Skip to main content

ISO 13849-1:2023 for Hydraulic and Pneumatic Safety Functions

On a hydraulic or pneumatic handling machine, the safety functions that stop a cylinder, hold a load, or vent a valve bank run through valves, and ISO 13849-1:2023 specifies a methodology for the design and integration of the safety-related parts of control systems that perform such safety functions, for high demand and continuous modes of operation. UTEC Industrial designs, engineers, machines, fabricates, and installs custom material handling systems for aerospace and heavy industry from its Spokane Valley, WA facility, integrating Allen-Bradley PLC and motion control with in-house CNC machining, heat treating, and stress relief. This article covers valve reliability figures, cycling and monitoring, and where lockout begins. The safety function is fixed at the design and engineering links of the chain, design → engineering → parts machining → fabrication → assembly → weld fatigue → stress relief → drives → controls → tuning → monitoring, and it is carried out at the controls, tuning, and monitoring links.

What does ISO 13849-1:2023 cover, and which fluid-power parts fall inside it?​

ISO 13849-1:2023 "specifies a methodology and provides related requirements, recommendations and guidance for the design and integration of safety-related parts of control systems (SRP/CS) that perform safety functions, including the design of software." It applies to SRP/CS for high demand and continuous modes of operation, including their subsystems, "regardless of the type of technology and energy (e.g. electrical, hydraulic, pneumatic, and mechanical)," and it "does not apply to low demand mode of operation." It "does not specify the safety functions or required performance levels (PLr) that are to be used in particular applications," and it "does not give specific requirements for the design of products/components that are parts of SRP/CS." It is Edition 4, published 2023-04 by ISO/TC 199 at 152 pages, and it replaced the 2015 edition. The IFA's 2023 summary adds that, by definition 3.1.44, demand in high demand mode is "more frequent than once a year."

Inside a fluid-power circuit, IFA Report 2/2017e, on the 2015 edition, says the area of valves "controlling hazardous movements or states" should in particular be considered a safety-related part of the control system, while "The drive elements and the components for energy conversions and transmission in fluid power systems generally lie outside the scope of the standard." IFA Report 1/2025 carries the same text for the 2023 edition (paraphrase translated from the German). Rexroth's compact-hydraulics note states, for a single component: "The valve alone does not fulfill a complete, self-contained safety function" (ISO 13849-1:2023; Hauke M, Bömer T, Büllesbach K-H, DGUV 2023, §2, p. 3; Hauke M, Schaefer M, Apfeld R, et al., IFA Report 2/2017e, 2019, p. 101; Hauke M, Bömer T, Werner C, et al., IFA Report 1/2025, p. 125; Bosch Rexroth Oil Control S.p.A., RE 18350-51/04.25, 2025, p. 3).

What changed in the 2023 edition for hydraulic and pneumatic safety functions?​

The IFA's overview of the fourth edition says the 2015 changes "were merely editorial," while the 2023 update reorganized the core sections to map first the specification of safety functions and then the design process. Points it records that bear on fluid power:

  • Validation moved into Part 1. Validation, "previously included in part 2 of the standard, has now been placed in part 1 as section 10 – largely unchanged in terms of content."
  • Alternative procedure narrowed. The procedure in subsection 6.1.9 for mechanical, (electro-)hydraulic and (electro-)pneumatic components without reliability data "only applies if it is impossible to use the good engineering practice method provided in Annex C.2"; where the output-part procedure is now applied to the input part, in Categories 2, 3 and 4 "like in Category 1, only well-tried components are permitted."

