Welcome to "Frequently Asked Questions". Below you will discover a variety of questions and answers relating to different attributes of our products and their operation in various reverse pulse filter applications.

Our highly qualified R&D Engineers have years of experience and specialist knowledge in this field, if you have any further questions please click on the following e-mail address Technical Support.

Are all of our enclosures UL approved, and what part is approved?

A . Only the hazardous enclosures, that is the dust ignition proof (DIP) and explosion proof (FP), carry UL approval. The remaining enclosures are Nema4 and carry CSA certification.

IMPORTANT NOTE:
The UL approval is on an engineering specification basis and is only valid for the entire hazardous enclosure assembly. Any modification to this product after it has left the factory will invalidate the UL approval, leaving the persons performing the change liable in case of a product failure.

Blow Tube Design and Manufacturing Considerations

1. Design Considerations:
   
•  No of Bags - The blow tube design forms part of the overall system design, however it should be appreciated that as the number of bags per blow tube increases the potential effect on the pressure distribution along the blow tube also increases. That is, a blow tube with plain drilled equally sized holes can suffer from 2 problems. It has been proved both theoretically and by experiment that as the Nozzle area to pipe area (An/Ap) increases, the outflow angle from each port except the last also increases, potentially allowing the air jet to miss the bag mouth of the first few bags. In addition, a greater amount of energy in flow from the valve has been converted into dynamic pressure necessary to flow to the greater nozzle area, thus leaving less energy in the form of static pressure. Consequently, the first few holes can also suffer from reduced static pressure and cleaning potential. Go-Co redresses this problem as Go-Co nozzles are designed to straighten the flow and the Go-Co software calculates new nozzle sizes which compensate for the static pressure effects.
  
  
•  Wall Thickness- Schedule 40 pipe should always be used, otherwise problems relating to either too much flexibility or induced flow turbulence may result. Refer to Technical Note 01-09-01 for more details.
  
  
2. Manufacturing Considerations:
   
   
   •  Hole Alignment- The alignment of the drilled holes is important to maximizing the cleaning potential. The Go-Co nozzle can tolerate slight misalignment in the drilled holes.
     
     
   •  Hole Deburring - All holes need to be debured inside and out. Any burrs will cause a negative effect on the flow coefficient of the hole.

A. Unfortunately integral pilot valves are unsuitable for high temperature applications, even though viton versions are available. The viton components in these valves lend the product chemical resistance, however temperature of application is still limited by the coil and coil encapsulation.

Goyen solenoid coils are encapsulated in self-extinguishing nylon. This material begins to soften at ambient temperatures of 80°C and should never be used where ambient temperatures are beyond 100°C. Also, as temperature increases resistance in the coil windings also increases, markedly reducing performance of the coil.

In practice it is best to use the solenoid coils at temperatures less than 80°C.

Common Causes of Valve Return Spring Failures

A. Valve spring failures can generally be categorized into failure related groups, namely diaphragm resonance induced failures and material defect failures. With the majority of cases identified as resonance or system related. Through our collective experience with resolving valve spring failures we have identified a number of likely related causes which can be used as a diagnostic aid if future problems occur, these include:

1.  Resonance Induced Failures
   
   

   Case #	Cause	Description	Check
   1	Slow to Open	Should the main diaphragm be slow to open then the valve disc can beexcited into resonance by the speeding flow through the gap betweenthe body and diaphragm seat.	Pilot valve opening time >= 50ms. Pilot tube ID >= 4mm. Pilot tube length <= 1m. Silencers are not clogged.
   2	Partially Opening valve	When the diaphragm hovers in the partially open position again the diaphragm can be excited into resonance by the flow.	Pilot valve opening time >= 50ms. Pilot tube ID >= 4mm. Pilot tube length <= 1m. Silencers are not clogged.
   3	Slow to Close valve	Similar to case 1 where the gap occurs before the diaphragm fully closes.	Air leaks from pilot tube connections or from CA and main covers screws. Porosity. Bleed pin partially blocked.
   4	Inlet Pipe turbulence	Flow turbulence occurs at the inlet port if the flow is tripped in some way, for eg large diameter changes with hose connections and heavy gauge wall pipe, which can then induce diaphragm resonance.	Heavy gauge wall pipe (only use Sch 40). Sharp edges and burrs at saw cut off sections and flame cut openings. Extra short connecting pipes, especially where rubber hose connections are used.
   5	System Induced Resonance	Abrupt changes in the header pressure on valve opening or closing can induce resonance in the header to occur. Consequently, this causes the valve diaphragm to resonate. A similar effect can be seen if the inlet supply system to header is undergoing a pressure transient due to outside influences.	Excessively small inlet pipe to header. excessively small header volume - refer Go-Co sizing requirements.
   6	Diaphragm not sealing	Poor diaphragm sealing can cause flow past the seat to occur which subsequently causes the diaphragm to resonate. This has been a problem after initial plant commissioning.	Excessively small inlet pipe to header. excessively small header volume - refer Go-Co sizing requirements.

 What is the difference between a Dust Ignition Proof and a Flame Proof enclosure?

A. The design of a Dust Ignition Proof (DIP) enclosure must prevent the ingress of dust into the enclosure, which may cause a hazardous situation. A Flame Proof (FP) enclosure, also sometimes known as an explosion proof enclosure, must prevent the escape of a flame from within the enclosure to atmosphere.

From an assembly perspective, these two enclosures are identical other than a neoprene gasket that is assembled between the mating flanges of the DIP enclosure. This gasket is designed to prevent the ingress of dust. An FP enclosure does not use a gasket, instead the flame path is controlled by a regulated clearance between the mating flanges as specified by EN50014, EN50018, and UL.

