Comprehensive Guide to QOC Closures


EMT’s Quick Opening Closures (QOCs) are versatile, safety-optimized components ideal for efficient access to pressurized vessels and pipelines across various industries. With advanced features like integrated safety locks, pressure alert valves, and adaptability to different working mediums, our QOCs set the standard for operational efficiency and safety.


Introduction to Quick Opening Closures (QOC)

Quick Opening Closures (QOCs) are crucial components in piping systems across various industries. According to the ASME Sec VIII Div 1 Boiler and Pressure Vessel Code, a QOC is defined as a pressure-containing component with a door that permits direct access to the interior of a pressurized vessel or pipe. It is designed to be opened and closed frequently and quickly, hence the name Quick Opening Closure. At EMT, we understand the critical role of QOCs in operations ranging from routine maintenance, and internal inspection, to the launching and receiving of pipeline pigs in oil and gas industries. Our QOCs are designed to ensure ease of access while maintaining the highest safety standards. The importance of QOCs in a piping system cannot be overstated as they provide efficient access, reduce downtime, and ensure the safety of operational personnel.


Orientation and Connection Types in QOC

EMT’s QOCs are versatile and can adapt to various installation requirements. They are designed to accommodate three types of orientation: horizontal, vertical, or inclined. This adaptability allows our QOCs to integrate seamlessly into a wide range of piping systems. In horizontal applications, our closures are typically used on pig launchers and receivers, filters, separators, and storage tanks. Vertical applications, on the other hand, are common in tower vessels and vertical separators. Our QOCs can also be used in inclined applications where the vessel or pipeline is installed at an angle. In terms of connection types, EMT offers full and reduced access designs. Full access closures allow for the maximum possible opening for access to the pipeline or vessel, making them ideal for applications that require extensive interior access. Reduced access closures, while providing a smaller opening, offer a more compact design and are typically quicker to open and close. For inclined or declined vessels, we offer mitered designs. These closures are specifically designed to match the angle of the pipe, ensuring a perfect fit and efficient operation. At EMT, we strive to provide tailored solutions to meet the specific needs of each project, ensuring the highest levels of operational efficiency and safety.


Product Parameters

  • nominal diameter DN: ≤1800mm, custom sizes available on request
  • Designed and Manufactured in Accordance With ASME Division VIII, ASME B31.3, ASME B31.4, & ASME B31.8
  • Orientation: Horizontal, Vertical, or Inclined
  • Pressure Class:150#, 300#, 600#, 900#, 1500#
  • working medium: oil, gas, water
  • design temperature: -50℃~300℃
  • pipe thickness: 6mm~100mm

The above is an example of product indicators, other blind plate specifications are implemented according to industry standards.


  • Hub & Door:SA-105, SA-350 LF2, A-694 F48, Triple Certified
  • Pressure Alert Valve:A-316 Stainless Steel
  • Locking Segments:SA-182, F6A, CL2
  • O-Ring: BUNA-N, Viton, Customer Specified


  • Material: Carbon Steel, Stainless, Other available upon request
  • Weld Bevel: Customer Specified weld bevel
  • Flanged: Available on request
  • Coating: Per Customer Specifications


Essential Accessories and Enhancements for QOCs

At EMT, we understand that the functionality of our Quick Opening Closures (QOCs) extends beyond just providing access to the interior of a vessel or pipe. They can serve as a platform for a variety of auxiliary components that enhance the usability and functionality of the system.

Available accessories for our QOCs include sight glasses for visual inspection without opening the closure, nozzles for introducing or extracting fluids, drains for removing liquids, gauges for monitoring pressure, and sampling ports for collecting fluid samples for analysis. These additions can significantly increase the efficiency and versatility of the system.

Safety is our utmost priority at EMT. We have integrated safety features into our QOCs to ensure a high level of protection for operators. These include an integrated safety lock to prevent accidental opening of the closure under pressure and a pressure alert valve that indicates the presence of residual pressure before opening.


New Developments and Innovations in QOC Design

In our continuous pursuit of excellence, EMT is proud to introduce our patented QOC system. This new system is a testament to our commitment to innovation, safety, and efficiency.

Our patented QOC system brings multiple enhancements to the traditional closure design. The system includes safety measures that greatly reduce the risk of accidents during operation. We have also simplified the operation process, minimizing the effort and time required to operate the closure.

The improved design integrates the locking mechanisms, providing a robust and secure lock that can withstand high pressures. The system also incorporates weather seals to protect the internal components from corrosion due to harsh weather conditions. Rust protection is integrated into the design, ensuring the longevity and reliability of our closures.

Role of QOCs in different Working Mediums

EMT’s QOCs are designed to be versatile, and capable of handling different working mediums including oil, gas, and water. This adaptability makes our closures suitable for a wide range of industries, from oil and gas to water treatment and beyond.

Our closures are built to withstand the challenges associated with these different mediums. For instance, they can handle the high pressures typically associated with oil and gas systems, and the corrosive nature of certain water systems.

Regardless of the working medium, our QOCs maintain a high standard of safety and efficiency. They are designed to operate reliably within a wide temperature range, from -50℃ to 300℃, making them suitable for a broad range of operating conditions.

Through these innovations and enhancements, EMT strives to provide QOCs that meet the diverse needs of our clients, ensuring safety, reliability, and efficiency across different working mediums and industry applications.


In conclusion, Quick Opening Closures (QOCs) play a crucial role in a multitude of applications across various industries, exemplifying versatility and utility. They are an essential component in piping systems, serving critical functions from routine maintenance to internal inspections and more. The seamless integration of our QOCs into different orientations and connection types highlights their adaptability, making them an indispensable tool in diverse operational settings. EMT’s QOCs are not only designed for efficiency but also prioritize safety. Our integrated safety features, along with a wide range of available accessories, significantly enhance the operational capabilities of our closures. The ability of our QOCs to handle different working mediums, from oil and gas to water, further underscores their versatility and applicability in a variety of operational environments. Looking towards the future, we at EMT remain committed to pushing the boundaries of QOC design. Our patented QOC system represents a significant step forward in this journey, offering improved safety measures and operational ease. We will continue to innovate and refine our designs, focusing on enhancing safety, efficiency, and longevity. In the ever-evolving landscape of industry needs, EMT is dedicated to providing QOC solutions that not only meet but exceed our clients’ expectations. We understand the importance of reliable and safe access to pressurized vessels and pipelines, and we are committed to delivering products that uphold the highest standards of quality and safety. With EMT’s QOCs, customers can expect a product that is robust, reliable, and ready for the challenges of the future.


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