Part 2 is in transition. ISO 13849-2:2012, the validation part, shows on its iso.org page stage 90.92 and says it is "Expected to be replaced by ISO/DIS 13849-2 within the coming months." The draft, Edition 3 at stage 40.60, is retitled "Application of principles for the design and validation," and its draft abstract says it "provides requirements for the application of basic and well-tried safety principles and conditions for possible fault exclusions" and "provides guidance for the design and the validation of mechanical, pneumatic, hydraulic, and electrical systems" for SRP/CS designed in accordance with ISO 13849-1:2023. IFA Report 1/2025 expects no fundamental changes to Part 2 apart from deleting its former normative part (paraphrase translated from the German) (Hauke M, Bömer T, Büllesbach K-H, DGUV 2023, pp. 1-2, §6.6, p. 7; ISO 13849-2:2012; ISO/DIS 13849-2; Hauke M, Bömer T, Werner C, et al., IFA Report 1/2025, p. 19).

How is a fluid-power safety function specified before the circuit is designed?​

The IFA's 2023 overview says safety functions "now need to be defined in detail as part of a safety requirements specification (SRS)," each still based on the risk assessment and risk reduction process of ISO 12100. Among the listed items, these decide a fluid-power circuit:

  • the triggering event and the required reaction to reach the intended safe state;
  • the required performance level PLr;
  • the "permitted response time, i.e. the time between demanding the safety function and achieving the safe state";
  • the operating modes in which the function must be active;
  • "behaviour of the machine in the event of energy loss, e.g. a requirement for non-return valves directly on a cylinder or additional mechanical brakes," with separation into two safety functions also possible;
  • the demand rate and the conditions permitting a restart.

The same overview says the informative Annex A "can be used ... to determine the required performance level (PLr) unless it is specified in a product standard (type-C standard)."

Response time on a pneumatic axis includes venting. SMC's safety exhaust valve manual says the time to vent "is a function of" the valve's flow capacity, silencer restriction, protected volume, air pressure and system restrictions, and "The end user is expected to establish the time taken to vent." In a pneumatic Category 2 example intended for applications with rare access to the danger zone, IFA Report 1/2025 states the Category 2 requirement the example meets: testing takes place immediately on demand of the safety function, and the total time to detect the failure and bring the machine to a non-hazardous state is shorter than the time to reach the hazard. That total time takes into account, for example, the overrun distance, which depends among other things on the venting time and the valve switching times (paraphrase translated from the German) (Hauke M, Bömer T, Büllesbach K-H, DGUV 2023, pp. 2-4; ISO 12100:2010; SMC Corporation, Doc. no. VPX400-TF224-035EN, 2024, §2.12.4; Hauke M, Bömer T, Werner C, et al., IFA Report 1/2025, p. 146).

Which categories do hydraulic and pneumatic safety circuits use?​

ISO 13849-1:2023 defines Categories B and 1 to 4: single-channel structures that rely on component reliability (B and 1, with well-tried components in Category 1), a single channel with fault detection (2), a structure in which a single fault does not lead to the loss of the safety function (3), and one in which faults are also detected so that their accumulation does not lead to that loss (4). The IFA's 2023 overview records what changed. In Category 2, "the main feature ... will be fault detection in the functional channel instead of the checking of the safety function," at least with "low" diagnostic coverage, "i.e. 60% fault detection," for each part of the channel; "The test rate must be at least 100 times higher than the demand rate, or testing occurs immediately upon demand of the safety function and prevents the hazard"; and the MTTFD of the test channel "must be greater than half the MTTFD of the entire functional channel." For Category 4, "the accumulation of (up to two) undetected dangerous failures must not lead to the loss of the safety function."

IFA Report 2/2017e, on the 2015 edition, states, as its own observation, that "The structures of most fluid power control systems are engineered in Categories 1, 3 or 4."

SMC's dual-spool safety exhaust valve manual says that when de-energized "the spools return to the venting position by spring force," that in the venting position "a single fault cannot cause both spools to switch to the ON position," and that when properly integrated into a suitable safety control system the valve is compatible with systems up to Category 4 PL e. Its diagnostic coverage "has been determined to be 99% when properly integrated with a safety controller," and "CCF analysis is the responsibility of the system integrator" (ISO 13849-1:2023; Hauke M, Bömer T, Büllesbach K-H, DGUV 2023, §6.1, pp. 5-6; Hauke M, Schaefer M, Apfeld R, et al., IFA Report 2/2017e, 2019, p. 102; SMC Corporation, Doc. no. VPX400-TF224-035EN, 2024, p. 1, §2.7, §2.12.7-§2.12.8).

