Internal devices are used in separators to speed up the separation process and reduce the size and cost of the separator. Proper selection of internal devices can reduce the cost of a separator by as much as 50%. Similarly, improper selection of internals can reduce the capacity of the separator by as much as 50%.
Most internal devices are installed in the vapor section to remove liquid droplets from the gas. The diameter will increase approximately 20% if there is no mist pad or another coalescing device in the vapor section. The diameter can be reduced approximately 10% by installing coalescing or other devices in addition to a mist pad.
Selection of internal devices will depend upon the composition and quality of the flow entering the separator. Coalescing devices should not be installed if there is a likelihood they will become plugged with wax, sand or corrosive products. A stainless steel mist pad can be installed in a corrosive gas flow without danger of becoming plugged with corrosive products.
Centrifugal devices are highly effective in removing mist from the gas as long as the gas flow is high enough to maintain proper velocity in the centrifuge. These devices are most effective when the inlet flow is mainly gas flowing at a fairly constant rate.
Each liquid outlet should always have vortex breakers installed. Without these devices, a funneling effect may occur when liquid is withdrawn, and gas will flow out with liquid.
An inlet deflector plate is another internal device that can be used in all separators. This device causes the liquid entering the separator to change direction (normally to the side or down) and prevents it from flowing out to the middle of the vessel and thereby reducing the effectiveness of the vapor section.
EXERCISE 10 Answer questions about the text.
1. Why must water and dissolved salts be removed from crude?
2. When can gas cause formation of hydrates?
3. What do trunk lines connect?
4. How are the devices which test, log, unblock and clean oil pipelines known?
5. Why it is necessary to make a proper selection of internal devices in separators?
6. What does the selection of internal devices depend upon?
7. Why should each liquid outlet have vortex breakers installed?
EXERCISE 11 Open brackets and use active or passive form of the verb.
1. At the gathering center, the oil (to treat) __________ to bring it up to pipeline and refinery specification.
2. When high-pressure gas (to expand) __________ to a lower temperature, considerable cooling takes place.
3. Trunk lines (to connect) __________ the gathering center to the refinery or tanker terminal
4. Most internal devices (to install) __________ in the vapor section to remove liquid droplets from the gas.
5. Internal devices (to use) __________ in separators to speed up the separation process and reduce the size and cost of the separator.
EXERCISE 12 Insert the omitted words from the text
1. Water and dissolved salts can seriously corrode chokes, valves and pipe walls, and must therefore__________ the crude before it is transported.
2. Natural gas may also require treatment at the gathering center, particularly if it contains__________.
3. In product pipelines, pigs can be used to separate two or more different oil products, which__________ at the same time through a single line.
4. Improper selections of __________can reduce the capacity of the separator by as much as 50%.
5. Coalescing devices should not be installed if there is a likelihood they will become plugged with__________ or__________.
6. This device causes the liquid entering the separator to change __________ and prevents it from __________out to the middle of the vessel and thereby reducing the effectiveness of the vapor section.
| Internals, corrosive products, direction, water vapor, wax, sand, are being sent, be removed from, flowing. |