The DIP and FP enclosures carry separate approvals and the two kinds of enclosures cannot be used interchangeably.

  Go-Co Says: Nozzle > 22mm

Go-Co Message:
"The estimated nozzle size is greater than 22mm, the largest nozzle size available with the Go-Co cleaning system. Reduce the number of filter bags per row."

Meaning:
The cleaning system being modelled requires a Go-Co nozzle size larger than that offered by Goyen. Currently 22mm is the largest nozzle size offered.

Action:
A large nozzle diameter is the result of a large reverse flow requirement.

To make the system workable you can do one or more of the following:

• Reduce the cleaning velocity factor.
• Reduce the design flow rate of cartridge (for cartridges only).
• Reduce the air to cloth ratio, bag length, bag diameter, or all three (for bag systems only).
• Reduce the number of filters per blowtube.
• Increase the valve and blow tube sizes.
• Increase the operating header pressure.

Go-Co Says: Nozzle < 4mm

Go-Co Message:
"Nozzle required < 4mm. Increase the number of bags cleaned or decrease the size of the valve."

Meaning:
The cleaning system being modelled requires a Go-Co nozzle size smaller than that offered by Goyen. Currently 4 mm is the smallest nozzle size offered.

Action:
A very small nozzle diameter is the result of a highly restricted reverse flow requirement. To make the system workable you can do one or more of the following:

• Increase the cleaning velocity factor.
• Increase the design flow rate of cartridge (for cartridges only).
• Increase the air to cloth ratio, bag length, bag diameter, or all three (for bag systems only).
• Increase the number of filters per blowtube.
• Decrease the valve and blow tube sizes.
• Decrease the operating header pressure.  

Go-Co Says: Nozzle area is greater that 150%

Go-Co Message:
"The calculated total nozzle area is greater than 150% of the valve outlet area. This may lead to inconsistent valve performance and poor filter cleaning. Either decrease the number of filters being serviced by the valve, or select a larger valve."

Meaning:
Although each individual nozzle size is offered by Goyen, the sum of all the nozzle areas along the blowtube is greater than 150% of the cross-sectional area of the blowtube. Under these conditions valve performance may be marginal, and the blowtube is unable to provide sufficient air-flow to meet the cleaning requirements at each nozzle.

Action:
A large total nozzle area is the result of a large reverse flow requirement.

To make the system workable you can do one or more of the following:

• Reduce the cleaning velocity factor (1.1 is marginal).
• Reduce the design flow rate of cartridge (for cartridges only).
• Reduce the air to cloth ratio, bag length, bag diameter, or all three (for bag systems only).
• Reduce the number of filters per blowtube.
• Increase the valve and blow tube sizes.
• Increase the operating header pressure.

What length and size tube should be used with the 3d type remote pilot valves?

A. All testing at Milperra is performed with 6mm pilot lines no longer than 1000mm and with a bore of 4mm diameter. Pilot lines with a smaller bore restrict the exhaust of the dust collector valve and may prevent the valve from opening. Where the valve does open it is well established that even a small reduction in the bore of the pilot line will slow down the opening of the valve noticeably.

Pilot lines of excessive length can also prevent a dust collector valve opening. This problem occurs when the pilot valve closes before the pilot line and dust collector valve is adequately exhausted to lift the diaphragm. The length at which this becomes a problem may vary between valves and installations, however a length of 1000mm is regarded as safe for most, if not all, applications. Where longer lines are required, the line length may be compensated in many cases by increasing the electrical on-time of the remote pilot valve. Naturally, the shorter the pilot line the faster the response of the dust collector valve to the remote pilot valve.

It is also worthwhile noting that pilot tubes with small bores or excessive length have been known to contribute to diaphragm and spring resonance in the dust collector valve, where the diaphragm fails to open properly. Diaphragm and spring resonance are known contributors to the premature failure of these components.

What surface finish requirement is called for when mounting MM valves?

A. The original Goyen Tech Spec CAS-3 stipulates surface finish to SA 1163.
When the MM group of products were first put on the market, a suitable specification was hard to establish.
The AS 1163 only goes part the way to satisfying an adequate body to header mounting arrangement.
The following passages of the specification are the only valid information and are written as follows:

Section 10:
Freedom of Surface Defects
The section shall be free from lamination, surface flaws and other defects detrimental to its use for structural purposes.

Section 11:
11.1 Grinding
When removal of surface defects by grinding is adopted, the ground area shall be well flared and the remaining wall thickness in the ground area shall be not less than 90% of the nominal thickness.
11.2 Depositing weld metal
Welding used in the repair of surface defects shall be performed in accordance with AS 1554.1, using low - hydrogen electrodes compiling with AS 1553.
Welds shall be sound the weld metal being thoroughly fused without undercutting or overlap.
The weld metal shall project at least 1.5 mm above the rolled surface and the projected metal shall be removed by grinding flush with the rolled surface.

Section 12:
Removal of upset
Hollow sections are produced by electric resistance welding shall have the external upset removed. 

What size pipe fits DD Valves and Bulkhead fittings?

A.The range of 20, 25, 40 & 45 DD valves and bulkhead fittings, have been designed to accept "Schedule 40 welded and seamless wrought steel pipe" outside diameters as per ANSI B36.10M-1985

Schedule 40 pipe size	Pipe Outside Diameter
20 (3/4")	26.67 mm (1.050")
25 (1")	33.4 mm (1.315")
40, 45 (1.5")	48.26 mm (1.900")

All DD valve / bulkhead inlet outlets, are designed with sufficient clearance for schedule 40 sizes plus out of Tolerance conditions as ovality, adequate fitment should occur.