3.4.2 Student Book © 2004 Propane Education & Research CouncilPage 1 3.4.2 Types and Functions of Valves and Fittings Used in Bulk Plant Containers and

3.4.2 Student Book © 2004 Propane Education & Research Council Page 1

3.4.2

Types and Functions of Valves and Fittings Used in Bulk Plant Containers and Piping Systems

Controlling the flow of propane in a transfer system requires a variety of valves, fittings, and other devices.

In this module you will learn to identify:

(1) Piping system rejection criteria

(2) Manual shut-off valves

(3) In-line automatic check valves

(4) Flow monitors

(5) Internal valves


Identifying Piping System Rejection Criteria

PIPING SYSTEM REJECTION CRITERIA

Plant operators should not conduct bulk plant transfer operations with a piping system found to have any condition identified below for loading or unloading liquefied compressed gases.

1. Any external leak identifiable without the use of instruments

2. Bolts that are loose, missing or severely corroded

3. Manual stop valves that will not actuate

4. Rubber hose connectors with any condition outlined in the hose rejection criteria shown later in this section

5. Stainless steel flexible connectors with damaged reinforcement braid

6. Internal valves that fail to close or that permit leakage through the valve detectable without the use of instruments

7. Pipes or joints that are severely corroded


Identifying Manual Shut-Off Valves

Manual shut-off valves are used to control the flow of propane through pumps, compressors, meters, and to reroute liquid or vapor through different sections of piping. Manual shut-off valves found in propane transfer systems include:

• Globe valves

• Angle valves

• Ball valves

• Gate valves

Manual shut-off valves are sometimes fitted with a hydrostatic relief valve to protect the system from excess pressure when liquid becomes trapped between two shut-off valves.



Globe Valves

Courtesy of Fisher Controls Co

Figure 1. Globe Valve



Angle Valves

Courtesy of Fisher Controls Co

Figure 2. Angle Valve



“Snap-Acting” Globe Valves

Courtesy of Rego Co

Figure 3. Snap Acting Valves



Ball Valves— A ball valve typically consists of a brass or stainless steel ball with a hole through it and one or two valve seats. When the valve is opened, the ball is rotated so the hole through the ball lines up directly with the valve inlet and outlet. This straight-through design provides minimum restriction to the flow of

propane through the valve.

Courtesy of Jomar International

Figure 4. Ball Valve



Gate Valves— are designed to be fully open to allow straight, full, and free flow of propane or fully closed to allow no flow at all.

Courtesy of Maxon Corp.

Figure 6. Gate Valve



Maintaining Manual Shut-Off Valves

• Valve stem or operator shaft leaks• Check for loose or missing handwheels or levers • Hydrostatic relief valves-- be sure the valve outlet is clear of debris,

trash, and paint; replace the rain cap if it is missing


Identifying In-Line Automatic Check Valves

Types of In-Line Automatic Check Valves

• Back flow check valves including emergency shutdown valves (ESVs)

• Excess flow check valves



Back Flow Check Valves— allow the flow of propane in only one direction

through the transfer system.

Figure 7. Swing-Away Check Valve

Courtesy of Fisher Controls Co.



Back Flow Check Valves— allow the flow of propane in only one direction

through the transfer system.

Figure 8. Back Flow Check Valve




Excess Flow Check Valves — Unlike the back check valves, excess flow valves allow propane to flow in either direction through the valve.

Figure 9. Excess Flow Check Valve




Maintaining Check Valves

• It is recommended that periodic tests be safely conducted on check valves to ensure proper operation.

• Frequent checks for propane leakage must also be made around the valve body seams and valve connections.

• Re-check the capacity of the excess flow valve before replacing piping with a different size or adding additional components such as valves, fittings, or increasing pipe length.

• Any test of an excess flow valve will not prove that the valve will close in an emergency situation.

• Remember the limitations of excess flow valves. Depend on them only for the protection they are designed to provide and no more.


