ESD Pressure Compensators

Application
A suitable liquid is required to lubricate the seal faces. Even though the consumption of this seal liquid may be extremely small at a sealing gap of < 1 µm in height, a certain amount needs to be kept available in order to ensure significantly long periods of no-maintenance. If this lubricant is kept in an enclosed space (seal chamber), then pressurization of this space to values that lie above the vessel pressure can avoid the product to be sealed from penetrating into the seal chamber and from escaping via the atmospheric seal side.

Differently designed seal liquid storage vessels, modifications to hydraulic installations, accessories and instruments as well as design variations of the seal chamber itself offer individual advantages with respect to operational safety, service life and automation.

The pressure compensator type VGD is designed for applications of up to 40 bar and offers all functions of a thermosiphon vessel. Pressure compensators type VD can be used up to 100 bar.

The pressure compensator VDH features a hermetically sealed piston rod. It is mainly used where hermetical sealing is needed, such as for the ÉKATO magnetically driven agitator type ESM.

Standard pressure compensators are fitted with various accessories such as refill pumps, pressure safety valves and monitoring devices.

Application Data VGD
Working limits: ESD34 and ESD44
Volume: 1.5 liter
Pressure ratio: 1 : 1.07 (standard)
Working pressure: up to 40 bar
Cooling water flow rates for optional cooling water jacket:
Shaft diameter from 40 to 100 mm Qmin > 50 l/h
above 100 mm Qmin > 70 l/h

Application Data VD
Working limits: ESD34H
Volume: VD120: 1.0 liter
VD060: 0.3 liter
Pressure ratio: 1 : 1.07 (standard)
Working pressure: up to 70 bar
Cooling water flow rates for optional cooling water jacket:
Shaft diameter from 40 to 100 mm Qmin > 50 l/h
above 100 mm Qmin > 70 l/h

Application Data VDH
Working limits: ESD44ESM
Volume: VDH120: 0.8 liter
VDH060: 0.2 liter
Pressure ratio: 1 : 1 (standard)
Working pressure: up to 100 bar
Cooling water flow rates for optional cooling water jacket:
Shaft diameter from 40 to 100 mm Qmin > 50 l/h
above 100 mm Qmin > 70 l/h

Quality
ESD mechanical seals are designed on criteria ensuring minimum leakage rates involving usage of FEA. In contrast to other principles they therefore only require small reserves of lubricant. The result are both safe and low-cost solutions.

All ESD mechanical seals and accessories are suitable for applications in hazardous areas and are TÜV certified in accordance with ATEX standard 94/9/EC.

Function
In order to avoid having to operate the seal liquid chamber of a mechanical seal with a constant pressure overlay of maximum pressure at alternating vessel pressure, a spring loaded piston pressure compensator can be used as hydraulic component.

The pressure compensator receives its primary pressure (vessel pressure) via a reference line which is linked to the seal flange. Due to construction characteristics the vessel pressure is boosted by a factor of 1.07 and transferred to the seal liquid. By this the pressure inside the seal housing automatically remains 7% above the vessel pressure independent of absolute values.

By applying the pressure compensator seal ring loads are minimized which has the advantage of reduced heat generation, smaller power requirement as well as less wear on the seal rings.

The piston of the pressure compensator stands still during operation; in the case of loss of seal liquid the piston moves. The seal liquid level is visible at the switch head. As an alternative, Namur-switches can be fitted which make remote control of the liquid level inside the pressure compensator possible and which can, for example, operate an automatic refill-unit.