pneumatic cylinder control safety -...

Pneumatic Cylinder Control Safety

Eric Cummings – ROSS CONTROLSGlobal Industry Manager - SafetyEric.cummings@rosscontrols.com

803-622-1161

19 June 2013 www.rosscontrols.com 1

Agenda Ross Controls Introduction

Cylinder control basics

Safety control basics

What is the best solution?

19 June 2013 2

The ROSS Controls Story Founded in 1921 by Charlie Ross Design, manufacture and sale or pneumatic valves and systems for

industrial equipment 1954 – First double valve ever developed by ROSS 1962 – Developed first pneumatic energy isolation device 2005 – DM2 ™

19 June 2013 3

Global Facilities

ROSS Controls - Madison Heights

ROSS Controls - Troy, MI ROSS UK Ltd.

ROSS Asia - Japan

ROSS Europa GmbH - Germany

ROSS Controls - Lavonia, GA

ROSS South America ROSS IndiaROSS China19 June 2013 4

Safety IndustryCurrent Committees with ROSS

RepresentationANSI Z244 Control of Hazardous Energy - Lockout Tagout

ANSI B11.0 General Safety Requirements & Risk Assessment

ANSI B11.1 Mechanical Power Press

ANSI B11.2 Hydraulic and Pneumatic Presses

ANSI B11.19 Performance Criteria for Safeguarding

ANSI B11.26 (Former TR6) Safety Control Systems for Machine Tools

ANSI B155.1 Packaging and Packaging Related Converting Machinery

ANSI B11.151 Plastics Machinery

CSA Z432 Guarding of MachineryCSA Z460 Control of Hazardous Energy - Lockout - Tagout

19 June 2013 www.rosscontrols.com 5

Risk Assessment

Other standards requiring risk assessment:

• CSA Z432

• ANSI B11.0

• ANSI B11.19

• RIA 15.06

• ANSI/PMMI B155.1• ISO 13849

B11.0 Safety of Machinery General Safety Requirements and Risk Assessment

Task Based Hazard Analysis

Determine:

• People exposed

• Tasks required

• Severity of hazard

• Exposure to the hazard

•Consider:

•Foreseeable misuse

•Failure modes

Risk Assessment

Cylinder Control BasicsSpring return cylinder

19 June 2013 www.rosscontrols.com 8

Double acting cylinder

Cylinder Control Basics

19 June 2013 www.rosscontrols.com 9

What are the applications?• Automation• Packaging• Palletizing• Stacking• Cylinder presses• Tensioning• Winding• Cutting• Doors

Any linear motion requiring force.

Cylinder Control BasicsSpring return cylinder• Force = pressure x area – spring force• Speed function of air supply flow rate

19 June 2013 www.rosscontrols.com 10

Cylinder Control Basics

13

2

Single Acting Cylinder Retracted

Spring return cylinder

19 June 2013 www.rosscontrols.com 11

3 1

2

Single Acting Cylinder Extended

Push

Cylinder Control BasicsSpring return cylinder

19 June 2013 www.rosscontrols.com 12

Cylinder Control BasicsSpring return cylinder - vertical• Force = pressure x area – spring force + gravity• Speed function of air supply flow rate

