Frequently asked questions
It is inevitable that you will encounter various small problems in use in procurement and use. The following questions and answers may help you understand the cause of the problem.
The conventional butterfly valve is rubber lined concentric butterfly one used only at low pressure (<1.6 MPa). Its disk axis is at the center of the flow passage and seating belt. This kind of valve is sealed by jamming the rubber seat between disc and body under the action of external force. This sealing is usually called enforced sealing. The defects are :
Difficult to control the sealing pressure ratio;
Too much of wear and short service life.
Low operation pressure .
Limit applicable media, as water, gas and oil .
Originated from space technology, the high performance butterfly valve was developed in 70s, its features are:
The disc rotation center is offset from axis of pipeline and the sealing plane, which makes the disk being swung out upon opening, thereby eliminating the usual wear points at the top and bottom of the valve seat.
The seat of the HP butterfly valve, such as BONSF’s is of flexible lip type design, which uses the fluid sealing principle to attain reliable sealing, thus completely different from the enforced sealing principle of the conventional butterfly valve.
Long service life( up to 1 million cycles reached in testing) ; Low torque (about 30% lower than the conventional butterfly valve’s); higher operation pressure(to 10 MPa) ; and wide range of applicable media.
Invention of this kind of butterfly valves opens up possibilities for replacing gate valves with butterfly valves in a greater range of pressure service. With only one third of the weight of gate valves, about two thirds of the price of the corresponding gate valves, HP butterfly valves will surely have a bright future in the industrial field.
The stem packing is a dynamic seal. It may be loosened after a period of use or due to the vibration of handling and shipment, thus causing stem leakage. In this case you may tighten the bonnet bolts properly to eliminate the leakage.
The material of the soft seats for ball and butterfly valves of our company is specially produced with patent formula. Its quality is guaranteed by the inspection at all levels. The case you mentioned usually is due to the sharp particles or metal chip left in the pipelines during installation, which scratches the seating surfaces. Therefore, it is very important to remove such foreign matter from the pipeline prior to installation and to keep seating surfaces clean during and after installation.
If a valve is not operated for a long time, the motion parts may be stuck and bound due to molecular adsorption between them and viscous foreign substance, thus turning the torque bigger. Cycle and inspect valve periodically, for instance, once a month. For series G valves you can inject proper cleaning or lubricant agents through the sealant fittings to clean the valve and discharge the accumulated dirt through the body drain fitting to ensure the valve function.
The temperature-pressure curve of valve body on the catalogs of our company shows the maximum permissible working pressure of a valve of specified material under the specific temperature. As temperature increases, the appropriate working pressure decreases. This is an important factor to ensure the operation safety of a valve or even a system, because of this customers must refer to the curve while making an order or a choice.