Forged valve installation and maintenance methods-part two
Feb 12, 2019
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2. Field operation
Care must be taken during installation and construction. Do not hit the valve made of brittle material.
Before installation, the forged valves should be inspected one by one, check the specifications and models and inspect if there is any damage, especially for the valve stem. Also turn a few times to see if it is skewed, because it is most likely to hit the valve stem during transportation. Also remove debris from the forged valve.
When the forged valve is lifted, the rope should not be attached to the handwheel or the valve stem to avoid damage to these parts and should be attached to the flange.
Be sure that the piping connected to the forged valve is cleaned up. Compressed air can be used to blow off iron oxide chips, mud sand, welding slag and other debris. Not only dose these debris easily scratch the sealing surface of the forged valve, but also large particles (such as welding slag) can block the small valve and make it invalid.
When installing the forged valve beside a screw, the sealing packing (line linen plus lead oil or Teflon raw material tape) should be wrapped on the pipe thread, and should not be put into the forged valve to avoid the accumulation inside the valve, for fear that the circulation of the medium will be affected.
When installing a flanged forged valve, pay attention to tightening the bolt symmetrically and evenly. The valve flange and the pipe flange must be parallel and the clearance is reasonable to avoid excessive pressure or even cracking of the valve. Pay particular attention to brittle materials and forged valves that are not strong enough.
The forged valve to be welded to the pipe shall be spot welded first, then the closing member shall be fully opened and then welded.
3. Protection facilities
Some forged valves must also have external protection, which is heat preservation and cold insulation. Heat exchanger steam pipelines are sometimes added to the insulation layer. What kind of forged valve should be kept warm or cold? That is determined according to production requirements. In principle, if the medium in the forged valve reduces the temperature too much, it will affect the production efficiency or freeze the forged valve, so it needs heat preservation or even tracing heat. If the forged valve is exposed, it is unfavorable to production or cause frost and other undesirable phenomenon, it needs to keep cold. Thermal insulation materials are asbestos, slag cotton, glass wool, perlite, diatomaceous earth, vermiculite, etc.; cold insulation materials are cork, perlite, foam, plastic and so on.
4. Packing replacement
For the forged valves stored in storage, some padding are not good for sealing, and some do not match the media used, which requires replacement of the padding.
Forged valve manufacturers can not consider all the different types of medium for practical use. Generally, the packing box is always filled with ordinary packing. But, in actual operation, the packing must be compatible with the medium.
When replacing the packing, press it in circles one by one. The seam of each circle is preferably 45 degrees, and the seam between the circle and the following circle is staggered by 180 degrees. The height of the packing should be considered with the room for the gland to continue to be compacted. At the same time, the packing chamber should be pressed by the bottom of the gland to the appropriate depth. This depth can generally be 10-20% of the total depth of the packing chamber.
For forged valves with high requirements, the seam angle is 30 degrees. The seam between the circle and the circle is staggered by 120 degrees.
When compacting the packing, turn the valve stem at the same time to keep the packing even all around and prevent it from being too compact. When tightening the gland, apply even force without tilt.