Shaft Seal Coolant Flow Control

The present invention relates to a control system for barrier fluid circulation used in double seal-type shaft seals typically used in pumps and other rotating equipment. Typically, barrier fluids use an external supply of cooling fluid such as water which aids in sealing and can serve to cool the seals.

Double seals are used in severe sealing conditions. A barrier fluid is introduced between the seals to serve several purposes, including: to lubricate and cool the outboard seal that normally does not see the working fluid; or to flush or dilute any working fluid (actual fluid being pumped by the pump) that should leak past the inboard seal; or to lubricate the inboard seal when the working fluid has poor lubricating qualities; or to cool the inboard seal. Double seal installations typically utilize barrier fluids in one of two ways: a closed system using pressure tanks and heat radiators and a recirculating system for continuously reusing the barrier fluid; or an open flush system where a continuous supply of barrier fluid passes through the seal arrangement only once before disposal or collection.

For an open flush system, modern environmental laws and conservation efforts demand improved monitoring and control to minimize the barrier fluids used in these systems. It is advantageous for a system to allow the user to establish the minimal flow rate that is necessary to cool the seal while maintaining the necessary barrier fluid pressure.

It is an object of the present invention to provide a method, a control system and apparatus for maintaining proper barrier fluid pressure within a seal arrangement while minimizing the amount of barrier fluid flow through the seal arrangement. It is an object of the present invention to provide, for a double seal arrangement, a minimal amount of barrier fluid flow between the inboard and outboard seals to lubricate and cool the outboard seal, to flush or dilute any working fluid that should leak past the inboard seal, to lubricate the inboard seal when the working fluid has poor lubricating qualities, and to cool the inboard seal. It is an object of the present invention to provide an apparatus which allows fine tuning adjustment of the barrier fluid flow rate and to provide control valves which resist clogging.

The objects of the invention are inventively achieved in that a control valve manifold is provided which has a first and second controlled passage therethrough for adjusting the barrier fluid flow rate and the barrier fluid pressure between an inboard and outboard seal. Additionally, a novel control valve arrangement is provided which resists clogging. Unlike the typical "V" flow control valve, where the flow is adjusted based on clearance between a movable valve plug element and the valve body wall, particularly the inner space between a V-shaped notch cut in the valve plug element and the wall of the valve body, the control valve constructed in accordance with the principles of the present invention controls flow rate or pressure based on the extent of registry of an elongate orifice formed through an otherwise closed-ended cylindrical valve element with an outlet of the valve body.

The orifice of the closed-ended valve element is preferably increasing in width in an axial direction of movement of the valve element to permit a wide range of flow rates corresponding to movement of the valve element. The orifice has angled side walls opening outwardly to prevent clogging. By configuring the exit orifice in this manner, solids contained in the fluid tend to settle on the floor of the valve, especially since the flow direction through the valve makes a right angle when it flows through the orifice.

In order to reduce the amount of barrier fluid used by the system, each gallon of fluid flowing through the seal must remove a calculated amount of heat from the system notwithstanding the desire to reduce the flow rate of barrier fluid. In order to prevent damage to the seal, the maximum temperature at which heat can be safely transferred for fluid, such as water, is 160 to 180.degree. F. prior to leaving the seal. Above this temperature range, water may be converted to steam during pressure fluctuations of the system. The formation of steam within the seal arrangement is detrimental, dramatically shortening the life of the seal. By using a lower temperature range of water exiting the seal, the amount of water required to remove heat from the system is increased. For example, if the ambient water temperature is 70.degree. F., and the water flow is initially adjusted to discharge at a temperature of 100.degree. F., water usage can be reduced by 71% by increasing the discharge temperature to 175.degree. F.

The control valves constructed in accordance with the principles of the present invention allow for fine adjustments at the higher barrier fluid temperatures and lower flow rates required to remove heat from the system. Furthermore, the control valves are designed to resist clogging by providing a 90.degree. fluid turn to the exit orifices of the control valves. The system ensures that the necessary barrier fluid pressure is maintained while the flow rates for quenching the double seal installation are reduced to a minimum.

FIG. 1 is an elevational view of the control manifold of the present invention with the remaining portions of the system shown schematically;

FIG. 2 is a longitudinal sectional view of the manifold shown in FIG. 1; and

FIG. 3 is a sectional view taken generally along line III--III of FIG. 2.

FIG. 1 illustrates the control manifold 10 of the present invention. The manifold has a hexagonal outside shape. The manifold 10 receives barrier fluids such as water from a supply line 14 and delivers barrier fluid to a seal 16 such as a double seal having an inboard seal and an outboard seal (not shown). The barrier fluid typically is delivered between the inboard and outboard seal. The supply line 14 delivers barrier fluid through a shut-off valve 16, through a check valve 18 to an inlet 20 of the manifold 10. The manifold 10 delivers barrier fluid from an outlet 24 to the seal assembly 16 and the barrier fluid is returned to a return inlet 26 to the manifold 10 and thereafter drained at a drain outlet 30 to a drain line 34 to be disposed or recycled. A temperature gauge 38 monitors the temperature of the water returned at the inlet 26 and a pressure gauge 40 monitors the pressure at that point. A flow control valve 42 is provided on one side of the manifold 10 and a pressure control valve 44 is provided at a respective opposite side.

