Mechanical Seal (Phớt cơ khí): Sử dụng các vòng phớt áp sát vào nhau để tạo thành một lớp chắn giúp ngăn chất lỏng hoặc khí thoát ra ngoài. Đây là công nghệ tiên tiến và thường được ưa chuộng trong các ngành công nghiệp đòi hỏi độ kín cao.
Gland Packing (Đệm chèn): Sử dụng vật liệu chèn, thường là sợi chịu nhiệt, được đặt trong hộp đệm quanh trục bơm. Khi siết lại, nó tạo ra một lực ép giúp ngăn ngừa rò rỉ. Đây là phương pháp truyền thống và vẫn được dùng trong một số ứng dụng đơn giản.
| Mechanical Seals Vs Gland Packing | ||||
| NO. | Description | Mechanical seal | Gland Packing | Note |
| 1 | Installation time | Installation time is high, due to the pump would have to be taken off-line and disassembled | Installation time is very less. The packing can be replaced immediately. | The Installation time for mechanical seal usually takes seven to eight hours (include flushing system). Normally the installation duration will depend on the size of the mechanical seal. On the other hand, glad packing installation will take a maximum of one to two hours and it will depend upon the size of shaft and number of gland packing rings required. |
| 2 | Capital cost | Very high | Very cheap when compare with mechanical seal | |
| 3 | Spare cost | Spares to be maintained. High spare cost. | Spare is not applicable. | |
| 4 | Skill requirement | Skilled manpower is required for mechanical installations, removal and assembly | Minimal training is sufficient for gland packing installations and removal. | |
| 5 | Leakage rate | Very minimal leakage | Leakage will be high | |
| 6 | Product loss | Very minimal | Huge production loss when compare with mechanical seal | This is one of the major parameters for selecting mechanical seal over the gland packing. By using mechanical seal the loss of product due to leakage in reduced more than 99.95% when compared with gland packing. As per gland packing thumb rule, leakage of pumping fluid is essential for extending the life of gland packing. The leakage rate of well tighten gland packing is 10 drop/minutes (but in actual site condition it will very high). Total leakage rate for per day shall be (10 drops/min) x 60 x 24 = 14400 drops (approximately 0.72 liters) As per the above estimation, by using gland packing the production loss will be 0.72 litres. If you consider the pump is running for One year, then the product loss will be 0.72 x 365 = 262.8 liters In the case of mechanical seal (assuming single mechanical seal) the product loss will be not more than 1 litres for a year. |
| 7 | Power Consumption | Very less power consumed | Power consumption is very high | The amount of power required to drive a mechanical seal is very less compare the pump having gland packing. In the case of Gland Packing, the sealing will take place by pressing the gland packing against the gap between the casing and shaft to control the leakage. Also, the number of packing required for the seal is pend on the stuffing box pressure and depth of the stuffing box. Usually, the number of packing rings used for the pumps will be between to 3 to 7 packing rings. Usually, the power will increase with an increase in the number of packing rings. On the other hand, the mechanical seal having primary seal faces which are having very less frictional losses. Due to this mechanical seal will consume 80% power (assuming mechanical seal with pumping ring) less than the gland packing. |
| Why Use Packing? | When packing fails it simply starts to leak more and so can be readjusted and tightened to reduce the leak with the pump remaining in service. Whereas mechanical seal failure can necessitate the shutdown of the pump. This is why pump packing is the primary source of packing for fire pumps and other applications that can’t risk catastrophic failure. | |||
