Transcript 3.5.12 CETP Instructor PowerPoint Template

3.5.12
Reducing Cargo Tank Vapor Pressure Using
a Plant Compressor
In order to use compressor to unload transports and recover
the vapor left in the cargo tank, it is important to understand
the process of reducing vapor pressure.
In this module you will identify:
(1) U.S. DOT regulations pertaining to unloading operations and
attendance requirements
(2) Reasons for reducing cargo tank pressure
(3) Procedures for recovering propane vapor using the bulk
plant compressor
3.5.12 Student Book  © 2004 Propane Education & Research Council
Page 1
DOT Regulations Pertaining to Unloading Operations
U.S. Department of Transportation regulations require
that qualified persons be “in attendance” throughout the
process of loading a cargo tank motor vehicle.
The person who is responsible for loading the cargo tank is also
responsible for ensuring that it is so attended.
A person is “qualified” if he/she
• has been made aware of the nature of the hazardous
material
• has been instructed on the procedures to be followed in
emergencies
• is authorized to move the cargo tank
• has the means to do so .
3.5.12 Student Book  © 2004 Propane Education & Research Council
Page 1
DOT Regulations Pertaining to Unloading Operations
3. The qualified person attending the unloading operation
must remain within 25 feet of the cargo tank when the
internal self-closing stop valve is open.
4. The qualified person attending the unloading operation
must have an unobstructed view of the cargo tank and
delivery hose to the maximum extent practicable,
except during short periods when it is necessary to
activate controls or monitor the receiving container.
5. When unloading the transport cargo tank using the
plant compressor, the vehicle engine must not be
running during the unloading operation.
3.5.12 Student Book  © 2004 Propane Education & Research Council
Page 1 & 2
DOT Regulations Pertaining to Unloading Operations
6. The cargo tank must be equipped with a passive
emergency discharge control system no later than the
cargo tank’s first pressure test scheduled after July 1,
2001. After that date it must have a means to
automatically shut off the flow of product without the
need for human intervention within 20 seconds of an
unintentional release caused by a complete separation
of a liquid delivery hose (passive shut-down capability).
3.5.12 Student Book  © 2004 Propane Education & Research Council
Page 2
Reasons for Reducing Cargo Tank Pressure
Tank Car or Cargo
Tank
Pressure, psig
33,000 Gal. Cap
Tank Car—Gal. of
LP-gas
10,600 Gal. Cap
Cargo Tank—
Gal. of LP-gas
175
1170
375
150
970
310
125
770
246
100
570
182
75
370
118
50
170
54
Figure 1. Vapor Left in a Railroad Tank Car or Transport Cargo Tank
Expressed in Gallons of Liquid LP-Gas
3.5.12 Student Book  © 2004 Propane Education & Research Council
Page 2
Reasons for Reducing Cargo Tank Pressure
Figure 2. Propane Evacuation Time
for a 33,000 Water Gallon Tank Car
3.5.12 Student Book  © 2004 Propane Education & Research Council
Page 3
Reasons for Reducing Cargo Tank Pressure
It is not economical, however, to operate the compressor for
the time required to recover the maximum possible amount of
propane. To do so requires expense of unloading attendant
time, electricity, and wear and tear on the compressor.
More than half of economically recoverable vapor is removed
in the first hour of compressor operation. For that reason,
many common carriers and propane marketers who operate
company-owned transports, limit the vapor recovery time.
3.5.12 Student Book  © 2004 Propane Education & Research Council
Page 3
Vapor Recovery Procedures
Plant vapor compressors are used in unloading operations for
the following reasons:
1. It saves time and eliminates the hazards associated with
using the transport unloading pump.
2. It allows for recovery of some of the propane that remains in
cargo tanks after the liquid has been unloaded.
3. It prepares the cargo tank for inspections, maintenance, or
repairs.
3.5.12 Student Book  © 2004 Propane Education & Research Council
Page 3
Vapor Recovery Procedures
Step 1:
Position the transport at the unloading bulkhead
connected to a compressor.
Step 2:
Examine the plant piping and flow control valves
to determine how vapor will move from the cargo
tank to the suction side of the compressor and
into the liquid section of the bulk storage tanks.
3.5.12 Student Book  © 2004 Propane Education & Research Council
Page 4
Vapor Recovery Procedures
Figure 3. Typical Plant Compressor
3.5.12 Student Book  © 2004 Propane Education & Research Council
Page 4
Vapor Recovery Procedures
S
TO
RAG
E
TANK
CO
M
P
R
DIS
CHA
LIQ
UIDTRAP
(S
UCTIO
N)
Figure 4. 4-Way Valve
Vapor Flow—Position One
Page 4
CARG
OTANK
3.5.12 Student Book  © 2004 Propane Education & Research Council
Vapor Recovery Procedures
Figure 5. Compressor and Bulk Plant Connections and Valves
3.5.12 Student Book  © 2004 Propane Education & Research Council
Page 5
Vapor Recovery Procedures
Operation of Valves for
Cargo Tank Unloading
4-Way Valve
Position Two
Valve A
Closed
Valve B
Open
Valve C
Open
Figures 6 & 7. 4-Way Valve & Piping Valve Positions
3.5.12 Student Book  © 2004 Propane Education & Research Council
Page 5
Vapor Recovery Procedures
Step 3:
Check the Liquid Level Gauges on the Storage
Tank(s).
Step 4:
Connect the Bulkhead Vapor Hose to the Cargo
Tank (if not already connected for liquid
unloading).
Step 5:
Inspect the compressor and check the crankcase
oil level in the sight glass or by using the dipstick.
Step 6:
Open the vent on the compressor’s liquid trap, if
so equipped, or if not, verify that liquid is not
present in the vapor hose and suction line.
3.5.12 Student Book  © 2004 Propane Education & Research Council
Page 5 - 7
Vapor Recovery Procedures
Step 7:
Verify that the 4-way valve is in the proper
position for unloading the cargo tank. Check all
in-line valves and bulk tank valves for proper
open or closed position.
Step 8:
Ensure that all shutoff valves are open in the
vapor hose and cargo tank connection.
Step 9:
Start the compressor in accordance with
manufacturer's instructions.
3.5.12 Student Book  © 2004 Propane Education & Research Council
Page 7
Vapor Recovery Procedures
Step 10:
Closely monitor the cargo tank, compressor and
receiving tank(s), ready to stop the compressor if
any abnormal operating condition is noticed.
Stop the compressor when the cargo tank
pressure is reduced to the desired reading or the
time allowed for vapor recovery has elapsed
Step 11:
Close all valves in the transfer hose and on the
cargo tank.
Step 12:
Close all valves in both the suction and
discharge vapor piping circuits. Close the
ESV(s) at the transfer bulkhead, and the
appropriate liquid and vapor valves in the bulk
storage tank(s), if applicable.
3.5.12 Student Book  © 2004 Propane Education & Research Council
Page 7
Vapor Recovery Procedures
Step 13:
Disconnect the Transfer Hose and Prepare the
Transport for Travel.
If for any reason the transfer operation is interrupted,
or the attendant must leave the area, the compressor
must
be
shutdown
and
transfer
hoses
disconnected as outlined in step 13. DO NOT leave
transfer hoses connected to a cargo tank while
unattended by a qualified person.
3.5.12 Student Book  © 2004 Propane Education & Research Council
Page 7 & 8
Time to See If You Got the Key Points of
This Module…
• Complete the Review on page 9 & 10.
• See if you are ready for the Certification
Exam by checking off the
performance criteria on page 11 &
12.
3.5.12 Student Book  © 2004 Propane Education & Research Council
Pages 9 - 12