The Gates Safety Guide

Introduction to Preventive Maintenance

Unexpected industrial hose failures can lead to equipment damage, production downtime, and severe safety risks, including injury or death. Implementing a robust preventive maintenance program is crucial for ensuring operational continuity and safety.

Preventive maintenance involves:

• Scheduled hose replacement regardless of current condition.
• Early identification of potential problems before they cause failure.
• Maintaining equipment operation by preventing critical component failures.
• Ensuring the correct hose is used for each specific application.
• Replacing hoses exhibiting signs of deterioration or damage before they fail.

Benefits of a Preventive Maintenance Program

• Eliminates costly repairs.
• Reduces production downtime caused by hose failures.
• Promotes a safer work environment.
• Minimizes expenses related to EPA spill cleanups.
• Increases the overall service life of hoses.

Key Components of a Preventive Maintenance Program

Preventive Knowledge

• Proper hose selection and application understanding.
• Correct coupling selection and attachment methods.
• Adherence to maintenance and storage guidelines.
• Compliance with agency specifications.

Preventive Action

• Regular, periodic inspections.
• Hydrostatic pressure testing.
• Scheduled hose replacement.
• Proper hose storage practices.
• Effective troubleshooting techniques.

Understanding Industrial Hoses

An industrial hose is a flexible, reinforced tube designed for conveying liquids, solids, and gases. These hoses are subjected to significant wear and tear, including dragging, coiling, and pressure, making proper selection and maintenance essential for longevity, performance, and safety.

Industrial hoses serve three primary purposes:

1. Transferring materials like gases, liquids, solids, and mixtures.
2. Acting as flexible connectors to absorb surges and vibrations.
3. Protecting other hoses, pipes, and wires as a conduit.

A typical industrial hose consists of three basic elements:

• Tube: The innermost component, designed to be resistant to the specific fluid or solid being conveyed.
• Reinforcement: Provides strength to withstand working pressure and vacuum, often consisting of multiple layers of fabric, yarn, or wire.
• Cover: The outermost layer, protecting the tube and reinforcement from environmental factors like ozone, weather, abrasion, and heat.

Proper Hose Selection using STAMPED

Selecting the correct hose for the application is the first step in preventive maintenance. The STAMPED acronym serves as a guide:

• S - Size: Inside diameter (ID), outside diameter (OD), length, and flow rate requirements.
• T - Temperature: Ambient and internal temperatures, and their impact on the conveyed material.
• A - Application: Where and how the hose will be used, frequency of use, environmental conditions, special construction needs, conductivity requirements, and government or industrial standards.
• M - Material: Chemical name(s) and state (liquid, solid, gas), suitability for food, pharmaceuticals, cosmetics, or dry bulk materials.
• P - Pressure: Working pressure and maximum surge pressure, and any vacuum requirements.
• E - End: Type of end connections, quantity needed, and any special packaging or branding requirements.

For assistance with hose selection, consult the Gates Industrial Hose Catalog or contact Gates Product Application.

Proper Coupling Selection

Choosing the correct coupling is vital for hose safety and performance. Recommendations are typically found in the Gates Industrial Hose Catalog. For critical applications such as corrosive chemical transfer, LP gas, oil field drilling, petroleum products transfer, steam, and aircraft ground fueling, specific couplings are required, and substitutions should not be made without proper authorization.

Factors influencing coupling selection include attachment options, availability, cost, material compatibility, quality, and ease of handling. Always ensure the coupling end type matches the port and avoid mixing thread types.

Static Electricity Grounding

The movement of dry materials through hoses can generate hazardous static electricity. Grounding is essential to prevent sparks that could ignite fires or cause explosions, and to prevent severe shocks.

Grounding can be achieved through:

• Static conductive materials in the tube or cover.
• The bent wire method, where a helix wire is pulled out, bent, and made to contact the coupling.
• The metal staple method, where a staple is inserted to connect the static conductor or wire reinforcement to the coupling.

All grounding methods require testing for electrical continuity using an ohmmeter, with a maximum allowable resistance of 20 thousand ohms per foot of hose.

