SubscribeWhen we talk about Spiders in the filtration industry, we are not referring to the “creepy-crawly” 8-legged order of arachnids.
Instead, we are talking about the aluminum or stainless steel rigid or open-mesh plates that are fitted over the ends of various types of filter elements.
There are 2 basic purposes of the spiders in the vessels: 1. to keep the elements separated to equalize flow around the elements, and to provide paths for the coalesced water drop to fall to the sump; and 2. to give support to the "free" ends of the elements (the ends not rigid against the deckplate).
Keeping the coalescers from touching each other will enhance the coalescing process by giving room between the coalescers for the water to fully form into drops 1/8 to ¼ inch in diameter, and then having room to fall by gravity to the sump at the bottom of the vessel. Another reason to keep the socks from touching each other is to reduce the microbial growth area. Have you ever seen a light or dark grayish or blackish line running vertically down a coalescer? This is microbial growth.
It is very important to support the free ends of elements, particularly the heavy coalescers in horizontal vessels. Without a spider supporting the free ends, and without the spider being rigidly clamped or clipped to the vessel interior, the free ends can be exposed to heavy vibration which could eventually loosen the mounting ends leading to bypass, or even rupture the mounting ends.
Spiders in the various vessels should not be allowed to become "unbonded charge collectors." There should always be a solid electrical path from the spider to the vessel shell. This can be accomplished through the tie rods that make solid contact with the spider, or by contact with a metal clip attached to the side of the vessel. In some filter/separator vessels there might be 2 spiders (see Fig. 1).
The spider for the separators is electrically bonded to the tie rods that are bonded to the vessel. However, the other spider on the screw-base coalescers might not be bonded to anything (it thus becomes an "unbonded charge collector" which could lead to fires in the vessel). Insure that these spiders are bonded electrically to the vessel by attaching to a metal clip, or by a braided stainless steel wire to the separator spider (see Fig. 2).
When converting a pre-filter (micronic) vessel from open-ended elements with tie rods to screw-base elements, ensure the spider is somehow bonded to the vessel either by support clips on the vessel interior or by the braided stainless steel wire to the baffle plate (see Fig. 3). We have seen a pre-filter vessel with no internal baffle plate. The purpose of the baffle plate or angle iron is to divert flow to the top of the vessel so the full flow does not all work against the nearest elements. Without the baffle plate, the nearest elements to the inlet can be torn apart. This vessel had been converted to screw-base filter elements, and had an unbonded spider at the top. There was visual and audio evidence of internal electrical discharge. Spiders, properly bonded, are important components of filter vessels!
