0 • Home • Contact Us Enter search keyword Mechanical Engineering 4 UOnline Club For Mechanical Engineers • AutoMobile • Design • Latest Technology • Material Science • Student Resources » • Technical Stuff • Videos Categorized | Technical Stuff API Mechanical Seal Flushing Plan – Part 1 Posted on 12 June 2011. Tags: API Mechanical Seal Flushing Plans, API plans, flushing plans, seal flushing Why flushing is required? In mechanical seal heat is generated between the rotating and stationary seal face. If more amount of heat is generated between the faces cause the mechanical seal failure. In order to avoid the seal failure flushing fluid is injected between the seal face. There are different types of flushing plans used depend upon the conditions. These are following condition for selecting suitable mechanical seal flushing plan for both the supplier and vendor. • Nature of working fluid (pumping fluid)such as toxic, corrosiveness, hazards chemicals. • Suspended solid particles in the pumping fluid. • Temperature of pumping fluid • Vapour pressure of pumping fluid API Plans: They are various types of flushing plans used in most of the industrial pumps. Now we see the API standard plans in detail. Ads by Google Mechanical Seal Pump Seal Hand Water Pump Heat Pump Costs Page 1 of 11 API Mechanical Seal Flushing Plans-Part 1 | Mechanical Engineering 4 U 5/17/2012 http://www.mechanicalengineering4u.com/technical-stuff/api-mechanical-seal-flushing-pla...
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Posted on 12 June 2011. Tags: API Mechanical Seal Flushing Plans, API plans, flushing plans, seal flushing
Why flushing is required?
In mechanical seal heat is generated between the rotating and stationary seal face. If more amount of heat is generated between the faces cause the mechanical seal failure. In order to avoid the seal failure flushing fluid is injected between the seal face. There are different types of flushing plans used depend upon the conditions.
These are following condition for selecting suitable mechanical seal flushing plan for both the supplier and vendor.
• Nature of working fluid (pumping fluid)such as toxic, corrosiveness, hazards chemicals.• Suspended solid particles in the pumping fluid.• Temperature of pumping fluid• Vapour pressure of pumping fluid
API Plans:
They are various types of flushing plans used in most of the industrial pumps. Now we see the API standard plans in detail.
Ads by Google Mechanical Seal Pump Seal Hand Water Pump Heat Pump Costs
Page 1 of 11API Mechanical Seal Flushing Plans-Part 1 | Mechanical Engineering 4 U
In this mechanical seal plan the dead-ended seal chamber with no flush line arrangement. In which the pumping fluid pass through the back of impeller and fill the seal chamber. There by the seal faces were cooled. The pressure in the seal chamber is controlled by the expeller at the back of the impeller. In the case of moderate temperature services large bore open throat seal chamber is used. On the other hand for high temperature services cooling jacket seal chamber is used. Process fluid must have adequate boiling point margin to avoid vaporization between the seal faces. Often used in combination with steam quench Plan 62.
API Flushing Plan 02
Advantages:
• Simple no environmental controls• Economic design of pump
Disadvantages:
• The plan only used for clean fluids• Pump back clearance is very important because change in back clearance cause change in seal chamber
pressure.• Increase in throttle bush clearance also cause change in seal chamber pressure.
API PLAN 11
Seal flush is taken from the pump discharge through an orifice. The function of orifice is to regulate the flow rate of flushing fluid to the seal chamber. In this plan use an orifice with a minimum 3 mm diameter based on the calculate flow rates to size orifice to adequate seal chamber flow. The flush fluid is injected directly over the seal faces with piping at 12 O clock position. In multistage pumps we get the flushing from the most convenient pump area.
Page 2 of 11API Mechanical Seal Flushing Plans-Part 1 | Mechanical Engineering 4 U
• Flushing fluid taken from the discharge, hence increase seal chamber pressure and allow the fluid with less vapour margin
Disadvantage:
• Used for clean fluid• Typical failure mode is a clogged orifice – check temperatures at pipe ends
API PLAN 13
In this mechanical seal plan the flushing fluid enter the seal chamber from the back of the impeller. In which the seal chamber pressure is normally 1 to 1.5 times greater than the suction pressure. Hence it is re-circulating the flushing back to the pump suction. This type of flushing plan is mostly used in vertical pumps and continuous seal chamber venting is also provided. There by seal chamber heat is removal. In the case of moderate temperature fluids with moderate solids vent piping loop prior to starting vertical pumps. The size of orifice is determined by calculating the flow rates of fluid to the seal chamber normally the size of an orifice with a minimum 3 mm diameter is used in most of the industrial pumps.
