Bottom loading arms for Liquefied gases
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      The comprehensive range of OPW Top- and Bottom loading arms for liquefied gases are designed to offer maximum flexibility and safety during (off)loading operations. Applications are found in the transfer of LPG, Gas condensate and similar media into Railcars or Tank trucks. Connections can be made at the rear, side or top. Typically consisting of a product and vapour arm the set is mounted on a stand post. A set generally consists of a 3”/dn80 product arm and 2”/dn50 vapour arm. For higher throughputs a 4”/dn100 product arm with 3”/dn80 vapour arm is available.
      Shut-off or loading valve, purge- or relief line, safety break away coupler as well as position indication and parking lock are often selected as useful options. Coupling systems to accommodate any customer standard are available.
      When not in use the unit can be folded together for convenient, compact storage away from the traffic flow.
  • Features/Benefits
  • Accessories/Options
  • Loader Library
  • Loader Tech
  • Production Specification
  • Downloads

Features and Benefits

• Dimensioned to suit customers working envelope
• Easy to handle, smooth operation
• Compact storage when not in use
• Balanced end swivel assembly for easy handling
• Swivels equipped with grease nipple
• Durable construction
• Available in 2” / dn50, 3” / dn80 , 4” / dn100 with ASA or DIN flanges
• Inverted intermediate swivel and/or inlet orientation possible
• Boom arm can be made with upwards or downwards slope
• Wide range of swivel seal material available
• Pre-balanced at the factory to minimise installation and commissioning time
• Alternative materials of construction 316/316L Stainless Steel

Accessories / Options

Hi-Level Alarm- An effective means to prevent overfilling of tank is always suggested. In many cases both a primary (metering, scale/weight) and secondary (Hi-Level Alarm on Loading Arm) may be in place.
♦ For Clear, Light Non-Viscous Materials 

♦ For Dark, Viscous Materials
   A variety of probe styles, manufacturers can be adapted to fit on your OPW Loading Arm. We have experience with most major overfill brands.

Vapor Recovery- Concern for the environment and your employees is of utmost concern. Several options are available to help retain and recover harmful vapors and avoid excessive splashing, each customized to fit your application. For more information on Vapor Recovery Solutions: Loading Systems Catalog

Heating – Loading Arms can be fully or partially jacketed for efficient handling of asphalt, molten sulfer, waxes, resins and other products that are highly viscous or tend to solidify at ambient temperatures. For more information on Heated Loading Solutions: Loading Systems Catalog

Loading Arm Insulation – OPW can provide a Custom Insulation Package designed specifically for your loading arm. Unlike field-applied insulation, these packages are completely removable and reusable, making them the ideal solution for loading arm use. 

Loading Arm Insulation Spec’s:
• Removable & Reusable
• Safer – Heated arms can pose a potential burn hazard to operators. OPW Insulation Packages ensures that the loading arm is properly insulated to protect your personnel.
• Superior Heat Retention 
• Durable 
• Construction Details:     - Inner Jacketing – 17 oz/sq. yd Teflon® Impregnated Fiberglass Cloth
    - Outer Jacketing - 17 oz/sq. yd Teflon® Impregnated Fiberglass Cloth
    - Insulation – 2” THK, low-density Fiberglass
    - Thread - Teflon®-coated Fiberglass Thread 
    - Attachments - Teflon® Cloth Belts with stainless-steel double-D rings; drawstring flaps with Nomex Cord
    - I.D. Tags – Stainless-steel embossed

Grounding/Bonding – Suggested for many top/splash loading applications. Available as an option on all Loading Arm designs. 
The electronic grounding unit MT30 allows safe loading and unloading of mobile tanks (mounted on trucks, wagons or trolleys and also big bags) in which flammable substances are poured at high speed generating electrostatic charges that can cause sparks and explosions.

Protects your equipment, piping and personnel in the event of an unintended pull-away. A consideration whenever you are making a tight connection to a truck or railcar.  

With OPW, you have many options at your disposal for your loading arm termination connections. From the original quick-disconnect Kamlok® coupling to our Epsilon™ dry disconnect coupling, we have a coupling to meet your needs. 

