Gaskets and Piping Flashcards
What are pipe blinds?
Slim discs that are placed between pipe flanges.
These are used for LOTO purposes.
What are the two types of pipe blinds mentioned in the module?
- Pancake style
- Spectacle style
These are in-line blinds, and should not be confused with flange blinds, which are used to close off the ends of piping systems.
As it pertains to piping, what are volute blinds?
Blinds that are used to seal the pump volute after removing the pump body.
What is the main disadvantage of pancake blinds vs. spectacle blinds?
Pancake blinds → the flanges have to be spread in order to remove the blind.
Vs. spectacle blinds, where the piping system is designed to accomodate the blind.
With piping blinds, a ____ blind is installed in a piping system that is designed to accomodate the blind, and doesn’t require the flanges to be spread to install it.
Spectacle blinds
How many gaskest are required for:
1. Spectacle blinds?
2. Pancake blinds?
3. Flange blinds?
- Spectacle → 2 gaskets
- Pancake → 2 gaskets
- Flange → 1 gasket
What are three hazards that need to be monitored for when purging a piping system?
- Toxic compounds
- Explosive gases
- Insufficient oxygen
Normal O₂ levels should be around 21% to 22% by volume.
What precautions need to be taken when purging a piping system with CO₂?
CO₂ forms a corrosive substance when mixed with water.
Precautions should be taken if there is a chance that this can happen.
As it pertains the gas detection, OH&S regulations require that you implement procedures to safeguard against what two things?
- Hazards related to the presence of harmful substances.
- Lack of oxygen where workers a present.
What formula is used to convert psi to in.Hg?
Pressure(in.Hg) = Pressure(psi) × 2.036
1 psi = 2.036 in.Hg
This type of gas detector is a hand-held unit that consists of a bellows-type pump and detector tubes.
Sniffer gas detector
Changing the type of detector tube changes the type of gas detected.
How do the detector tubes work in a sniffer type gas detector.
The gas will cause the reactant in the tube to change colour.
The degree of colour change indicates the concentraction levels of the gas.
This type of gas detector contains sensors, controllers and alarm indicators all in one portable unit that is designed to clip to clothing.
Personal gas detectors
These are often called sniffers
What is the %LEL of a gas?
% lower explosive limit
This is the lowest concentration of a gas or vapour that will burn in air.
What needs to be taken into consideration when mounting permanent gas detectors?
The characteristics of the gas
Heavier gas, the sensor will be mounted closer to the ground, while lighter than air results in the sensor being mounted higher up.
What are the common types of gasket joints used in industry?
- Flat face (unconfined)
- Raised face (unconfined)
- Tongue and groove (confined)
- Male and female flange (partial confinement)
- Ring joint (self-confined)
These gasket joints are essential for preventing leakage in various applications, including turbines and compressors.
What is the purpose of a gasket in a sealing application?
To fill the voids or irregularities of the joining faces of the mating parts
Gaskets are softer sealing elements that help achieve a proper seal by accommodating surface imperfections.
True or False: Practical static sealing does not depend on the smoothness of sealing surfaces.
False
Smooth sealing surfaces are crucial for effective sealing and minimizing leakage.
True or false: The ring joint is classified as self-confined.
True
Self-confined joints provide a specific sealing mechanism that does not rely on external pressure.
What machining processes can be involved in achieving sealing surfaces?
- Machining
- Grinding
- Lapping
These processes are vital to ensure the sealing surfaces are sufficiently smooth to prevent leakage.
What is meant by ‘static sealing’?
Forcing a softer sealing element to fill the voids of mating parts
This concept emphasizes the need for proper contact between the gasket and the surfaces to achieve a leak-proof seal.
What is the significance of surface smoothness in gasket applications?
Smoother surfaces seal better.
Smooth surfaces help ensure better sealing and reduce the risk of leakage.
What type of joint is the ‘tongue and groove’ classified as?
Confined
This type of joint provides a more secure fit and minimizes the chance of leakage.
Identify if the following flanges are confined/unconfined/partially confined/self/contained:
- Flat face
- Raised face
- Tongue and groove
- Male and female flange
- Ring joint
- Flat face → unconfined
- Raised face → unconfined
- Tongue and grove → confined
- Male and female flange → partial confinement
- Ring joint → self-confined
What does it mean when a flange is “confined”?
Where the gasket in the flange is located within a recess or groove.
