures, specially designed slings and spreader bars shall be 200% load tested (2 x Rating) annually with comprehensive inspection every 90 days. Hoist anchorage including lift eyes, pad eyes, eyebolts, and swivel ring bolts, for support of portable hoists such as block and tackle, chain falls and come-a-longs shall be 125% load tested (1.25 x Rating) prior to first use and after rework with comprehensive inspection every 90 days. Overhead hoists/cranes, trolley/monorail and portable chain hoists shall be 125% load tested (1.25 x Rating) prior to first use, after rework, and annually thereafter with written, dated signed comprehensive inspection every 30 days covering hooks, ropes, and brakes.

(Response from sling manufacturer)

MIRSCO LIFTING SLINGS A Division of Midwest Rubber


OWL Constructors Cheyenne, WY ATTN: Neil Blooding

Dear Mr. Blooding,

This letter and the attached copy of certification are in response to your inquiry of the above date through our distributor's sales representative, (Aviation Industrial Supply). All of our nylon lifting slings meet or exceed all industry and OSHA standards. The rated capacity as listed on the leather identification tag and in our sales literature is based on a 5 to 1 safety factor as all slings are supposed to be.

When nylon lifting slings are "proof-tested" for the purposed of certification they are pulled at the respective bearing points, (at the eyes in a type 3 sling or at the triangles in a type 1 or 2 sling), to twice the rated "vertical" working capacity. We are completely confident in the manufacturing techniques and stitch methods employed in our slings and do regularly test random batches to assure continuing quality control.

If you desire proof-testing for any of our slings we can accommodate you at a nominal testing charge. Sling certifications are free of charge. Attached is a copy of our certification form. If we can be of any further service please contact us or Aviation Industrial Supply.

Respectfully Yours,

Michael A. Reis


MIRSCO LIFTING SLINGS A Division of Midwest Rubber







(Response from WYOSHA)

April 19, 1988

Mr. Neil Blooding Owl Constructors Box 548 Cheyenne, WY 82003

Re: Load testing of synthetic slings

Dear Mr. Blooding:

On a previous occasion you contacted this agency with regard to load testing synthetic slings at 200 percent their rated capacity. At that time you were given a copy of the Wyoming Occupational Health and Safety rules for Construction. The specific standard that you were shown then , and still should take into account, is Chapter VIII, Section 2.e.(2) which states, "Rated capacity shall not be exceeded."

Section 2.e.(1),(a),(b), and (c) requires that the employer shall have each synthetic web sling marked or coded to show the name or trademark of the manufacturer, rated capacities for the type of hitch, type of material. This would give anyone using the sling all of the pertinent information required to use it safely.

Section 2.a.(1) of the same chapter states that "Rigging equipment for material handling shall be inspected prior to use on each shift, and as necessary during its use, to ensure that it is safe. Defective rigging equipment shall be removed from service." This rule is to assure that any type of rigging equipment is inspected before each shift that it would be used on and replaced if there is a problem with it.

The only place that load testing of rigging equipment is required is under Section 2.a.(4) which states, "Special custom design grabs, hooks, clamps, or other lifting accessories, for such units as modular panels, prefabricated structures and similar materials, shall be marked to indicate the safe working loads and shall be proof-tested prior to use to 125 percent of their rated load." This rule requires load testing only of special custom-designed equipment, not slings, and not on a monthly cycle but only a one-time test.

Mr. Neil Blooding Page Two

After reviewing the above stated rules, it would be this agency's contention that any sling load tested to 200 percent of its rated capacity would be overloading the sling. With Section 2.e.(2) that sling would have to be removed from service due to the fact that the working capacity of the sling would not be known after such a tremendous amount of overloading has occurred.

If you have any questions concerning this matter, feel free to contact me.


John T. Chambers Assistant Administrator


(Boeing's response to letters.)

2-5056-88JH-059 May 3, 1988

To: W. E. Bayless WE-00

cc: C. F. Dobes 3H-53 E. W. Wright WE-00

Subject: Proof Load Testing of Synthetic Web Slings

  Reference: (a) Letter, J. T. Chambers to N. Blooding, dated April
    19, 1988, same subject.

(b) Wyoming Occupational Health and Safety Rules and Regulations for Construction, Section 2a(2).

(c) Safety Requirements Document, D407-21160-1 Paragraph

(d) Letter, M. A. Reis (Muresco Lifting Slings) to Constructors, dated 3/23/88, same subject.

(e) Memo ASPE 77-49, J. D. Boal to J. P. Pollack, dated October 12, 1977, subject: Nylon Web Test Report.

Mr. Neil Blooding has objected to the periodic proof load test load of 200% of safe working load (SWL), required by reference (c), as being excessive and damaging to the sling. Mr. Blooding maintains that the proof load is limited by reference (b), which states "Rigging equipment shall not be loaded in excess of its recommended safe working load...". This position was collaborated with the Wyoming Occupational Safety and Health office in reference (a).

It is our contention that the intent of the quoted requirement is to prohibit lifting working loads which exceed the rated load capacity of the sling. It does not apply to loads used in proof testing.

The Boeing Proof Test load requirement for synthetic web slings is twice the rated capacity (200% SWL), as specified in reference (c). This is confirmed as an OSHA standard by the reference (d) letter.

The claim has been made that proof load testing every 90 days will cause damage to the sling form the effect of fatigue. This claim is invalid based on the following information:

1. Boeing performed tests on nylon web slings, reference (e), which showed that nylon web slings did not experience any significant loss of strength under repetitive loading even with loads exceeding the rated breaking strength of the webbing by 10 percent. This loading would be equivalent to a proof load of 550% SWL.

2. Breaking strength of the test samples was first determined by testing eleven samples to destruction. The breaking strength of the weakest sample was 124% of the rated breaking strength; average was 130% of rated breaking strength (650% SWL); indicating that the webbing more than met the legal requirement for strength.

3. The test samples were subjected to 13 to 16 repeated loads of 110% of rated breaking strength (550% SWL) without allowing time between loads for recovery, then pulled to destruction. This was considered a very severe test, as the nylon was not allowed to cool after being heated by the energy developed by the applied load. Single load tests would not be this severe. Final breaking strengths ranged from 121% to 132% of rated breaking strength. Average was 126% of rated breaking strength.

4. To simulate the effect of periodic proofload testing, nine samples were loaded to 120% of rated breaking strength (600% SWL) four times, allowing a recovery period of one day between loadings, then pulled to destruction. The weakest of these samples developed 128% of rated breaking strength; the strongest, 130% of rated break. Average was 129% of rated strength (645% SWL). This was 99% of the average strength of the original unloaded samples.

Consideration of the precoding data leads to the following conclusions:

1. The proof load of 200% of rated load is the one prescribed by OSHA for nylon web slings, 4 and is observed by the sling manufacturer.

2. Proof testing at 200% SWL repeated every 90 days will have no detrimental effect on the strength of the sling. Tests conducted by Boeing have shown that nylon web slings can withstand severe and frequent repeated tests at loads of over 550% SWL with a strength loss of less than 2 percent.

The Boeing requirements as currently written comply with the intent of OSHA and will not be changed at this time. Questions may be addressed to Larry Pierce on (206) 395-1976, M/S 1E-62.

J.W. Heltzel 2-5056 1E-62 Job 8-18