Cartridge Seals

Mechanical Seal Gets Aggressive

Mechanical Seal Gets Aggressive

Mechanical seal, the retailer of teen and twenty-something fashions, has made a turnaround from negative profits to profits and then some. The company now competes with retailer Forever 21 when it comes to quick turnaround of trendy clothing and accessories sold at affordable prices.

One of the major differences however, between mechanical seal and Forever 21 stores is in the customer service and closing of the sale. Forever 21 sales associates watch over the dressing rooms and ring up the sales without being annoying or pushy about selling clothing. In other words they assist the customers where needed without being overbearing or annoying.

mechanical seal’s sales associates, however, have taken a turn for the pushy ever since the launch of the Seal Deal card. Purchased for , the card can be shown at the time of purchase at any mechanical seal store for 10 percent off of each item regardless of whether it is a regular, sale or clearance-priced piece of merchandise. The card is good for one year from the date of purchase.

Shoppers at mechanical seal can be assured that not only will a sales associate attempt to sell customers more clothes as they are shown a dressing room, but that they will be pushed to purchase a Seal Deal card while at the register.

It would be only slightly annoying if customers were asked if they were interested in purchasing the card and then that be the end of it, but some sales associates have become pushy and aggressive.

The typical sales pitch for the card includes the associate telling a customer that if they purchase the card in addition to the clothes they buy, the card is free. For example, if a customer spends approximately, 0 on one transaction at mechanical seal, and they buy the Seal Deal Card, they receive 10 percent off of each item purchased. The 10 percent savings from each item purchased then theoretically goes toward the price tag of the Seal Deal card making it “free.”

Any smart shopper knows however, that the card is not free because a customer is paying for it out of their 10 percent savings from the card. While a person may not have had the savings without the card in the original purchase transaction, they also did not have to spend the on a card.

Incidentally, the card is a good deal if someone frequently shops at mechanical seal. Customers should be smart in deciding whether or not the card is something that will save them money in the future based on how much they normally buy at mechanical seal. If someone is making at least one purchase per month at mechanical seal, then they might consider the card.

This individual not only went into the sales pitch of how the card would be free because of the amount of clothes being purchased, but she was also unprofessional enough to say (in front of the customer) to another sales associate that if she was able to sell the Seal Deal card in this transaction, she would have made her quota for the month.

After the associate was told the customer bought a Seal Deal card about 2 months ago, the associate went on to say that it would be better to spend another to buy a new one because it came in a “new case.” This “new case” would be code for the cheap, plastic-hinged box that the card came in. In addition, she said the customer would save more with a new card “because it was a newer card.”

This, of course, would be a bold-faced lie since a customer receives 10 percent off each item in every transaction regardless of when the card was purchased.

These sorts of sales tactics are embarrassing and more than likely do not truly reflect the mechanical seal company. However, in general the sales push to buy these cards, which are a good deal in some cases, has become annoying and in some cases, bullying. If the company continues to push their sales associates to meet these quotas and demand more from the customer, they are going to end up not having any customers, which was their problem not more than five years ago (although that was due to poor choices of inventory and pricing).

On a recent visit to the mechanical seal store at the Mall of Orange in Orange, CA, one sales associate was so bent on selling a Seal Deal card, she felt compelled to lie about the potential savings.

Noncontact mechanical seal

Noncontact mechanical seal

A noncontact mechanical seal has a seal ring which includes a sealing face portion formed by ventilative porous materials and a ventilating portion to pass a gas of a high pressure side to the sealing face portion from the back side of said sealing face portion. The sealing face portion is preferably a porous ring independently formed of said seal ring and mounted on the seal ring providing a space at the back side thereof. The seal ring preferably is provided with a small diameter thin portion at the portion forming the bottom of the space.

Noncontact seals are utilized to seal gas or the like. Noncontact seals include seal faces where high pressure gas is induced to keep the seal faces out of contact with each other. Such noncontact seals are provided at the sealing face with a very slightly tapered portion, a circle groove, a thin air flow hole or a spirally radial groove to induce high pressure gas to the sealing face thereof.

