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2024 Gas > Regulators > Flashcards

Regulators Flashcards

1
Q

What is a common misconception about regulators?

A

‘A regulator is a regulator’ is misleading.

Many consumers believe all regulators function the same, which is not true.

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2
Q

What happens if the wrong kind of regulator is installed?

A

It will generally render a gas system inoperable.

Installing an improper or faulty regulator can create severe hazards.

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3
Q

What are the two main purposes of gas regulators?

A
  • To reduce the supply pressure to a safe operating pressure for the building or connected appliance(s)
  • To maintain a constant downstream pressure, regardless of changes in gas flow or upstream pressure.
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4
Q

What can happen if a gas appliance receives too much fuel?

A

It will overfire.

This means the appliance overheats and does not perform safely or according to its design specifications.

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5
Q

What does underfiring mean in the context of gas appliances?

A

The appliance will not produce enough heat to operate economically nor will it perform to its design standards.

This occurs when there is insufficient fuel due to a lack of pressure.

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6
Q

What are the three main classifications for gas pressure regulators?

A
  • Service regulators
  • Line pressure regulators
  • Appliance regulators.
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7
Q

Where are service regulators typically used?

A

On the natural gas service line to a building at the gas meter.

They reduce the service pressure to the desired building pressure.

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8
Q

True or False: Regulators can be acquired from any source without concerns.

A

False.

Acquiring a regulator from unverified sources may lead to wasted money and safety hazards.

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9
Q

Fill in the blank: If a gas appliance receives excessive pressure, it will _______.

A

overfire.

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10
Q

Fill in the blank: If a gas appliance receives insufficient pressure, it will _______.

A

underfire.

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11
Q

What is a pilot-operated regulator?

A

A high-capacity, direct-operated regulator with a second, sensitive, direct-operated ‘pilot’ regulator attached.

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12
Q

Where are pilot-operated regulators typically used?

A

In commercial, institutional, and industrial buildings.

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13
Q

What is the primary function of a direct-operated service regulator?

A

To supply an automatic adjustment of flow to meet downstream gas demand.

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14
Q

How is a direct-operated regulator defined?

A

As any self-contained valve and actuator combination that opens and closes in direct response to changes in downstream pressure.

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15
Q

Do direct-operated regulators require a power source for their operation?

A

No.

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16
Q

Fill in the blank: A pilot-operated regulator is a _______ regulator.

A

[high-capacity, direct-operated]

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17
Q

True or False: Direct-operated service regulators are only found in residential applications.

A

False.

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18
Q

What type of buildings primarily use pilot-operated regulators?

A

Commercial, institutional, and industrial buildings.

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19
Q

List the components that make up a direct-operated regulator.

A
  • Valve
  • Actuator
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20
Q

What is the lockup pressure in a regulator?

A

The downstream pressure that rises above the setpoint, forcing the valve disk against the tapered edge of the orifice.

Lockup pressure ensures that the regulator closes tightly.

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21
Q

How is the accuracy of a regulator determined?

A

By the amount of flow it can pass for a given amount of droop; the closer the regulator pressure is to the setpoint, the more accurate it is.

Droop refers to the decrease in pressure from the setpoint under load.

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22
Q

What are the four main factors affecting droop?

A
  • Spring Rate
  • Sensitivity of the spring
  • Downstream pressure range
  • Design of the regulator

Each factor plays a role in how closely the regulator can maintain the setpoint under varying conditions.

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23
Q

Define spring rate in the context of a regulator.

A

The amount of force required to compress the spring one inch.

A spring with a higher rate requires more force for the same compression compared to a spring with a lower rate.

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24
Q

What effect does a lighter spring have on droop?

A

It is more sensitive to changes in downstream pressure, causing less droop and more accurate pressure control.

This is important for applications requiring precise pressure management.

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25
Q

For a downstream pressure of 10 inches water column, which spring range is more accurate?

A

A spring with a pressure range of 6 - 12 in. w.c. is more accurate than one with a range of 10 - 16 in. w.c.

The accuracy is tied to how closely the spring range aligns with the operating pressure.

26
Q

True or False: A spring with a higher pressure range will always provide better accuracy.

A

False

Accuracy is influenced by how well the spring rate and pressure range match the actual operating conditions.

27
Q

Fill in the blank: The accuracy of a regulator is primarily affected by _______.

A

[droop]

Droop is influenced by various factors including spring rate and downstream pressure.

28
Q

What controls the flow rate through a regulator?

A

Orifice size and the pressure difference on either side of the orifice

The flow rate increases when the valve disk moves away from the valve seat, but only to a certain limit.

29
Q

What happens to the flow rate when the regulator’s restricting element is fully open?

A

The pressure drop across the orifice will increase with very little increase in flow rate

This phenomenon is illustrated in the pressure fall-off figure.

30
Q

What is the relationship between pressure drop and regulator accuracy?

A

The greater the difference in pressure between inlet and outlet, the more difficult it is for the regulator to maintain accuracy

This is why propane systems typically use two regulators.

31
Q

According to CSA B149.1 code, what is required for all permanent installations involving propane?

A

Two stage reduction

This code mandates that the pressure between the first and second stage regulator shall not exceed 10 Psig.

