Through Agility and Speed, Windrock Cracks Tough Environmental Issue on Spotlight PUC’s
Designing products for a harsh environment can be challenging in the Oil and Gas Industry. Windrock recently designed and released a new IIoT enabled product line called Spotlight. The product had some initial issues upon installing units in the field that the Windrock team overcame through disciplined testing, applying experience and lessons learned from field applications. The Windrock team was agile and quick to find a solution to replace all the units in the field with a new design with no disruption to the customer’s business. This paper specifically addresses how Windrock went beyond the IP (International Protection) rating system to address water intrusion and how we have changed design and test practices to design for the harsh Oil and Gas midstream outdoor environment.
For the Spotlight product, Windrock released product into the field in two phases: the first phase was Beta site testing and the second phase was release to production. Prior to the production release, IP testing was performed at a third party laboratory where the Spotlight PUCs (Peripheral Universal Connection Module) tested and passed up to IP65.
The Beta site tests passed the beta qualifications, and the IP testing passed the environmental qualifications. Therefore, the product was released to production. Several months after the initial installations, the PUCs started to experience field failures. The company promptly replaced the product in the field and sent the failed PUCs back for investigation, where Windrock tackled the issue promptly.
Process for Addressing Water Ingress
PUC Failure Analysis
Review of Field Data
The PUCs returned to Windrock were investigated with a joint team between engineering and quality. The investigation found that water ingress failure occurred with this equipment.
The following failures were identified:
- Evidence of water condensation was found by reviewing the drip and evaporated salt pattern
- Evidence of pressure-washing was found by detecting cleaning agent dissolved in water and extreme corrosion of the aluminum housing interior
- Evidence of water ingress directly from outdoor moisture
A brainstorm session ensued on the potential failure modes that may have presented water ingress. All fasteners, gaskets, LED (light emitting diode) windows, and all potential water-entry points were considered. A test plan was generated to replicate the failures and perform condensation calculations.
Replication and Identification of Fault Causes
Water immersion tests were conducted such that two baths with different temperatures were used. One bath was filled with ice and was 32 degrees Fahrenheit, and the other bath was at 170 degrees Fahrenheit.
Figure 1: Temperature Immersion Testing: PUC is fully submersed in 170 degree Fahrenheit water.
When the PUC was soaked in the hot water, the interior air temperature rose, and forced-out air through the gasket. The hot PUC was dipped into the cool immersion bath, and the air inside the PUC generated a vacuum which bent the lid and breached the gasket seal, thereby allowing water to enter the PUC. This test demonstrated that during severe thunderstorms where temperature changes drastically from hot to cold, that the gasket could potentially breach allowing water to enter the PUC. It was also determined that the torque limits of the screws holding the lid onto the housing base has a functional torque band with upper and lower limits.
Figure 2: Pressure Washer Testing: PUC being subjected to 3000 psi.
It was found that under intense pressure washing that the label may peel off and allow water intrusion at the LED windows.
Condensation calculations conducted covered two scenarios:
- A completely sealed PUC where the PUC is assembled within an initial environmental condition and is not allowed to breathe.
- An unsealed version of the PUC is allowed to breathe and the ambient environmental conditions can be drawn into the PUC housing.
Figure 3: Psychrometic Chart: Dew point calculations were conducted using the chart above.
Psychrometric charts were used to determine the change in the relative humidity within the housing of the PUC. With much electrical equipment, especially with sealed panels and housings, the energy output from the circuits drive a temperature gradient within the housing that lowers relative humidity below that of the surrounding environment. In this case, the efficient PUC circuitry typically consumes less than three Watts and for the purpose of these calculations is considered negligible. The outcome of the condensation calculation determines that it is possible to reach the dew point with minimal temperature change (approximately 12 degrees Fahrenheit). The level of condensation where the moisture is stripped from the air in the housing can increase as the ambient temperature decreases.
The prevailing pattern of wind in North America is from West to East. As the air from the Pacific hits the coastal mountains it is lifted to a higher elevation, and is consequently cooled and dried out. This effect of enthalpy (energy) reduction also occurs over high elevations over the Rocky Mountains. As this low-enthalpy air moves eastward, it can encounter hot and humid air (having high enthalpy) moving up from the Gulf of Mexico. This differential in enthalpy between the two air masses East of the Rockies is known to cause violent thunderstorms. One hypothesis of PUC water intrusion was that a hot PUC may cool quickly causing the interior air within the PUC to loose pressure approximating the ideal gas law. This vacuum may cause outdoor water intrusion during a thunderstorm if a seal is breached under vacuum.
Several design modifications were implemented to mitigate all causes of water intrusion:
- A new PUC lid was designed with the following features:
- A lid having higher structural stiffness such that under vacuum or positive pressure, the flexion would not breach a seal
- Removal of LED windows to remove possibility of water ingress through holes
- Overlapped lid to housing with interior groove to fit gasket, such that the gasket would not be exposed to direct water pressure
- New gasket design for the lid to body interface
- Interior desiccant pack to prevent any condensation
- New manufacturing quality control measure to ensure torque specifications are within limits for all fasteners
Design Change Validation
The immersion tests were repeated successfully with the enhanced design changes demonstrating no water ingress. In addition, IP69 testing was performed successfully by a third party laboratory. The new PUCs were sent to the field, and found not to experience any water ingress.
Although the design may follow IP standards and traditional validation techniques, it is important to recognize the harsh environmental factors that may exceed commonly used testing and certification standards. Design validation and Beta-site testing may be custom designed beyond the customary standards to suite the harsh environmental factors presented in the outdoor oilfields. The PUCs were replaced at each customer site by Windrock technicians with little or no interruption to the customer’s business.