A blind flange is an essential piece of equipment used in pressure testing as well as the pipeline industry in general. These reinforced ridges are used to seal off a section of pipe or nozzles that are not connected to valves or other piping. They are commonly used for testing the flow of gas or liquid through active pipelines. These flanges have specific pressure ratings which are needed to run smoothly, including 150, 300, 600, and 900 series.
Many times, a pipe or tank is equipped with a surplus of nozzles that are not always needed. Blind flanges can be used to seal off any redundant nozzles in order to maintain the desired pressure to correctly carry out a pressure test. This is when flanges with different pressure ratings becomes important.
The pressure rating of the flange is dependent on the amount of pressure within the pipeline system. Typically, the lower the pressure rating of the flange, the smaller the outer diameter as well as the lower the number of bolts used. As blind flange pressure ratings raise, so does the outer diameter, number of bolts, and bolt hole sizes. So, for example, a blind flange with a pressure rating of 600 pounds will be much thicker and require bolts that are larger in size and quantity than a blind flange with a pressure rating of 150 pounds.
Gaskets are mechanical devices used to seal flanges that will fill the spaces and irregularities between two mating flanges and prevent the leakage of fluids. The type of gasket needed is dependent on the type of blind flange being used. There are many different types of blind flanges, however the two types are raised face (RF) or flat faced (FF). If the flange is raised faced a standard ring gasket that is appropriate for the service and/or test is recommended. On the other hand, if it is flat faced then a full-face gasket should be used.
The most common reason the flange is flat faced is because it is not designed to handle the bending forces that result when using a ring gasket or a raised face flange against a flat faced flange. Gaskets with a solid center are often utilized to protect the blind flange from being exposed to fluids being used while performing a pressure test. Carbon steel blind flanges are a cheaper type of metal to use but are not necessarily built to withstand certain chemicals. Solid center gaskets can effectively act as a protective barrier between the fluid and the flange when using cheaper metal flanges.
Using flanges with the right pressure rating for the job is crucial to avoiding pressure testing failure and the hazards that come with it. Everyone involved in any given pressure test are in potential danger if calculations are off by even the smallest amount. Therefore, it is extremely important to hire a professional crew to conduct your pipeline pressure test. Hydrotest Pros specializes in pressure testing. Our certified crew has extensive knowledge of using the correct blind flanges for any given job and understands the importance of conducting a safe and effective hydrostatic pressure test. The next time you’re looking for a crew to safely test your pipeline system give us a call. We can mobilize out to your job site 24-7, 365 days a year!