Where do MTTFD values for hydraulic valves come from?​

IFA Report 2/2017e, on the 2015 edition, ranks the sources: the manufacturer "and for example his technical data sheet, should be given preference here over all other sources," and the standard's typical values "are however very conservative estimates, and their use is therefore recommended only if the data sources indicated above are not available." For hydraulic components it says "an MTTFD of 150 to 1,200 years is proposed in EN ISO 13849-1 ... provided certain conditions are met," conditional on the basic and well-tried safety principles of EN ISO 13849-2 for hydraulic valves, graded "as a function of nop," the number of actuations per year.

ISO 13849-1:2023, Annex C, Table C.1 gives typical MTTFD values for hydraulic components graded by nop, and a typical B10D value for pneumatic components, for use when its conditions are met. IFA Report 1/2025 lists those conditions: the component manufacturer confirms on the data sheet that basic safety principles, and for Categories 1 to 4 well-tried safety principles, were applied in design; the manufacturer specifies the application and operating conditions; and the SRP/CS designer and the user apply the principles in implementation and operation (paraphrase translated from the German). Rexroth's 2025 note states one band: "For hydraulic components, the standard ISO 13849-1:2023 stipulates an MTTFD value of 150 years with nop ≥ 1000000 cycles per year, assuming that basic and well-tried safety principles are applied."

IFA explains why the figures depend on conditions: "the failure behaviour of hydraulic valves is characterized less by random failures than by failures due to wear," with causes "primarily systematic, such as excessive stress, unfavourable conditions of use, or lack of maintenance" (Hauke M, Schaefer M, Apfeld R, et al., IFA Report 2/2017e, 2019, pp. 56, 268-269; ISO 13849-1:2023; Hauke M, Bömer T, Werner C, et al., IFA Report 1/2025, pp. 252-253; Bosch Rexroth Oil Control S.p.A., RE 18350-51/04.25, 2025, p. 2).

How are B10 and B10D values for pneumatic valves turned into an MTTFD?​

ISO 19973-2:2015 says "The lifetime of pneumatic and electro-pneumatic directional control valves is usually given as a number of cycles." Festo's application note defines B10 as "the number of cycles until 10 % of the tested valves have failed," determined to ISO 19973-1:2015 and ISO 19973-2:2015 at standard conditions of 6.3 bar ± 0.3 bar, 23 °C ± 10 °C ambient and medium temperature, a 5 µm filter, a +7 °C dew point and no added lubrication; where an application differs, "the user should evaluate whether an adjustment of the B10 value is necessary."

B10 becomes B10D through the ratio of dangerous failures. The IFA's 2023 overview gives B10D = B10/RDF where RDF is known, notes that previously "50% dangerous failures should be assumed as an estimate, i.e. B10D = 2 * B10," and adds that "the T10D value is limited to a maximum of 2 * T10 where the RDF is below 50%." Festo says an RDF of 50% "must not be assumed" for some components, such as locking units and holding brakes, for which "an RDF of 100% should be assumed."

IFA Report 2/2017e, on the 2015 edition, gives the conversion: nop = (dop × hop × 3,600 s/h) / tcycle; MTTFD = B10D / (0.1 × nop); and T10D = B10D / nop, an approximation it says is of adequate quality "only up to attainment of the T10D value." As UTEC's own arithmetic, with SMC's stated B10D of 1,083,893 cycles for its dual-spool safety exhaust valve, which SMC says "is estimated from SMC life tests under SMC test conditions," and an assumed duty of 240 days a year, 16 hours a day and one venting every 120 s:

  • nop = 240 × 16 × 3,600 / 120 = 115,200 cycles per year;
  • MTTFD = 1,083,893 / (0.1 × 115,200) ≈ 94 years;
  • T10D = 1,083,893 / 115,200 ≈ 9.4 years.

