High Flow Sonde Housings
► What is a sonde
|► Data Sheet (pdf)|
|► Instructions (pdf)|
|► The History of our housing|
The Brewis High Flow Sonde Housing has been specially designed to give the high flow rates needed to drive mud motors. It is a rear load housing which uses an annular flow design.
Boring Heads, bent subs or jetting assemblies can easily be fitted to the front.
● Accepts all Digitrak™ 2
& 4 battery transmitters and Eclipse cable sondes.
● Very high flow rate to drive mud motors or for jetting.
● Annular flow design cools and cushions the transmitter during long bores.
● Manufactured from AISI 4145 Alloy steel with stainless steel internal components.
● 6 Diameters -
● Simple Mechanical Indexing to align the transmitter.
" S***" said the demonstrator.
"What’s that?" I asked, pointing to the tubular object.
"Ah," came the reply, "That’s the sonde."
"But why," I asked "do you have a design whereby you machine away 50% of the sonde housing’s torsional strength, put an unprotected electronic device costing £2000 inside and then allow it to marinade in mud by neglecting to seal the cover plate?" " It makes it easy for the operator" was the reply. I thought he was joking……
Further inspection revealed that the jets in the front were blocked with bentonite, as were the several 6mm holes bored the length of the housing to pass bentonite from the starter rod through to the jets. "How do you clear dried-out bentonite from a 6mm hole, 500mm long?" I asked. "With difficulty." came the depressed reply.
I designed a simple boring head for this customer. It had jets and gun-drilled flow ducts similar to the sample model, but I was determined that the costly electronic equipment would not be subjected to the abuse, albeit unintentional, caused by this oft used but less than satisfactory design. The new housing was rear entry and incorporated a capsule to protect the sonde and keep it clean and dry. The sonde capsule, consisted of an acetal tube threaded at each end, and front and rear caps screwed in and sealed by means of "O" rings, thus providing a watertight container. When inserted into the capsule, the sonde located on a dog on the rear of the front cap and, in turn, the capsule front cap was stepped to locate on a mating step when the capsule assembly was inserted into the boring head. Thus the angular position of the sonde was aligned exactly to the steering shoe on the front of the boring head. The windows of every sonde housing are always sealed with some form of flexible filler to prevent ingress of mud and debris but this is often breached in the aggressive environment underground. Despite this, the sonde is safe and protected in its capsule.
The boring head worked well, but the time and cost of gun-drilling the flow ducts, together with their propensity to become blocked caused me to consider further how the design might be simplified to facilitate manufacture or even to eliminate the flow ducts entirely. This was eventually achieved by introducing a second acetal tube of larger diameter as a liner to the steel body of the housing, into which the front and rear caps of the body were sealed using "O" rings. (Figure 2-Sectional drawing and Figure3-Operating Notes) The capsule end caps were re-designed and made from wear resistant stainless steel, and the sonde capsule was held concentric with the body liner, thus creating an annular flow path for the bentonite. Thus, instead of one large hole and, say, five small holes, only one slightly larger hole has now to be drilled through the body of the housing, saving time and cost.
This innovative design of sonde housing / boring head has significant benefits for the driller when compared with the more conventional designs:-
·Because of its large cross sectional area, the annular flow path cannot become blocked. The majority of sonde failures are due to overheating caused by the blockage of flow ducts and jets. If the supply of bentonite fails, the heat generated in drilling cooks the head and the sonde with it. With the annular design, this cannot happen. Furthermore, when the sonde batteries require charging or changing, the complete capsule is withdrawn from the rear of the housing, thus opening up the entire bore of the unit for cleaning. If the front cap of the head is also unscrewed and removed, the body and liner may be flushed through, inspected and maintained as necessary.
· The sonde capsule is totally enclosed by the bentonite flowing past it, thus completely insulating the sonde from the heat generated in the drilling process and preventing a rise in ambient temperature by continually flushing away that heat.
·The immersion of the sonde capsule in pressurised bentonite cushions the sonde from vibration and shock by acting as a damper or shock absorber.
·A 6mm annular flow path may have 15 or 20 times the cross sectional area of the 6-off 6mm diameter gun drilled flow ducts in a head of conventional design. The actual flow of bentonite through a head of this new design is vast, and is limited often by the capacity of the pump or the size of the jets. It is absolutely ideal for use with mud motors, which rely on very high flow rates to work effectively. Flow rates of up to 500 gallons per minute have been recorded on test.
Despite this novel use of plastics to create the flow path, the unit has great longevity. After long periods of continual use the capsule end caps become contoured by the flow of bentonite, but the original machining marks in the acetal tubes are still clearly visible.
This product has been designed primarily for use with the Digitrak range of sondes; 2 battery, 4 battery and eclipse models, both as a walkover and wireline systems but other makes can be accommodated. To change from wireline to walkover operation, the seals in the capsule back cap gland are replaced with a simple plug, a procedure which takes a few seconds.
The unit may be configured for jetting using a steering shoe, for drilling hard ground using a tri-cone cutter and bent sub, or for drilling rock using a front cap, mud-motor and driven cutter.
When used in conjunction with a mud motor, the sonde has to be aligned with the crank on the mud motor to indicate the 12 o’clock position. This is achieved by "dogging" the sonde to the inside of the capsule front cap whilst the dogs on the outside locate in the castellations on the body front cap, giving an angular position accurate to a few degrees.
Customer satisfaction and commercial viability
Steve Edwards and Bill Ettel, the managers of Digitrak Europe routinely advise their customers that, in terms of function, ease of use, accuracy, reliability, and longevity, the Brewis High Flow Housing is the best available anywhere in the world. They impress on them that the advanced design of this product enhances the performance of their equipment, whereas inferior housings detract. Designed originally to accept API threaded drillpipe, its application is being extended with the provision of adaptors to suit the equipment of all major drill rig manufacturer. Digitrak’s implicit and unwavering faith in this product has resulted in its selection in Europe for use with their new Short Steering Tool (SST) which utilises magnetometers for accuracy rather than conventional electronics. This has necessitated its manufacture in non magnetic stainless steel and some redesign of the steering and jetting arrangements.
Brewis Engineering Ltd
UK Company No. 04684538