The correct sizing of the valve is also important. Choosing the right valve means adjusting the valve size to the expected flow rate in the system. It is important to remember that absolute numbers in risk analysis are difficult to calculate and usually useless. In this case, we refer specifically to the calculation of the exact and specific leakage rate of a valve, which prevents a SIF from reaching a safe state in relation to the specific hazard against which it is intended to protect. What is important is not the absolute numbers, but the limits. All you really need to know is whether a leakage rate above a certain value prevents a RIS from not enforcing its security measure. A previous blog on Kenexis` website, which examined seal shut-off (TSO) requirements for valves as part of a safety-related function, generated a lot of interest in the engineering community. A link to this blog is presented below. (c) boilers for heating water. Each boiler for heating water must be equipped with at least one safety valve and one temperature limiting valve or one pressure-temperature pressure relief valve. The valve temperature must not exceed 99°C (210°F). (b) hot water boilers. Each hot water boiler must be equipped with at least one safety valve.
Know what makes a valve the right choice Valves control the flow of gas and liquid in almost all processes and systems. As common as they are, choosing the right valve can sometimes be time-consuming and confusing. The function determines the design of standard valve types. Here are some of the most common types of valves: Knowing where to start makes valve selection faster and easier That`s it. Knowing certain information in advance makes choosing the right valve easier and safer. There will always be complications such as application requirements, operating conditions and chemical compatibility. Starting with the basic requirements for valves, it simplifies and accelerates valve selection: (a) The requirements for pressure relief valves for hot water boilers shall conform to the information in section IV, section 4, section 4 of the ASME Code for Boilers and Pressure Receptacles (incorporated by reference; see 46 CFR 53.01-1), unless otherwise specified in this section. In many cases, it is possible to determine whether or not the leakage rate prevents reaching a safe state in relation to the protected hazard through a workshop discussion with a multidisciplinary team.
However, in some cases, a procedural calculation must be made for the calculation. At the end of this analysis, the indication of the permissible leakage rate need not be a specific value, but a limit, for example: The leakage rate < 1% of the nominal valve flow rate and, if a valve classification is required, it may be specified as Class I or N/A. In the case of the hydrotreating anti-backflow valve, the valve is designed to prevent backflow, causing overpressure and rupture of the supply drum. The question to be answered is, "Will a leakage rate of 1% of the nominal flow rate still result in overpressure and drum failure?" In this case, the answer is no. The feed drum is equipped with a pressure relief valve which, when designed in accordance with the recommendations of API 521, can relieve 10% of the nominal return condition. Therefore, a watertight barrier is not a functional safety requirement for RIS. After writing this blog, Kenexis regularly received requests for instructions on how best to determine whether or not a leak valve is necessary and to facilitate workshops to make this determination and document the results. For this reason, we decided to prepare this blog to explain the process and give an example.
Tip 4 – Check valves have special requirements Make sure the new check valve works as intended. Consider the required response time as well as the crack pressure required to open the valve. August 30, 2011 Ms. Michele D. Jones Functional Safety Team Leader BP Exploration (Alaska) Inc. P.O. Box 196612 Anchorage, Alaska 99519-6612 Dear Ms. Jones, Thank you for your letter dated February 14, 2011 to the Regional Office of the Occupational Safety and Health Administration (OSHA) in Seattle. His letter was forwarded to the Directorate of Enforcement Programs (EPD) for response.
They had questions about the OSHA Lockout/Tagout standard (§1910.147) and the use of local valves as equipment insulation for energy control. Here are your paraphrased scenarios, questions and answers. Scenario 1: A worker replaces the pressure gauge or other instruments on a process line or control device (running). The task consists of three steps. First, the device to be replaced is isolated from its power source by closing a valve. Second, the pressure in the device is bled dry, usually by slightly loosening a connection (fitting) to dissipate the trapped fluid and pressure. Third, the device is removed and replaced. You specified that this work item can usually be completed in a short period of time and is always within reach of the worker who performs the task.
They believe that the worker has complete and exclusive control of the valve at all times to prevent the unexpected release of hazardous energy. In the event that the employee leaves the work area, the valve will be locked and marked (LOTO) according to your energy insulation policy. In accordance with your energy insulation policy, other employees will also be alerted when this task is performed, and staff will be trained and regularly audited to ensure they never leave the workplace without a proper LOTO. In your telephone communication with a representative of my staff, you compared this to the exclusive control device for wired and plugged electrical appliances. Question: Does replacing the pressure gauge or other instrument on a treatment line or equipment unit while the line or equipment is running require locking and marking the shut-off valve? Answer: Yes, with a few exceptions, § 1910.147 requires control of the release of stored energy by locking or labeling if the energy insulation device cannot be locked. Unless the requirements of 8 1910.147, including written procedures and the attachment of locks or labels or both; If followed, the worker`s proximity to the valve is not a sufficient means of controlling hazardous energy. You indicated that the time required to complete the task is usually short and that you believe that the worker who is at hand has complete control of the valve at all times. In the scenario you have defined, the employee can be removed from the workspace or leave for an emergency or other urgent need without locking and marking the device in accordance with your energy insulation policy. With respect to your assumption that the operator has sole control of the valve, similar to that provided by 29 CFR § 1910.147(a)(2)(iii)(A), this particular exemption is limited by its own terms to wired and plug-in electrical equipment1.
OSHA has also considered whether the other minor maintenance and maintenance exceptions under Section 1910.147(a)(2) are applicable and has determined that the exceptions do not apply to the scenario you describe. In addition, the standard requires that all hazardous energy sources be controlled. If the pressure gauge (or other instrument) has a different power source, such as an electrical connection, that power source would also require hazardous energy control under § 1910.333(b), which also requires written procedures and the installation of locks and labels. Scenario 2: A worker cleans or replaces the filter in a pumping system. Filters are usually placed in parallel (operation and standby) with shut-off valves in front and behind the filter and a drain valve on the filtration unit. Alternatively, the piping of each filter can be arranged so that a set of duplex valves (two ball valves in an integral housing with a common valve control handle) can isolate a single filter by actuating (rotating) a single handle.