Page 3 of 11API Mechanical Seal Flushing Plans-Part 1 | Mechanical Engineering 4 U
If the seal chamber pressure is very high then it indicates that to select the proper orifice and throat bushing sizing. Typical failure mode is a clogged orifice – check temperatures at pipe ends
Advantages:
• Used for fluid which contain moderate solid particles
Disadvantage:
• Due to the presence of solid particles, orifice clogging is takes place this leads to seal failure.• Only used for vertical pumps
API PLAN 14
In this mechanical seal flushing plan the fluid from discharge and recirculation back to the pump suction with orifices. This type of flushing plan is the combination of Plan 11 and 13 there by the seal chamber heat is removed. Increase seal chamber pressure and fluid flow rate is determined by the seal chamber inlet and outlet orifice. This type of seal plan is used on vertical pumps and Clean fluids at moderate temperatures. Increase boiling point margin of flushing fluid with proper orifice and throat bushing sizing. Flush should be directed over seal faces, Vent piping loop prior to starting vertical pumps
Page 4 of 11API Mechanical Seal Flushing Plans-Part 1 | Mechanical Engineering 4 U
This type of mechanical seal plan is used for the flushing fluid with high temperature. This plan is similar to API plan 02 but it consisting of circulation ring for circulates the flushing fluid to the heat exchanger to reduce the temperature of the flushing before it reach the seal face. This type of flushing plan is used for high temperature service typically less than 177oC. If reduce fluid temperature to increase vapour margin.
API Flushing Plan 21
Page 5 of 11API Mechanical Seal Flushing Plans-Part 1 | Mechanical Engineering 4 U
If the flushing fluid is over 80 oC, Seal cooler and piping must have air vents at highest elevation. Venting the seal chamber before starting the pump is very important because to avoid the dry run of mechanical seal. Calculate the flow rates to size an orifice for adequate seal chamber flow Increase boiling point margin with proper orifice and throat bushing sizing. Regularly monitor device inlet and outlet temperatures for signs of clogging or fouling
API PLAN 23
This mechanical Seal flush plan is similar to API plan 11 the only difference is the fluid from the pump discharge is cooled by a cooler before the seal chamber as shown in the figure. This is the standard flush plan for hot water services such as used in boiler feed water pump. Efficient seal cooling with low cooler duty increase fluid vapour margin. This plan is used for high temperature service, hot hydrocarbons and Boiler feed water and hot water over 80oC.
API Flushing Plan 23
Seal cooler and piping must have air vents at highest elevation. The piping arrangement is shown below.
Page 6 of 11API Mechanical Seal Flushing Plans-Part 1 | Mechanical Engineering 4 U
Seal chamber requires close clearance throat bushing to isolate hot process fluid from the cold seal chamber flushing fluid. Regularly monitor cooler inlet and outlet temperatures for signs of plugging or fouling.
API PLAN 31
In this type mechanical seal flush plan is used for the pumping fluid consisting of solid particles. The flushing fluid from pump discharge is passing through a cyclone separator for separating the suspended solids from the pumping fluid. Centrifuged solid particles are returned to pump suction from the cyclone separator. Seal chamber heat is flushed by the fluid from the cyclone separator. This type of flushing plan is used for dirty or contaminated fluids, water with sand or pipe slug etc..,
Cyclone separator works best on solids with a specific gravity twice the process fluid. Seal chamber pressure must be nearly equal to suction pressure for proper flows. The piping should not include an orifice and is not expected to vent the seal chamber.
Page 7 of 11API Mechanical Seal Flushing Plans-Part 1 | Mechanical Engineering 4 U
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Page 10 of 11API Mechanical Seal Flushing Plans-Part 1 | Mechanical Engineering 4 U