However it is hard (it increases the cost) to form the tapered portion, the groove or the hole with a high accuracy. In noncontact seals the seal faces are not completely noncontact; they contact each other slightly owing to vibration and/or poor accuracy of machining. Such contact causes wear of the sealing faces and deformation of the grooves follows. Thus the sealing ability of noncontact seals become worse as the sealing faces wear and therefore noncontact seals cannot keep providing stable and reliable sealing.

Furthermore the hole and the groove can sometimes be bigger than the required size because of difficulty of forming of small grooves, holes or the like and because of the need to make an allowance for the wear of sealing faces caused by vibration. Such a bigger groove and hole permits entry of more air, that separates the sealing faces too much and makes fine adjustment of the gap between the sealing faces difficult.

In such mechanical seal shown in FIG. 1, the high pressure gas in the high pressure side X flows through the ventilating groove 70, the porous ring 6 and the porous sealing face 11 toward the rotary seal ring 2. The gas in the relief space 60 maintains some gas pressure. The distribution of the pressure at the sealing face of the nonrotary seal ring 1 is shown in FIG. 2 as lines a, b and c. A line d represents the pressure which the back end of the nonrotary seal ring 1 receives. When the sealing face of the nonrotary seal ring 1 is closest to the sealing face of the rotary seal ring 2, as shown in FIG. 1 the pressure on the face is high as shown by line c. When the nonrotary seal ring 1 is more distant from the rotary seal ring 2, as shown in FIG. 5, the pressure decreases in the gap therebetween as shown by line a and this creates a vacuum force. Thus the pressure in the gap will then increase the balance with the force pushing the nonrotary seal ring 1 toward the rotary seal ring 2 at the line b, and the operation is carried out at this stable condition.

Since ventilation (or flowing the gas) through the porous ring 6 can be made very small, the gap between the nonrotary seal ring 1 and the rotary seal ring 2 can be very small. The gap is adjustable by controlling the balance factor of the nonrotary seal ring 1 and/or the ventilation of the porous materials of the porous ring 6. The ventilation may be decreased by reducing the number or the diameter of pores, so that the gap between the nonrotary seal ring 1 and the rotary seal ring 2 can be reduced. On the other hand the gap can be enlarged by increasing the number or the diameter of the pores. Such adjustment of the gap can be controlled by adjusting the thickness in the axial direction of the porous ring 6.

It is easier to mount the porous ring 6 on the nonosmotic ring 5 than to form holes on sealing faces in the prior art. The small diameter thin portion 76 of the nonosmotic ring 5 gives elasticity to the nonosmotic ring 5 to bend the portion 76 so as to move the outer fringe 62 apart from the rotary seal ring 2, which prevents improper contact between the outer fringe 62 and the rotary seal ring 2 and the extraordinary torque generated at the rotary seal ring 2 by such contact. Furthermore the relief groove 60 provides the porous ring 6 with the thin portion 61 which also gives elasticity to the porous ring 6 per se and the unwanted contact between the outer fringe 62 and the rotary seal ring 2 is further effectively prevented thereby.

FIG. 3 shows a graph indicating the difference of the values of leakage and contact torque between the noncontact mechanical seal of FIG. 1 and the noncontact mechanical seal of the prior art which include holes for ventilation and cannot provide elasticity. White circles indicate the rotation torque of the embodiment of FIG. 1 and white triangles indicate the leakage of the embodiment. Black circles indicate the rotation torque of the prior art and black triangles indicate the leakage of the prior art. The abscissa expresses the gas pressure of the sealed gas in the high pressure side X.

Since the mechanical seal of the invention provides an elasticity effect at the outer fringe 62, unwanted contact does not happen and therefore the rotation torque is small. Furthermore it is obvious that the leakage is larger at higher pressure than the prior art because of the small gap of the sealing faces. On the other hand, the torque of the prior mechanical seal increase as the pressure in the high pressure side X increases as shown by the black circles in FIG. 33, which is caused by the bending of the outer fringe of the sealing ring of the prior art toward the opposite counter sealing ring due to the pressure in the high pressure side X.

