The vertical stuffing box-type pressure vessel failed the horizontal pressure testing
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A vertical stuffing box-type pressure vessel is currently undergoing a horizontal hydrostatic test; the stuffing used is flexible graphite, and it is compressed by tightening a large nut, which in turn exerts pressure on 6 layers of flexible graphite. The operating pressure is 2.3 bar on the shell side and 2.5 bar on the tube side. During testing of the shell side, water leaked through the connections at the stuffing, resulting in a failure of the test. The same problem was observed when testing the container in an upright position. In my opinion, the pressure test failed because insufficient force was applied when tightening the large nut, which prevented proper compression of the flexible graphite and thus led to inadequate sealing. 1. How to address the pressure testing issue, with a test water pressure of 4.8 and a design pressure of 3.2. 2. Can a pressure difference test be used, that is, a pressure test of 0.2 MPa in the tube side is sufficient?
You can’t use the differential pressure test; does your packing consist of only 6 layers of flexible graphite?
Filler box-type heat exchangers are not recommended for pressures above 25 kilograms.
It’s just that “” is not recommended for use; since the client insisted on it, we had no choice but to use it. Now there are problems with the water pressure.
Why can’t a pressure difference test be used? The packing consists of only 6 layers of flexible graphite, which are tightened by hand; I now suspect that the force applied manually is not sufficient to deform the packing enough in order to achieve sealing (although special tools were designed to assist with tightening, and all the workers pooled their efforts). The reason for this issue remains unknown
Leakage during a hydrostatic test indicates a sealing issue. If a pressure difference is used for the test, there may be no leaks during that test, but can it be ensured that the pressure difference remains at or below that of the hydrostatic test throughout the equipment’s operation? This includes situations such as startup and shutdown, normal operating conditions, as well as emergency conditions – all possible operational scenarios. If it’s not possible to maintain that pressure difference during use, then does the hydrostatic test lose its meaning?
As I recall, when we used packing for sealing, it was two layers of packer tape, three layers of flexible graphite, then again three layers of packer tape and three layers of flexible graphite, and finally three more layers of packer tape. Pressured to 3.6 MPa with no leakage
My stuffing box is DN200; sealing is achieved by manually tightening structures similar to nuts in order to compress and deform the stuffing box. Is this the case for you? “Does “two layers of packing” refer to steel-reinforced rings similar to round bars with a diameter of 3 mm?
What was said upstairs makes sense; I recall that the containers were also subjected to pressure difference hydrostatic tests. I just can’t remember under what circumstances such tests were carried out I now suspect that the biggest issue with this container lies in its sealing; in my opinion, the design itself is fine – the problem is how to ensure proper sealing at the packing gland
Asbestos packing is made of asbestos ropes woven together, and it is square in shape. We use a packing gland to press it.