Hose Inspections

Periodic inspections are critical for ensuring hose safety and maximum performance. Inspections should occur before, during, and after use. Factors influencing inspection frequency include the criticality of the application, operating temperatures, pressures, and environmental conditions.

Level 1 Inspection (Ongoing/Daily)

Look for:

• Hose cover damage (cuts, cracks, abrasion).
• Stiffness or hardness of the hose, indicating potential cracking.
• Changes in color, suggesting chemical attack or aging.
• Cover blisters, indicating chemical incompatibility or early leakage.
• Kinked or flattened hose, restricting flow.
• Leakage, including puddles or weeping.
• Damaged hose reinforcement.

Level 2 Inspection (Requires Equipment Shutdown)

Conduct a more thorough evaluation, including:

• Visual inspection for leakage (never do this under pressure).
• Hydrostatic pressure testing (using water, never compressed gas or flammable fluids).
• Inspection of the hose tube for hardness, color change, cracks, or blisters.

Level 2 inspections should ideally occur during regular equipment shutdowns or at least every three months.

Hose Handling and Maintenance Tips

• Never exceed the rated working pressure or allow pressure spikes above the maximum.
• Avoid running over hoses with equipment or vehicles.
• Never pull a hose by its coupling; this can kink the hose and weaken the coupling bond.
• Support heavy hoses properly to prevent internal reinforcement damage.
• Avoid over-bending hoses to the point of kinking; adhere to minimum bend radius specifications.
• Protect covers exposed to excessive wear with sleeves or pads.
• Remove kinked or crushed hose from service immediately and test before reuse.
• Remove and test any hose assembly subjected to abuse.
• Visually inspect and pressure test hose at regular intervals, especially for critical applications.
• Check for fluid seepage at the coupling and remove any hose that fails inspection.

Hose Cleaning

Cleaning methods vary based on hose type, residual material, cleanliness requirements, and available facilities. Always wear appropriate protective clothing.

• Select cleaning solutions that dissolve residual material without damaging the hose assembly. Consult MSDS and Chemical Resistance Tables for compatibility.
• Flushing or immersing in a cleaning bath should not exceed the hose's maximum working pressure or temperature.
• Steam cleaning is generally not recommended due to high temperatures accelerating aging. If used, do not exceed maximum temperature ratings and never use superheated steam.
• The shuttle method for cleaning is not recommended due to potential for injury and hose damage.

For chemical and food hoses, drain after each use, flush with appropriate solutions, dispose of waste properly, and store in a clean, dry environment away from sunlight. Avoid cross-contamination by dedicating hoses to specific materials.

Hose Storage

• Store hoses in a cool, dry room with moderate humidity, ideally between 50°F and 75°F, not exceeding 100°F.
• Keep hoses out of direct sunlight and away from heat and ozone sources (e.g., arc welders, electric motors).
• Store hoses in their original shipping containers or wrapping for protection.
• Store hoses shipped straight, straight; those shipped in coils or bales should be stored horizontally.
• Use a first-in, first-out basis for storage.
• Do not hang coiled hose on hooks or stack them too high, as excessive weight can cause damage.

RMA Hydrostatic Testing Procedures

All hose and couplings should be hydrostatically tested at regular intervals, varying by hose type. The procedure involves laying the hose straight, conducting a visual inspection, and then filling it with water (never flammable fluids or compressed gas) while bleeding out air. The hose is then pressurized to the recommended level and examined for leaks or bulges.

Safety Precaution: Hose under pressure is dangerous; take necessary safety precautions.

Specialty Hose Considerations

Acid/Chemical Hose

Proper selection is critical. Use the Gates Industrial Hose Catalog's Chemical Resistance Table and Hose Finder. Ensure compatible couplings are used. Operators must wear protective clothing, monitor pressure and temperature, and never leave operating hoses unattended. Always drain and flush hoses after use, disposing of waste safely. Routine maintenance, including daily inspections and hydrostatic pressure tests every 90 days, is essential. Electrical conductivity should also be inspected.

