OSHA's mechanical power press standard at 29 CFR 1910.217 keeps presence sensing devices (PSDs) as guarding tools, not initiators, unless an installation meets the separate Presence Sensing Device Initiation (PSDI) regime under paragraph (h) [S1][S4]. On 2026-09-01 OSHA submitted the PSDI information collection for OMB review under RIN 91:56221, keeping the 1988 PSDI rule actively enforced rather than dormant [S3].
PSD scope under 1910.217(c)(3)(iii) covers light curtains, optical fields, and radio frequency (capacitive) fields; a PSD is permitted to stop or prevent a stroke when the operator's hands intrude the sensing field, but 1910.217(c)(3)(iii)(b) flatly prohibits using the PSD itself as the tripping means to initiate slide motion outside of full PSDI conformance [S1][S4]. This is the boundary every safeguarding plan must respect before any light curtain retrofits or TOF-style optical sensor installations proceed.
Stopping time, safety distance, and the 0.912 s trap
Presence sensing device placement is governed by the press stopping time plus the PSD response time, both plugged into the OSHA safety distance formula so the slide cannot close on an intruding hand [S9]. In a documented 2000-ton air-clutch installation the measured stopping time reached 0.912 s, forcing the safeguarding plan to add both vertical and horizontal light curtains plus rigid perimeter guarding, because operators had to enter the press bed to load large piece parts [S5].
Where stopping performance is marginal the corrective action is not to mute the curtain, it is to add mechanical perimeter guards so that walk-through is physically impossible. OSHA's 1998-12-23 interpretation explicitly states that muting the light curtain after the upstroke cycle is a violation of 1910.217(c)(3)(iii)(d), since the slide can re-initiate downstroke before the operator clears the field [S5]. The same logic shows up in any machine safety distance calculation where brake wear eats into the original safety margin.
Control reliability and the 1910.217(b)(13) requirement
Any device wired into the press control loop, including optical or RF presence sensors used as two-hand controls, must satisfy the control reliability requirement at 1910.217(b)(13) if the device can affect point-of-operation protection [S4]. Control reliability means a single component failure does not prevent the normal stop command from stopping the press, and the system either stops the slide or refuses the next stroke until the fault is cleared [S1][S4].
OSHA has held since the 1992 Data Instruments letter that specialized optical or capacitive two-hand devices still fall under 1910.217(c)(3)(iii) when they perform a safeguarding function, and any such use that initiates slide motion without PSDI conformance is a 1910.217(c)(3)(iii)(b) violation [S4]. Practically, the integrator must wire a Category-1 or higher safety relay (per the conventional IEC 62061 / ISO 13849-1 reading that the standard assumes) and document the cross-fault monitoring that 1910.217(b)(13) requires, and the power supply feeding the safety circuit must be the same one that drops the clutch and applies the brake.
PSDI under 1910.217(h): the single-stroke exception
PSDI is a tightly bounded exception that lets the presence sensing field both guard and initiate the next stroke, but only on presses whose physical configuration prevents any person from passing completely through the sensing field and remaining in the danger zone [S7]. The rule is a single-stroke regime: each PSD clearance starts exactly one stroke, after which the press must recycle the operator's trip command before the next stroke can fire [S7].
The PSDI paperwork collection cycle keeps this clause alive on the regulatory books: extensions ran on 2025-09-23 (90 FR 45815) and again on 2026-08-19 (91 FR 53665), and a fresh OMB submission for the PSDI standard appeared on 2026-09-01 at 91 FR 56221 [S3]. For shops evaluating PSDI, the gating decision is mechanical geometry first, electronics second: if a hand or arm can enter, traverse, and exit the field into the die area, PSDI is not a legal option, period [S7]. Similar geometry-driven exclusion logic governs hydraulic press safeguarding, though hydraulic presses are excluded from 1910.217 by paragraph (a)(5) [S1].
Foot pedals, two-hand trips, and antirepeat on full-revolution clutches
Full-revolution clutch presses must use a single-stroke mechanism under 1910.217(b)(3)(i), and any single-stroke function dependent on springs must use compression springs on a guided rod or in a tube to prevent coil interleaving on breakage [S1]. Two-hand trips on the same class of press must include an antirepeat feature per 1910.217(b)(6)(ii), and on multi-operator presses each operator needs a dedicated, concurrently operated hand-control set under 1910.217(b)(6)(iii) [S1].
Foot pedals on part-revolution presses must carry a non-slip pad, a guarded return path, and an enclosed counterweight travel; the pedal is treated as a single failure point in the mechanical seal sense, meaning one broken spring cannot leave the press in a run-and-stuck state [S1]. Part-revolution clutches are required to release and apply the brake the moment the external engaging means is removed, deactivated, or de-energized, which is the hardware foundation every PSDI retrofit leans on [S1].
Excluded machines and the boundary OSHA draws
1910.217(a)(5) lists press brakes, hydraulic and pneumatic power presses, bulldozers, hot bending and hot metal presses, forging presses and hammers, and riveting machines as excluded categories, so a safeguarding plan written under 1910.217 for one of these machines is a citation waiting to happen [S1]. The standard also assigns reconstruction and modification responsibility under 1910.217(a)(4) to the person doing the rebuild, who must bring the press back into paragraph (b) compliance, not just leave the original guard set in place [S1].
Where 1910.217 does apply, the complementary electrical reference points to keep on the desk are the safeguarding language in 1910.212 (general machine guarding) and the control-circuit language in NFPA 79, which the OSHA letters cite as the working definition of control reliability for the press [S1][S4]. For plants standardizing the safety circuit, that is also the point where the power distribution design has to provide a guaranteed-fail-safe disconnect path.
OSHA's 2021 update and the open question for 2026
The 50-year-old standard got its only formal substantive revision in 1988, when PSDI was added, and a 2021-07-28 Federal Register notice (86 FR 40651) opened a public docket on the Mechanical Power Presses Update [S3][S10]. OSHA then renewed the PSDI information collection in 2023-05-26, 2023-09-14, 2024-06-07, 2024-12-13, 2025-09-23, 2026-08-19, and again on 2026-09-01, signalling that the rule is in active use rather than headed for retirement [S3].
Two verifiable signals to watch: the resolution of the 2021-07-28 update rulemaking referenced in TRC's industry summary, and any new Federal Register entry that changes the power cable routing rules around the press bed, since 1910.217(f) still leaves non-PSD entry points to mechanical guards [S6][S8]. The next reliable checkpoint is whether the 2026-09-01 OMB submission yields a substantive PSDI revision or another routine extension, which will tell integrators whether to design for the 1988 PSDI text or hold for a rewritten clause [S3].