SMC limits the mission time to "Maximum 20 years or when the number of cycles = B10D, whichever occurs first," and says reaching 20 years requires SMC "overhaul every 5 years"; SMC also expects the user to convert the B10D into a time from the application's operating cycles. By the same arithmetic, at that assumed duty the cycle limit is reached, and the valve is replaced, at about 9.4 years. Rexroth's 2025 note gives "TM = 20 years respectively TM = 10 years for electronic components such as sensors and switches (maximum duration of use according to ISO 13849-1:2023)" (Bosch Rexroth Oil Control S.p.A., RE 18350-51/04.25, 2025, p. 2; Festo SE & Co. KG, Document 100396, 2023, §10-§10.1; ISO 19973-1:2015; ISO 19973-2:2015; Hauke M, Bömer T, Büllesbach K-H, DGUV 2023, §12, p. 9; Hauke M, Schaefer M, Apfeld R, et al., IFA Report 2/2017e, 2019, pp. 272-273; SMC Corporation, Doc. no. VPX400-TF224-035EN, 2024, §2.2, §2.12.5, §7.2, §8.9.1).

Why do rarely switched valves fail, and how often should they be cycled?​

IFA Report 2/2017e, on the 2015 edition, names the failure modes. On pneumatic valves with soft seals that stay in one switching position "for a longer period, the seals may swell," or "the lubricating film may collapse," increasing resistance to operation; "On hydraulic valves, silting may occur when the valve remains in the same switching position for a longer period," as fine dirt particles settle in the sealing gap and cause the valving element to stick. It says a high force surplus, such as spring force, "must generally be engineered for return of the valving element," and that these effects "must be prevented by cyclical switching, to which the standard now refers," with test cycles "at intervals for example of less than eight hours." IFA Report 1/2025 repeats these points for the 2023 edition, with intervals of, for example, under 8 h (translated from the German). ISO 13849-1:2023 itself refers to cyclic switching as a measure against failures of valves that remain unswitched for long periods.

The suppliers' intervals differ, and each applies only to its own products:

  • Festo: under its stated reference conditions, Festo recommends "that all valves should be switched at least once a week," with exceptions it lists for valves suitable for low-demand mode and for valves whose operating instructions specify forced dynamization, and for safety components "the specifications of the operating instructions for the switching frequency must always be observed. An extension is not permissible."
  • SMC: "If the machine is not in operation, the product should have the diagnostic test applied at least once per week," and to declare Category 4 the diagnostic test "shall be performed at least once per day ... automatically by a safety controller."
  • Rexroth: "Seizures may occur after a prolonged period in which the control elements are not used"; it advises regular switching "at reasonable periods."

As engineering reasoning, a heavy machine that sits idle over a weekend or a plant shutdown is the case these figures address, so the PLC sequence includes a cycling or test routine before the first production move (Hauke M, Schaefer M, Apfeld R, et al., IFA Report 2/2017e, 2019, p. 47; Hauke M, Bömer T, Werner C, et al., IFA Report 1/2025, pp. 64-65; ISO 13849-1:2023; Festo SE & Co. KG, Document 100396, 2023, §6-§6.3; SMC Corporation, Doc. no. VPX400-TF224-035EN, 2024, §4.1-§4.2; Bosch Rexroth Oil Control S.p.A., RE 18350-51/04.25, 2025, p. 2).

How is a valve monitored to reach diagnostic coverage?​

Festo's application note, which cites the 2015 edition of ISO 13849-1 and the 2012 edition of ISO 13849-2, writes that "According to EN ISO 13849, direct or indirect monitoring is necessary for safety-related valves from category 2 in order to achieve the required level of diagnostic coverage," and that monitoring needs dynamization to detect static failures; it says the possible static failures are listed in EN ISO 13849-2 Table B.3, including "Change in switching times" and "Non-switching ... or incomplete switching."

