Using the Safety Arm
- Identify the specific load restrictions when using the safety arm.
- Perform the correct sequence for deploying and stowing the safety arm.
- Determine the maximum unloaded body weight capacity based on hinge distance and body length.
- Hydraulic controls — Raise the body to working height and lower it slowly until the cup contacts the arm.
- Safety arm — Support an unloaded raised body during maintenance or inspection.
- Base support bracket — Secure the safety arm in the vertical position to receive the body load.
- Hanger — Stow the safety arm securely when the hoist is fully lowered for operation.
Never go under a loaded raised body. The safety arm supports an unloaded body only.
How It Works
Load Limitations
The safety arm is designed to support an unloaded body only. You must never go under a loaded raised body, as the arm is not rated for the additional weight of a payload.
Engagement Sequence
Proper engagement requires rotating the arm to a vertical position and pushing it down into its base support bracket. The hoist must then be lowered slowly until the cup makes contact with the arm to ensure a stable mechanical block.
Capacity and Leverage
The weight capacity of a single safety arm varies significantly based on the distance from the hinge and the total length of the body. As the distance from the hinge increases, the supported weight capacity increases, though longer bodies (16 ft) have lower weight ratings at the same hinge distance compared to 12 ft bodies.
Step-by-Step Procedure
0/5 doneMax unloaded body weight — one arm (lb)
| 50" from hinge — 12 ft / 16 ft body | 2,569 / 1,927 |
| 60" from hinge — 12 ft / 16 ft body | 3,083 / 2,313 |
| 80" from hinge — 12 ft / 16 ft body | 4,111 / 3,083 |
Diagnostic Chart
| Symptom | Check | Spec / Expected | Likely cause & fix |
|---|---|---|---|
| Safety arm will not rotate to vertical. | Verify body is raised to sufficient working height and hydraulic power is shut off. | Per the applicable manual | The body is not raised high enough to clear the arm's rotation path or the hanger. Basis: Premium Supply Scissor Hoist Manual |
| Uncertainty if 16 ft body exceeds arm capacity at 60 inches. | Compare actual body weight against the 60 inch hinge distance rating. | 2,313 | The unloaded body weight may exceed the rated capacity for that specific hinge distance. Basis: Premium Supply Scissor Hoist Manual |
| Cup does not align with the safety arm during lowering. | Ensure the arm is pushed fully down into its base support bracket. | Per the applicable manual | The arm was rotated but not properly seated in the base support bracket before lowering. Basis: Premium Supply Scissor Hoist Manual |
At the Bay: Diagnose the Case
CASE 1 / 3
Safety arm will not rotate to vertical.
- Test
- Compare
- Correct
Select the next check
Basis: Premium Supply Scissor Hoist Manual. A likely cause is a hypothesis; confirm it with the applicable service procedure before repair.
Common Bay Mistakes
- ✕ Going under a loaded raised body.
- ✕ Lowering the hoist quickly onto the safety arm.
- ✕ Failing to shut off hydraulic power once the body is at working height.
- ✕ Forgetting to stow the arm in the hanger before fully lowering the hoist.
Quick Check
Practice only — not scored.
Plan the Service Sequence
Planning practice only. Follow the applicable manufacturer's instructions, employer safety program and qualified supervision on real equipment.
Plan the first action. Compare the service steps with the bay mistakes.
Hands-on: Shop Test Equipment
Hydraulic Pressure & Relief Gauge
0–5,000 psi gauge on the pump pressure port, DC clamp meter, battery voltmeter
🛠 Equip your bay for this test →Symptom: Routine check before a customer pickup.
Spec limits used
- 3,200 psi — Primary relief (factory preset) (KTI Hydraulics Troubleshooting Manual 2019)
- 1,500 psi — Secondary relief, circuit 111 (KTI Hydraulics Troubleshooting Manual 2019)
- below 9 V — Low-voltage alarm (KTI remote)
- illustrative only — Motor current & voltage drop (General shop practice)
Simulated readings for practice. Always follow the manufacturer's procedure and values on a real trailer.
Source: Premium Supply Scissor Hoist Manual — 8