Railway Tank Cars: Reasons to always use OEM parts
Would you ask Chevy to recommend a component for a Ford? Would you use a GE component on a Whirlpool appliance? Of course not, so why make this mistake with Tank Cars?
If you are not using OEM repair kits and seals –
Your component warranty is voided and may also be foul of its AAR Approvals. If you are relying on your third-party suppliers guarantees that their program and recommendations will save you from regulatory and environmental penalties, think again. It might be worth asking that vendor how many times they’ve previously had to admit liability and how much their insurance would pay in the event of a catastrophe. If you have not re-written your service procedures to include the use of these unsanctioned non-OEM parts, also expect to incur additional regulatory penalties.
OEM vs Aftermarket – Behind the Scenes
On average it takes an OEM 5 years to perfect a repeatable and consistent manufacturing process for a particular product line.
Conversely a NON-OEM part is a ‘quick’ copy. These parts are often replicated based on sample measurements and not from drawings. As such there is no way of knowing if samples used are on the small or larger end of excepted manufacturing tolerances. Furthermore, there are often details that not shown on design drawings, but have, with experience, been incorporated into the manufacturing processes.
Non-OEM parts use different machinery in differing environments (humidity & temperature) and are not privy to exact material formulas or finishes. When a Non-OEM vendor makes a recommendation, it is nothing more than an educated guess at what MIGHT work best. When it comes to non-OEM parts, there are no quality or performance guarantees as typically no testing has been conducted. Below is a brief explanation of what goes into the design and formulation of OEM parts and why they should be your only choice.
SEALS – THE MOST UNDERATED AND OFTEN BLAMED COMPONENT
What makes for a good seal? After all there are no Association of American Railways (AAR) seal tests….
Let’s use an O-Ring as the simplest example of why you could be tempting disaster… Any given O-Ring only consists of 50-60% of the base rubber (EPDM, BUNA, VITON etc.), the balance is made up of various fillers, accelerators, aging retardants and other chemicals additives, all of which are then either sulfur or peroxide cured. These factors all go into determining the O-Rings characteristics, such as hardness (durometer), chemical compatibility/ gas permeation range, temperature range, compression force (force required to compress an O-ring to maintain adequate sealing), tensile strength (psi required to rupture the rubber) and overall toughness
In addition, OEM’s cycle and test their formulas and finishes tens-of-thousands of times in a given application; constantly improving performance, longevity and safety. OEM’s know that their seals/ O-Rings will always meet the necessary requirements because they control the inputs. Should something change with their vendors, they intimately know how those changes impact performance and what remedies are required.
So – when you purchase non-OEM seals, ask them what they know about their product. How was it cured? Does it have any special coatings, is formula better suited for static or dynamic environments?
REPAIR KITS - Any given valve is designed, manufactured and tested using OEM parts. It is the sum of these parts (valve seats, stem packings, seals etc.) that together pass the stringent tests imposed by the AAR. It is these meticulous components that allow a liquid valve to be API 607 compliant or for a safety relief valve to correctly discharge and wholly seal at the precise pressures.
VALVE SEATS – These components are engineered and machined to very exact measurements to ensure they provide repeated and optimal performance. Most are designed to creep immediately with a measured amount of wear factored in, while other seats are engineered to engineered to roll/ flex and never creep. Regardless of design, OEMs conduct months if not years of environmental, pressure and stress testing to understand how their seats perform.
Similar to seals, manufacturers blend proprietary formulas of PTFE to safeguard against catastrophic failures. Not all PTFE’s are equal and will adversely react with certain commodities, which why it is of paramount importance that you consult with the OEM regarding your compatibility requirements. It is for all of the above that gives OEMs the ability to warranty their products.
STEMS & STEM PACKINGS – Stems are quite possibly the most sensitive part of a valve. Their dimensions, construction material and finishing processes dictate not only how much abuse a valve and physically handle, but also its ability to seal.
Stem Packings have been a much-discussed issue at recent AAR Tank Car Committee meetings and as the last line of defense, it is imperative that everything complies with manufacturer specifications. Each manufacturer implements their own design philosophy which in turn is engineered to work differently and is based around a unique stem design. Some packings require tightening, some are self-tightening/ spring-loaded, while others include external live-loading features. Some use a V-Ring design versus a standard block and yet, not every V-Ring design works in the same way. Combined with the need to perfectly fit in and around the actual stem and then within the body of the valve, it is very easy to see how failures can occur.
CONCLUSION -
This article only scratches at the differences between OEM and Replica parts. Some of these replacement components may seems benign, but is it worth saving a few dollars or trying to standardize suppliers when the risks of failure can run into the thousands if not millions of dollars. There is no scenario where taking this risk makes any sense. It is therefore TransQuip's recommendation you ensure not only your internal purchasing, but also your repair shops always consult the OEM with any questions, queries or concerns.
TransQuip is the exclusive supplier of Fort Vale, Jamesbury & Rego service components. For any questions regarding repair kits for these products, please contact us at 904-388-6699 or visit our website at www.transquip.com.