The ventilation of the porous ring 6 may not substantially change as the face of the porous ring 6 wears, which is contrary to prior noncontact mechanical seal. This provides stable and reliable sealing.

Mechanical seal assembly with improved fluid circulation

Mechanical seal assembly with improved fluid circulation

A seal assembly for a mechanical seal includes a rotatable shaft with at least one mechanical seal disposed about the shaft, the seal having a rotatable face coupled to the shaft and a stationary face, wherein the respective faces of the seal are in contact with one another, and a chamber for holding a cooling fluid, disposed about the shaft and in communication with the faces of the seal, and a closed loop fluid path disposed about the outer diameter of the shaft, preferably or in a non linear manner, in fluid communication with the chamber, for circulating fluid about the seal faces.

A variety of mechanical seals have been developed for use along a shaft, often in the context of pumps. One typical configuration is a mechanical seal with one stationary face and one rotating face. The rotating face of the seal rotates with the shaft of the pump, while the stationary face of the seal is generally coupled to the housing of the pump. In order to provide a tight seal, the two faces are typically in contact with each other. The frictional contact between the faces generates heat.

In order to dissipate heat, a fluid may be added to help transfer the heat away from the seal faces. Typically, a small fluid chamber is disposed about the shaft, so that the fluid is in communication with the seal face. As these mechanical seals are frequently used in a double or tandem configuration, the chamber may be disposed along the shaft, between and including the two mechanical seals. Often, a cooling fluid reservoir is added, with an auxiliary pump to circulate the fluid between the reservoir and the chamber. However, the addition of an auxiliary pump adds cost, requires additional space, and adds another component that is subject to failure, thereby reducing reliability.

There are many applications where a mechanical seal is subjected to fluid at the ID of the face. One of the most common is that of an unpressurized tandem seal where the barrier fluid is in contact with the ID of the primary seal and at the OD of the secondary seal. There is circulation of the barrier fluid into and out of the seal chamber by means of some type of pumping device that is usually part of the secondary seal rotating element. This circulation is adequate for cooling the secondary seal but is less than satisfactory for cooling the primary seal. This lack of cooling performance for the primary seal is due to the inability of the fluid to circulate to the ID of the seal.

Another application where cooling is needed at the seal face is in a vertical pump gear box seal oriented with the gear box oil at the ID of the seal. Gravity ensures that oil is at the ID of the face. However, during dynamic operation this fluid can not circulate with the bulk fluid in the gear box. This leads to increased seal temperature and possibly coking of the oil at one or both of the seal faces. Coking leads to increased leakage and damage to seal faces.

Rather than use an auxiliary pump, other configurations have built a “pumping rotor” into the system. See, e.g., U.S. Pat. No. 4,466,619 to Adams U.S. Pat. No. 4,560,173 to Adams et al. A slotted sleeve is fitted concentrically about the shaft, whereby the rotational movement of the shaft aids in circulating fluid along a fairly linear path, drawing the fluid from the reservoir into the chamber through an inlet, moving it radially around the shaft, and pushing it out of the chamber through an outlet and back into the reservoir. Another type of seal uses screw-type threads on the shaft to move the fluid between an inlet and an outlet. However, the fluid may only be moved in one direction in the chamber, between the inlet and the outlet, and away from the mechanical seal.

Because of the seal mechanisms themselves, it is generally not possible to position an inlet or outlet directly adjacent a seal face. Thus there is a space in the chamber between the inlet and outlet, which define the path of circulation, and the seal face, where the heat is generated and where the fluid will be heated the most. This causes a “dead end” space in the chamber between the seal faces and the respective inlet and outlet, where the cooling fluid is substantially stagnant, and does not circulate with the rest of the fluid. In the “pumping rotor” configuration discussed above, the radial circulating action occurs in a “band” that is aligned with the inlet and outlet; fluid outside this band remains substantially uncirculated. In the screw type circulator discussed above, these dead spots occur on either side of the inlet and outlet, as the fluid is substantially circulated only between the inlet and outlet. In the double or tandem configuration, there is generally a band or path of circulation between the seals, but there is inadequate circulation directly at the seal faces, where circulation is most necessary.