The pressure control valve 44 is identically configured as the flow control valve 42 except facing axially in an opposite direction. To simplify the description, only the flow control valve 42 will be described in detail.

The flow control valve 42 comprises a bushing 50 having male threads 52 engaged to female threads 54 of a body 56 of the manifold 10. An O-ring 58 is provided between the bushing 50 and a bore 60 of the body 56 to seal the bushing 50 to the body 56. The bushing provides an internal channel 62 open to a stepped threaded bore 64. Axially arranged within the bore 64 and the channel 62 is a valve element 70. The valve element 70 comprises from left to right, a valve body 72, a pin 74, a wave spring 76, a valve adjuster 78 with surrounding male threads 80, and a secondary O-ring 82. A lock nut 84 is threadingly engaged around the male threads 80 of the valve adjuster 78 and locks the adjuster to the bushing.

The valve body 72 tightly interfits within an axial bore 90 which is open to the stepped threaded bore 64. The valve body 72 extends from the axial bore an adjustable distance into an annular channel 92 formed by the stepped threaded bore 64 which flow communicates with the outlet 24. The valve body has an open end 94 flow communicating with the inlet 20 and an elongate tapered orifice 96 shown more clearly with respect to the pressure control valve 44. The elongate orifice 96 is tapered to have its widest clearance 98 at a trailing end of the valve body 72 with respect to the direction of flow. The orifice 96 has a tapered profile which allows fine tuning adjustment of the valve over its axial range of motion especially for low flow rates.

At an opposite end of the valve body 72 is a closed head portion 100 which moves reciprocally within the bushing channel 62. At an end of the closed head portion 100 is an aperture 101 for receiving the pin 74. Between the head portion 100 and the adjuster 78 is a spring 76. The pin 74 is fixed in the adjuster 78 within a pin bore 104 and is slidable into the aperture 101. The adjuster 78 is threaded into the bushing 50 and by progressing the adjuster 78 into or out of the bushing 50, the adjuster becomes an axial direction limit stop for the valve body 72 toward the right of FIG. 3. Water pressure and velocity within the valve body 72 will maintain the valve body 72 toward the right and against the adjuster 78.

Flow through the inlet 20 proceeds through the open end 94 of the valve body 72 and through the orifice 96 into the annular channel 92 and out of the outlet 24. To adjust the flow rate, the adjuster 78 is threaded into or out of the bushing 50 which adjusts the amount of the orifice 96 which is in flow communication with the annular channel 92. After adjustment is made, the lock nut 84 can be tightened against the bushing to fix the position of the adjuster 78. The adjuster 78 is rotated to progress through the bushing 50 by a hexagonal socket 110 shown with regard to the valve 44. An allen wrench or the like is inserted into the indent 110 to adjust the valve.

FIG. 2 shows the temperature gauge 38 protruding into the inlet region 26 with a thermocouple 38a located within a thermowell 38b.

FIG. 3 illustrates the aperture 96 which has angular aperture walls which resist clogging thereof. An angle A equal to 60.degree. is advantageous.

The construction of the connection between the valve body 72 and the adjuster 78 allows for some degree of axial flexibility provided by the wave spring 76 and the pin 74 acting as a guide.

A method for coordinating the setting of the valves 42, 44 is as follows. First, the valves 42, 44 are fully opened. Next, the supply valve 16 is slowly opened to purge air from the system. The pressure control valve 44 is then slowly closed until the desired barrier fluid pressure is reached. Then, the flow control valve 42 is slowly closed until the pressure begins to drop in the manifold. The barrier fluid pressure within the manifold is then reset using the pressure control valve 44. Next, time is allotted for the discharge temperature of the barrier fluid to stabilize, the time period being typically 10-15 minutes. The flow control valve 42 is then closed, typically one turn clockwise. The pressure control valve 44 is readjusted to maintain the desired pressure. The temperature of the barrier fluid at the discharge is then allowed to stabilize once again. If the temperature as stabilized is still too low, that is, less than the optimal temperature for a minimized barrier fluid flow rate, the flow control valve 42 is turned another turn clockwise and the pressure control valve 44 is readjusted to maintain the desired pressure. The discharge temperature is again allowed to stabilize and if the temperature is still low the flow control valve 42 is closed one turn clockwise and the pressure control valve 44 is readjusted to maintain the desired pressure. This procedure is repeated until the discharge temperature approaches the desired discharge temperature, wherein the procedure is repeated with the adjustment to the flow control valve 42 incremented at quarter turns rather than full turns clockwise.

Although the present invention has been described with reference to a specific embodiment, those of skill in the art will recognize that changes may be made thereto without departing from the scope and spirit of the invention as set forth in the appended claims.