The IFA's 2023 overview says that in the table of fault-detection examples there are now notes in place of DC ranges: an FMEA "must generally be used as the basis for determining the DC," and, when outputs are monitored or input or output signals are cross-monitored without dynamic testing, the test rate can limit DC: the IFA's examples allow a DC of 99% only for tests that occur at least once a month, and estimate tests that occur less often than once a year at a DC of 0%.

SMC's dual-spool valve carries pressure sensors whose data "should be confirmed" on every switch-on and switch-off, automatically by a safety controller, and if a failure of one channel is detected "the safety controller shall use the remaining channel to maintain the safe state." In IFA Report 1/2025's pneumatic Category 2 example, comparing the travel and time behaviour of the hazardous movement, measured by a position sensor, with the switching state of the directional valve, evaluated in a PLC, is the basis for the valve's DC of 60%, which is also the DCavg, rated "low" (translated from the German). A valve's own spool feedback for control is a different signal; the proportional versus servo valves article covers one maker's statement that it must not be used to switch off safety-relevant functions (Festo SE & Co. KG, Document 100396, 2023, §6.4; Hauke M, Bömer T, Büllesbach K-H, DGUV 2023, §13, p. 10; SMC Corporation, Doc. no. VPX400-TF224-035EN, 2024, §4.1; Hauke M, Bömer T, Werner C, et al., IFA Report 1/2025, p. 146).

What are basic and well-tried safety principles for valves, and who confirms them?​

IFA Report 2/2017e summarizes the hydraulic principles in Annex C of EN ISO 13849-2 in its 2012 edition. The most important basic safety principles "include the use of suitable materials and manufacturing procedures, and the principles of isolation, pressure limitation, protection against unexpected start-up, and a suitable temperature range." The well-tried principles it names include "overdimensioning/safety factors," speed limitation by a resistance for a defined volumetric flow, force limitation, an appropriate range for the operating conditions, "monitoring of the condition of the pressure medium, the use of well-tried springs, and sufficient overlap in piston-type valves." ISO 13849-2:2012, Annex C, also lists faults for hydraulic components and the conditions under which some of them may be excluded.

Festo, citing the 2012 edition, writes that "The safety principles listed in ISO 13849-2 refer to systems" and that within the limits of a component "all of these safety principles can never apply"; a "well-tried" confirmation "must always be checked by the user," who must first deny it where, among other cases, there is "Heavy contamination by dust." Rexroth writes that "Hydraulic components which are not compliant with the relevant safety principles are not suitable for application in safety-related parts of control systems," and that its products with a stated MTTFD comply, where applicable, with ISO 13849-2:2012. On fault exclusion, the IFA's 2023 overview records a restriction now in subsection 6.1.10: "A PL e for subsystems must not be based on fault exclusions alone" (Hauke M, Schaefer M, Apfeld R, et al., IFA Report 2/2017e, 2019, pp. 268-269; ISO 13849-2:2012; Festo SE & Co. KG, Document 100396, 2023, §8-§9; Bosch Rexroth Oil Control S.p.A., RE 18350-51/04.25, 2025, p. 2; Hauke M, Bömer T, Büllesbach K-H, DGUV 2023, §6.7, p. 7).

How is a fluid-power safety function validated?​

The IFA's 2023 overview says the new section 10, Validation, "has been taken over entirely from sections 4 to 12 of EN ISO 13849-2," with the content and requirements "essentially ... unchanged": a validation plan, a validation protocol, and validation through analysis and testing. It adds that "irrespective of the category, at least a functional test of the safety functions is required in addition to the analysis," and that during the transition "the more recent requirements from part 1 take priority."

SMC says the performance of the system "should be validated by test after each installation" and under "all foreseeable operating conditions of pressure, flow and volume," and that after installation and maintenance the user should apply operating pressure and power and "perform appropriate functional and leakage tests." Festo says that because diagnostic measures "cannot normally detect all possible faults," the safety-relevant parameters should be recorded and documented with external measuring devices before or during commissioning, for directional control valves at least "the control signals, movement characteristics, signals from the sensors, pressures at the valve outputs, leakage."