19 June 2013 www.rosscontrols.com 13

Cylinder Control Basics

13

2

Spring return cylinder safety issues:• Speed control extending

19 June 2013 www.rosscontrols.com 14

Cylinder Control Basics

13

2

Spring return cylinder safety issues:• Speed control retracting

19 June 2013 www.rosscontrols.com 15

Cylinder Control Basics

13

2

Spring return cylinder safety issues:• Speed control extending and retracting

19 June 2013 www.rosscontrols.com 16

Cylinder Control BasicsSpring return cylinder risk assessment

Risk Result

Inherent motion De-energizing causes return motion

Cylinder spring breaks Cylinder does not return

Valve sticks open Cylinder continues moving or does not return

Valve sticks closed No motion

Speed of tooling Motion too fast or slow

19 June 2013 www.rosscontrols.com 17

Cylinder Control Basics

13

2

Spring “extend” cylinder safety issues:• Speed control extending and retracting

19 June 2013 www.rosscontrols.com 18

Cylinder Control BasicsSpring “return” cylinder risk assessment

Risk Result

Inherent motion De-energizing causes extend motion

Cylinder spring breaks Cylinder does not extend

Valve sticks open Cylinder continues moving or does not extend

Valve sticks closed No motion

Speed of tooling Motion too fast or slow

What is the function and the risk if that function does not occur?

19 June 2013 www.rosscontrols.com 19

Cylinder Control Basics

19 June 2013 www.rosscontrols.com 20

Double acting cylinder• Force right = pressure x cylinder area• Force left = pressure x (cylinder area – rod area)• Speed function of air supply flow rate

1

2

3

4

Cylinder Control Basics

19 June 2013 www.rosscontrols.com 21

Double acting cylinder• 4/2 spring return valve

1

2

3

4

Cylinder Control Basics

19 June 2013 www.rosscontrols.com 22

Double acting cylinder• 4/2 spring return valve

1

2

3

4

Cylinder Control Basics

19 June 2013 www.rosscontrols.com 23

Double acting cylinder• Limit flow (speed) into one end

1

2

3

4

Cylinder Control Basics

19 June 2013 www.rosscontrols.com 24

Double acting cylinder• Limit flow (speed) into both ends• Can cause jerky motion

1

2

3

4

Cylinder Control Basics

19 June 2013 www.rosscontrols.com 25

Double acting cylinder• Limit flow (speed) out of both ends• Only works with back pressure present

1

2

3

4

Cylinder Control Basics

19 June 2013 www.rosscontrols.com 26

Double acting cylinder• Limit flow (speed) out of both ends• Limits flow (speed) into cylinder after lockout

Cylinder Control BasicsDouble acting cylinder risk assessment (4/2 spring return)

Risk Result

Inherent motion De-energizing causes return motion

Valve sticks open Cylinder continues moving or does not return

Valve sticks closed No motion

Speed of tooling Motion too fast or slow

Reapplication of air Rapid motion could result after lockout

19 June 2013 www.rosscontrols.com 27

1

2

3

4 Power

19 June 2013 www.rosscontrols.com 28

Cylinder Control BasicsDouble acting cylinder• 4/2 detented valve

1

2

3

4Power

Cylinder Control BasicsDouble acting cylinder• 4/2 detented valve

19 June 2013 www.rosscontrols.com 29

Double‐Acting Cylinder Retracted

1

2

3

4

Jam Example

UNEXPECTED MOVEMENT

JamPinched

Cylinder Control Basics

19 June 2013 www.rosscontrols.com 30

Cylinder Control BasicsDouble acting cylinder risk assessment (4/2 detented)

Risk Result

Inherent motion Motion does not stop until stroke completed

Valve sticks Cylinder continues moving or does not return

Pressurized cylinder Rapid motion after jam cleared

Speed of tooling Motion too fast or slow

Reapplication of air Rapid motion could result after lockout

19 June 2013 www.rosscontrols.com 31

1 35

24

24

1 35

241 35

5/3 Closed Center

5/3 Open Center

5/3 Power Center

Cylinder Control Basics5/3 directional control valves

19 June 2013 www.rosscontrols.com 32

1 35

24

Cylinder Control Basics5/3 Closed Center

Risk Result

Valve sticks Cylinder continues moving or does not return

Trapped pressure Must be addressed

Trapped pressure Rod side has less force

Center position untested Normal operation may not use center function that is depended on for the safety function

Rapid motion Will result after lockout, if trapped pressureremoved

Speed of tooling Motion too fast or slow

19 June 2013 www.rosscontrols.com 33

Cylinder Control Basics5/3 Open Center

19 June 2013 www.rosscontrols.com 34

24

1 35

Risk Result

Valve sticks Cylinder continues moving or does not return

Inertia & gravity Cylinder continues moving

Center position untested Normal operation may not use center function that is depended on for the safety function

