What are the pressure relief valve options from Carilo Valve?

Understanding Carilo Valve’s Pressure Relief Valve Portfolio

When you’re specifying pressure relief valves (PRVs), the options from Carilo Valve are designed to meet a wide spectrum of industrial demands, focusing on safety, reliability, and precise performance. Their portfolio is generally segmented by the type of media (gas, steam, or liquid), set pressure ranges, and specific industry applications like oil and gas, power generation, and chemical processing. The core families include conventional spring-loaded valves, pilot-operated PRVs (POPRVs), and those built for specialized services, each with distinct advantages in terms of capacity, stability, and materials of construction.

Conventional Spring-Loaded Pressure Relief Valves: The Workhorse

This is the most common type of PRV, and Carilo Valve’s offerings here are engineered for robust performance. The fundamental principle is straightforward: system pressure acts against a spring. When the pressure force exceeds the spring force, the valve opens to discharge the overpressure. Carilo’s designs often incorporate features like adjustable blowdown rings, which allow engineers to fine-tune the difference between the set pressure (when the valve starts to open) and the reseat pressure (when it closes). This is critical for systems where minimizing process media loss is important. Their spring-loaded valves are typically specified for set pressures ranging from vacuum to over 1,500 psi (approximately 100 bar), with orifice sizes defined by ASME standards (e.g., D, E, F, G) that determine flow capacity.

The materials are selected based on the service. For non-corrosive applications like air or nitrogen, carbon steel bodies with stainless steel trim are standard. For more aggressive media—such as sour gas in oil and gas or corrosive chemicals—valves are constructed from full stainless steel (e.g., SS316), Hastelloy, or Monel. The following table outlines typical specifications for a standard spring-loaded valve from Carilo for general service.

Pilot-Operated Pressure Relief Valves (POPRVs): High Capacity and Tight Sealing

For applications requiring a larger flow capacity or where a tight seal up to the set pressure is non-negotiable, Carilo Valve’s pilot-operated PRVs are the preferred choice. Unlike spring-loaded valves, the main sealing element in a POPRV is kept closed by system pressure itself, controlled by a separate, smaller pilot valve. This design offers several key benefits. First, the blowdown is very predictable and can be set very close to the set pressure, minimizing system pressure fluctuations. Second, they can handle much higher capacities and backpressures compared to conventional valves. This makes them ideal for protecting large vessels, long pipelines, and heat exchangers.

A typical POPRV from Carilo might be specified for a set pressure of 500 psi with a blowdown as tight as 2-3%. They are exceptionally well-suited for gas and vapor service where their flow coefficient (Kd) is often higher. The pilot system itself can be equipped with options like a manual open lever for testing, a pneumatic assist for remote operation, or a tamp-proof seal for set pressure integrity. Because the main spring is isolated from the process fluid, these valves can also be more durable in dirty service conditions, though the pilot line requires protection from clogging.

Specialized Valves for Unique Industrial Challenges

Beyond the standard offerings, Carilo provides valves tailored for extreme or specific conditions. This is where their engineering expertise truly shines, addressing problems that off-the-shelf valves can’t handle.

Thermal Relief Valves: These are small, often threaded, valves designed to protect liquid-filled systems from thermal expansion. For example, a section of pipe blocked by a closed valve that is exposed to sunlight can experience a dangerous pressure build-up. A Carilo thermal relief valve, with a set pressure just above the normal operating pressure (e.g., 25-50 psi above), will open to relieve this small volume of fluid and then reseat. They are compact, with orifice sizes like ‘D’ or smaller, and are commonly made from stainless steel for corrosion resistance.

Bellows-Sealed Valves: In applications with significant backpressure—either built-up (from discharge piping) or superimposed (from another source)—a standard PRV’s performance is compromised. The backpressure acts on the disc, affecting the set pressure. Carilo’s bellows-sealed models incorporate a flexible metal bellows that creates a seal between the process inlet and the valve outlet. This bellows isolates the top of the disc from the backpressure, ensuring the set pressure remains accurate. The bellows themselves are a critical component, often made from stainless steel 316 and designed to withstand thousands of cycles. They are essential in refinery and chemical plant manifolds where multiple valves discharge into a common header.

Low-Pressure/Cryogenic Service Valves: Protecting tanks storing liquefied gases like LNG or liquid nitrogen requires valves that operate reliably at very low temperatures and often very low set pressures. Carilo’s valves for this service use special low-temperature steels (like ASTM A352 LCB/LCC) and extended bonnets to keep the spring operating at a warmer temperature, preventing it from becoming brittle. The seats and seals are made from materials like PCTFE or specialized elastomers that remain flexible at cryogenic temperatures, ensuring a bubble-tight seal.

Key Selection Criteria and Performance Data

Choosing the right Carilo Valve option isn’t just about type; it’s about matching detailed performance characteristics to your system’s needs. Here are some of the high-density data points engineers must consider.

Certifications and Compliance: Carilo Valve products are typically designed and manufactured to comply with major international standards, which is a critical factor for global projects. Look for certifications like ASME Section VIII (Boiler and Pressure Vessel Code), API 526 (flanged steel pressure relief valves), PED 2014/68/EU for the European market, and CRN registration for Canada. These are not just stamps; they guarantee that the valve’s design, materials, and testing meet rigorous safety requirements.

Flow Capacity (Capacity Certification): The most important performance metric is the flow capacity, certified by an authorized body. This is expressed as a certified coefficient of discharge (Kd) or a certified flow capacity in terms of air (for gas) or water (for liquid). For example, a Carilo valve with an ‘H’ orifice might have a certified capacity of 1,200 SCFM of air at a given set pressure. This data is essential for calculating the required orifice size to ensure the valve can relieve the maximum potential overpressure scenario. The table below contrasts typical capacity and application data for the two main valve types.

Materials and Trim: The selection of materials goes beyond the body. The ‘trim’—the internal parts like the disc, seat, and guide—can be specified in different materials. A standard trim might be stainless steel, while a ‘hard trim’ option with Stellite-faced seats and discs is available for services with erosive particles or where frequent cycling is expected. This extends the valve’s service life significantly but comes at a higher initial cost.

Ultimately, navigating the options means starting with a clear understanding of your own process conditions: the media, its temperature and pressure, the required relief capacity, and any special environmental or operational challenges. With that data in hand, the specific models and configurations from Carilo Valve’s extensive range can be identified to provide a safe and efficient pressure relief solution.