Top hinged vent in closed position

Top hinged vent opening under blast loading

Top hinged vent can be re set after explosion

Additional Information

Selecting a Release Pressure

State the minimum required opening/release pressure. This can be factory set. Note – it may be necessary when stating this to consider local climatic conditions to allow for wind and other salient external effects which may exceed the release pressure and cause the vent to open when not required.

Under normal operating conditions the vent can be closed after having been released and will be ready to operate again upon closure. It should be checked for correct operation however to ensure the blast pressure that the unit has vented has not been greater than anticipated and in consequence could have damaged or misaligned the vent unit or an uneven or quasi static pressure wave may have twisted the unit.

Fitting Instructions

 Preparing the unit for installation – single and multi-unit system

The vent panels and outer frame are usually delivered as a single item. Unless specifically requested otherwise, the outer frame will already be prepared on site for fixings. Ensure that the fixings that are going to be used are aligned with suitable fixing points in the wall aperture. Do not fix into thin sheet metal or cladding materials.

When the unit is fixed into the wall aperture the vent panels should open and close freely. Ensure that the unit is not fitted in twist and is well packed around each fixing point to avoid stretching or compressing the clearances around the hinged panels. These will have been factory checked before dispatch. The fixing tabs around the outer main frame are factory prepared for fixings. They project inwards (or sideways for surface fixing) enabling the whole assembly to be installed without the need to dismantle components. The face fix option is to be installed on the surface of the wall construction.

The assembly can be broken down into smaller components, but this is not recommended if it can be avoided. Realigning components on site is much more difficult than in a factory environment. In addition, the inner frame assemblies are sometimes bedded on sealant, and this would have to be broken and reinstated making the entire process arduous.

Note: Always check that the latch is in the open position when closing the vent panel. If not, manually move the latch into the correct position. See images left.

The cable restraint is fitted last, after the whole assembly has been installed into the building aperture. This is a steel wire cable wrapped in a plastic sheath to minimise scuffs and scratches to the local paint finish.

Fit one end to one of the outer assembly fixing bolts (suitable for M12 fixings) and the opposite end to the angled plate which is bolted through underneath the inner pull handle. This will accept an M8 nut and bolt with washer.

Loop the cable generally as shown and test the panel to ensure that the cable does not snag on anything when opened.

The cable restraint is intended to minimise the travel of the opening vent flap and also act as a further restraint should the panel begin to fail due to excessive overpressure. It is not a guaranteed solution to the potential of catastrophic failure due to excessive overpressure or resultant quasi static forces often resulting from internal blast and gas pressures.

Under normal operating conditions the blast vent may open and close many times and each time the unit should be checked for damage or distortion which can always occur should the internal blast loading be more onerous than anticipated or the unit undergo a non-uniform blast load.

Check that the vent itself has not become loose around its fixings into the wall, that all screws and fixing bolts are tight and that the vent itself closes and seats into the outer frame. Also look at the Release Unit clearances and adjustments as detailed separately. Although not a direct component of the Pressure Release Vent it is always worth checking that all mastics and sealants are intact and show no sign of degradation either following an incident or as just part of the maintenance regime. All of these points should be included within the company maintenance programme.

Finally, after installation and as ongoing maintenance, clean the unit with a non-abrasive proprietary cleaning agent to protect the surface coating of the units. Continue to check the surface finishes regularly and reinstate immediately to prevent rust forming or debris collecting and trapping water.

Note: Local risk assessments should always be undertaken when installing blast vents to protect both members of Staff and also the General Public. A Blast Vent can open suddenly and without prior warning when releasing internal blast pressures. It is also possible that parts of the unit under higher than anticipated blast pressures can break free. Insufficient venting area of the building can also increase localised pressure on release vents. Any of these types of instances can cause injury and it is important to provide sufficient space where blast vents are installed to accommodate and mitigate this potential for injury. Consideration should be given to incorporating warning signs and suitably cordoned areas as just one means of providing personnel protection.

Use signage to warn persons that there is the potential of an explosion in the immediate vicinity.

In addition to the vent unit suddenly opening and releasing gas pressure there is always the risk of catastrophic failure of the vent components and other building items such as windows, doors, roof and walls. Any of these items can produce fragmentation and become a potential hazard. It is always advisable to carry out an independent risk and product risk assessment in these areas. This is very important.

Note: Precise pressure adjustment is not possible due to the location of the strike, the amount of gasket compression, friction, etc. The listed values are a guide only, and if the release pressure is critical, the pressure must be measured directly at the door after installation for more accuracy. The estimated variance is plus or minus 2 full turns.

Note: Precise pressure adjustment is not possible due to the location of the strike, the amount of gasket compression, friction, etc. The listed values are a guide only, and if the release pressure is

critical, the pressure must be measured directly at the door after installation for more accuracy. The estimated variance is plus or minus 2 full turns.

To adjust, have the latch in the door closed position (see illustration above), wherein one rivet which holds the laminated cam together is exposed.

Turn the adjusting screw counter-clockwise to its loosest position, making sure that the square nut does not come off the ball pin and the nut has full thread engagement. Using the Latch Release Force Adjustment Chart (below) as a guide, tighten the adjusting screw clockwise a half turn at a time until the desired pressure setting is reached. It should be possible to feel the adjusting screw slipping into the relaxed position at each half turn. For example, if you wanted 107 lbs. pressure setting on a #4 latch, you would tighten the adjusting screw 10 half turns (10 x 4.935) + (58 lbs. min.) = 107 lbs.

If the latch is mounted, adjustment can be made by turning the adjustment screw to its tightest position and backing off to the desired setting. Latches can be factory adjusted upon request for additional cost. For example, if you wanted 107 lbs pressure setting on a #4 latch, you tighten the adjustment screw clockwise to its maximum position. Then you would loosen the adjustment screw counter-clockwise 36 half turns {285 lbs max. - (36 x 4.935)} = 107 lbs