UTEC Industrial performs factory acceptance testing and on-site commissioning on the machines it builds (Hauke M, Bömer T, Büllesbach K-H, DGUV 2023, §8, p. 8, and p. 2; SMC Corporation, Doc. no. VPX400-TF224-035EN, 2024, §2.12.4, §7.1; Festo SE & Co. KG, Document 100396, 2023, §5.3.3).

Where do safety functions end and lockout begin?​

The federal lockout standard, 29 CFR 1910.147, defines an energy isolating device as "A mechanical device that physically prevents the transmission or release of energy," listing among others "a line valve; a block," and it states that "Push buttons, selector switches and other control circuit type devices are not energy isolating devices."

OSHA's 2021 letter on pneumatic fail-closed valves applies this to valves on a process pump, not a machine safety circuit. Valves closed and de-energized by disconnecting their air tubing did not qualify: the valve "in its current configuration does not meet the definition of an energy isolating device ... since it is not capable of being locked out," and the device "must be capable of being locked out without the need to dismantle, rebuild, or replace or permanently alter its energy control capability." As engineering reasoning by analogy, a de-energized safety exhaust valve or a safe-state output from a safety controller performs a safety function, and the lockable isolation valve remains the energy isolating device for servicing.

OSHA's 2019 Request for Information says control circuit type devices "are specifically excluded from OSHA's definition of an EID," that technological advances suggest that "at least in some circumstances, control circuit type devices may be at least as safe as EIDs," and that OSHA is "evaluating criteria used by consensus standards," citing ISO 13849-1 in its 2015 edition among them. An RFI requests information; it does not change the rule (OSHA 29 CFR 1910.147-1989; OSHA Standard Interpretation 2021; Federal Register, 84(97), 22756, 22758, 2019).

What controls and sensing carry a fluid-power safety function?​

The sources name the signals and the logic that evaluates them:

  • Pressure behind the exhaust valve. IFA says that on pneumatic systems "an exhaust valve is frequently used in conjunction with a pressure switch"; SMC's dual-spool valve has a fault-detection sensor and an output-port sensor, checked by the safety controller on each switching.
  • Actuator position and timing. In IFA Report 1/2025's Category 2 example, a position measuring system on the hazardous movement is compared with the valve switching state in a PLC, and the electrical control of that directional valve must not come from the same PLC (translated from the German).

As engineering reasoning, on an Allen-Bradley system the standard controller runs the sequence, the valve-cycling routine, and the condition alarms, and the safety-related parts carry the stop, hold, and vent functions to their own category and PL, with the two kept separate in the program and the wiring. UTEC Industrial programs Allen-Bradley ControlLogix and CompactLogix controllers over EtherNet/IP and builds UL 508A panels for the handling machines it fabricates (Hauke M, Schaefer M, Apfeld R, et al., IFA Report 2/2017e, 2019, p. 101; SMC Corporation, Doc. no. VPX400-TF224-035EN, 2024, §2.2, §4.1; Hauke M, Bömer T, Werner C, et al., IFA Report 1/2025, p. 146).

Where does the fluid-power safety function sit in the design-to-monitoring chain?​

As engineering reasoning, the SRS and the circuit come first, and each later link keeps the figures they assume:

  • Design and engineering: the SRS, the PLr, the category, response and vent times, load-holding valves at the cylinder, and the valve data sheets that carry MTTFD or B10D values.
  • Parts machining, fabrication, and assembly: manifold faces, cylinder mounts, and brake or locking-unit brackets that the energy-loss function relies on.
  • Weld fatigue and stress relief: the welded frame that carries a held load when the safety function holds it.
  • Drives, controls, and tuning: safety controller logic, valve-cycling routines, and pressure and position monitoring set to the response time.
  • Monitoring: cycle counts against each valve's B10D, switching-time trends, and replacement dates within the mission time.

