Pressure Regulators And Orifices Flashcards
Function Of a regulator
Reduces and maintains a set pressure while compensating for demand changes
The Restricting Element (orifice and valve plug)
The restricting element (orifice and valve plug) is the point at which the gas entering a regulator goes through the greatest restriction
What is a leak limiting device used for?
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
When is a leak limiting device used
For 2psig or lower pressures in a well ventilated space only
What two devices are used to control excess pressure?
Internal and external relief valves
How is regulator freeze up identified
By a lack of gas to the burners (slow or sluggish operation). Freeze up is initially identified by a lack of gas to burner
What does a plugged vent cause
Excessively high pressure
What position does gas valve fail in
Closed
When Venting two or more pressure regulators together
The area of the single vent line shall have an area not less than twice the area of the connected bleed vents
When venting two or more over pressure relief devices together
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)
Name the four types of pressure regulators
Service
System
Appliance
Servo
What close the valve stem
Gas pressure
Name the three elements of a regulator
The restricting element (orifice or valve stem)
The measuring element (diaphragm)
The loading element (spring or weight)
How are ball check limiting devices installed
Regulator vent to restrict the volume of gas escaping from the regulator vent in case of diaphragm rupture
Allowable leakage in event of diaphragm rupture for CH4
2.5 cubic foot per hour
Allowable leakage in event of diaphragm rupture for C3H8
1 cubic foot per hour
Ball check limiting devices restricted to
2 PSIG
Who can install and service the service regulator for natural gas
Only the utility company, usually set at 7” w.c.
upon request it can be set at higher point
System regulator is used for
Where building gas pressure is higher than what is require by the appliance. Low pressure 14” w.c or less
Appliance regulator is used for
Is found in gas valve train or appliance manifold.
Without appliance regulator, the appliance is subject to pressure fluctuation.
Servo Regulator
The most common type of appliance regulator incorporated into a combination gas valves.
Pilot operated
Two diaphragms available
Single Diaphragm, 1 Diaphragm
Self-operating regulator
Propane, First stage regulator
Maximum pressure output 10 PSI (recommended between 5-10 PSI)
Input can be as high as 200PSI
Propane, Second stage regulator
Inlet: 10PSI max
Outlet: 11” w.c
What is the second stage regulator commonly referred as
System regulator
Dual stage regulator
Dual stage regulator regulates the two stages.
By code what must be installed upstream of a regulator ?
Manual shut-off valve.
What will happen if a regulator is installed backwards
Regulator will lock up and not allow gas to pass through it.
What must you ensure when installing a regulator
Ensure that all packing material have been removed
Can regulators be by-passed
no, it must never be by-passed, and you are not allowed to install a by-pass piping line.
Regulator should be installed how and with the vent facing?
Horizontally and vents facing plane
Dual stage regulator is for permanent or temporary installation
Temporary
Maximum allowable pressure for.
One- and two-family dwelling.
commercial.
industrial
dwellings: 2 PSIG
Commercial: 20PSIG
Industrial: 65 PSI (natural gas)
Where can regulators be vented
Well, ventilated area or outside via a vent line.
What will happen if the vent supplying the regulator is restricting the flow
Problems in maintaining steady outlet pressure. (Hunting)
What must be done if a leak limiter is used on a propane system
Must be vented in a well-ventilated area such as outside.
What happen when a regulator freeze.
The operation of a regulator is stopped by moisture, freezing somewhere inside a regulator
What is a sign of a regulator freeze up
Identified by a lack of gas at the appliance burners
External freeze up
Ice that form can actually be inside the atmospheric chamber.
To prevent position the regulator in such manner that the least moisture gets in.
Inside Freeze up
Inside the gas passages of the regulator body.
Cause: possible moisture in the gas.
A regulator with a lot of frost on the exterior head and body is a good indication of an undersized regulator
Name the 4 orifices types
Plug type
Cap type
Adjustable type
pilot type
What do you need to know in order to size the orifices
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
High altitude appliance is de-rated by 10% from
2000 to 4500ft past this altitude 4% each 1000 ft
What must you do to allow discrepancies in hand drilling
You will not select the exact size, instead use a slightly smaller drill bit. Recommended is 2 sizes smaller.
What should you do when using the drill gauge
use the shank of the drill bit. range from 1 to 80
What is to be taken into consideration when clocking a meter
You must have at least 3 revolutions to prove a better accuracy
(size of proving dial/ number of seconds per rev.)*3600