Rapid motion Will result after lockout, if trapped pressureremoved

Speed of tooling Motion too fast or slow

Cylinder Control Basics5/3 Power Center

19 June 2013 www.rosscontrols.com 351 35

24

Risk Result

Valve sticks Cylinder continues moving or does not return

Trapped pressure Must be addressed

Trapped pressure Rod side has less force

Center position untested Normal operation may not use center function that is depended on for the safety function

Rapid motion Will result after lockout, if trapped pressureremoved

Speed of tooling Motion too fast or slow

19 June 2013 www.rosscontrols.com 36

Cylinder Control BasicsRodless cylinder• Equal force on each side of the piston

19 June 2013 www.rosscontrols.com 37

Cylinder Control BasicsLoad Holding - Pilot Operated Check• Traps pressure in the cylinder for load holding• Removal of trapped pressure

• Automatic• Manual

19 June 2013 www.rosscontrols.com 38

Cylinder Control BasicsLoad Holding - Pilot Operated Check

Risk Result

Control Valve sticks Cylinder continues moving or does not return; pilot operated check non-functional

Trapped pressure Must be addressed

Load Holding

Cylinder brakes are applied by removing the air pressure Rod brake – stops a moving load

Rod lock – holds load in placeHazard

Direction

19 June 2013 www.rosscontrols.com 39

Cylinder Control Basics

Perform a risk assessment• Pneumatics is one of the energy sources• Must consider:

• Failure modes• Foreseeable misuse

Safety Control Basics

19 June 2013 www.rosscontrols.com 40

Two primary desired results:

1. Remove fluid power pressure to prevent movement and a hazard (remove motive force)

2. Trap fluid power to prevent movement and a hazard or use mechanical means

Safety Control Basics

19 June 2013 www.rosscontrols.com 41

Fluid Power Exhaust Circuit

19 June 2013 www.rosscontrols.com 42

•What is considered severe?

• Per EN 13736 & B11.2 there is a risk of injury if:Force > 150 N (33.8 lbf)Weight of tooling > 15 kg (33 lbs)

• Requires redundancy and/or monitored restraint

Safety Control Basics

Bore " Area Force (100) Force (80)

0.313 0.0767 7.7 6.1

0.438 0.1503 15.0 12.0

0.563 0.2485 24.9 19.9

0.750 0.4418 44.2 35.3

0.875 0.6013 60.1 48.1

1.063 0.8866 88.7 70.919 June 2013 www.rosscontrols.com 43

5/2 CROSSMIRROR Dual crossflow spool valve Faults to known output condition Check valve on inlet Fault indicator

Cylinder Return Function

19 June 2013 www.rosscontrols.com 44

Hoze Failure• Senses hose failure & reduces flow to a safe level• Prevents hose whip injury & damage

EU 983-1996/5.3.4.3.2 requires all hoses tubing to be guarded or protected in case of failure

30 CFR 56.13021 & 57.03021 US Mine Safety & Health Administration requires guarding or protection on all hoses ¾” or larger

ANSI GSR - 2008 7.11 Machine design shall minimize potential hazards from: Sudden hazardous movement of a hose resulting from leakage or component failure

19 June 2013 www.rosscontrols.com 45

What can be done to address pneumatic hazards?

Remove the motive force – exhaust down stream air

Selectively trap pressure if needed Provide way to remove pressure

Use mechanical devices when required

Maintain the Control Integrity of the safety system

Safety Valves

19 June 2013 www.rosscontrols.com 46

Pneumatic Cylinder Control Safety

Eric Cummings – ROSS CONTROLSGlobal Industry Manager - SafetyEric.cummings@rosscontrols.com

803-622-1161

19 June 2013 www.rosscontrols.com 47