For US component data, the National Fluid Power Association's list of active NFPA standards includes NFPA/T2.12.11-2-2007 (R2024), hydraulic fluid power components assessment of reliability by testing, and NFPA/T3.5.30-2008 (R2024), measurement of the response time of hydraulic solenoid operated directional control valves; as engineering reasoning, a specification can ask which method produced a valve's reliability data (National Fluid Power Association 2024; ISO 13849-1:2023).

Related Articles

References​

  • ISO 13849-1:2023: Safety of machinery — Safety-related parts of control systems — Part 1: General principles for design. International Organization for Standardization, 2023.
  • ISO 13849-2:2012: Safety of machinery — Safety-related parts of control systems — Part 2: Validation. International Organization for Standardization, 2012.
  • ISO/DIS 13849-2: Safety of machinery — Safety-related parts of control systems — Part 2: Application of principles for the design and validation (Draft International Standard). International Organization for Standardization (undated web documentation, accessed October 2026).
  • ISO 19973-1:2015: Pneumatic fluid power — Assessment of component reliability by testing — Part 1: General procedures. International Organization for Standardization, 2015.
  • ISO 19973-2:2015: Pneumatic fluid power — Assessment of component reliability by testing — Part 2: Directional control valves. International Organization for Standardization, 2015.
  • ISO 12100:2010: Safety of machinery — General principles for design — Risk assessment and risk reduction. ISO, 2010.
  • Hauke, M., Bömer, T., Büllesbach, K.-H. Fourth edition of EN ISO 13849-1: Most important new features in 2023 at a glance. German Social Accident Insurance (DGUV), 2023.
  • Hauke M, Schaefer M, Apfeld R, et al. Functional Safety of Machine Controls – Application of EN ISO 13849 (IFA Report 2/2017e). Deutsche Gesetzliche Unfallversicherung (DGUV), 2019.
  • Hauke M, Bömer T, Werner C, et al. Funktionale Sicherheit von Maschinensteuerungen – Anwendung der DIN EN ISO 13849 (IFA Report 1/2025). Deutsche Gesetzliche Unfallversicherung (DGUV), 2025. [In German.]
  • Bosch Rexroth Oil Control S.p.A. Reliability Coefficients MTTFD for Functional Safety According to ISO 13849: MTTFD Values for Compact Hydraulics (RE 18350-51/04.25). Bosch Rexroth, 2025.
  • SMC Corporation. Instruction Manual: Safety Exhaust Valve, Series VPX400 (Doc. no. VPX400-TF224-035EN). SMC Corporation, 2024.
  • Festo SE & Co. KG. Safety Application Note ISO 13849: Circuit Safety-Subfunctions Pneumatic — Features of Directional Control Valves (Document 100396, Version 1.10). Festo, 2023.
  • OSHA 29 CFR 1910.147-1989: The Control of Hazardous Energy (Lockout/Tagout). Occupational Safety and Health Administration, 1989.
  • OSHA Standard Interpretation: Energy Isolation Device Requirements (pneumatic actuated fail-closed valves as energy isolating devices). Occupational Safety and Health Administration, 2021.
  • OSHA. "The Control of Hazardous Energy (Lockout/Tagout); Request for Information." Federal Register, 84(97), 22756–22762, May 20, 2019.
  • National Fluid Power Association (2024): Find a Standard. National Fluid Power Association, 2024.

Ready to Discuss a Material Handling System?​

UTEC Industrial designs, engineers, machines, fabricates, and installs custom material handling systems for heavy industry, from the stress-relieved structure and drives to the Allen-Bradley PLC controls, tuning, and monitoring that run them, at its Spokane Valley, WA facility. Send UTEC the application, loads, and duty cycle to start a system review.

Request a Quote →

Questions? Call (509) 922-1832 or email sales@utec.co

Last updated on