This provides for better sealing, but makes it more difficult to replace the gasket.
What is the main difference between an O-ring (squeeze type) and a flat gasket?
The O-ring’s sealing ability increase as internal pressure increases.
With static O-ring seals, the O-ring must protude by ____% above the land in order to ensure proper sealing.
10%
A flat gaskets sealing ability is affected by what three things?
- Thickness of the gasket
- Bolt load pressure it has to withstand
- Internal and hydrostatic end forces
What are the two types of flange finishes?
- Smooth
- Serrated
What are the two types of serrated flange finishes?
- Concentric groove
- Spiral groove (phonographic)
When it comes to a serrated flange finish, what is a phonographic finish?
The same as a spiral groove.
Identify the following type of serrated flange finish:
Concentric grooved face
Identify the folloiwng type of serrated flange finish:
Spiral grooved face.
This type of gasket joint allows the gasket to flow freely, either towards or away from the fluid pressure under loading and are primarily used where system pressures are low to moderate.
Flat-faced unconfined
What can happen to a flat faced unconfined gasket joint if the system pressures are too high and the bolt loading is too light?
The gasket can blow out.
This is an unconfined gasket, so there is nothing holding it in place aside from the bolt loading.
What is the maximum pressure that a raised face unconfined gasket should be used to?
900 psi
What do the three markings on a raised face unconfined flange indicate?
- pipe size ∅
- pressure class (not pressure rating)
- ring joint groove number (if any, these may be excluded)
Identify the type of flange along with what the markings on the flange indicate:
Flange → Raised face unconfined flange
Ax3 → Trademark/company name
6” → nominal pipe size
300 → Class 300 pressure rating
Do not confuse Class 300 pressure rating as the pressure rating. Class 300 ≠ 300 psi.
With raised face flanges, a raised flange face of 1.________” is generally used for pressure classes up to 900, while a rasied flange face of 2.________” is used for pressure classes above 900.
- 1/16”
- 1/4”
This type of flange and gasket design provide the gasket no freedom to move and is considered good for high-pressure applications.
Tongue and groove confined gaskets
What is the primary purpose of a gasket:
a) To separate two flanges.
b) To form a seal between flanges and equipment housings.
c) To reduce noise in piping systems.
d) To increase bolt tension.
b) To form a seal between flanges and equipment housings.
True or false: In general, tongue and groove confined gaskets use a metallic gasket.
True
This has to do with the higher pressures seen with this type of flange.
- What is the main advantage of tongue and groove gaskets?
- What is the main disadvantage?
- They help to centre the gasket.
- They require closer tolerances and care in connecting.
What does it mean when a gasket is semi-confined?
The gasket is confined on its two flat sides and on the outside edge.
One edge (the inner) is free to move.
This design provides good support for the gasket and protection from blowout because of the confinement provided by the outside edge.
This type of flange design is basically a flange face that has grooves machined into both flanges, and is a good choice for high-pressure, high-temperature and corrosive environments.
Self-contained ring joints
This type of gaskets are compact and adapted for high-pressure, high-temperature and corrosive conditions.
Solid metal ring gaskets
Why do solid metal ring gaskets not need a high level of bolt loading to achieve a tight seal?
The ring has a wedge like shape that concentrates the sealing pressure under bolt loading.
The flanges used with this type of gasket must be harder than the gasket.
What are three common designs of solid metal ring gaskets?
- Delta seal ring
- Oval seal ring
- Octagonal seal ring gaskets
When disassembling solid metal ring gaskets, how should the flanges be moved away from each other during disassembly?
They must be pulled straight back.
This is due to the rings sitting a groove, which prohibits them from being slid out until there is enough flange separation.
Where is the greatest compressive force exerted on a gasket in a flange?
Closest to the bolt circle
What is a critical consideration when choosing a gasket material?
a) Ability to withstand UV radiation
b) Compatibility with flange and joint design
c) Color of the material
d) Weight of the gasket
b) Compatibility with flange and joint design
True or false: Gasket thickness has no effect on the alignment of internal components.
False
Changing gasket thickness can cause pipe strain.
True or false: The material of a gasket must be able to flow into irregularities of mating surfaces under bolt loading.
True
This provides the sealing ability of the gasket.
True or false: Gaskets are unaffected by temperature extremes and corrosive environments.
False
Gasket material must be compatible with the medium it is sealing.