Identifying Commonly Used Flow Monitors

Flow Monitors— are installed in certain transfer lines to give a visual indication

that liquid is passing through a liquid line. Typical applications include:

• Railcar unloading lines

• Manual bypass lines

• Transport unloading lines

• Bobtail loading lines

The most common flow monitors used in propane networks are:

• sight glasses

• flow indicators.



Sight Glass (Back Check Valve)

Figure 10. Sight Glass

Courtesy of Rego Co.



Flow Indicators

Figure 11. Flag Flow Indicator

Courtesy of Rochester Gauges, Inc.

Figure 12. Back Check with Built-in Flow Indicator




Maintaining Flow Monitors

• Regardless of the type of indicator used, it must be checked frequently during any transfer operation to ensure that propane is passing through the line.

• All connections, pointers, and body seams should also be checked frequently for propane leakage.

• Pointers on flow indicators should be checked to ensure they are intact and move properly.

• A sight glass should be kept clean so that the product flow is easy to see.


Identifying Internal Valves

Excess Flow Check Valves— are not positive shut-off devices. The primary difference between the excess flow valve and the internal valve is the static condition of the valves. Excess flow valves remain open at all times, except during liquid transfer operations (in situations when flow exceeds the rating of the valve).


Figure 13. Internal Valves



Manually Operated Internal Valves (Spring-Loaded Internal Valves)

The manually operated internal valve combines the features of a manual shutoff valve with an automatic excess flow valve function.

Courtesy of Rego Co.

Figure 14. Internal Valve Operation



Manually Operated Internal Valves (Spring-Loaded Internal Valves)

Internal valves may be closed manually in a number of ways:

• manually at the installed location

• from a remote location with a cable or air actuated system

• by the fusible link in the cable or air line in the event of fire

NFPA 58 and U.S. DOT regulations require that all cargo tank liquid discharge connections be equipped with internal valves that remain closed except during the actual transfer operations.



Actuator for Manually Operated Valves


Figure 15. Actuator with a Cable Operated Fusible Link



Actuator for Manually Operated Valves


Figure 16. Latch/Remote Release Mechanism



Pneumatic Actuator for Manually Operated Valves— Internal valves can also be fitted with an air cylinder that permits the valve to be opened

and closed pneumatically from a remote station.


Figure 17. Air Cylinder Operators



Manually Operated Valves

Figure 18. Closing Flow Rates of Manual Operated Internal Valves

Typical Closing Rates of Manually Operated

Internal Valves (Full Coupling

Connection Connection

Size Liquid, gpm at 25 psi at 100 psi

1¼ inch 50 9,700 16,000

2 inch 90 31,950 54,500

3 Inch 325 — —

4 inch 800 — —

3.4.2 Student Book © 2004 Propane Education & Research Council Pages 16 - 17


Testing Spring-Loaded Internal Valves

• Testing Excess Flow Feature*

• Tight Shut-Off Test

*NOTE:A break or leak downstream of an excess flow valve that does not allow a flow equal to or greater than the valve's excess flow rating, will not actuate the excess flow valve, and will result in an uncontrolled release of product. After the excess flow valve closes, the leakage through the equalizing hole must be controlled or a hazard can be created. For this reason, the Operator must be familiar with the closure controls for the internal valve and close the internal valve immediately.



Maintenance of Internal Valves— Frequent cleaning of the sensing line filter can prevent clogging the orifice that bleeds off the pressure under the pilot stem or diaphragm to allow the valve to close.

• Manufacturer's literature details the recommended procedures for maintenance and repair

• Internal valves should be inspected frequently for gas leakage at all body seams and the connections to the pump and tank.

• Operating cables should also be checked frequently. Also check the fusible links

• Check pneumatic hydraulic operators for proper operation.

3.4.2 Student Book © 2004 Propane Education & Research Council Pages 19 & 21

Time to See If You Got the Key Points of This Module…

• Complete the Review on pages 19 & 20.

• See if you are ready for the Certification Exam by checking off the performance criteria on page 21.

Documents

3.4.2 Student Book © 2004 Propane Education & Research CouncilPage 1 3.4.2 Types and Functions of Valves and Fittings Used in Bulk Plant Containers and