Field Engineering Bulletin - Sundyne

1 14845 West 64th Avenue, Arvada, Colorado 80007 USA Tel: 303-425-0800 Fax: 303-425-0896 Bulletin No. Sunflo Pump Seal Plans EFFECTIVE: APRIL 11, 2006 Rev: A An overriding majority of pump problems are not with the pump, but with the mechanical seals. Pump mechanical seals need three conditions for successful operation: 1. Clean Liquid 2. Cool Liquid 3. Low Pressure Liquid The single seal auxiliary kit drawings are used to provide any one or all of these requirements for single seal pumps. Process fluid is altered to satisfy the mechanical seal, and then reunited with the main stream inside the pump. There is no loss in net flow rate, and no contamination of the process from external sources. The environmental seal plans should be employed based on past experience and common sense.

2 Many applications will not require that an auxiliary system be used for the mechanical seal. However, when a customer inquires about a harsh service or experiences repeated seal failures, it is important to supply the proper environmental seal kit. Consult the factory whenever necessary. Although these kits will resolve a majority of seal problems, the following guidelines apply to double and tandem seals used for severe services. DOUBLE SEAL APPLICATIONS Double seals should be used whenever the single seal auxiliary kits prove unsuccessful. Hot water applications (in excess of 260 F (127 C)) always require double seals. Water services between 180 F (82 C) and 260 F (127 C) can use double seals if process cooling cannot be tolerated. Conversely, the single seal cooling plans 21 & 41 can be used with double seals above 260 F (127 C) as long as the heat exchanger is resized for adequate cooling and the buffer outlet can be plumbed into the pump suction line. Finally, double seals are an excellent method for sealing hazardous or poisonous liquids that cannot leak into the workmen s environment.

3 Double seals must have a pressurized buffer system (15 psig (1 bar) above seal cavity pressure) that circulates approximately 2 gpm ( l/m) of process compatible buffer fluid. A Plan 53 is normally used with double seals. The buffer fluid should be cool water, seal oil, or some other liquid that is easy for the mechanical seals to handle. TANDEM SEAL APPLICATIONS Tandem seals may be used instead of a single seal for leak detection and backup. Typically, an atmospheric buffer system is employed with provision for self-circulation or forced circulation of to 2 gpm ( to l/m) required to control the seal temperature. The buffer may be cool water, oil or other suitable non-volatile liquid. Field Engineering Bulletin Title: Sunflo Pump Seal Plans Rev A Bulletin No. Page 2 of 13 A description of the auxiliary seal kit numbering system will aid in selecting the proper seal kit. KF XX XX XX Kit, Flush (Single seals only) Similar to API Plan 11 12 13 Pump Model Number 21 FL = P-1000 23 = P-1500 Varies Note 1 31 UT = P-2000 32 SP = P-3000 41 52 53 Note 1: Varies based on process conditions, heat exchanger, etc.

4 Refer to individual kit drawings for specific information about orifice sizing, flush flow rate, maximum pressure, and maximum temperature limits. SEAL FLUSH PLANS Below is a brief description of the seal flush plans available for Sunflo pumps. PLAN 11 This kit circulates process fluid from the pump discharge, through an orifice, then into the seal cavity. It maintains an ample supply of gas-off when the seal cavity pressure is below atmospheric pressure. Plan 11 is recommended when vacuum can be detected in the seal flush port during pump operation. This occasionally occurs on low suction pressure units (less than 20 psig ( bar)) that do not have an inducer. PLAN 12 Plan 12 is similar to plan 11 except a filter or strainer is added to the flush line. This kit is used to provide a clean seal flush in the event the product contains abrasives or fouling material which cannot be removed by a centrifugal separator.

5 Satisfactory seal life may be achieved by filtering to a maximum particle size of two microns. The orifice must be sized to allow 1 to 2 gpm ( to l/m) of clean product flow into the seal flush port. This kit may be helpful in machine tool coolant service and paper shower service (where the water contains wood pulp). Title: Sunflo Pump Seal Plans Rev A Bulletin No. Page 3 of 13 PLAN 13 Plan 13 is similar to plan 11 except the flow exits the seal chamber and returns to the pump suction. This auxiliary seal kit recirculates liquid and entrained vapors from the seal cavity chamber, through a tubing orifice, then back to the pump suction. The amount of recirculation is regulated by the inch ( mm) tubing inside diameter and the length specified on each kit drawing. This kit provides maximum circulation around the mechanical seal face and helps to ensure that liquid, not vapor, is available at the seal faces.

