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ASME PALD 14-1989 — Scissors Type Mobile Lifts Safety Standard
✂️ ASME PALD-14-1989 is the Scissors Type Mobile Lifts volume of the Safety Standard for Portable Automotive Lifting Devices. Approved by ANSI on April 25, 1989 and issued on May 31, 1989, this edition covers mobile lifting devices whose lifting members raise and lower in a scissors action, prescribing complete safety requirements for design, marking, testing, instructions, operation, maintenance, and inspection — a key safety reference for raising one end of a vehicle in automotive repair shops.
💡 The decisive difference from swing type lifts (PALD-13) is the mechanism: scissors lifts have lifting members that move in an opposing scissors action; swing lifts pivot about a point. Both are pneumatic and both raise the wheels of one end of a vehicle free of the ground.
1. Scope and Framework 📌
This is the complete 1989 edition, issued with an automatic addenda subscription service. The volume is organized into seven sections plus an illustration:
| Section | Content | Key Points |
|---|---|---|
| Section 1 | Scope, Purpose, Classification, and Illustration | Pneumatic scissors lifts, the only classification |
| Section 2 | Definitions | base, proof load, rated capacity, saddle, etc. |
| Section 3 | Design | Operating controls, travel limits, overload, proof load |
| Section 4 | Product Marking and Identification | Capacity, manufacturer ID, date code, warnings |
| Section 5 | Design Qualification Testing | Proof, travel limit, load loss, sustaining, release tests |
| Section 6 | Product Instructions and Warnings | Operator instruction content |
| Section 7 | Operation, Maintenance, and Inspection | Usage precautions and inspection procedures |
This volume applies to pneumatic scissors type mobile lifts — a pair of laterally spaced lifting members raising and lowering in a scissors action, arranged to contact the vehicle at two points across its axis of symmetry on the bumper, bumper supports, or frame members, to raise the wheels of one end of a vehicle free of the ground. The boundary with ANSI B30.1, Jacks, is explicit.
⚠️ Hazards of scissors type mobile lifts — dropping, tipping, or slipping of vehicles or components from improperly secured loads, overloading, off-centered loads, use on other than hard level surfaces, or use for purposes not intended — cannot be fully precluded by mechanical means. Only careful, competent, trained, and qualified personnel should operate them.
2. Technical Requirements and Specifications 🔧
Core design requirements of Section 3:
- Operating Controls (3.1): visible, accessible, no pinch points or sharp edges; the release system requires intentional positive action to prevent accidental lowering.
- Travel Limit (3.2): a positive means prevents the load from being raised or moved beyond the design limit of travel.
- Overload Capacity (3.3): all lifts shall meet para. 3.4 as minimum overload capacity.
- Proof Load (3.4): lifts shall perform the proof load test of para. 5.1.1 with a proof load of 150% of rated capacity.
- Secondary Load Holding Means (3.5): prevents unrestricted lowering in the event of loss of air pressure.
- Saddles (3.6): raised protrusions act as load restraints, and means limit the outward lateral adjustment of the saddles.
| Design Item | Requirement | Verification |
|---|---|---|
| Operating controls | Visible, accessible, positive-action release | Design review |
| Travel limit | Positive limiting means | Travel Limit Test 5.1.2 |
| Proof load | 150% of rated capacity | Proof Load Test 5.1.1 |
| Instantaneous load loss | Bounce ≤ 12 in. (300 mm) | Load Loss Test 5.1.3 |
| Load sustaining | 1 min ≤ 1/8 in. (3 mm); 10 min ≤ 3/16 in. (4.8 mm) | Load Sustaining Test 5.1.4 |
| Secondary holding | Auto stop on air loss, descent ≤ 7 in. (178 mm) | Holding Means Test 5.1.5 |
| Descent control | ≤ 3 in./s (75 mm/s) | Release Test 5.1.6 |
3. Design Qualification Testing 🔬
Per Section 5, for each design or design change that may affect the lift’s ability to meet this volume, sample lifts built to design specifications shall be proof tested; conformance requires no functional damage and no detriment to operating characteristics. The tests include the proof load test (5.1.1, lift/sustain/lower through full travel), travel limit test (5.1.2), instantaneous load loss test (5.1.3, unique to pneumatic lifts — ground clearance no more than 12 in./300 mm), load sustaining test (5.1.4), secondary load holding means test (5.1.5), and release test (5.1.6).
🚨 The instantaneous load loss behavior of a scissors mechanism differs from a swing type: the momentum characteristics of the scissors arms change faster on unloading. During the test, the lifting member, saddles, and attachments must remain affixed to the lift assembly to prevent bounce injuries. Lifts failing any qualification test must not be marketed.
4. Engineering Practice Essentials 🛠️
- 🔍 Procurement and acceptance: verify rated capacity, manufacturer identification, and date code; obtain design qualification test records and confirm all test items are complete.
- 🔧 Operating discipline: use only on hard level surfaces; distribute loads evenly on the saddles in the vehicle manufacturer’s specified areas; transfer the vehicle to proper supports immediately after lifting.
- 📊 Inspection and maintenance: per Section 7, regularly inspect pneumatic components, scissors structure, pivot points, and saddles; take the lift out of service on wear, deformation, or air leakage.
- 📋 Training and labeling: keep warning labels complete and legible and instructions current; operators must be trained and qualified.
💡 This edition became effective 3 months after issuance, with prospective application only. Subscribe to addenda to track later revisions (e.g., PALD-14a-1990) that update proof load tiering and other clauses.
5. Frequently Asked Questions ❓
❓ Q: What jobs suit a scissors type mobile lift?
A: Jobs in automotive shops that require raising one end (front or rear axle) of a vehicle free of the ground — tire changes, brake service, and similar work; the lift can be moved between work areas without a load.
A: Jobs in automotive shops that require raising one end (front or rear axle) of a vehicle free of the ground — tire changes, brake service, and similar work; the lift can be moved between work areas without a load.
❓ Q: Why does 3.6 limit the outward lateral adjustment of the saddles?
A: Excessively wide saddle adjustment moves the load off the lift’s centerline and increases tipping moment; limiting the range keeps the two sides loaded evenly and the lift stable.
A: Excessively wide saddle adjustment moves the load off the lift’s centerline and increases tipping moment; limiting the range keeps the two sides loaded evenly and the lift stable.
❓ Q: What happens if air supply is lost?
A: Per 3.5, the lift must be equipped with a secondary load holding means that automatically stops the lift and prevents unrestricted lowering; the 5.1.5 test requires descent within 7 in. (178 mm).
A: Per 3.5, the lift must be equipped with a secondary load holding means that automatically stops the lift and prevents unrestricted lowering; the 5.1.5 test requires descent within 7 in. (178 mm).
🔍 Q: How do PALD-14-1989 and its addenda work together?
A: The 1989 edition is the base; later addenda (e.g., PALD-14a-1990) revise clauses by replacement pages. For complete reference use the consolidated text of the 1989 edition plus all addenda.
A: The 1989 edition is the base; later addenda (e.g., PALD-14a-1990) revise clauses by replacement pages. For complete reference use the consolidated text of the 1989 edition plus all addenda.
