An Overview of Valve Inspection and Testing
Industries like oil and gas, chemicals, and petrochemicals are several sectors that use flammable substances at scale. This presents a unique set of fire-related risks, including leaks, explosions, accidents, and injuries to staff. Flammable substances are even more dangerous because of the high pressures of processing or transporting them across vast distances. This combination of combustibility and pressure needs to be managed very effectively throughout production and logistics cycles. Industrial valves help reduce these risks by managing flow, pressure, speed, leakage, and fire safety. Industrial businesses must regularly conduct control valve inspections, safety valve inspections, and valve testing to ensure consistent and reliable valve quality.
What is a Valve?
Valves are of different types and perform both control and safety functions depending on how they are used. Essentially, a valve is a tool used to block, redirect, or adjust a liquid or gas level of flow. They are used to control pressure and ensure that fluids and gases are within the pressure thresholds. This provides both safety and operational efficiency. Fire safety valves are temperature-sensitive devices that are designed to automatically close and block the flow of material in the case of a fire. Valves may be of different types based on the mechanisms in place. For instance, spring-loaded valves use spring packs and trigger assemblies to get into action. Ball valves leverage metal to metal sealing to prevent leakage and contain graphoil seals and a floating ball.
Why is Valve Testing Important?
One of the vital components in oil and gas inspections is valve inspection and testing. Since valves manage pressure and help ensure safety during leaks, fires, or other incidents, they are essential in ensuring safety and operational viability. As a result, oil and gas industry regulated industry bodies like API outline several protocols to be followed in the design, installation, operation, inspection, and testing of valves.
They outline procedures for testing gas safety valves, and inspection teams must submit detailed gas valve test reports. Valve testing is also vital in ensuring that oil and gas companies are better equipped to handle accident and injury insurance claims from workers and make insurance claims when accidents occur and they experience business loss. Compliance with stipulated regulations on valves and valve inspections also helps lower insurance rates for infrastructure protection.
International Standards for Valve Testing and Inspection
Valves used in oil and gas are regulated by the American Petroleum Institute (API); for instance, fire tests have been developed by API for oil and gas. These must be rigorously implemented during valve inspection and testing. Diverse codes, including API 607, BS 6755, ISO 10497, BS 5146, and API 6FA, are among the most widely used fire valve testing standards. In addition, other standards are used in valves’ design, testing, and operation, including those laid down by bodies like the American Society of Mechanical Engineers (ASME) and the International Organization of Standardization (ISO). For instance,
- API 598 is perhaps the most universally accepted valve testing and inspection standard.
- FCI 70-2, “Control Valve Seat Leakage,” outlines control valves’ procedures and leakage rate classes.
- MSS SP70 specifies design standards, testing procedures, and acceptance criteria for cast iron gate valves, among other widely used international regulations.
Standards like API6D require that all valves with an API stamp be tested and certified according to 6D protocols. This means that regardless of the application and type of valve, they must undergo three types of valve testing, including Hydrostatic seat tests, shell tests, and stem backseat tests.
Essential Types of Valve Inspection and Testing
Inspectors use different types of tests to assess the integrity of valves. For instance, during fire safety tests, they expose valves to fires with temperatures between 750 and 1000 degrees Celsius for as long as half an hour to check the seat and sealing. They use heat monitors such as thermocouples and calorimeter cubes. Leakage is also checked to see if it is within acceptable limits. They also conduct various tests using pressure safety valve inspection checklists.
Valve Shell Test
Valve shell tests are also known as body tests and are conducted by procedures outlined by manufacturers, which are designed based on stipulations in API 598 (Valve Inspection and Testing) and ASME B16.34 (Valves — Flanged, Threaded, and Welding End). The valve is partially open during this type of test, and the valve body is tested using hydrostatic pressure. Inspectors check to see any leaks from the packing gland or valve body. The valve is cleared in such inspections only if there is no leakage. These tests last anywhere between 15 – 300 seconds based on valve size.
Valve Seat Leak Test
Once valve shell tests are completed, valve seat leak tests are conducted. Similarly, these tests are conducted according to manufacturer procedures based on API and ASME standards. According to test protocol, the valve is completely closed, the inlet or outlet is exposed to hydrostatic pressure, and the quantum of leakage from the other side of the valve is measured. API standards prescribe that the valves are tested at 110% of the maximum allowable pressure level at thirty-eight degrees Celsius in such testing procedures. The leak pressure tests are conducted anywhere between 15-120 seconds based on valve size.
Pressure Safety Valve Inspection
Pressure safety valves are usually spring-loaded systems opened by rapid pop action under pressure beyond thresholds. When pressure increases, it allows fluid to enter the huddling chamber causing extra pressure for opening force. Inspectors test pressure safety valves to ensure they comply with regulations laid down. Some of these include the API recommended practices for sizing and selection, seat tightness, and pressure-relieving and depressing systems. In addition, inspectors check valves for corrosion, damage, water or ice accumulation, debris, and tampering.
Backseat Valve Test
The backseat is a valve function that allows technicians to replace or repair valve packing while the valve is in service. Inspectors keep the packing gland loose or test without packing at all. The body is tested using hydrostatic pressure, and leakage is checked from the packing gland. Testing procedures follow guidelines in the API Std. 598 and are likewise conducted at 110% of maximum allowable pressure at thirty-eight degrees Celsius.
Valve inspections can be tedious, especially since they must follow numerous regulations and standards and involve large amounts of field data captured in various formats. Fielda helps inspectors conveniently gather data through customizable digital checklists. In addition, they can easily attach evidence, photos, and supplementary documents at one go from their mobile devices. And once data is captured, operational leads can review reports, schedule maintenance work, and share updates with management in real-time.