Thus there exists the need for a circulation device for mechanical seals which provides circulation to the seal faces, preferably without the use of auxiliary pumps, which can circulate fluid about the seal faces beyond the respective inlet and outlet locations, and which operates under rotation of the shaft in either direction.

An important feature of the present invention is the ability to circulate the fluid within the “dead end” space at the opposed faces of the seal. Although fluid cannot be pumped beyond this point, the present invention provides both radial and axial circulation, lifting the heated fluid away from the opposed seal faces and replacing it with cooler fluid.

Another important feature of the present invention is that it operates effectively upon rotation of the shaft in either direction. Thus the mechanical seal remains cooled regardless of the direction of shaft rotation.

Outside type mechanical seal device

Outside type mechanical seal device

The invention discloses an outside type mechanical seal device disposing the mechanical seal main body at the atmospheric side so as to stop leak of shaft seal of rotary shaft, comprising an annular stopper ring fixed on the rotary shaft by a setbolt, an annular flange bolted to the fixed side, plural protrusions formed integrally at positions confronting the stopper ring outer circumference in the flange at specified intervals to the outer circumference.

Spacers interposed between the inside of the protrusions and the outer circumference of the stopper ring, and cap bolts detachably driven into the stopper ring through the protrusions and spacers from outside the protrusions, wherein the axial center of rotary shaft of the stopper ring disposed on the rotary shaft is securely positioned in the radial direction and thrust direction, and the entire outside type mechanical seal composed of multiple parts is formed into one integral unit, thereby facilitating the assembling performance.

Mechanical seal devices have been hitherto classified in two types, that is, the inside type mechanical seal having the mechanical seal main body disposed at the fluid side such as liquid and gas, and the outside type mechanical seal having the mechanical seal main body disposed at the atmospheric side, and the inside type mechanical seal has been available in the integrated unit type, whereas the outside type mechanical seal device is not available in the integrated unit type at the present.

Accordingly, in the conventional outside type mechanical seal, it required an experienced skill in assembling the mechanical seal consisting of multiple parts including flange, seat ring, rotary ring, stopper ring, spring, O-ring and others, between the rotary shaft and the fixed side (for example, the stuffing box of the pump), and the assembling performance was poor.

It is hence a primary object of the invention to present an outside type mechanical seal device capable of securely positioning in the radial direction and thrust direction to the axial center of the rotary shaft of the stopper ring disposed on the rotary shaft, integrating the entire mechanical seal composed of multiple parts into one unit, and facilitating the assembling performance.

An outside type mechanical seal device capable of achieving more secure positioning in the radial direction and thrust direction to the axial center of the rotary shaft of the stopper ring disposed on the rotary shaft.

Since the stopper ring can be securely positioned thus in the radial direction and thrust direction, the entire mechanical seal device made of multiple parts can be integrated into a unit.

Therefore, when assembling the mechanical seal device, the integrated unit is assembled between the rotary shaft and the stuffing box of the pump as the fixed side as described below, and the assembling job may be facilitated, so that any particular skill is not needed in assembling.

That is, to assemble the mechanical seal device, to assemble the mechanical seal device, in the first place, the integrated unit of mechanical seal device is inserted into the rotary shaft, and the stuffing box of the pump casing is incorporated. In this state, using the flange bolt not shown from the atmospheric side AI, and using the grooves, the flange bolt is tightened into the screw hole (not shown) of the stuffing box side, and the integrated unit of the mechanical seal device is bolted to the stuffing box.