6 Plan 13 is recommended for light hydrocarbon services and any other time the process vapor pressure is above atmospheric pressure. It can be helpful whenever a centrifugal separator is ineffective; such as saltwater processes and applications involving suspended wood particles. Refer to the Plan 31 description for further details. PLAN 21 Plan 21 is similar to plan 11 except with cooling. This auxiliary seal kit causes the vapor pressure of fluid in the seal cavity to be below atmospheric pressure when the remainder of the pumpage is not. Allowance is made for friction reheating the fluid as it crosses the mechanical seal face so that the fluid remains in the liquid phase. A small portion of liquid is tapped off the pump discharge then forced through an orifice, heat exchanger, and to the seal cavity. The heat exchanger must be located downstream of the orifice to avoid using expensive, high pressure heat exchangers.

7 The cool seal flush reduces scuffing on the seal faces and chipping on the inside diameter of the seal nose. Hot water applications between 180 F and 230 F (82 C and 110 C) use a 2x9 cooler (Young 201 or equal); between 230 F and 260 F (110 C and 127 C) requires a 3x9 cooler (Young 301 2 pass or equal); above 260 F (127 C) use double seals. PLAN 23 This kit circulates process fluid with a pumping ring in the seal chamber to a heat exchanger and back to the seal chamber. This kit offers efficient seal cooling with low cooler duty. This kit is good for high temperature applications such as hot hydrocarbons and boiler feed water. Title: Sunflo Pump Seal Plans Rev A Bulletin No. Page 4 of 13 PLAN 31 Plan 31 is similar to plan 11 except an abrasive separator is added to the flush line. This kit provides clean fluid to the mechanical seal. Generous internal clearances in Sunflo s allow the pump to pass particles as large as 400 microns, but the seal needs to be protected from abrasion.

8 The centrifugal separator removes 95% of harmful particulates that are heavier than the process density, and can increase seal life threefold. Dirty fluid is orificed from the pump discharge into the separator where an additional 60 psig ( bar) pressure drop occurs. Clean process liquid rises to the top and enters the seal compartment via an unrestricted path. Concentrated dirty fluid recirculates back to the pump suction through an orifice sized to accommodate seal cavity pressure rise. Union orifices must be used to simplify replacement of eroded orifice plates. The centrifugal separator eliminates scratches on the seal face and chipping on the outside diameter of the seal nose. It is effective only if suspended solids can separate out of a process sample in less than ten minutes. Dissolved solids (saltwater), and low density particulates (wood pulp and paper fines) need either a cool, clean external flush or Plan 13.

9 PLAN 32 This kit provides the seal flush from a clean external source. Plan 32 is used when the process is difficult to condition in a way that provides sufficient cooling and lubrication to the seal. It is beneficial when the process contains components which may cause abrasive wear or impede the free movement of the seal. Seal chamber pressure will increase as well as fluid vapor margin. This kit is good for high temperature and dirty service applications. PLAN 41 Plan 41 is a combination of plans 21 and 31. This auxiliary seal kit combines the cooling capability of Plan 21 with cleaning provided by Plan 31. Process fluid is cleaned first to reduce fouling downstream in the heat exchanger. Orifice sizing is based on the centrifugal separator s requirement because pressure drop in the heat exchanger is negligible. The centrifugal separator can effectively clean the process if suspended solids settle out of a sample in less than ten minutes.

10 It will not work against wood pulp and paper fines or dissolved solids such as saltwater. A 2x9 heat exchanger adequately cools water processes that are between 180 F and 230 F (82 C and 110 C). A 3x9 2 pass heat exchanger is used for water inlet temperatures between 230 F and 260 F (110 C and 127 C). Water above 260 F (127 C) requires double seals. Title: Sunflo Pump Seal Plans Rev A Bulletin No. Page 5 of 13 PLAN 52 This kit provides an atmospheric buffer between the tandem seals. Normally, this is required for environmental protection reasons. The buffer kit may be vented to a flare stack through an orifice with an upstream pressure switch which will alarm should the primary (inboard) seal fail. The kit should have three main features: 1. Alarm / shutdown for an increase in buffer pressure (loss of primary seal). 2. A means to ensure that loss of buffer is detected. 3. Circulation is assured through the seal area by proper self-circulating design, or by the use of a circulating pump.