Air Hose

Increase air hose life by avoiding oil contamination, keeping hoses away from heat sources, ensuring ferrules are not crushed, relieving excess pressure after use, and avoiding running over hoses. Reversing hose end-for-end at regular intervals distributes wear.

LPG Hose

Use only LPG hoses that meet or exceed Underwriter Laboratories Standards and use recommended, tested couplings. For natural gas, do not exceed 50 psi and ensure use in a well-ventilated environment. LPG hoses require frequent inspection and hydrostatic testing, with schedules adjusted based on usage severity.

Petroleum Hose

Use hoses suitable for the application, especially for suction or return lines requiring internal support and vacuum rating. Use only recommended couplings and attachment methods. Re-coupling used hose should only be considered in emergency situations after evaluation and testing. Periodically inspect hose assemblies for cover abrasion, cracks, cuts, and discoloration, which can indicate degradation or chemical incompatibility. Test hose assemblies at rated working pressure periodically.

Steam Hose

Steam hose failure can cause serious injury. Use steam hose exclusively for steam. Couple steam hose to a length of pipe to separate it from the steam source. Ensure an accurate pressure gauge and shut-off valve are installed. Operators must wear protective clothing and never open a steam valve when the hose is free. Always drain steam hose when not in use to prevent internal damage from absorbed water turning to steam.

RMA standards recommend pressure testing steam hose every 90 days for the first year and monthly thereafter. Tests involve visual inspection and pressurization with water to twice the maximum rated working pressure for five minutes, checking for leaks or bulges.

Troubleshooting Common Hose Problems

Many hose problems stem from misapplications. Common issues and their solutions include:

• Hose burst: Caused by exceeding working pressure or twisting during attachment. Solutions include checking system pressure, using higher-rated hoses, and employing swivel couplings.
• Hose tube swells or deteriorates: Indicates incompatibility with the conveyed material or temperature. Solutions involve identifying materials and temperatures and consulting compatibility charts or product application specialists.
• Hose tube becomes hard, cracks, and leaks: Often due to excessive heat or oxidation. Solutions include selecting hoses with higher temperature ratings and reducing system temperature or oil aeration.
• Coupling blows off: Resulting from incorrect coupling use, improper insertion, or incorrect crimping. Solutions involve checking compatibility, reviewing crimp specifications, and ensuring proper routing to avoid stress.
• Hose inner tube collapsed: Occurs when a hose is not designed for high vacuum or has poor adhesion. Use hoses designed for vacuum and check routing to avoid exceeding minimum bend radius.
• Hose flattened: Caused by twisting, kinking, or being run over. Solutions include checking routing, using swivel couplings, and employing crush-resistant hoses.
• Wire reinforcement rusts: Often due to cover damage allowing moisture ingress. Protect the hose against abrasion, check temperature and chemical compatibility, and consider pin-pricking the cover to allow gas escape.
• Hose leaks profusely without bursting: May be due to high-velocity erosion or fluid velocity. Consider a larger diameter hose to reduce velocity.
• Hose leaks or bursts, cover deteriorated: Indicates hose aging and environmental effects. Check the hose's code date and establish a maintenance replacement schedule.
• Hose tube worn through: Caused by abrasive material. Select hoses with thicker, more abrasion-resistant tubes, rotate hoses, or use larger diameter hoses to reduce velocity.
• Hose burst at end of coupling: Can be due to exceeding pressure ratings, sharp bending over the coupling, or incorrect attachment. Use higher pressure hoses, bend restrictors, and follow recommended coupling procedures.
• Hose cover blistered: May indicate incompatibility with the material being transferred or gas permeation. Select compatible hoses and consider pin-pricking the cover or using hoses with higher density tubes.
• Cover soft, gummy, discolored: Suggests incompatibility with material or temperature. Select a compatible hose cover.
• Discharge pressure/volume too low: Could be due to low pump output or hose/coupling restriction. Increase pump output, check for kinks, or increase hose/coupling diameter.