In short, according to claim of the invention, by the thickness of the plural spacers interposed between the inside of the protrusions and the outer circumference of the stopper ring, the stopper ring disposed on the rotary shaft is positioned in the radial direction to the axial center of the rotary shaft, and the cap bolt penetrates through the spacer to be screwed in the stopper ring, the stopper ring is positioned in the thrust direction (axial direction) to the rotary shaft.

In this way, since the stopper can be positioned securely in both radial direction and thrust direction, the entire mechanical seal composed of multiple parts can be integrated into a unit. Therefore, when assembling the mechanical seal, only the integrated unit may be incorporated between the rotary shaft and the fixed side, and the assembling job may be facilitated, thereby not requiring any particular skill.

Drive pins in a mechanical seal

Drive pins in a mechanical seal

Mechanical seal provides a sealing between a rotatable shaft and a housing. The seal has a stationary part for connection to the housing and a rotary part for rotation with the shaft. Mating sealing faces are carried by the stationary and rotary parts and the rotary parts are mounted on the drive shaft for rotation therewith. Each sealing face is held relatively stationary to their respective stationary or rotary part by means of at least one link member extending therebetween. The link member is arranged for at least limited longitudinal rotation.

A mechanical seal comprises a “floating” component which is mounted axially movably around the rotary shaft of, for example a pump and a “static” component which is axially fixed, typically being secured to a housing. The floating component has a flat annular end face, i.e. its seal face, directed towards a complementary seal face of the static component. The floating component is urged towards the static component to close the seal faces together to form a sliding face seal, usually by means of one or more springs. In use, one of the floating and static components rotates; this component is therefore referred to as the rotary component. The other of the floating and static components does not rotate and is referred to as the stationary component.

Those seals whose floating component is rotary are described as rotary seals. If the floating component is stationary, the seal is referred to as a stationary seal.

If the sliding seal between the rotary and stationary components are assembled and pre-set prior to despatch from the mechanical seal manufacturing premises, the industry terminology for this is “cartridge seal”. If however the rotary and stationary components are despatched individually (unassembled) from the mechanical seal manufacturing premises, the industry terminology for this is “component seal”.

Seal faces are generally held to their relevant stationary or rotary components by a mechanism that is called drive ring. One of the common mechanisms is the use of slots on the back of seal face and lugs on the drive ring or vice versa. FIG. 1 shows four slots on the seal face and four lugs on the drive ring. FIG. 2 shows two lugs on the seal face and two lugs on the drive ring. Rotation will be transferred from the seal faces to the drive ring at rotary faces or vice versa at the stationary faces.

Seal faces are mainly supplied from various grades of silicon carbide, tungsten carbide, ceramics and carbon. Carbon is categorised as a soft face.

The contact between the slots and lugs is mainly point contact. Under point contact, soft or brittle seal faces are more prone to failure than hard faces, especially in high pressure and large seal size applications. The failure may start by notch propagation around the contact point which gradually grows until it destroys the seal face.

Instead of having lugs on the drive ring, some designs employ drive pins that are pressed firmly into holes in the drive ring. These pins cannot move or rotate from their location. FIG. 3-2 illustrates the use of two pins to drive a lug on the seal face when the seal rotates either in clockwise or counter-clockwise direction. If the mechanical seal is designed to only rotate in one direction, one pin can be used for each lug. Alternatively, the pin may be square, cylindrical or any other shape

The pin’s head may have different shapes which are related to the contact area at the slot. FIG. 6 illustrates a different shape for the head of the floating pin illustrates a different contact area between the floating pin and its relevant slot.

The type of drive can be switched for rotary and stationary faces according to application. Similarly, some pieces of equipment such as shaft and pin in FIG. 8 may be stationary and the other pin may be rotary. It should be understood that the invention may be used with metallic components as well as nonmetallic components.

Depending upon the application of the seal, a floating pin of the present invention may be located at any position or angle relative to the seal faces.It should be understood that the invention may be employed for either rotary or stationary seals and single or double mechanical seal, whether designed in a cartridge or component seal format.