After successive years of unprecedented growth, the tank car industry is facing numerous challenges. New regulations for stricter tank car standards have been mandated, estimated to cost $2.9 billion to retrofit the current fleet. According to the Association of American Railroads (AAR), crude-by-rail saw a 17% decline in 2015. At the last AAR meeting in Colorado Springs, CO., the Department of Transportation (DOT), unveiled drastic new measures of accountability. Starting this year, shippers and terminals are going to be held accountable and responsible for NARs.
Shippers at risk
No official figures have been released for 2015, but as of June 2015, NARs increased by 19%. The most common culprit being the manway, with the four leading issues being loose bolts, missing gaskets, deteriorated gaskets and misaligned gaskets.
AAR guidelines
The AAR does not approve any gaskets nor does it approve facilities that manufacture them. AAR Pamphlet 34 (Recommended Methods for Safe Loading & Unloading of Tank Cars) only has the following to say on gaskets:
a.2.1.16.3 - The manway gasket is in place, intact, has not taken a permanent compression set that interferes with sealing ( … )
b.3.4.5 – If the manway was opened during the operation, be sure to inspect the manway gasket for damage, deterioration and proper alignment ( … )
c.Section 4 (Reprint of AAR Manual Appendix D) – 6.2 – Install a new gasket compatible with the commodity to be transported ( … )
Lack of standards
Gaskets take a compression set after first use. It is compression set/ creep that results in loose bolts, accounting for over 50% of manway related NARs. Whether you are using a rubber (BUNA, Viton, etc.) gasket or a PTFE (Teflon) gasket, all will take a compression set. Suppliers advise or recommend that you not use their gasket more than once. Some recommend that you wait 24 hours after torqueing their gaskets and apply a final retorque before using.
Finding a solution
Recognizing that the answer was not one of material selection, but rather inadequate seal design, Parker’s Integrated Sealing Systems Business Unit took on the challenge of offering a sealing solution that completely eliminated all the leading causes of NARs, as well as offering a gasket that could be reused. In developing a solution, Parker sought feedback from a variety of industry experts with extensive experience using manway gaskets, including petroleum/chemical companies, as well as the AAR and DOT. With their input, Parker designed and patented its Sure Torque gasket, featuring a stainless steel (primary seal) insert and over-molded elastomers. To verify its design, Parker then tested its Sure Torque gasket with the four most popular gaskets in the industry. Results can be found below.
Test Parameters:
- Test used a heavily used manway fitting at room temperature
- Secured using the recommended star pattern over three passes to 250 ft-lbs
- Pressurized in 10 psi increments up to 165 psi and monitored for 24 hours
- Repeat steps 1-3 until test gasket failed
An engineered solution
Sealing and maintaining bolt torque is not a unique challenge for tank cars. The Parker Sure Torque Manway Gasket incorporates an integrated stainless steel ring that specifically resolves the four leading issues that cause manway NARs. It is the only gasket that can be reused, while only needing to be torqued once, can’t fall into the manway, greatly simplifies installation and minimizes maintenance procedures.
To learn more, view our video on the Parker Sure Torque Manway Nozzle Gasket below.
Summary
Much is being done to improve the safety of the existing fleet of tank cars as well as the specifications for new builds. Although expensive to retrofit, the AAR has been thorough in overseeing the necessary changes to ensure the best outcome for all parties.
Similarly, although traffic is down for the tank car industry, especially crude-by-rail, it’s not all doom and gloom. The Enbridge and Sandpiper pipelines have been delayed subject to environmental reviews. Existing pipeline networks do not extend to East Coast refineries and Canada’s oil production is forecast to grow faster than pipelines can be built, making crude-by-rail the only viable alternative.
As the industry moves forward with safer technologies, more inspectors and changes in who is accountable for NARs, now is the time to take a long hard look at how tank cars are sealed.
For more information, contact the sealing experts at Parker.
This article contributed by Emanuel Guerreiro, Industrial Market Development Manager, Parker Hannifin Integrated Sealing Systems Business Unit.
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