Line D ? Valve Train Components

Question 1

Define a Valve Train.

Answer 1

The combination of valves, controls, piping, and tubing of an appliance upstream from the manifold through which gas is supplied to the appliance and by which gas is controlled

Question 2

Where will you find the minimum standards for the design of fuel trains?

Answer 2

CSA B149.3, specifically annex B

Question 3

What three factors will determine the number and type of components in the valve train?

Answer 3

The appliance input, type/number of burners and gas pressure.

Question 4

When gas and another fuel are used in a dual or combination burner, a manual isolation valve shall be provided upstream of the main gas valve train components but downstream of the pilot line connection.

True / False

Answer 4

True (B149.3 6.1)

Question 5

Where will you find the symbol legend for gas valve train components?

Answer 5

Figure B.1 in CSA B149.3

Question 6

What types of valve can be used for the manual shut-off of a valve train?

Answer 6

A valve approved for use with gas, and can be a Plug, ball or eccentric type B149.1 6.18.1

Question 7

What percentage above or below regulator set pressure can we operate at, through the firing range of an appliance?

Answer 7

B149.3 4.4
10% boost (above set point)
10% droop (below set point)

Question 8

According to the B149.3, at what inlet pressure does a regulator need to be of a lockup style?

Answer 8

0.5 psig (3.5 kPa)

Question 9

Define Overpressure Protection Device:

Answer 9

A device that under abnormal conditions will act to reduce, restrict, or shut off the supply of gas flowing into a system to prevent gas pressure in that system from exceeding the rated pressure of the system components.

Question 10

What is the primary automatic valve used to start and stop the flow of gas?

Answer 10

Safety shut-off valve

Question 11

The downstream safety shutoff valve should be quick-opening, to provide smooth and reliable lighting of the burners.

True / False

Answer 11

False (B149.3 8.1.3 It should be slow-opening)

Question 12

What is the maximum closing time required for a safety shut-off valve?

Answer 12

1 second

Question 13

What is incorporated in a safety shut-off valve to make it a proof of closure switch?

Answer 13

An end switch that makes when the valve is in the closed position.

Question 14

The tightness of a SSOV closure is assumed to be good and does not need to be checked when servicing equipment.

True / False

Answer 14

False

Question 15

What components are included in a double block and bleed?

Answer 15

A double block and bleed has two SSOV and a vent valve installed between them

Question 16

Electrically, what type of automatic vent valve shall be used?

Answer 16

Normally open so that it closes when energized.

Question 17

On a 3” Valve train what size does that valve and vent line pipe need to be?

Answer 17

1 ¼”

Question 18

How shall the the safety vent valve (SVV) be wired in relation to the safety shut-off valves?

Answer 18

In parallel

Question 19

What is a valve proving system?

Answer 19

A system that proves the effective closure of safety shut-off valves by detecting leakage. It can consist of a programming unit, a measuring device, valves, and other functional assemblies.

Question 20

When is an input flow control valve required?

Answer 20

On installations where the firing rate is automatically changed

Question 21

Where is a test firing valve located?

Answer 21

Downstream of all safety shut-off valves on the valve train and as close to the burner as is practicable.

Question 22

What is the purpose of the test firing valve?

Answer 22

• The purpose of a test firing valve is to give the Technician the ability to isolate the main burner and test/adjust the other valve train components while energized and live/gasified without firing the main burner.
• The test firing valve is also used for manual control of the first main burner firing during commissioning. It gives the technician the opportunity to observe and listen to light-off under a more manual control.

Question 23

The test firing valve must not have stops in the OPEN and CLOSED positions?

True / False

Answer 23

False B149.3 6.2(d)