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HVAC 261 > Pressure Regulators And Orifices > Flashcards

Pressure Regulators And Orifices Flashcards

1
Q

Function Of a regulator

A

Reduces and maintains a set pressure while compensating for demand changes

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2
Q

The Restricting Element (orifice and valve plug)

A

The restricting element (orifice and valve plug) is the point at which the gas entering a regulator goes through the greatest restriction

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3
Q

What is a leak limiting device used for?

A

To limit the amount of gas escaping if the diaphragm ruptures 1 cu.ft./hr for propane and 2.5 cu ft/hr for natural gas

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4
Q

When is a leak limiting device used

A

For 2psig or lower pressures in a well ventilated space only

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5
Q

What two devices are used to control excess pressure?

A

Internal and external relief valves

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6
Q

How is regulator freeze up identified

A

By a lack of gas to the burners (slow or sluggish operation). Freeze up is initially identified by a lack of gas to burner

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7
Q

What does a plugged vent cause

A

Excessively high pressure

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8
Q

What position does gas valve fail in

A

Closed

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9
Q

When Venting two or more pressure regulators together

A

The area of the single vent line shall have an area not less than twice the area of the connected bleed vents

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10
Q

When venting two or more over pressure relief devices together

A

The area of the single vent line shall have an area equal to the largest relief opening plus 50% of the total area of the other relief valve openings (5.5.2)

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11
Q

Name the four types of pressure regulators

A

Service
System
Appliance
Servo

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12
Q

What close the valve stem

A

Gas pressure

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13
Q

Name the three elements of a regulator

A

The restricting element (orifice or valve stem)
The measuring element (diaphragm)
The loading element (spring or weight)

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14
Q

How are ball check limiting devices installed

A

Regulator vent to restrict the volume of gas escaping from the regulator vent in case of diaphragm rupture

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15
Q

Allowable leakage in event of diaphragm rupture for CH4

A

2.5 cubic foot per hour

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16
Q

Allowable leakage in event of diaphragm rupture for C3H8

A

1 cubic foot per hour

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17
Q

Ball check limiting devices restricted to

A

2 PSIG

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18
Q

Who can install and service the service regulator for natural gas

A

Only the utility company, usually set at 7” w.c.
upon request it can be set at higher point

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19
Q

System regulator is used for

A

Where building gas pressure is higher than what is require by the appliance. Low pressure 14” w.c or less

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20
Q

Appliance regulator is used for

A

Is found in gas valve train or appliance manifold.
Without appliance regulator, the appliance is subject to pressure fluctuation.

21
Q

Servo Regulator

A

The most common type of appliance regulator incorporated into a combination gas valves.

Pilot operated

22
Q

Two diaphragms available

A

Single Diaphragm, 1 Diaphragm

Self-operating regulator

23
Q

Propane, First stage regulator

A

Maximum pressure output 10 PSI (recommended between 5-10 PSI)
Input can be as high as 200PSI

24
Q

Propane, Second stage regulator

A

Inlet: 10PSI max
Outlet: 11” w.c

25
Q

What is the second stage regulator commonly referred as

A

System regulator

26
Q

Dual stage regulator

A

Dual stage regulator regulates the two stages.

27
Q

By code what must be installed upstream of a regulator ?

A

Manual shut-off valve.

28
Q

What will happen if a regulator is installed backwards

A

Regulator will lock up and not allow gas to pass through it.

29
Q

What must you ensure when installing a regulator

A

Ensure that all packing material have been removed

30
Q

Can regulators be by-passed

A

no, it must never be by-passed, and you are not allowed to install a by-pass piping line.

31
Q

Regulator should be installed how and with the vent facing?

A

Horizontally and vents facing plane

32
Q

Dual stage regulator is for permanent or temporary installation

A

Temporary

33
Q

Maximum allowable pressure for.
One- and two-family dwelling.
commercial.
industrial

A

dwellings: 2 PSIG
Commercial: 20PSIG
Industrial: 65 PSI (natural gas)

34
Q

Where can regulators be vented

A

Well, ventilated area or outside via a vent line.

35
Q

What will happen if the vent supplying the regulator is restricting the flow

A

Problems in maintaining steady outlet pressure. (Hunting)

36
Q

What must be done if a leak limiter is used on a propane system

A

Must be vented in a well-ventilated area such as outside.

37
Q

What happen when a regulator freeze.

A

The operation of a regulator is stopped by moisture, freezing somewhere inside a regulator

38
Q

What is a sign of a regulator freeze up

A

Identified by a lack of gas at the appliance burners

39
Q

External freeze up

A

Ice that form can actually be inside the atmospheric chamber.
To prevent position the regulator in such manner that the least moisture gets in.

40
Q

Inside Freeze up

A

Inside the gas passages of the regulator body.
Cause: possible moisture in the gas.

41
Q

A regulator with a lot of frost on the exterior head and body is a good indication of an undersized regulator

A
42
Q

Name the 4 orifices types

A

Plug type
Cap type
Adjustable type
pilot type

43
Q

What do you need to know in order to size the orifices

A

Altitude approved for the appliance.
Input rating
type of gas being used
numbers of orifices sharing the load
gas pressure at the manifold or orifice

44
Q

High altitude appliance is de-rated by 10% from

A

2000 to 4500ft past this altitude 4% each 1000 ft

45
Q

What must you do to allow discrepancies in hand drilling

A

You will not select the exact size, instead use a slightly smaller drill bit. Recommended is 2 sizes smaller.

46
Q

What should you do when using the drill gauge

A

use the shank of the drill bit. range from 1 to 80

47
Q

What is to be taken into consideration when clocking a meter

A

You must have at least 3 revolutions to prove a better accuracy

48
Q

(size of proving dial/ number of seconds per rev.)*3600

A
49
Q
A

HVAC 261 (3 decks)

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