Vacuum Breaker
OPW Engineered Systems Vacuum Breakers permit quick, positive evacuation of the arm after the loading operation is complete. Suggested for any top load/submerged fill application. 
• Model 476SA – Aluminum with stainless steel internals, fluorocarbon seal, ½ MNPT , OPW Model 476SA-0150
•Model 489 – 316 Stainless Steel construction, metal seat, MNPT, available in ½” (OPW Model 489-0050) and 1” (OPW model 489-0060)

Lockdown- available to help insure that your loading arm stays securely in vehicle during loading operation. Several options available depending on your application. 

Deflectors – Loading arm drop tube can be provided with deflector to help minimize the risk of staic build-up and/or product foaming. Can also be used to redirect the upward pressure in order to keep the arm from attempting to rise out of tank during loading. 
463 Deflector (Cone) 
- Aluminum Construction 
- 3” & 4”, FNPT 

464 Deflector (Tee) 
- Aluminum Construction 
- 3” & 4”, FNPT 

Strainers- Loading arm drop tube can be provided with a cast aluminum suction strainer when unloading tank cars. Helps prevent scale and other foreign objects from being sucked into line.
341 Suction Strainer 
- Cast Aluminum 
- Galvanized steel screen 
- 3” & 4” FNPT 

Loading Valves
6400 Series Horizontal Valve – OPW Loading Valves are designed to shut off flow without causing shock in the pipeline.  Adjustable closure rate 
3” & 4” sizes, Aluminum Construction 
TTMA Flanged connections 
Ball Valves (per application/specification)

Pnuematic Counterbalancing – an alternative to conventional spring balanced loading arm, pneumatics provide the ultimate in loading arm design.

Loader Library

All OPW Loading Arms can be customized to fit your specific application requirements. We do offer a series of Standard/ optimized solutions that are commonly specified. These optimized selections can be expedited to meet faster delivery requirements.

• 3” Top Unloading Arm
       Ductile Iron/Carbon Steel/ Aluminum Construction
       Aluminum Load Valve
       77” x 77” x 43” Drop
With remote (B32RF-3)

Same as above in 4” (B32F-4)
       With remote (B32RF-4)

• Same as above in 6” (B32F-6)
       With remote (B32RF-6)

• 3” Top loading Arm
       Stainless Steel/PTFE Construction
       78” x 90” x 66” Drop
       60”x 60” x 60” Drop

Loader Tech

Loading Arm Velocities What size pipe do I need?

Velocity in ft/sec.


Velocity in m/sec.

GPM 2" 3" 4" 6" L/min. 2" 3" 4" 6"
100 9.6       400 3.1      
125 12       600 4.6 2.1    
150 14.3       800 6.1 2.8    
175 16.8       1000 7.7 3.5 2  
200 19.1 8.7     1250 9.6 4.4 2.5  
225 21.5 9.8     1500   5.2 3  
250 23.9 10.8     1750   6.1 3.5  
300   13 7.5   2000   7 4  
350   15.2 8.8   2250   7.9 4.5 2
400   17.4 10.1   2500   8.7 5.1 2.2
450   19.6 11.4   2750     5.6 2.4
500   21.7 12.6 5.6 3000     6.1 2.6
550   23.9 13.8 6.1 3250     6.6 2.9
600     15.1 6.6 3500     7.1 3.1
650     16.4 7.2 3750     7.6 3.3
700     17.6 7.8 4000     8.1 3.6
750     18.9 8.3 4500     9.1 4
800     20.2 8.9 5000       4.5
900     22.7 10 5500       4.9
1000       11.1 6000       5.3
1200       13.3 6500       5.8
1300       14.4 7000       6.2
1400       15.6          
1500       16.7          
1600       17.8          
1700       18.9          
1800       20          
Velocities above 15 ft./sec. (4.6 m/sec.) are generally not recommended - Bold are recommended.

Loading Arm Configurations

Production Specification



Materials of construction
Inlet swivel
Carbon steel
Intermediate swivel
Carbon steel
End swivel assembly
Carbon Steel
Swivel seals
Buna, EPDM, Fluorocarbon, PTFE
Boom arm
Carbon Steel
Primary arm
Carbon Steel
End assembly
Carbon Steel