BCIT: Millwright Level 3 (Hydraulics: Accessories 1)

How can hydraulic fluid that comes in contact with your skin for prolonged periods harm you?

Hydraulic fluid can be harmful if it comes in contact with your skin for prolonged periods because it may cause cancer.

How can a pinhole hydraulic leak harm you?

A pinhole hydraulic leak can cause an injection injury due to the high pressure of the fluid.

Why should a dynamic seal have some leakage?

A dynamic seal should have some leakage to provide lubrication for the seal and the shaft.

What condition must the surfaces of a metal-to-metal seal be in before assembly?

The surfaces of a metal-to-metal seal must be flat and free of impurities before assembly.

What tightening pattern must you use to avoid distortion when bolting rectangular surfaces together?

A spiral tightening pattern must be used to avoid distortion when bolting rectangular surfaces together.

How can you determine the correct torque value when you assemble a hydraulic component?

The correct torque value is determined using a torque wrench and the component’s service manual.

What is the main purpose of a backup ring for an O-ring?

A backup ring protects the O-ring from stretching and extrusion under pressure.

What type of sealant should you use on tapered pipe threads in hydraulics?

Liquid sealant should be used on tapered pipe threads in hydraulic systems.

Which O-ring should have the tightest fit?

A static O-ring should have the tightest fit.

What type of piston rings should you use when no cylinder creep can be tolerated?

Non-metallic piston rings should be used when no cylinder creep is allowed.

How can you keep the contaminants in new oil out of a hydraulic system?

Contaminants in new oil can be kept out of a hydraulic system by using a filter.

How can you minimize contamination due to assembly of pipe joints?

Contamination can be minimized during assembly by using straight-thread or O-ring boss (ORB) fittings.

At which three (3) points can contaminants get into a hydraulic system?

Contaminants can enter a hydraulic system from new oil, rod or shaft seals, and loose fittings.

List three (3) ways in which components can generate contaminants.

Components generate contaminants through erosion, cavitation, and aeration.

What information does the code 18/16/14 give you?

The code 18/16/14 indicates that in a particle test there are 18 particles larger than 2 microns, 16 particles larger than 5 microns, and 14 particles larger than 15 microns.

List three (3) factors that require a higher cleanliness level.

A higher cleanliness level is required for non-petroleum fluids, systems with shock loads, and applications where safety is critical.

List three (3) things you can do to meet target cleanliness levels.

Target cleanliness levels can be maintained by ensuring fittings are tight, repairing leaks as soon as possible, and changing the fluid before system breakdown.

What is the most convenient way to find out if you have achieved a target cleanliness level?

A portable particle counter is the most convenient way to verify that a target cleanliness level has been achieved.

Why should you use a strainer instead of a filter on the pump inlet?

A strainer should be used on the pump inlet because it provides less flow resistance than a full filter.

What is the purpose of a bypass on a filter?

The purpose of a bypass on a filter is to prevent collapse of the filter if the pressure drop becomes too high.

How can you tell when a filter needs to be changed?

A filter needs to be changed when the pressure drop across the filter causes the bypass to operate.

What is the best choice of filter for a hydraulic system?

A depth-type filter is the best choice for a hydraulic system.

What are the four (4) locations for filters in a hydraulic system?

Filters in a hydraulic system are typically located in the return line, at the pump inlet or outlet, and off-line.

With respect to position, which type of filter is required for a pressure-compensated pump that frequently runs on standby?

An off-line filter is required for a pressure-compensated pump that frequently runs on standby.

Why is an off-line filter more efficient than a pressure line filter?

An off-line filter is more efficient because it operates without pressure pulsations.

Which type of filter is recommended for the reservoir breather?

A 3-micron filter is recommended for the reservoir breather.

What information does β₅ = 10 give you?

β₅ = 10 indicates that the filter is 90% efficient at capturing 5-micron particles.

Besides efficiency, which four (4)other specifications are needed when selecting filters?

Other filter specifications include flow capacity, contaminant-holding capacity, pressure rating, and fluid compatibility.

Name the two (2) main reasons for eliminating leaks in a hydraulic system.

Leaks in a hydraulic system must be eliminated for safety and to prevent catastrophic failure.

Above what temperature can you expect petroleum-based hydraulic fluid to ignite?

Petroleum-based hydraulic fluid can ignite at temperatures above 250°C.

How can minor leaks cause serious damage to a hydraulic system?

Minor leaks can allow contaminants to enter, causing serious system damage.

Name two (2) major classes of seals used in rotary pumps.

The two major classes of seals in rotary pumps are dynamic seals and static seals.

Should a valve poppet form a positive or a non-positive seal with its seat?

A valve poppet should form a positive seal with its seat.

How far should a static O-ring protrude above the groove?

A static O-ring should protrude approximately 10% of its diameter above the groove.

Which tool should you use to remove an O-ring?

An O-ring pick should be used to remove an O-ring.

When you install a high-pressure lip seal on a shaft with a shoulder, what must you use to protect the lip from damage?

A thimble must be used to protect the lip of the seal from damage.

Why is it very important for the rod seals in a cylinder to be in good condition?

Rod seals must be in good condition to prevent contaminants from entering the cylinder.

Is new oil clean enough to use in a hydraulic system or does it have to be filtered before you install it?

New oil must be filtered before it is used in a hydraulic system.

What is a major source of built-in contamination?

Tapered threads are a major source of built-in contamination.

What causes generated contamination?

Generated contamination is caused by moving parts in the system.

What three particle sizes are measured for ISO contamination level specifications?

ISO contamination levels are measured for 2-micron, 5-micron, and 15-micron particles.

Which type of fluid requires the highest cleanliness level, petroleum-based fluids or non-petroleum-based fluids?

Non-petroleum-based fluids require the highest cleanliness level.

Which type of pump requires an off-line filter?

A pressure-compensated pump requires an off-line filter.

Which filter in the system has to be rated at the relief pressure of the system?

The pressure line filter must be rated at the system relief pressure.

Which filter is best for the breather on a reservoir?

A 3-micron filter with a breather is best for the reservoir.