32
Q

What is the maximum pressure allowed between the first and second stage regulator according to CSA B149.1?

A

10 Psig

This is a requirement for all permanent propane installations.

33
Q

Fill in the blank: The flow rate through a regulator is controlled by the _______ size.

A

orifice

34
Q

True or False: The flow rate will continue to increase indefinitely as the valve disk moves away from the valve seat.

A

False

The flow rate increases only up to a certain point before it stabilizes.

35
Q

What is the significance of using two regulators in propane systems?

A

To maintain accuracy and manage pressure drop

This helps in achieving stable operation and compliance with safety codes.

36
Q

What is the effect of using a larger orifice in service and line pressure regulators?

A

It allows the valve disk to travel less distance to deliver the required flow rate, reducing droop.

Droop refers to the decrease in pressure at the outlet of the regulator as the flow rate increases.

37
Q

What happens when an orifice is oversized in a regulator?

A

It can cause instability and sensitivity to fluctuating pressures, leading to cycling.

Cycling occurs when the valve disk opens and closes repeatedly due to rapid changes in downstream pressure.

38
Q

Define cycling in the context of pressure regulators.

A

The tendency for the valve disk to open and close repeatedly due to fluctuating pressures.

This is exacerbated by larger volumes of gas flowing through the regulator.

39
Q

What is the bathtub stopper effect in regulators?

A

It occurs when the valve disk is pulled into the seat, stopping flow due to fluid forces when the orifice is oversized.

This effect is named for the way a bathtub stopper functions, where minimal movement stops the flow.

40
Q

What is the impact of a larger orifice on lockup pressure?

A

It requires a higher lockup pressure to force the disk into the seat.

Lockup pressure is the pressure at which the regulator stops the flow of gas.

41
Q

How does an oversized orifice affect the wear of valve components?

A

It typically produces faster wear on the valve disk and orifice due to the disk being close to the seat.

As flow rates increase, the wear on these components also increases.

42
Q

When selecting an orifice size for a regulator, what should be prioritized?

A

Select the smallest orifice size that provides the required flow rate, largest practical diaphragm, and lightest spring rate.

This approach ensures optimal regulator performance.

43
Q

True or False: A larger orifice always improves the performance of a pressure regulator.

A

False.

Oversizing can lead to instability and increased wear on components.

44
Q

What tool is commonly used to change the orifice in regulators?

A

A standard or deep socket.

This tool allows for easy adjustments to the orifice size.

45
Q

What is a Pitot tube used for in a regulator?

A

To improve regulator accuracy by measuring lower pressure areas

The Pitot tube connects the diaphragm casing with a low pressure, high velocity region within the regulator body.

46
Q

How does the Pitot tube affect the regulator’s response to downstream pressure changes?

A

It causes the regulator to respond more dramatically to changes in downstream pressure

The Pitot tube tricks the regulator into sensing a lower pressure, leading to greater adjustments.

47
Q

What happens to the pressure sensed by the Pitot tube when downstream pressure (P2) drops?

A

It may drop more significantly than the actual downstream pressure

For example, when P2 drops from 10 Psig to 9 Psig, the Pitot tube may sense a drop from 8 Psig to 6 Psig.

48
Q

What is the primary advantage of using a Pitot tube in a regulator?

A

It decreases droop

Droop refers to the decrease in pressure under the diaphragm required to move the disk for flow.

49
Q

What does the term ‘boost’ refer to in the context of using a Pitot tube?

A

When Pz increases instead of decreases under certain conditions

This occurs when the regulator with a Pitot tube does not require as low a pressure to supply the required flow.

50
Q

Fill in the blank: The pressure at the low velocity region measured by the Pitot tube is _______ than at P2 further downstream.

A

lower

This lower pressure allows for more responsive regulation.

51
Q

True or False: The Pitot tube makes the regulator less sensitive to changes in downstream pressure.

A

False

The Pitot tube increases the sensitivity of the regulator to changes in downstream pressure.

52
Q

What is the relationship between the diaphragm pressure and the flow requirement when a Pitot tube is used?

A

The diaphragm pressure must drop less to supply the required flow

This is because the Pitot tube allows for more effective regulation.

53
Q

What is a lever style regulator?

A

A variation of the simple direct-operated regulator that uses a lever to gain mechanical advantage.

54
Q

What is the primary function of a lever in lever style regulators?

A

To provide a higher shutoff force.

55
Q

What does a larger diaphragm in a regulator result in?

A

Increased sensitivity.

56
Q

What is P2 in the context of a regulator?

A

Downstream pressure.

57
Q

What does Po represent in a regulator?

A

Pressure under the diaphragm.

58
Q

What is the main advantage of lever design in regulators?

A

Increased lockup force without added cost, size, and weight.

59
Q

True or False: Lever style regulators increase sensitivity by using a larger diaphragm.

A

False.

60
Q

Fill in the blank: Lever style regulators multiply the force produced by the _______.

A

[diaphragm]

61
Q

What type of regulators are typically of the lever style?

A

Service and line pressure regulators.

62
Q

How do lever style regulators operate compared to other direct-operated regulators?

A

They operate in the same manner but use a lever for mechanical advantage.

2024 Gas (3 decks)

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